Merge master.kernel.org:/pub/scm/linux/kernel/git/wim/linux-2.6-watchdog
[linux-2.6] / block / ll_rw_blk.c
1 /*
2  * Copyright (C) 1991, 1992 Linus Torvalds
3  * Copyright (C) 1994,      Karl Keyte: Added support for disk statistics
4  * Elevator latency, (C) 2000  Andrea Arcangeli <andrea@suse.de> SuSE
5  * Queue request tables / lock, selectable elevator, Jens Axboe <axboe@suse.de>
6  * kernel-doc documentation started by NeilBrown <neilb@cse.unsw.edu.au> -  July2000
7  * bio rewrite, highmem i/o, etc, Jens Axboe <axboe@suse.de> - may 2001
8  */
9
10 /*
11  * This handles all read/write requests to block devices
12  */
13 #include <linux/config.h>
14 #include <linux/kernel.h>
15 #include <linux/module.h>
16 #include <linux/backing-dev.h>
17 #include <linux/bio.h>
18 #include <linux/blkdev.h>
19 #include <linux/highmem.h>
20 #include <linux/mm.h>
21 #include <linux/kernel_stat.h>
22 #include <linux/string.h>
23 #include <linux/init.h>
24 #include <linux/bootmem.h>      /* for max_pfn/max_low_pfn */
25 #include <linux/completion.h>
26 #include <linux/slab.h>
27 #include <linux/swap.h>
28 #include <linux/writeback.h>
29 #include <linux/interrupt.h>
30 #include <linux/cpu.h>
31 #include <linux/blktrace_api.h>
32
33 /*
34  * for max sense size
35  */
36 #include <scsi/scsi_cmnd.h>
37
38 static void blk_unplug_work(void *data);
39 static void blk_unplug_timeout(unsigned long data);
40 static void drive_stat_acct(struct request *rq, int nr_sectors, int new_io);
41 static void init_request_from_bio(struct request *req, struct bio *bio);
42 static int __make_request(request_queue_t *q, struct bio *bio);
43
44 /*
45  * For the allocated request tables
46  */
47 static kmem_cache_t *request_cachep;
48
49 /*
50  * For queue allocation
51  */
52 static kmem_cache_t *requestq_cachep;
53
54 /*
55  * For io context allocations
56  */
57 static kmem_cache_t *iocontext_cachep;
58
59 static wait_queue_head_t congestion_wqh[2] = {
60                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
61                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
62         };
63
64 /*
65  * Controlling structure to kblockd
66  */
67 static struct workqueue_struct *kblockd_workqueue;
68
69 unsigned long blk_max_low_pfn, blk_max_pfn;
70
71 EXPORT_SYMBOL(blk_max_low_pfn);
72 EXPORT_SYMBOL(blk_max_pfn);
73
74 static DEFINE_PER_CPU(struct list_head, blk_cpu_done);
75
76 /* Amount of time in which a process may batch requests */
77 #define BLK_BATCH_TIME  (HZ/50UL)
78
79 /* Number of requests a "batching" process may submit */
80 #define BLK_BATCH_REQ   32
81
82 /*
83  * Return the threshold (number of used requests) at which the queue is
84  * considered to be congested.  It include a little hysteresis to keep the
85  * context switch rate down.
86  */
87 static inline int queue_congestion_on_threshold(struct request_queue *q)
88 {
89         return q->nr_congestion_on;
90 }
91
92 /*
93  * The threshold at which a queue is considered to be uncongested
94  */
95 static inline int queue_congestion_off_threshold(struct request_queue *q)
96 {
97         return q->nr_congestion_off;
98 }
99
100 static void blk_queue_congestion_threshold(struct request_queue *q)
101 {
102         int nr;
103
104         nr = q->nr_requests - (q->nr_requests / 8) + 1;
105         if (nr > q->nr_requests)
106                 nr = q->nr_requests;
107         q->nr_congestion_on = nr;
108
109         nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
110         if (nr < 1)
111                 nr = 1;
112         q->nr_congestion_off = nr;
113 }
114
115 /*
116  * A queue has just exitted congestion.  Note this in the global counter of
117  * congested queues, and wake up anyone who was waiting for requests to be
118  * put back.
119  */
120 static void clear_queue_congested(request_queue_t *q, int rw)
121 {
122         enum bdi_state bit;
123         wait_queue_head_t *wqh = &congestion_wqh[rw];
124
125         bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
126         clear_bit(bit, &q->backing_dev_info.state);
127         smp_mb__after_clear_bit();
128         if (waitqueue_active(wqh))
129                 wake_up(wqh);
130 }
131
132 /*
133  * A queue has just entered congestion.  Flag that in the queue's VM-visible
134  * state flags and increment the global gounter of congested queues.
135  */
136 static void set_queue_congested(request_queue_t *q, int rw)
137 {
138         enum bdi_state bit;
139
140         bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
141         set_bit(bit, &q->backing_dev_info.state);
142 }
143
144 /**
145  * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
146  * @bdev:       device
147  *
148  * Locates the passed device's request queue and returns the address of its
149  * backing_dev_info
150  *
151  * Will return NULL if the request queue cannot be located.
152  */
153 struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
154 {
155         struct backing_dev_info *ret = NULL;
156         request_queue_t *q = bdev_get_queue(bdev);
157
158         if (q)
159                 ret = &q->backing_dev_info;
160         return ret;
161 }
162
163 EXPORT_SYMBOL(blk_get_backing_dev_info);
164
165 void blk_queue_activity_fn(request_queue_t *q, activity_fn *fn, void *data)
166 {
167         q->activity_fn = fn;
168         q->activity_data = data;
169 }
170
171 EXPORT_SYMBOL(blk_queue_activity_fn);
172
173 /**
174  * blk_queue_prep_rq - set a prepare_request function for queue
175  * @q:          queue
176  * @pfn:        prepare_request function
177  *
178  * It's possible for a queue to register a prepare_request callback which
179  * is invoked before the request is handed to the request_fn. The goal of
180  * the function is to prepare a request for I/O, it can be used to build a
181  * cdb from the request data for instance.
182  *
183  */
184 void blk_queue_prep_rq(request_queue_t *q, prep_rq_fn *pfn)
185 {
186         q->prep_rq_fn = pfn;
187 }
188
189 EXPORT_SYMBOL(blk_queue_prep_rq);
190
191 /**
192  * blk_queue_merge_bvec - set a merge_bvec function for queue
193  * @q:          queue
194  * @mbfn:       merge_bvec_fn
195  *
196  * Usually queues have static limitations on the max sectors or segments that
197  * we can put in a request. Stacking drivers may have some settings that
198  * are dynamic, and thus we have to query the queue whether it is ok to
199  * add a new bio_vec to a bio at a given offset or not. If the block device
200  * has such limitations, it needs to register a merge_bvec_fn to control
201  * the size of bio's sent to it. Note that a block device *must* allow a
202  * single page to be added to an empty bio. The block device driver may want
203  * to use the bio_split() function to deal with these bio's. By default
204  * no merge_bvec_fn is defined for a queue, and only the fixed limits are
205  * honored.
206  */
207 void blk_queue_merge_bvec(request_queue_t *q, merge_bvec_fn *mbfn)
208 {
209         q->merge_bvec_fn = mbfn;
210 }
211
212 EXPORT_SYMBOL(blk_queue_merge_bvec);
213
214 void blk_queue_softirq_done(request_queue_t *q, softirq_done_fn *fn)
215 {
216         q->softirq_done_fn = fn;
217 }
218
219 EXPORT_SYMBOL(blk_queue_softirq_done);
220
221 /**
222  * blk_queue_make_request - define an alternate make_request function for a device
223  * @q:  the request queue for the device to be affected
224  * @mfn: the alternate make_request function
225  *
226  * Description:
227  *    The normal way for &struct bios to be passed to a device
228  *    driver is for them to be collected into requests on a request
229  *    queue, and then to allow the device driver to select requests
230  *    off that queue when it is ready.  This works well for many block
231  *    devices. However some block devices (typically virtual devices
232  *    such as md or lvm) do not benefit from the processing on the
233  *    request queue, and are served best by having the requests passed
234  *    directly to them.  This can be achieved by providing a function
235  *    to blk_queue_make_request().
236  *
237  * Caveat:
238  *    The driver that does this *must* be able to deal appropriately
239  *    with buffers in "highmemory". This can be accomplished by either calling
240  *    __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
241  *    blk_queue_bounce() to create a buffer in normal memory.
242  **/
243 void blk_queue_make_request(request_queue_t * q, make_request_fn * mfn)
244 {
245         /*
246          * set defaults
247          */
248         q->nr_requests = BLKDEV_MAX_RQ;
249         blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
250         blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
251         q->make_request_fn = mfn;
252         q->backing_dev_info.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
253         q->backing_dev_info.state = 0;
254         q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
255         blk_queue_max_sectors(q, SAFE_MAX_SECTORS);
256         blk_queue_hardsect_size(q, 512);
257         blk_queue_dma_alignment(q, 511);
258         blk_queue_congestion_threshold(q);
259         q->nr_batching = BLK_BATCH_REQ;
260
261         q->unplug_thresh = 4;           /* hmm */
262         q->unplug_delay = (3 * HZ) / 1000;      /* 3 milliseconds */
263         if (q->unplug_delay == 0)
264                 q->unplug_delay = 1;
265
266         INIT_WORK(&q->unplug_work, blk_unplug_work, q);
267
268         q->unplug_timer.function = blk_unplug_timeout;
269         q->unplug_timer.data = (unsigned long)q;
270
271         /*
272          * by default assume old behaviour and bounce for any highmem page
273          */
274         blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
275
276         blk_queue_activity_fn(q, NULL, NULL);
277 }
278
279 EXPORT_SYMBOL(blk_queue_make_request);
280
281 static inline void rq_init(request_queue_t *q, struct request *rq)
282 {
283         INIT_LIST_HEAD(&rq->queuelist);
284         INIT_LIST_HEAD(&rq->donelist);
285
286         rq->errors = 0;
287         rq->rq_status = RQ_ACTIVE;
288         rq->bio = rq->biotail = NULL;
289         rq->ioprio = 0;
290         rq->buffer = NULL;
291         rq->ref_count = 1;
292         rq->q = q;
293         rq->waiting = NULL;
294         rq->special = NULL;
295         rq->data_len = 0;
296         rq->data = NULL;
297         rq->nr_phys_segments = 0;
298         rq->sense = NULL;
299         rq->end_io = NULL;
300         rq->end_io_data = NULL;
301         rq->completion_data = NULL;
302 }
303
304 /**
305  * blk_queue_ordered - does this queue support ordered writes
306  * @q:        the request queue
307  * @ordered:  one of QUEUE_ORDERED_*
308  * @prepare_flush_fn: rq setup helper for cache flush ordered writes
309  *
310  * Description:
311  *   For journalled file systems, doing ordered writes on a commit
312  *   block instead of explicitly doing wait_on_buffer (which is bad
313  *   for performance) can be a big win. Block drivers supporting this
314  *   feature should call this function and indicate so.
315  *
316  **/
317 int blk_queue_ordered(request_queue_t *q, unsigned ordered,
318                       prepare_flush_fn *prepare_flush_fn)
319 {
320         if (ordered & (QUEUE_ORDERED_PREFLUSH | QUEUE_ORDERED_POSTFLUSH) &&
321             prepare_flush_fn == NULL) {
322                 printk(KERN_ERR "blk_queue_ordered: prepare_flush_fn required\n");
323                 return -EINVAL;
324         }
325
326         if (ordered != QUEUE_ORDERED_NONE &&
327             ordered != QUEUE_ORDERED_DRAIN &&
328             ordered != QUEUE_ORDERED_DRAIN_FLUSH &&
329             ordered != QUEUE_ORDERED_DRAIN_FUA &&
330             ordered != QUEUE_ORDERED_TAG &&
331             ordered != QUEUE_ORDERED_TAG_FLUSH &&
332             ordered != QUEUE_ORDERED_TAG_FUA) {
333                 printk(KERN_ERR "blk_queue_ordered: bad value %d\n", ordered);
334                 return -EINVAL;
335         }
336
337         q->ordered = ordered;
338         q->next_ordered = ordered;
339         q->prepare_flush_fn = prepare_flush_fn;
340
341         return 0;
342 }
343
344 EXPORT_SYMBOL(blk_queue_ordered);
345
346 /**
347  * blk_queue_issue_flush_fn - set function for issuing a flush
348  * @q:     the request queue
349  * @iff:   the function to be called issuing the flush
350  *
351  * Description:
352  *   If a driver supports issuing a flush command, the support is notified
353  *   to the block layer by defining it through this call.
354  *
355  **/
356 void blk_queue_issue_flush_fn(request_queue_t *q, issue_flush_fn *iff)
357 {
358         q->issue_flush_fn = iff;
359 }
360
361 EXPORT_SYMBOL(blk_queue_issue_flush_fn);
362
363 /*
364  * Cache flushing for ordered writes handling
365  */
366 inline unsigned blk_ordered_cur_seq(request_queue_t *q)
367 {
368         if (!q->ordseq)
369                 return 0;
370         return 1 << ffz(q->ordseq);
371 }
372
373 unsigned blk_ordered_req_seq(struct request *rq)
374 {
375         request_queue_t *q = rq->q;
376
377         BUG_ON(q->ordseq == 0);
378
379         if (rq == &q->pre_flush_rq)
380                 return QUEUE_ORDSEQ_PREFLUSH;
381         if (rq == &q->bar_rq)
382                 return QUEUE_ORDSEQ_BAR;
383         if (rq == &q->post_flush_rq)
384                 return QUEUE_ORDSEQ_POSTFLUSH;
385
386         if ((rq->flags & REQ_ORDERED_COLOR) ==
387             (q->orig_bar_rq->flags & REQ_ORDERED_COLOR))
388                 return QUEUE_ORDSEQ_DRAIN;
389         else
390                 return QUEUE_ORDSEQ_DONE;
391 }
392
393 void blk_ordered_complete_seq(request_queue_t *q, unsigned seq, int error)
394 {
395         struct request *rq;
396         int uptodate;
397
398         if (error && !q->orderr)
399                 q->orderr = error;
400
401         BUG_ON(q->ordseq & seq);
402         q->ordseq |= seq;
403
404         if (blk_ordered_cur_seq(q) != QUEUE_ORDSEQ_DONE)
405                 return;
406
407         /*
408          * Okay, sequence complete.
409          */
410         rq = q->orig_bar_rq;
411         uptodate = q->orderr ? q->orderr : 1;
412
413         q->ordseq = 0;
414
415         end_that_request_first(rq, uptodate, rq->hard_nr_sectors);
416         end_that_request_last(rq, uptodate);
417 }
418
419 static void pre_flush_end_io(struct request *rq, int error)
420 {
421         elv_completed_request(rq->q, rq);
422         blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_PREFLUSH, error);
423 }
424
425 static void bar_end_io(struct request *rq, int error)
426 {
427         elv_completed_request(rq->q, rq);
428         blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_BAR, error);
429 }
430
431 static void post_flush_end_io(struct request *rq, int error)
432 {
433         elv_completed_request(rq->q, rq);
434         blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_POSTFLUSH, error);
435 }
436
437 static void queue_flush(request_queue_t *q, unsigned which)
438 {
439         struct request *rq;
440         rq_end_io_fn *end_io;
441
442         if (which == QUEUE_ORDERED_PREFLUSH) {
443                 rq = &q->pre_flush_rq;
444                 end_io = pre_flush_end_io;
445         } else {
446                 rq = &q->post_flush_rq;
447                 end_io = post_flush_end_io;
448         }
449
450         rq_init(q, rq);
451         rq->flags = REQ_HARDBARRIER;
452         rq->elevator_private = NULL;
453         rq->rq_disk = q->bar_rq.rq_disk;
454         rq->rl = NULL;
455         rq->end_io = end_io;
456         q->prepare_flush_fn(q, rq);
457
458         elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
459 }
460
461 static inline struct request *start_ordered(request_queue_t *q,
462                                             struct request *rq)
463 {
464         q->bi_size = 0;
465         q->orderr = 0;
466         q->ordered = q->next_ordered;
467         q->ordseq |= QUEUE_ORDSEQ_STARTED;
468
469         /*
470          * Prep proxy barrier request.
471          */
472         blkdev_dequeue_request(rq);
473         q->orig_bar_rq = rq;
474         rq = &q->bar_rq;
475         rq_init(q, rq);
476         rq->flags = bio_data_dir(q->orig_bar_rq->bio);
477         rq->flags |= q->ordered & QUEUE_ORDERED_FUA ? REQ_FUA : 0;
478         rq->elevator_private = NULL;
479         rq->rl = NULL;
480         init_request_from_bio(rq, q->orig_bar_rq->bio);
481         rq->end_io = bar_end_io;
482
483         /*
484          * Queue ordered sequence.  As we stack them at the head, we
485          * need to queue in reverse order.  Note that we rely on that
486          * no fs request uses ELEVATOR_INSERT_FRONT and thus no fs
487          * request gets inbetween ordered sequence.
488          */
489         if (q->ordered & QUEUE_ORDERED_POSTFLUSH)
490                 queue_flush(q, QUEUE_ORDERED_POSTFLUSH);
491         else
492                 q->ordseq |= QUEUE_ORDSEQ_POSTFLUSH;
493
494         elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
495
496         if (q->ordered & QUEUE_ORDERED_PREFLUSH) {
497                 queue_flush(q, QUEUE_ORDERED_PREFLUSH);
498                 rq = &q->pre_flush_rq;
499         } else
500                 q->ordseq |= QUEUE_ORDSEQ_PREFLUSH;
501
502         if ((q->ordered & QUEUE_ORDERED_TAG) || q->in_flight == 0)
503                 q->ordseq |= QUEUE_ORDSEQ_DRAIN;
504         else
505                 rq = NULL;
506
507         return rq;
508 }
509
510 int blk_do_ordered(request_queue_t *q, struct request **rqp)
511 {
512         struct request *rq = *rqp;
513         int is_barrier = blk_fs_request(rq) && blk_barrier_rq(rq);
514
515         if (!q->ordseq) {
516                 if (!is_barrier)
517                         return 1;
518
519                 if (q->next_ordered != QUEUE_ORDERED_NONE) {
520                         *rqp = start_ordered(q, rq);
521                         return 1;
522                 } else {
523                         /*
524                          * This can happen when the queue switches to
525                          * ORDERED_NONE while this request is on it.
526                          */
527                         blkdev_dequeue_request(rq);
528                         end_that_request_first(rq, -EOPNOTSUPP,
529                                                rq->hard_nr_sectors);
530                         end_that_request_last(rq, -EOPNOTSUPP);
531                         *rqp = NULL;
532                         return 0;
533                 }
534         }
535
536         /*
537          * Ordered sequence in progress
538          */
539
540         /* Special requests are not subject to ordering rules. */
541         if (!blk_fs_request(rq) &&
542             rq != &q->pre_flush_rq && rq != &q->post_flush_rq)
543                 return 1;
544
545         if (q->ordered & QUEUE_ORDERED_TAG) {
546                 /* Ordered by tag.  Blocking the next barrier is enough. */
547                 if (is_barrier && rq != &q->bar_rq)
548                         *rqp = NULL;
549         } else {
550                 /* Ordered by draining.  Wait for turn. */
551                 WARN_ON(blk_ordered_req_seq(rq) < blk_ordered_cur_seq(q));
552                 if (blk_ordered_req_seq(rq) > blk_ordered_cur_seq(q))
553                         *rqp = NULL;
554         }
555
556         return 1;
557 }
558
559 static int flush_dry_bio_endio(struct bio *bio, unsigned int bytes, int error)
560 {
561         request_queue_t *q = bio->bi_private;
562         struct bio_vec *bvec;
563         int i;
564
565         /*
566          * This is dry run, restore bio_sector and size.  We'll finish
567          * this request again with the original bi_end_io after an
568          * error occurs or post flush is complete.
569          */
570         q->bi_size += bytes;
571
572         if (bio->bi_size)
573                 return 1;
574
575         /* Rewind bvec's */
576         bio->bi_idx = 0;
577         bio_for_each_segment(bvec, bio, i) {
578                 bvec->bv_len += bvec->bv_offset;
579                 bvec->bv_offset = 0;
580         }
581
582         /* Reset bio */
583         set_bit(BIO_UPTODATE, &bio->bi_flags);
584         bio->bi_size = q->bi_size;
585         bio->bi_sector -= (q->bi_size >> 9);
586         q->bi_size = 0;
587
588         return 0;
589 }
590
591 static inline int ordered_bio_endio(struct request *rq, struct bio *bio,
592                                     unsigned int nbytes, int error)
593 {
594         request_queue_t *q = rq->q;
595         bio_end_io_t *endio;
596         void *private;
597
598         if (&q->bar_rq != rq)
599                 return 0;
600
601         /*
602          * Okay, this is the barrier request in progress, dry finish it.
603          */
604         if (error && !q->orderr)
605                 q->orderr = error;
606
607         endio = bio->bi_end_io;
608         private = bio->bi_private;
609         bio->bi_end_io = flush_dry_bio_endio;
610         bio->bi_private = q;
611
612         bio_endio(bio, nbytes, error);
613
614         bio->bi_end_io = endio;
615         bio->bi_private = private;
616
617         return 1;
618 }
619
620 /**
621  * blk_queue_bounce_limit - set bounce buffer limit for queue
622  * @q:  the request queue for the device
623  * @dma_addr:   bus address limit
624  *
625  * Description:
626  *    Different hardware can have different requirements as to what pages
627  *    it can do I/O directly to. A low level driver can call
628  *    blk_queue_bounce_limit to have lower memory pages allocated as bounce
629  *    buffers for doing I/O to pages residing above @page.
630  **/
631 void blk_queue_bounce_limit(request_queue_t *q, u64 dma_addr)
632 {
633         unsigned long bounce_pfn = dma_addr >> PAGE_SHIFT;
634         int dma = 0;
635
636         q->bounce_gfp = GFP_NOIO;
637 #if BITS_PER_LONG == 64
638         /* Assume anything <= 4GB can be handled by IOMMU.
639            Actually some IOMMUs can handle everything, but I don't
640            know of a way to test this here. */
641         if (bounce_pfn < (min_t(u64,0xffffffff,BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
642                 dma = 1;
643         q->bounce_pfn = max_low_pfn;
644 #else
645         if (bounce_pfn < blk_max_low_pfn)
646                 dma = 1;
647         q->bounce_pfn = bounce_pfn;
648 #endif
649         if (dma) {
650                 init_emergency_isa_pool();
651                 q->bounce_gfp = GFP_NOIO | GFP_DMA;
652                 q->bounce_pfn = bounce_pfn;
653         }
654 }
655
656 EXPORT_SYMBOL(blk_queue_bounce_limit);
657
658 /**
659  * blk_queue_max_sectors - set max sectors for a request for this queue
660  * @q:  the request queue for the device
661  * @max_sectors:  max sectors in the usual 512b unit
662  *
663  * Description:
664  *    Enables a low level driver to set an upper limit on the size of
665  *    received requests.
666  **/
667 void blk_queue_max_sectors(request_queue_t *q, unsigned int max_sectors)
668 {
669         if ((max_sectors << 9) < PAGE_CACHE_SIZE) {
670                 max_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
671                 printk("%s: set to minimum %d\n", __FUNCTION__, max_sectors);
672         }
673
674         if (BLK_DEF_MAX_SECTORS > max_sectors)
675                 q->max_hw_sectors = q->max_sectors = max_sectors;
676         else {
677                 q->max_sectors = BLK_DEF_MAX_SECTORS;
678                 q->max_hw_sectors = max_sectors;
679         }
680 }
681
682 EXPORT_SYMBOL(blk_queue_max_sectors);
683
684 /**
685  * blk_queue_max_phys_segments - set max phys segments for a request for this queue
686  * @q:  the request queue for the device
687  * @max_segments:  max number of segments
688  *
689  * Description:
690  *    Enables a low level driver to set an upper limit on the number of
691  *    physical data segments in a request.  This would be the largest sized
692  *    scatter list the driver could handle.
693  **/
694 void blk_queue_max_phys_segments(request_queue_t *q, unsigned short max_segments)
695 {
696         if (!max_segments) {
697                 max_segments = 1;
698                 printk("%s: set to minimum %d\n", __FUNCTION__, max_segments);
699         }
700
701         q->max_phys_segments = max_segments;
702 }
703
704 EXPORT_SYMBOL(blk_queue_max_phys_segments);
705
706 /**
707  * blk_queue_max_hw_segments - set max hw segments for a request for this queue
708  * @q:  the request queue for the device
709  * @max_segments:  max number of segments
710  *
711  * Description:
712  *    Enables a low level driver to set an upper limit on the number of
713  *    hw data segments in a request.  This would be the largest number of
714  *    address/length pairs the host adapter can actually give as once
715  *    to the device.
716  **/
717 void blk_queue_max_hw_segments(request_queue_t *q, unsigned short max_segments)
718 {
719         if (!max_segments) {
720                 max_segments = 1;
721                 printk("%s: set to minimum %d\n", __FUNCTION__, max_segments);
722         }
723
724         q->max_hw_segments = max_segments;
725 }
726
727 EXPORT_SYMBOL(blk_queue_max_hw_segments);
728
729 /**
730  * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
731  * @q:  the request queue for the device
732  * @max_size:  max size of segment in bytes
733  *
734  * Description:
735  *    Enables a low level driver to set an upper limit on the size of a
736  *    coalesced segment
737  **/
738 void blk_queue_max_segment_size(request_queue_t *q, unsigned int max_size)
739 {
740         if (max_size < PAGE_CACHE_SIZE) {
741                 max_size = PAGE_CACHE_SIZE;
742                 printk("%s: set to minimum %d\n", __FUNCTION__, max_size);
743         }
744
745         q->max_segment_size = max_size;
746 }
747
748 EXPORT_SYMBOL(blk_queue_max_segment_size);
749
750 /**
751  * blk_queue_hardsect_size - set hardware sector size for the queue
752  * @q:  the request queue for the device
753  * @size:  the hardware sector size, in bytes
754  *
755  * Description:
756  *   This should typically be set to the lowest possible sector size
757  *   that the hardware can operate on (possible without reverting to
758  *   even internal read-modify-write operations). Usually the default
759  *   of 512 covers most hardware.
760  **/
761 void blk_queue_hardsect_size(request_queue_t *q, unsigned short size)
762 {
763         q->hardsect_size = size;
764 }
765
766 EXPORT_SYMBOL(blk_queue_hardsect_size);
767
768 /*
769  * Returns the minimum that is _not_ zero, unless both are zero.
770  */
771 #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
772
773 /**
774  * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
775  * @t:  the stacking driver (top)
776  * @b:  the underlying device (bottom)
777  **/
778 void blk_queue_stack_limits(request_queue_t *t, request_queue_t *b)
779 {
780         /* zero is "infinity" */
781         t->max_sectors = min_not_zero(t->max_sectors,b->max_sectors);
782         t->max_hw_sectors = min_not_zero(t->max_hw_sectors,b->max_hw_sectors);
783
784         t->max_phys_segments = min(t->max_phys_segments,b->max_phys_segments);
785         t->max_hw_segments = min(t->max_hw_segments,b->max_hw_segments);
786         t->max_segment_size = min(t->max_segment_size,b->max_segment_size);
787         t->hardsect_size = max(t->hardsect_size,b->hardsect_size);
788         if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags))
789                 clear_bit(QUEUE_FLAG_CLUSTER, &t->queue_flags);
790 }
791
792 EXPORT_SYMBOL(blk_queue_stack_limits);
793
794 /**
795  * blk_queue_segment_boundary - set boundary rules for segment merging
796  * @q:  the request queue for the device
797  * @mask:  the memory boundary mask
798  **/
799 void blk_queue_segment_boundary(request_queue_t *q, unsigned long mask)
800 {
801         if (mask < PAGE_CACHE_SIZE - 1) {
802                 mask = PAGE_CACHE_SIZE - 1;
803                 printk("%s: set to minimum %lx\n", __FUNCTION__, mask);
804         }
805
806         q->seg_boundary_mask = mask;
807 }
808
809 EXPORT_SYMBOL(blk_queue_segment_boundary);
810
811 /**
812  * blk_queue_dma_alignment - set dma length and memory alignment
813  * @q:     the request queue for the device
814  * @mask:  alignment mask
815  *
816  * description:
817  *    set required memory and length aligment for direct dma transactions.
818  *    this is used when buiding direct io requests for the queue.
819  *
820  **/
821 void blk_queue_dma_alignment(request_queue_t *q, int mask)
822 {
823         q->dma_alignment = mask;
824 }
825
826 EXPORT_SYMBOL(blk_queue_dma_alignment);
827
828 /**
829  * blk_queue_find_tag - find a request by its tag and queue
830  * @q:   The request queue for the device
831  * @tag: The tag of the request
832  *
833  * Notes:
834  *    Should be used when a device returns a tag and you want to match
835  *    it with a request.
836  *
837  *    no locks need be held.
838  **/
839 struct request *blk_queue_find_tag(request_queue_t *q, int tag)
840 {
841         struct blk_queue_tag *bqt = q->queue_tags;
842
843         if (unlikely(bqt == NULL || tag >= bqt->real_max_depth))
844                 return NULL;
845
846         return bqt->tag_index[tag];
847 }
848
849 EXPORT_SYMBOL(blk_queue_find_tag);
850
851 /**
852  * __blk_queue_free_tags - release tag maintenance info
853  * @q:  the request queue for the device
854  *
855  *  Notes:
856  *    blk_cleanup_queue() will take care of calling this function, if tagging
857  *    has been used. So there's no need to call this directly.
858  **/
859 static void __blk_queue_free_tags(request_queue_t *q)
860 {
861         struct blk_queue_tag *bqt = q->queue_tags;
862
863         if (!bqt)
864                 return;
865
866         if (atomic_dec_and_test(&bqt->refcnt)) {
867                 BUG_ON(bqt->busy);
868                 BUG_ON(!list_empty(&bqt->busy_list));
869
870                 kfree(bqt->tag_index);
871                 bqt->tag_index = NULL;
872
873                 kfree(bqt->tag_map);
874                 bqt->tag_map = NULL;
875
876                 kfree(bqt);
877         }
878
879         q->queue_tags = NULL;
880         q->queue_flags &= ~(1 << QUEUE_FLAG_QUEUED);
881 }
882
883 /**
884  * blk_queue_free_tags - release tag maintenance info
885  * @q:  the request queue for the device
886  *
887  *  Notes:
888  *      This is used to disabled tagged queuing to a device, yet leave
889  *      queue in function.
890  **/
891 void blk_queue_free_tags(request_queue_t *q)
892 {
893         clear_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);
894 }
895
896 EXPORT_SYMBOL(blk_queue_free_tags);
897
898 static int
899 init_tag_map(request_queue_t *q, struct blk_queue_tag *tags, int depth)
900 {
901         struct request **tag_index;
902         unsigned long *tag_map;
903         int nr_ulongs;
904
905         if (depth > q->nr_requests * 2) {
906                 depth = q->nr_requests * 2;
907                 printk(KERN_ERR "%s: adjusted depth to %d\n",
908                                 __FUNCTION__, depth);
909         }
910
911         tag_index = kzalloc(depth * sizeof(struct request *), GFP_ATOMIC);
912         if (!tag_index)
913                 goto fail;
914
915         nr_ulongs = ALIGN(depth, BITS_PER_LONG) / BITS_PER_LONG;
916         tag_map = kzalloc(nr_ulongs * sizeof(unsigned long), GFP_ATOMIC);
917         if (!tag_map)
918                 goto fail;
919
920         tags->real_max_depth = depth;
921         tags->max_depth = depth;
922         tags->tag_index = tag_index;
923         tags->tag_map = tag_map;
924
925         return 0;
926 fail:
927         kfree(tag_index);
928         return -ENOMEM;
929 }
930
931 /**
932  * blk_queue_init_tags - initialize the queue tag info
933  * @q:  the request queue for the device
934  * @depth:  the maximum queue depth supported
935  * @tags: the tag to use
936  **/
937 int blk_queue_init_tags(request_queue_t *q, int depth,
938                         struct blk_queue_tag *tags)
939 {
940         int rc;
941
942         BUG_ON(tags && q->queue_tags && tags != q->queue_tags);
943
944         if (!tags && !q->queue_tags) {
945                 tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC);
946                 if (!tags)
947                         goto fail;
948
949                 if (init_tag_map(q, tags, depth))
950                         goto fail;
951
952                 INIT_LIST_HEAD(&tags->busy_list);
953                 tags->busy = 0;
954                 atomic_set(&tags->refcnt, 1);
955         } else if (q->queue_tags) {
956                 if ((rc = blk_queue_resize_tags(q, depth)))
957                         return rc;
958                 set_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);
959                 return 0;
960         } else
961                 atomic_inc(&tags->refcnt);
962
963         /*
964          * assign it, all done
965          */
966         q->queue_tags = tags;
967         q->queue_flags |= (1 << QUEUE_FLAG_QUEUED);
968         return 0;
969 fail:
970         kfree(tags);
971         return -ENOMEM;
972 }
973
974 EXPORT_SYMBOL(blk_queue_init_tags);
975
976 /**
977  * blk_queue_resize_tags - change the queueing depth
978  * @q:  the request queue for the device
979  * @new_depth: the new max command queueing depth
980  *
981  *  Notes:
982  *    Must be called with the queue lock held.
983  **/
984 int blk_queue_resize_tags(request_queue_t *q, int new_depth)
985 {
986         struct blk_queue_tag *bqt = q->queue_tags;
987         struct request **tag_index;
988         unsigned long *tag_map;
989         int max_depth, nr_ulongs;
990
991         if (!bqt)
992                 return -ENXIO;
993
994         /*
995          * if we already have large enough real_max_depth.  just
996          * adjust max_depth.  *NOTE* as requests with tag value
997          * between new_depth and real_max_depth can be in-flight, tag
998          * map can not be shrunk blindly here.
999          */
1000         if (new_depth <= bqt->real_max_depth) {
1001                 bqt->max_depth = new_depth;
1002                 return 0;
1003         }
1004
1005         /*
1006          * save the old state info, so we can copy it back
1007          */
1008         tag_index = bqt->tag_index;
1009         tag_map = bqt->tag_map;
1010         max_depth = bqt->real_max_depth;
1011
1012         if (init_tag_map(q, bqt, new_depth))
1013                 return -ENOMEM;
1014
1015         memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
1016         nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG;
1017         memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long));
1018
1019         kfree(tag_index);
1020         kfree(tag_map);
1021         return 0;
1022 }
1023
1024 EXPORT_SYMBOL(blk_queue_resize_tags);
1025
1026 /**
1027  * blk_queue_end_tag - end tag operations for a request
1028  * @q:  the request queue for the device
1029  * @rq: the request that has completed
1030  *
1031  *  Description:
1032  *    Typically called when end_that_request_first() returns 0, meaning
1033  *    all transfers have been done for a request. It's important to call
1034  *    this function before end_that_request_last(), as that will put the
1035  *    request back on the free list thus corrupting the internal tag list.
1036  *
1037  *  Notes:
1038  *   queue lock must be held.
1039  **/
1040 void blk_queue_end_tag(request_queue_t *q, struct request *rq)
1041 {
1042         struct blk_queue_tag *bqt = q->queue_tags;
1043         int tag = rq->tag;
1044
1045         BUG_ON(tag == -1);
1046
1047         if (unlikely(tag >= bqt->real_max_depth))
1048                 /*
1049                  * This can happen after tag depth has been reduced.
1050                  * FIXME: how about a warning or info message here?
1051                  */
1052                 return;
1053
1054         if (unlikely(!__test_and_clear_bit(tag, bqt->tag_map))) {
1055                 printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
1056                        __FUNCTION__, tag);
1057                 return;
1058         }
1059
1060         list_del_init(&rq->queuelist);
1061         rq->flags &= ~REQ_QUEUED;
1062         rq->tag = -1;
1063
1064         if (unlikely(bqt->tag_index[tag] == NULL))
1065                 printk(KERN_ERR "%s: tag %d is missing\n",
1066                        __FUNCTION__, tag);
1067
1068         bqt->tag_index[tag] = NULL;
1069         bqt->busy--;
1070 }
1071
1072 EXPORT_SYMBOL(blk_queue_end_tag);
1073
1074 /**
1075  * blk_queue_start_tag - find a free tag and assign it
1076  * @q:  the request queue for the device
1077  * @rq:  the block request that needs tagging
1078  *
1079  *  Description:
1080  *    This can either be used as a stand-alone helper, or possibly be
1081  *    assigned as the queue &prep_rq_fn (in which case &struct request
1082  *    automagically gets a tag assigned). Note that this function
1083  *    assumes that any type of request can be queued! if this is not
1084  *    true for your device, you must check the request type before
1085  *    calling this function.  The request will also be removed from
1086  *    the request queue, so it's the drivers responsibility to readd
1087  *    it if it should need to be restarted for some reason.
1088  *
1089  *  Notes:
1090  *   queue lock must be held.
1091  **/
1092 int blk_queue_start_tag(request_queue_t *q, struct request *rq)
1093 {
1094         struct blk_queue_tag *bqt = q->queue_tags;
1095         int tag;
1096
1097         if (unlikely((rq->flags & REQ_QUEUED))) {
1098                 printk(KERN_ERR 
1099                        "%s: request %p for device [%s] already tagged %d",
1100                        __FUNCTION__, rq,
1101                        rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
1102                 BUG();
1103         }
1104
1105         tag = find_first_zero_bit(bqt->tag_map, bqt->max_depth);
1106         if (tag >= bqt->max_depth)
1107                 return 1;
1108
1109         __set_bit(tag, bqt->tag_map);
1110
1111         rq->flags |= REQ_QUEUED;
1112         rq->tag = tag;
1113         bqt->tag_index[tag] = rq;
1114         blkdev_dequeue_request(rq);
1115         list_add(&rq->queuelist, &bqt->busy_list);
1116         bqt->busy++;
1117         return 0;
1118 }
1119
1120 EXPORT_SYMBOL(blk_queue_start_tag);
1121
1122 /**
1123  * blk_queue_invalidate_tags - invalidate all pending tags
1124  * @q:  the request queue for the device
1125  *
1126  *  Description:
1127  *   Hardware conditions may dictate a need to stop all pending requests.
1128  *   In this case, we will safely clear the block side of the tag queue and
1129  *   readd all requests to the request queue in the right order.
1130  *
1131  *  Notes:
1132  *   queue lock must be held.
1133  **/
1134 void blk_queue_invalidate_tags(request_queue_t *q)
1135 {
1136         struct blk_queue_tag *bqt = q->queue_tags;
1137         struct list_head *tmp, *n;
1138         struct request *rq;
1139
1140         list_for_each_safe(tmp, n, &bqt->busy_list) {
1141                 rq = list_entry_rq(tmp);
1142
1143                 if (rq->tag == -1) {
1144                         printk(KERN_ERR
1145                                "%s: bad tag found on list\n", __FUNCTION__);
1146                         list_del_init(&rq->queuelist);
1147                         rq->flags &= ~REQ_QUEUED;
1148                 } else
1149                         blk_queue_end_tag(q, rq);
1150
1151                 rq->flags &= ~REQ_STARTED;
1152                 __elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 0);
1153         }
1154 }
1155
1156 EXPORT_SYMBOL(blk_queue_invalidate_tags);
1157
1158 static const char * const rq_flags[] = {
1159         "REQ_RW",
1160         "REQ_FAILFAST",
1161         "REQ_SORTED",
1162         "REQ_SOFTBARRIER",
1163         "REQ_HARDBARRIER",
1164         "REQ_FUA",
1165         "REQ_CMD",
1166         "REQ_NOMERGE",
1167         "REQ_STARTED",
1168         "REQ_DONTPREP",
1169         "REQ_QUEUED",
1170         "REQ_ELVPRIV",
1171         "REQ_PC",
1172         "REQ_BLOCK_PC",
1173         "REQ_SENSE",
1174         "REQ_FAILED",
1175         "REQ_QUIET",
1176         "REQ_SPECIAL",
1177         "REQ_DRIVE_CMD",
1178         "REQ_DRIVE_TASK",
1179         "REQ_DRIVE_TASKFILE",
1180         "REQ_PREEMPT",
1181         "REQ_PM_SUSPEND",
1182         "REQ_PM_RESUME",
1183         "REQ_PM_SHUTDOWN",
1184         "REQ_ORDERED_COLOR",
1185 };
1186
1187 void blk_dump_rq_flags(struct request *rq, char *msg)
1188 {
1189         int bit;
1190
1191         printk("%s: dev %s: flags = ", msg,
1192                 rq->rq_disk ? rq->rq_disk->disk_name : "?");
1193         bit = 0;
1194         do {
1195                 if (rq->flags & (1 << bit))
1196                         printk("%s ", rq_flags[bit]);
1197                 bit++;
1198         } while (bit < __REQ_NR_BITS);
1199
1200         printk("\nsector %llu, nr/cnr %lu/%u\n", (unsigned long long)rq->sector,
1201                                                        rq->nr_sectors,
1202                                                        rq->current_nr_sectors);
1203         printk("bio %p, biotail %p, buffer %p, data %p, len %u\n", rq->bio, rq->biotail, rq->buffer, rq->data, rq->data_len);
1204
1205         if (rq->flags & (REQ_BLOCK_PC | REQ_PC)) {
1206                 printk("cdb: ");
1207                 for (bit = 0; bit < sizeof(rq->cmd); bit++)
1208                         printk("%02x ", rq->cmd[bit]);
1209                 printk("\n");
1210         }
1211 }
1212
1213 EXPORT_SYMBOL(blk_dump_rq_flags);
1214
1215 void blk_recount_segments(request_queue_t *q, struct bio *bio)
1216 {
1217         struct bio_vec *bv, *bvprv = NULL;
1218         int i, nr_phys_segs, nr_hw_segs, seg_size, hw_seg_size, cluster;
1219         int high, highprv = 1;
1220
1221         if (unlikely(!bio->bi_io_vec))
1222                 return;
1223
1224         cluster = q->queue_flags & (1 << QUEUE_FLAG_CLUSTER);
1225         hw_seg_size = seg_size = nr_phys_segs = nr_hw_segs = 0;
1226         bio_for_each_segment(bv, bio, i) {
1227                 /*
1228                  * the trick here is making sure that a high page is never
1229                  * considered part of another segment, since that might
1230                  * change with the bounce page.
1231                  */
1232                 high = page_to_pfn(bv->bv_page) >= q->bounce_pfn;
1233                 if (high || highprv)
1234                         goto new_hw_segment;
1235                 if (cluster) {
1236                         if (seg_size + bv->bv_len > q->max_segment_size)
1237                                 goto new_segment;
1238                         if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
1239                                 goto new_segment;
1240                         if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
1241                                 goto new_segment;
1242                         if (BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len))
1243                                 goto new_hw_segment;
1244
1245                         seg_size += bv->bv_len;
1246                         hw_seg_size += bv->bv_len;
1247                         bvprv = bv;
1248                         continue;
1249                 }
1250 new_segment:
1251                 if (BIOVEC_VIRT_MERGEABLE(bvprv, bv) &&
1252                     !BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len)) {
1253                         hw_seg_size += bv->bv_len;
1254                 } else {
1255 new_hw_segment:
1256                         if (hw_seg_size > bio->bi_hw_front_size)
1257                                 bio->bi_hw_front_size = hw_seg_size;
1258                         hw_seg_size = BIOVEC_VIRT_START_SIZE(bv) + bv->bv_len;
1259                         nr_hw_segs++;
1260                 }
1261
1262                 nr_phys_segs++;
1263                 bvprv = bv;
1264                 seg_size = bv->bv_len;
1265                 highprv = high;
1266         }
1267         if (hw_seg_size > bio->bi_hw_back_size)
1268                 bio->bi_hw_back_size = hw_seg_size;
1269         if (nr_hw_segs == 1 && hw_seg_size > bio->bi_hw_front_size)
1270                 bio->bi_hw_front_size = hw_seg_size;
1271         bio->bi_phys_segments = nr_phys_segs;
1272         bio->bi_hw_segments = nr_hw_segs;
1273         bio->bi_flags |= (1 << BIO_SEG_VALID);
1274 }
1275
1276
1277 static int blk_phys_contig_segment(request_queue_t *q, struct bio *bio,
1278                                    struct bio *nxt)
1279 {
1280         if (!(q->queue_flags & (1 << QUEUE_FLAG_CLUSTER)))
1281                 return 0;
1282
1283         if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
1284                 return 0;
1285         if (bio->bi_size + nxt->bi_size > q->max_segment_size)
1286                 return 0;
1287
1288         /*
1289          * bio and nxt are contigous in memory, check if the queue allows
1290          * these two to be merged into one
1291          */
1292         if (BIO_SEG_BOUNDARY(q, bio, nxt))
1293                 return 1;
1294
1295         return 0;
1296 }
1297
1298 static int blk_hw_contig_segment(request_queue_t *q, struct bio *bio,
1299                                  struct bio *nxt)
1300 {
1301         if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
1302                 blk_recount_segments(q, bio);
1303         if (unlikely(!bio_flagged(nxt, BIO_SEG_VALID)))
1304                 blk_recount_segments(q, nxt);
1305         if (!BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)) ||
1306             BIOVEC_VIRT_OVERSIZE(bio->bi_hw_front_size + bio->bi_hw_back_size))
1307                 return 0;
1308         if (bio->bi_size + nxt->bi_size > q->max_segment_size)
1309                 return 0;
1310
1311         return 1;
1312 }
1313
1314 /*
1315  * map a request to scatterlist, return number of sg entries setup. Caller
1316  * must make sure sg can hold rq->nr_phys_segments entries
1317  */
1318 int blk_rq_map_sg(request_queue_t *q, struct request *rq, struct scatterlist *sg)
1319 {
1320         struct bio_vec *bvec, *bvprv;
1321         struct bio *bio;
1322         int nsegs, i, cluster;
1323
1324         nsegs = 0;
1325         cluster = q->queue_flags & (1 << QUEUE_FLAG_CLUSTER);
1326
1327         /*
1328          * for each bio in rq
1329          */
1330         bvprv = NULL;
1331         rq_for_each_bio(bio, rq) {
1332                 /*
1333                  * for each segment in bio
1334                  */
1335                 bio_for_each_segment(bvec, bio, i) {
1336                         int nbytes = bvec->bv_len;
1337
1338                         if (bvprv && cluster) {
1339                                 if (sg[nsegs - 1].length + nbytes > q->max_segment_size)
1340                                         goto new_segment;
1341
1342                                 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
1343                                         goto new_segment;
1344                                 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
1345                                         goto new_segment;
1346
1347                                 sg[nsegs - 1].length += nbytes;
1348                         } else {
1349 new_segment:
1350                                 memset(&sg[nsegs],0,sizeof(struct scatterlist));
1351                                 sg[nsegs].page = bvec->bv_page;
1352                                 sg[nsegs].length = nbytes;
1353                                 sg[nsegs].offset = bvec->bv_offset;
1354
1355                                 nsegs++;
1356                         }
1357                         bvprv = bvec;
1358                 } /* segments in bio */
1359         } /* bios in rq */
1360
1361         return nsegs;
1362 }
1363
1364 EXPORT_SYMBOL(blk_rq_map_sg);
1365
1366 /*
1367  * the standard queue merge functions, can be overridden with device
1368  * specific ones if so desired
1369  */
1370
1371 static inline int ll_new_mergeable(request_queue_t *q,
1372                                    struct request *req,
1373                                    struct bio *bio)
1374 {
1375         int nr_phys_segs = bio_phys_segments(q, bio);
1376
1377         if (req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
1378                 req->flags |= REQ_NOMERGE;
1379                 if (req == q->last_merge)
1380                         q->last_merge = NULL;
1381                 return 0;
1382         }
1383
1384         /*
1385          * A hw segment is just getting larger, bump just the phys
1386          * counter.
1387          */
1388         req->nr_phys_segments += nr_phys_segs;
1389         return 1;
1390 }
1391
1392 static inline int ll_new_hw_segment(request_queue_t *q,
1393                                     struct request *req,
1394                                     struct bio *bio)
1395 {
1396         int nr_hw_segs = bio_hw_segments(q, bio);
1397         int nr_phys_segs = bio_phys_segments(q, bio);
1398
1399         if (req->nr_hw_segments + nr_hw_segs > q->max_hw_segments
1400             || req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
1401                 req->flags |= REQ_NOMERGE;
1402                 if (req == q->last_merge)
1403                         q->last_merge = NULL;
1404                 return 0;
1405         }
1406
1407         /*
1408          * This will form the start of a new hw segment.  Bump both
1409          * counters.
1410          */
1411         req->nr_hw_segments += nr_hw_segs;
1412         req->nr_phys_segments += nr_phys_segs;
1413         return 1;
1414 }
1415
1416 static int ll_back_merge_fn(request_queue_t *q, struct request *req, 
1417                             struct bio *bio)
1418 {
1419         unsigned short max_sectors;
1420         int len;
1421
1422         if (unlikely(blk_pc_request(req)))
1423                 max_sectors = q->max_hw_sectors;
1424         else
1425                 max_sectors = q->max_sectors;
1426
1427         if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
1428                 req->flags |= REQ_NOMERGE;
1429                 if (req == q->last_merge)
1430                         q->last_merge = NULL;
1431                 return 0;
1432         }
1433         if (unlikely(!bio_flagged(req->biotail, BIO_SEG_VALID)))
1434                 blk_recount_segments(q, req->biotail);
1435         if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
1436                 blk_recount_segments(q, bio);
1437         len = req->biotail->bi_hw_back_size + bio->bi_hw_front_size;
1438         if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(req->biotail), __BVEC_START(bio)) &&
1439             !BIOVEC_VIRT_OVERSIZE(len)) {
1440                 int mergeable =  ll_new_mergeable(q, req, bio);
1441
1442                 if (mergeable) {
1443                         if (req->nr_hw_segments == 1)
1444                                 req->bio->bi_hw_front_size = len;
1445                         if (bio->bi_hw_segments == 1)
1446                                 bio->bi_hw_back_size = len;
1447                 }
1448                 return mergeable;
1449         }
1450
1451         return ll_new_hw_segment(q, req, bio);
1452 }
1453
1454 static int ll_front_merge_fn(request_queue_t *q, struct request *req, 
1455                              struct bio *bio)
1456 {
1457         unsigned short max_sectors;
1458         int len;
1459
1460         if (unlikely(blk_pc_request(req)))
1461                 max_sectors = q->max_hw_sectors;
1462         else
1463                 max_sectors = q->max_sectors;
1464
1465
1466         if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
1467                 req->flags |= REQ_NOMERGE;
1468                 if (req == q->last_merge)
1469                         q->last_merge = NULL;
1470                 return 0;
1471         }
1472         len = bio->bi_hw_back_size + req->bio->bi_hw_front_size;
1473         if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
1474                 blk_recount_segments(q, bio);
1475         if (unlikely(!bio_flagged(req->bio, BIO_SEG_VALID)))
1476                 blk_recount_segments(q, req->bio);
1477         if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(req->bio)) &&
1478             !BIOVEC_VIRT_OVERSIZE(len)) {
1479                 int mergeable =  ll_new_mergeable(q, req, bio);
1480
1481                 if (mergeable) {
1482                         if (bio->bi_hw_segments == 1)
1483                                 bio->bi_hw_front_size = len;
1484                         if (req->nr_hw_segments == 1)
1485                                 req->biotail->bi_hw_back_size = len;
1486                 }
1487                 return mergeable;
1488         }
1489
1490         return ll_new_hw_segment(q, req, bio);
1491 }
1492
1493 static int ll_merge_requests_fn(request_queue_t *q, struct request *req,
1494                                 struct request *next)
1495 {
1496         int total_phys_segments;
1497         int total_hw_segments;
1498
1499         /*
1500          * First check if the either of the requests are re-queued
1501          * requests.  Can't merge them if they are.
1502          */
1503         if (req->special || next->special)
1504                 return 0;
1505
1506         /*
1507          * Will it become too large?
1508          */
1509         if ((req->nr_sectors + next->nr_sectors) > q->max_sectors)
1510                 return 0;
1511
1512         total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
1513         if (blk_phys_contig_segment(q, req->biotail, next->bio))
1514                 total_phys_segments--;
1515
1516         if (total_phys_segments > q->max_phys_segments)
1517                 return 0;
1518
1519         total_hw_segments = req->nr_hw_segments + next->nr_hw_segments;
1520         if (blk_hw_contig_segment(q, req->biotail, next->bio)) {
1521                 int len = req->biotail->bi_hw_back_size + next->bio->bi_hw_front_size;
1522                 /*
1523                  * propagate the combined length to the end of the requests
1524                  */
1525                 if (req->nr_hw_segments == 1)
1526                         req->bio->bi_hw_front_size = len;
1527                 if (next->nr_hw_segments == 1)
1528                         next->biotail->bi_hw_back_size = len;
1529                 total_hw_segments--;
1530         }
1531
1532         if (total_hw_segments > q->max_hw_segments)
1533                 return 0;
1534
1535         /* Merge is OK... */
1536         req->nr_phys_segments = total_phys_segments;
1537         req->nr_hw_segments = total_hw_segments;
1538         return 1;
1539 }
1540
1541 /*
1542  * "plug" the device if there are no outstanding requests: this will
1543  * force the transfer to start only after we have put all the requests
1544  * on the list.
1545  *
1546  * This is called with interrupts off and no requests on the queue and
1547  * with the queue lock held.
1548  */
1549 void blk_plug_device(request_queue_t *q)
1550 {
1551         WARN_ON(!irqs_disabled());
1552
1553         /*
1554          * don't plug a stopped queue, it must be paired with blk_start_queue()
1555          * which will restart the queueing
1556          */
1557         if (blk_queue_stopped(q))
1558                 return;
1559
1560         if (!test_and_set_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags)) {
1561                 mod_timer(&q->unplug_timer, jiffies + q->unplug_delay);
1562                 blk_add_trace_generic(q, NULL, 0, BLK_TA_PLUG);
1563         }
1564 }
1565
1566 EXPORT_SYMBOL(blk_plug_device);
1567
1568 /*
1569  * remove the queue from the plugged list, if present. called with
1570  * queue lock held and interrupts disabled.
1571  */
1572 int blk_remove_plug(request_queue_t *q)
1573 {
1574         WARN_ON(!irqs_disabled());
1575
1576         if (!test_and_clear_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags))
1577                 return 0;
1578
1579         del_timer(&q->unplug_timer);
1580         return 1;
1581 }
1582
1583 EXPORT_SYMBOL(blk_remove_plug);
1584
1585 /*
1586  * remove the plug and let it rip..
1587  */
1588 void __generic_unplug_device(request_queue_t *q)
1589 {
1590         if (unlikely(blk_queue_stopped(q)))
1591                 return;
1592
1593         if (!blk_remove_plug(q))
1594                 return;
1595
1596         q->request_fn(q);
1597 }
1598 EXPORT_SYMBOL(__generic_unplug_device);
1599
1600 /**
1601  * generic_unplug_device - fire a request queue
1602  * @q:    The &request_queue_t in question
1603  *
1604  * Description:
1605  *   Linux uses plugging to build bigger requests queues before letting
1606  *   the device have at them. If a queue is plugged, the I/O scheduler
1607  *   is still adding and merging requests on the queue. Once the queue
1608  *   gets unplugged, the request_fn defined for the queue is invoked and
1609  *   transfers started.
1610  **/
1611 void generic_unplug_device(request_queue_t *q)
1612 {
1613         spin_lock_irq(q->queue_lock);
1614         __generic_unplug_device(q);
1615         spin_unlock_irq(q->queue_lock);
1616 }
1617 EXPORT_SYMBOL(generic_unplug_device);
1618
1619 static void blk_backing_dev_unplug(struct backing_dev_info *bdi,
1620                                    struct page *page)
1621 {
1622         request_queue_t *q = bdi->unplug_io_data;
1623
1624         /*
1625          * devices don't necessarily have an ->unplug_fn defined
1626          */
1627         if (q->unplug_fn) {
1628                 blk_add_trace_pdu_int(q, BLK_TA_UNPLUG_IO, NULL,
1629                                         q->rq.count[READ] + q->rq.count[WRITE]);
1630
1631                 q->unplug_fn(q);
1632         }
1633 }
1634
1635 static void blk_unplug_work(void *data)
1636 {
1637         request_queue_t *q = data;
1638
1639         blk_add_trace_pdu_int(q, BLK_TA_UNPLUG_IO, NULL,
1640                                 q->rq.count[READ] + q->rq.count[WRITE]);
1641
1642         q->unplug_fn(q);
1643 }
1644
1645 static void blk_unplug_timeout(unsigned long data)
1646 {
1647         request_queue_t *q = (request_queue_t *)data;
1648
1649         blk_add_trace_pdu_int(q, BLK_TA_UNPLUG_TIMER, NULL,
1650                                 q->rq.count[READ] + q->rq.count[WRITE]);
1651
1652         kblockd_schedule_work(&q->unplug_work);
1653 }
1654
1655 /**
1656  * blk_start_queue - restart a previously stopped queue
1657  * @q:    The &request_queue_t in question
1658  *
1659  * Description:
1660  *   blk_start_queue() will clear the stop flag on the queue, and call
1661  *   the request_fn for the queue if it was in a stopped state when
1662  *   entered. Also see blk_stop_queue(). Queue lock must be held.
1663  **/
1664 void blk_start_queue(request_queue_t *q)
1665 {
1666         WARN_ON(!irqs_disabled());
1667
1668         clear_bit(QUEUE_FLAG_STOPPED, &q->queue_flags);
1669
1670         /*
1671          * one level of recursion is ok and is much faster than kicking
1672          * the unplug handling
1673          */
1674         if (!test_and_set_bit(QUEUE_FLAG_REENTER, &q->queue_flags)) {
1675                 q->request_fn(q);
1676                 clear_bit(QUEUE_FLAG_REENTER, &q->queue_flags);
1677         } else {
1678                 blk_plug_device(q);
1679                 kblockd_schedule_work(&q->unplug_work);
1680         }
1681 }
1682
1683 EXPORT_SYMBOL(blk_start_queue);
1684
1685 /**
1686  * blk_stop_queue - stop a queue
1687  * @q:    The &request_queue_t in question
1688  *
1689  * Description:
1690  *   The Linux block layer assumes that a block driver will consume all
1691  *   entries on the request queue when the request_fn strategy is called.
1692  *   Often this will not happen, because of hardware limitations (queue
1693  *   depth settings). If a device driver gets a 'queue full' response,
1694  *   or if it simply chooses not to queue more I/O at one point, it can
1695  *   call this function to prevent the request_fn from being called until
1696  *   the driver has signalled it's ready to go again. This happens by calling
1697  *   blk_start_queue() to restart queue operations. Queue lock must be held.
1698  **/
1699 void blk_stop_queue(request_queue_t *q)
1700 {
1701         blk_remove_plug(q);
1702         set_bit(QUEUE_FLAG_STOPPED, &q->queue_flags);
1703 }
1704 EXPORT_SYMBOL(blk_stop_queue);
1705
1706 /**
1707  * blk_sync_queue - cancel any pending callbacks on a queue
1708  * @q: the queue
1709  *
1710  * Description:
1711  *     The block layer may perform asynchronous callback activity
1712  *     on a queue, such as calling the unplug function after a timeout.
1713  *     A block device may call blk_sync_queue to ensure that any
1714  *     such activity is cancelled, thus allowing it to release resources
1715  *     the the callbacks might use. The caller must already have made sure
1716  *     that its ->make_request_fn will not re-add plugging prior to calling
1717  *     this function.
1718  *
1719  */
1720 void blk_sync_queue(struct request_queue *q)
1721 {
1722         del_timer_sync(&q->unplug_timer);
1723         kblockd_flush();
1724 }
1725 EXPORT_SYMBOL(blk_sync_queue);
1726
1727 /**
1728  * blk_run_queue - run a single device queue
1729  * @q:  The queue to run
1730  */
1731 void blk_run_queue(struct request_queue *q)
1732 {
1733         unsigned long flags;
1734
1735         spin_lock_irqsave(q->queue_lock, flags);
1736         blk_remove_plug(q);
1737
1738         /*
1739          * Only recurse once to avoid overrunning the stack, let the unplug
1740          * handling reinvoke the handler shortly if we already got there.
1741          */
1742         if (!elv_queue_empty(q)) {
1743                 if (!test_and_set_bit(QUEUE_FLAG_REENTER, &q->queue_flags)) {
1744                         q->request_fn(q);
1745                         clear_bit(QUEUE_FLAG_REENTER, &q->queue_flags);
1746                 } else {
1747                         blk_plug_device(q);
1748                         kblockd_schedule_work(&q->unplug_work);
1749                 }
1750         }
1751
1752         spin_unlock_irqrestore(q->queue_lock, flags);
1753 }
1754 EXPORT_SYMBOL(blk_run_queue);
1755
1756 /**
1757  * blk_cleanup_queue: - release a &request_queue_t when it is no longer needed
1758  * @kobj:    the kobj belonging of the request queue to be released
1759  *
1760  * Description:
1761  *     blk_cleanup_queue is the pair to blk_init_queue() or
1762  *     blk_queue_make_request().  It should be called when a request queue is
1763  *     being released; typically when a block device is being de-registered.
1764  *     Currently, its primary task it to free all the &struct request
1765  *     structures that were allocated to the queue and the queue itself.
1766  *
1767  * Caveat:
1768  *     Hopefully the low level driver will have finished any
1769  *     outstanding requests first...
1770  **/
1771 static void blk_release_queue(struct kobject *kobj)
1772 {
1773         request_queue_t *q = container_of(kobj, struct request_queue, kobj);
1774         struct request_list *rl = &q->rq;
1775
1776         blk_sync_queue(q);
1777
1778         if (rl->rq_pool)
1779                 mempool_destroy(rl->rq_pool);
1780
1781         if (q->queue_tags)
1782                 __blk_queue_free_tags(q);
1783
1784         if (q->blk_trace)
1785                 blk_trace_shutdown(q);
1786
1787         kmem_cache_free(requestq_cachep, q);
1788 }
1789
1790 void blk_put_queue(request_queue_t *q)
1791 {
1792         kobject_put(&q->kobj);
1793 }
1794 EXPORT_SYMBOL(blk_put_queue);
1795
1796 void blk_cleanup_queue(request_queue_t * q)
1797 {
1798         mutex_lock(&q->sysfs_lock);
1799         set_bit(QUEUE_FLAG_DEAD, &q->queue_flags);
1800         mutex_unlock(&q->sysfs_lock);
1801
1802         if (q->elevator)
1803                 elevator_exit(q->elevator);
1804
1805         blk_put_queue(q);
1806 }
1807
1808 EXPORT_SYMBOL(blk_cleanup_queue);
1809
1810 static int blk_init_free_list(request_queue_t *q)
1811 {
1812         struct request_list *rl = &q->rq;
1813
1814         rl->count[READ] = rl->count[WRITE] = 0;
1815         rl->starved[READ] = rl->starved[WRITE] = 0;
1816         rl->elvpriv = 0;
1817         init_waitqueue_head(&rl->wait[READ]);
1818         init_waitqueue_head(&rl->wait[WRITE]);
1819
1820         rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
1821                                 mempool_free_slab, request_cachep, q->node);
1822
1823         if (!rl->rq_pool)
1824                 return -ENOMEM;
1825
1826         return 0;
1827 }
1828
1829 request_queue_t *blk_alloc_queue(gfp_t gfp_mask)
1830 {
1831         return blk_alloc_queue_node(gfp_mask, -1);
1832 }
1833 EXPORT_SYMBOL(blk_alloc_queue);
1834
1835 static struct kobj_type queue_ktype;
1836
1837 request_queue_t *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
1838 {
1839         request_queue_t *q;
1840
1841         q = kmem_cache_alloc_node(requestq_cachep, gfp_mask, node_id);
1842         if (!q)
1843                 return NULL;
1844
1845         memset(q, 0, sizeof(*q));
1846         init_timer(&q->unplug_timer);
1847
1848         snprintf(q->kobj.name, KOBJ_NAME_LEN, "%s", "queue");
1849         q->kobj.ktype = &queue_ktype;
1850         kobject_init(&q->kobj);
1851
1852         q->backing_dev_info.unplug_io_fn = blk_backing_dev_unplug;
1853         q->backing_dev_info.unplug_io_data = q;
1854
1855         mutex_init(&q->sysfs_lock);
1856
1857         return q;
1858 }
1859 EXPORT_SYMBOL(blk_alloc_queue_node);
1860
1861 /**
1862  * blk_init_queue  - prepare a request queue for use with a block device
1863  * @rfn:  The function to be called to process requests that have been
1864  *        placed on the queue.
1865  * @lock: Request queue spin lock
1866  *
1867  * Description:
1868  *    If a block device wishes to use the standard request handling procedures,
1869  *    which sorts requests and coalesces adjacent requests, then it must
1870  *    call blk_init_queue().  The function @rfn will be called when there
1871  *    are requests on the queue that need to be processed.  If the device
1872  *    supports plugging, then @rfn may not be called immediately when requests
1873  *    are available on the queue, but may be called at some time later instead.
1874  *    Plugged queues are generally unplugged when a buffer belonging to one
1875  *    of the requests on the queue is needed, or due to memory pressure.
1876  *
1877  *    @rfn is not required, or even expected, to remove all requests off the
1878  *    queue, but only as many as it can handle at a time.  If it does leave
1879  *    requests on the queue, it is responsible for arranging that the requests
1880  *    get dealt with eventually.
1881  *
1882  *    The queue spin lock must be held while manipulating the requests on the
1883  *    request queue; this lock will be taken also from interrupt context, so irq
1884  *    disabling is needed for it.
1885  *
1886  *    Function returns a pointer to the initialized request queue, or NULL if
1887  *    it didn't succeed.
1888  *
1889  * Note:
1890  *    blk_init_queue() must be paired with a blk_cleanup_queue() call
1891  *    when the block device is deactivated (such as at module unload).
1892  **/
1893
1894 request_queue_t *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
1895 {
1896         return blk_init_queue_node(rfn, lock, -1);
1897 }
1898 EXPORT_SYMBOL(blk_init_queue);
1899
1900 request_queue_t *
1901 blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
1902 {
1903         request_queue_t *q = blk_alloc_queue_node(GFP_KERNEL, node_id);
1904
1905         if (!q)
1906                 return NULL;
1907
1908         q->node = node_id;
1909         if (blk_init_free_list(q)) {
1910                 kmem_cache_free(requestq_cachep, q);
1911                 return NULL;
1912         }
1913
1914         /*
1915          * if caller didn't supply a lock, they get per-queue locking with
1916          * our embedded lock
1917          */
1918         if (!lock) {
1919                 spin_lock_init(&q->__queue_lock);
1920                 lock = &q->__queue_lock;
1921         }
1922
1923         q->request_fn           = rfn;
1924         q->back_merge_fn        = ll_back_merge_fn;
1925         q->front_merge_fn       = ll_front_merge_fn;
1926         q->merge_requests_fn    = ll_merge_requests_fn;
1927         q->prep_rq_fn           = NULL;
1928         q->unplug_fn            = generic_unplug_device;
1929         q->queue_flags          = (1 << QUEUE_FLAG_CLUSTER);
1930         q->queue_lock           = lock;
1931
1932         blk_queue_segment_boundary(q, 0xffffffff);
1933
1934         blk_queue_make_request(q, __make_request);
1935         blk_queue_max_segment_size(q, MAX_SEGMENT_SIZE);
1936
1937         blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
1938         blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
1939
1940         /*
1941          * all done
1942          */
1943         if (!elevator_init(q, NULL)) {
1944                 blk_queue_congestion_threshold(q);
1945                 return q;
1946         }
1947
1948         blk_put_queue(q);
1949         return NULL;
1950 }
1951 EXPORT_SYMBOL(blk_init_queue_node);
1952
1953 int blk_get_queue(request_queue_t *q)
1954 {
1955         if (likely(!test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) {
1956                 kobject_get(&q->kobj);
1957                 return 0;
1958         }
1959
1960         return 1;
1961 }
1962
1963 EXPORT_SYMBOL(blk_get_queue);
1964
1965 static inline void blk_free_request(request_queue_t *q, struct request *rq)
1966 {
1967         if (rq->flags & REQ_ELVPRIV)
1968                 elv_put_request(q, rq);
1969         mempool_free(rq, q->rq.rq_pool);
1970 }
1971
1972 static inline struct request *
1973 blk_alloc_request(request_queue_t *q, int rw, struct bio *bio,
1974                   int priv, gfp_t gfp_mask)
1975 {
1976         struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
1977
1978         if (!rq)
1979                 return NULL;
1980
1981         /*
1982          * first three bits are identical in rq->flags and bio->bi_rw,
1983          * see bio.h and blkdev.h
1984          */
1985         rq->flags = rw;
1986
1987         if (priv) {
1988                 if (unlikely(elv_set_request(q, rq, bio, gfp_mask))) {
1989                         mempool_free(rq, q->rq.rq_pool);
1990                         return NULL;
1991                 }
1992                 rq->flags |= REQ_ELVPRIV;
1993         }
1994
1995         return rq;
1996 }
1997
1998 /*
1999  * ioc_batching returns true if the ioc is a valid batching request and
2000  * should be given priority access to a request.
2001  */
2002 static inline int ioc_batching(request_queue_t *q, struct io_context *ioc)
2003 {
2004         if (!ioc)
2005                 return 0;
2006
2007         /*
2008          * Make sure the process is able to allocate at least 1 request
2009          * even if the batch times out, otherwise we could theoretically
2010          * lose wakeups.
2011          */
2012         return ioc->nr_batch_requests == q->nr_batching ||
2013                 (ioc->nr_batch_requests > 0
2014                 && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
2015 }
2016
2017 /*
2018  * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
2019  * will cause the process to be a "batcher" on all queues in the system. This
2020  * is the behaviour we want though - once it gets a wakeup it should be given
2021  * a nice run.
2022  */
2023 static void ioc_set_batching(request_queue_t *q, struct io_context *ioc)
2024 {
2025         if (!ioc || ioc_batching(q, ioc))
2026                 return;
2027
2028         ioc->nr_batch_requests = q->nr_batching;
2029         ioc->last_waited = jiffies;
2030 }
2031
2032 static void __freed_request(request_queue_t *q, int rw)
2033 {
2034         struct request_list *rl = &q->rq;
2035
2036         if (rl->count[rw] < queue_congestion_off_threshold(q))
2037                 clear_queue_congested(q, rw);
2038
2039         if (rl->count[rw] + 1 <= q->nr_requests) {
2040                 if (waitqueue_active(&rl->wait[rw]))
2041                         wake_up(&rl->wait[rw]);
2042
2043                 blk_clear_queue_full(q, rw);
2044         }
2045 }
2046
2047 /*
2048  * A request has just been released.  Account for it, update the full and
2049  * congestion status, wake up any waiters.   Called under q->queue_lock.
2050  */
2051 static void freed_request(request_queue_t *q, int rw, int priv)
2052 {
2053         struct request_list *rl = &q->rq;
2054
2055         rl->count[rw]--;
2056         if (priv)
2057                 rl->elvpriv--;
2058
2059         __freed_request(q, rw);
2060
2061         if (unlikely(rl->starved[rw ^ 1]))
2062                 __freed_request(q, rw ^ 1);
2063 }
2064
2065 #define blkdev_free_rq(list) list_entry((list)->next, struct request, queuelist)
2066 /*
2067  * Get a free request, queue_lock must be held.
2068  * Returns NULL on failure, with queue_lock held.
2069  * Returns !NULL on success, with queue_lock *not held*.
2070  */
2071 static struct request *get_request(request_queue_t *q, int rw, struct bio *bio,
2072                                    gfp_t gfp_mask)
2073 {
2074         struct request *rq = NULL;
2075         struct request_list *rl = &q->rq;
2076         struct io_context *ioc = NULL;
2077         int may_queue, priv;
2078
2079         may_queue = elv_may_queue(q, rw, bio);
2080         if (may_queue == ELV_MQUEUE_NO)
2081                 goto rq_starved;
2082
2083         if (rl->count[rw]+1 >= queue_congestion_on_threshold(q)) {
2084                 if (rl->count[rw]+1 >= q->nr_requests) {
2085                         ioc = current_io_context(GFP_ATOMIC);
2086                         /*
2087                          * The queue will fill after this allocation, so set
2088                          * it as full, and mark this process as "batching".
2089                          * This process will be allowed to complete a batch of
2090                          * requests, others will be blocked.
2091                          */
2092                         if (!blk_queue_full(q, rw)) {
2093                                 ioc_set_batching(q, ioc);
2094                                 blk_set_queue_full(q, rw);
2095                         } else {
2096                                 if (may_queue != ELV_MQUEUE_MUST
2097                                                 && !ioc_batching(q, ioc)) {
2098                                         /*
2099                                          * The queue is full and the allocating
2100                                          * process is not a "batcher", and not
2101                                          * exempted by the IO scheduler
2102                                          */
2103                                         goto out;
2104                                 }
2105                         }
2106                 }
2107                 set_queue_congested(q, rw);
2108         }
2109
2110         /*
2111          * Only allow batching queuers to allocate up to 50% over the defined
2112          * limit of requests, otherwise we could have thousands of requests
2113          * allocated with any setting of ->nr_requests
2114          */
2115         if (rl->count[rw] >= (3 * q->nr_requests / 2))
2116                 goto out;
2117
2118         rl->count[rw]++;
2119         rl->starved[rw] = 0;
2120
2121         priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
2122         if (priv)
2123                 rl->elvpriv++;
2124
2125         spin_unlock_irq(q->queue_lock);
2126
2127         rq = blk_alloc_request(q, rw, bio, priv, gfp_mask);
2128         if (unlikely(!rq)) {
2129                 /*
2130                  * Allocation failed presumably due to memory. Undo anything
2131                  * we might have messed up.
2132                  *
2133                  * Allocating task should really be put onto the front of the
2134                  * wait queue, but this is pretty rare.
2135                  */
2136                 spin_lock_irq(q->queue_lock);
2137                 freed_request(q, rw, priv);
2138
2139                 /*
2140                  * in the very unlikely event that allocation failed and no
2141                  * requests for this direction was pending, mark us starved
2142                  * so that freeing of a request in the other direction will
2143                  * notice us. another possible fix would be to split the
2144                  * rq mempool into READ and WRITE
2145                  */
2146 rq_starved:
2147                 if (unlikely(rl->count[rw] == 0))
2148                         rl->starved[rw] = 1;
2149
2150                 goto out;
2151         }
2152
2153         /*
2154          * ioc may be NULL here, and ioc_batching will be false. That's
2155          * OK, if the queue is under the request limit then requests need
2156          * not count toward the nr_batch_requests limit. There will always
2157          * be some limit enforced by BLK_BATCH_TIME.
2158          */
2159         if (ioc_batching(q, ioc))
2160                 ioc->nr_batch_requests--;
2161         
2162         rq_init(q, rq);
2163         rq->rl = rl;
2164
2165         blk_add_trace_generic(q, bio, rw, BLK_TA_GETRQ);
2166 out:
2167         return rq;
2168 }
2169
2170 /*
2171  * No available requests for this queue, unplug the device and wait for some
2172  * requests to become available.
2173  *
2174  * Called with q->queue_lock held, and returns with it unlocked.
2175  */
2176 static struct request *get_request_wait(request_queue_t *q, int rw,
2177                                         struct bio *bio)
2178 {
2179         struct request *rq;
2180
2181         rq = get_request(q, rw, bio, GFP_NOIO);
2182         while (!rq) {
2183                 DEFINE_WAIT(wait);
2184                 struct request_list *rl = &q->rq;
2185
2186                 prepare_to_wait_exclusive(&rl->wait[rw], &wait,
2187                                 TASK_UNINTERRUPTIBLE);
2188
2189                 rq = get_request(q, rw, bio, GFP_NOIO);
2190
2191                 if (!rq) {
2192                         struct io_context *ioc;
2193
2194                         blk_add_trace_generic(q, bio, rw, BLK_TA_SLEEPRQ);
2195
2196                         __generic_unplug_device(q);
2197                         spin_unlock_irq(q->queue_lock);
2198                         io_schedule();
2199
2200                         /*
2201                          * After sleeping, we become a "batching" process and
2202                          * will be able to allocate at least one request, and
2203                          * up to a big batch of them for a small period time.
2204                          * See ioc_batching, ioc_set_batching
2205                          */
2206                         ioc = current_io_context(GFP_NOIO);
2207                         ioc_set_batching(q, ioc);
2208
2209                         spin_lock_irq(q->queue_lock);
2210                 }
2211                 finish_wait(&rl->wait[rw], &wait);
2212         }
2213
2214         return rq;
2215 }
2216
2217 struct request *blk_get_request(request_queue_t *q, int rw, gfp_t gfp_mask)
2218 {
2219         struct request *rq;
2220
2221         BUG_ON(rw != READ && rw != WRITE);
2222
2223         spin_lock_irq(q->queue_lock);
2224         if (gfp_mask & __GFP_WAIT) {
2225                 rq = get_request_wait(q, rw, NULL);
2226         } else {
2227                 rq = get_request(q, rw, NULL, gfp_mask);
2228                 if (!rq)
2229                         spin_unlock_irq(q->queue_lock);
2230         }
2231         /* q->queue_lock is unlocked at this point */
2232
2233         return rq;
2234 }
2235 EXPORT_SYMBOL(blk_get_request);
2236
2237 /**
2238  * blk_requeue_request - put a request back on queue
2239  * @q:          request queue where request should be inserted
2240  * @rq:         request to be inserted
2241  *
2242  * Description:
2243  *    Drivers often keep queueing requests until the hardware cannot accept
2244  *    more, when that condition happens we need to put the request back
2245  *    on the queue. Must be called with queue lock held.
2246  */
2247 void blk_requeue_request(request_queue_t *q, struct request *rq)
2248 {
2249         blk_add_trace_rq(q, rq, BLK_TA_REQUEUE);
2250
2251         if (blk_rq_tagged(rq))
2252                 blk_queue_end_tag(q, rq);
2253
2254         elv_requeue_request(q, rq);
2255 }
2256
2257 EXPORT_SYMBOL(blk_requeue_request);
2258
2259 /**
2260  * blk_insert_request - insert a special request in to a request queue
2261  * @q:          request queue where request should be inserted
2262  * @rq:         request to be inserted
2263  * @at_head:    insert request at head or tail of queue
2264  * @data:       private data
2265  *
2266  * Description:
2267  *    Many block devices need to execute commands asynchronously, so they don't
2268  *    block the whole kernel from preemption during request execution.  This is
2269  *    accomplished normally by inserting aritficial requests tagged as
2270  *    REQ_SPECIAL in to the corresponding request queue, and letting them be
2271  *    scheduled for actual execution by the request queue.
2272  *
2273  *    We have the option of inserting the head or the tail of the queue.
2274  *    Typically we use the tail for new ioctls and so forth.  We use the head
2275  *    of the queue for things like a QUEUE_FULL message from a device, or a
2276  *    host that is unable to accept a particular command.
2277  */
2278 void blk_insert_request(request_queue_t *q, struct request *rq,
2279                         int at_head, void *data)
2280 {
2281         int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
2282         unsigned long flags;
2283
2284         /*
2285          * tell I/O scheduler that this isn't a regular read/write (ie it
2286          * must not attempt merges on this) and that it acts as a soft
2287          * barrier
2288          */
2289         rq->flags |= REQ_SPECIAL | REQ_SOFTBARRIER;
2290
2291         rq->special = data;
2292
2293         spin_lock_irqsave(q->queue_lock, flags);
2294
2295         /*
2296          * If command is tagged, release the tag
2297          */
2298         if (blk_rq_tagged(rq))
2299                 blk_queue_end_tag(q, rq);
2300
2301         drive_stat_acct(rq, rq->nr_sectors, 1);
2302         __elv_add_request(q, rq, where, 0);
2303
2304         if (blk_queue_plugged(q))
2305                 __generic_unplug_device(q);
2306         else
2307                 q->request_fn(q);
2308         spin_unlock_irqrestore(q->queue_lock, flags);
2309 }
2310
2311 EXPORT_SYMBOL(blk_insert_request);
2312
2313 /**
2314  * blk_rq_map_user - map user data to a request, for REQ_BLOCK_PC usage
2315  * @q:          request queue where request should be inserted
2316  * @rq:         request structure to fill
2317  * @ubuf:       the user buffer
2318  * @len:        length of user data
2319  *
2320  * Description:
2321  *    Data will be mapped directly for zero copy io, if possible. Otherwise
2322  *    a kernel bounce buffer is used.
2323  *
2324  *    A matching blk_rq_unmap_user() must be issued at the end of io, while
2325  *    still in process context.
2326  *
2327  *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
2328  *    before being submitted to the device, as pages mapped may be out of
2329  *    reach. It's the callers responsibility to make sure this happens. The
2330  *    original bio must be passed back in to blk_rq_unmap_user() for proper
2331  *    unmapping.
2332  */
2333 int blk_rq_map_user(request_queue_t *q, struct request *rq, void __user *ubuf,
2334                     unsigned int len)
2335 {
2336         unsigned long uaddr;
2337         struct bio *bio;
2338         int reading;
2339
2340         if (len > (q->max_hw_sectors << 9))
2341                 return -EINVAL;
2342         if (!len || !ubuf)
2343                 return -EINVAL;
2344
2345         reading = rq_data_dir(rq) == READ;
2346
2347         /*
2348          * if alignment requirement is satisfied, map in user pages for
2349          * direct dma. else, set up kernel bounce buffers
2350          */
2351         uaddr = (unsigned long) ubuf;
2352         if (!(uaddr & queue_dma_alignment(q)) && !(len & queue_dma_alignment(q)))
2353                 bio = bio_map_user(q, NULL, uaddr, len, reading);
2354         else
2355                 bio = bio_copy_user(q, uaddr, len, reading);
2356
2357         if (!IS_ERR(bio)) {
2358                 rq->bio = rq->biotail = bio;
2359                 blk_rq_bio_prep(q, rq, bio);
2360
2361                 rq->buffer = rq->data = NULL;
2362                 rq->data_len = len;
2363                 return 0;
2364         }
2365
2366         /*
2367          * bio is the err-ptr
2368          */
2369         return PTR_ERR(bio);
2370 }
2371
2372 EXPORT_SYMBOL(blk_rq_map_user);
2373
2374 /**
2375  * blk_rq_map_user_iov - map user data to a request, for REQ_BLOCK_PC usage
2376  * @q:          request queue where request should be inserted
2377  * @rq:         request to map data to
2378  * @iov:        pointer to the iovec
2379  * @iov_count:  number of elements in the iovec
2380  *
2381  * Description:
2382  *    Data will be mapped directly for zero copy io, if possible. Otherwise
2383  *    a kernel bounce buffer is used.
2384  *
2385  *    A matching blk_rq_unmap_user() must be issued at the end of io, while
2386  *    still in process context.
2387  *
2388  *    Note: The mapped bio may need to be bounced through blk_queue_bounce()
2389  *    before being submitted to the device, as pages mapped may be out of
2390  *    reach. It's the callers responsibility to make sure this happens. The
2391  *    original bio must be passed back in to blk_rq_unmap_user() for proper
2392  *    unmapping.
2393  */
2394 int blk_rq_map_user_iov(request_queue_t *q, struct request *rq,
2395                         struct sg_iovec *iov, int iov_count)
2396 {
2397         struct bio *bio;
2398
2399         if (!iov || iov_count <= 0)
2400                 return -EINVAL;
2401
2402         /* we don't allow misaligned data like bio_map_user() does.  If the
2403          * user is using sg, they're expected to know the alignment constraints
2404          * and respect them accordingly */
2405         bio = bio_map_user_iov(q, NULL, iov, iov_count, rq_data_dir(rq)== READ);
2406         if (IS_ERR(bio))
2407                 return PTR_ERR(bio);
2408
2409         rq->bio = rq->biotail = bio;
2410         blk_rq_bio_prep(q, rq, bio);
2411         rq->buffer = rq->data = NULL;
2412         rq->data_len = bio->bi_size;
2413         return 0;
2414 }
2415
2416 EXPORT_SYMBOL(blk_rq_map_user_iov);
2417
2418 /**
2419  * blk_rq_unmap_user - unmap a request with user data
2420  * @bio:        bio to be unmapped
2421  * @ulen:       length of user buffer
2422  *
2423  * Description:
2424  *    Unmap a bio previously mapped by blk_rq_map_user().
2425  */
2426 int blk_rq_unmap_user(struct bio *bio, unsigned int ulen)
2427 {
2428         int ret = 0;
2429
2430         if (bio) {
2431                 if (bio_flagged(bio, BIO_USER_MAPPED))
2432                         bio_unmap_user(bio);
2433                 else
2434                         ret = bio_uncopy_user(bio);
2435         }
2436
2437         return 0;
2438 }
2439
2440 EXPORT_SYMBOL(blk_rq_unmap_user);
2441
2442 /**
2443  * blk_rq_map_kern - map kernel data to a request, for REQ_BLOCK_PC usage
2444  * @q:          request queue where request should be inserted
2445  * @rq:         request to fill
2446  * @kbuf:       the kernel buffer
2447  * @len:        length of user data
2448  * @gfp_mask:   memory allocation flags
2449  */
2450 int blk_rq_map_kern(request_queue_t *q, struct request *rq, void *kbuf,
2451                     unsigned int len, gfp_t gfp_mask)
2452 {
2453         struct bio *bio;
2454
2455         if (len > (q->max_hw_sectors << 9))
2456                 return -EINVAL;
2457         if (!len || !kbuf)
2458                 return -EINVAL;
2459
2460         bio = bio_map_kern(q, kbuf, len, gfp_mask);
2461         if (IS_ERR(bio))
2462                 return PTR_ERR(bio);
2463
2464         if (rq_data_dir(rq) == WRITE)
2465                 bio->bi_rw |= (1 << BIO_RW);
2466
2467         rq->bio = rq->biotail = bio;
2468         blk_rq_bio_prep(q, rq, bio);
2469
2470         rq->buffer = rq->data = NULL;
2471         rq->data_len = len;
2472         return 0;
2473 }
2474
2475 EXPORT_SYMBOL(blk_rq_map_kern);
2476
2477 /**
2478  * blk_execute_rq_nowait - insert a request into queue for execution
2479  * @q:          queue to insert the request in
2480  * @bd_disk:    matching gendisk
2481  * @rq:         request to insert
2482  * @at_head:    insert request at head or tail of queue
2483  * @done:       I/O completion handler
2484  *
2485  * Description:
2486  *    Insert a fully prepared request at the back of the io scheduler queue
2487  *    for execution.  Don't wait for completion.
2488  */
2489 void blk_execute_rq_nowait(request_queue_t *q, struct gendisk *bd_disk,
2490                            struct request *rq, int at_head,
2491                            rq_end_io_fn *done)
2492 {
2493         int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
2494
2495         rq->rq_disk = bd_disk;
2496         rq->flags |= REQ_NOMERGE;
2497         rq->end_io = done;
2498         WARN_ON(irqs_disabled());
2499         spin_lock_irq(q->queue_lock);
2500         __elv_add_request(q, rq, where, 1);
2501         __generic_unplug_device(q);
2502         spin_unlock_irq(q->queue_lock);
2503 }
2504 EXPORT_SYMBOL_GPL(blk_execute_rq_nowait);
2505
2506 /**
2507  * blk_execute_rq - insert a request into queue for execution
2508  * @q:          queue to insert the request in
2509  * @bd_disk:    matching gendisk
2510  * @rq:         request to insert
2511  * @at_head:    insert request at head or tail of queue
2512  *
2513  * Description:
2514  *    Insert a fully prepared request at the back of the io scheduler queue
2515  *    for execution and wait for completion.
2516  */
2517 int blk_execute_rq(request_queue_t *q, struct gendisk *bd_disk,
2518                    struct request *rq, int at_head)
2519 {
2520         DECLARE_COMPLETION(wait);
2521         char sense[SCSI_SENSE_BUFFERSIZE];
2522         int err = 0;
2523
2524         /*
2525          * we need an extra reference to the request, so we can look at
2526          * it after io completion
2527          */
2528         rq->ref_count++;
2529
2530         if (!rq->sense) {
2531                 memset(sense, 0, sizeof(sense));
2532                 rq->sense = sense;
2533                 rq->sense_len = 0;
2534         }
2535
2536         rq->waiting = &wait;
2537         blk_execute_rq_nowait(q, bd_disk, rq, at_head, blk_end_sync_rq);
2538         wait_for_completion(&wait);
2539         rq->waiting = NULL;
2540
2541         if (rq->errors)
2542                 err = -EIO;
2543
2544         return err;
2545 }
2546
2547 EXPORT_SYMBOL(blk_execute_rq);
2548
2549 /**
2550  * blkdev_issue_flush - queue a flush
2551  * @bdev:       blockdev to issue flush for
2552  * @error_sector:       error sector
2553  *
2554  * Description:
2555  *    Issue a flush for the block device in question. Caller can supply
2556  *    room for storing the error offset in case of a flush error, if they
2557  *    wish to.  Caller must run wait_for_completion() on its own.
2558  */
2559 int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
2560 {
2561         request_queue_t *q;
2562
2563         if (bdev->bd_disk == NULL)
2564                 return -ENXIO;
2565
2566         q = bdev_get_queue(bdev);
2567         if (!q)
2568                 return -ENXIO;
2569         if (!q->issue_flush_fn)
2570                 return -EOPNOTSUPP;
2571
2572         return q->issue_flush_fn(q, bdev->bd_disk, error_sector);
2573 }
2574
2575 EXPORT_SYMBOL(blkdev_issue_flush);
2576
2577 static void drive_stat_acct(struct request *rq, int nr_sectors, int new_io)
2578 {
2579         int rw = rq_data_dir(rq);
2580
2581         if (!blk_fs_request(rq) || !rq->rq_disk)
2582                 return;
2583
2584         if (!new_io) {
2585                 __disk_stat_inc(rq->rq_disk, merges[rw]);
2586         } else {
2587                 disk_round_stats(rq->rq_disk);
2588                 rq->rq_disk->in_flight++;
2589         }
2590 }
2591
2592 /*
2593  * add-request adds a request to the linked list.
2594  * queue lock is held and interrupts disabled, as we muck with the
2595  * request queue list.
2596  */
2597 static inline void add_request(request_queue_t * q, struct request * req)
2598 {
2599         drive_stat_acct(req, req->nr_sectors, 1);
2600
2601         if (q->activity_fn)
2602                 q->activity_fn(q->activity_data, rq_data_dir(req));
2603
2604         /*
2605          * elevator indicated where it wants this request to be
2606          * inserted at elevator_merge time
2607          */
2608         __elv_add_request(q, req, ELEVATOR_INSERT_SORT, 0);
2609 }
2610  
2611 /*
2612  * disk_round_stats()   - Round off the performance stats on a struct
2613  * disk_stats.
2614  *
2615  * The average IO queue length and utilisation statistics are maintained
2616  * by observing the current state of the queue length and the amount of
2617  * time it has been in this state for.
2618  *
2619  * Normally, that accounting is done on IO completion, but that can result
2620  * in more than a second's worth of IO being accounted for within any one
2621  * second, leading to >100% utilisation.  To deal with that, we call this
2622  * function to do a round-off before returning the results when reading
2623  * /proc/diskstats.  This accounts immediately for all queue usage up to
2624  * the current jiffies and restarts the counters again.
2625  */
2626 void disk_round_stats(struct gendisk *disk)
2627 {
2628         unsigned long now = jiffies;
2629
2630         if (now == disk->stamp)
2631                 return;
2632
2633         if (disk->in_flight) {
2634                 __disk_stat_add(disk, time_in_queue,
2635                                 disk->in_flight * (now - disk->stamp));
2636                 __disk_stat_add(disk, io_ticks, (now - disk->stamp));
2637         }
2638         disk->stamp = now;
2639 }
2640
2641 EXPORT_SYMBOL_GPL(disk_round_stats);
2642
2643 /*
2644  * queue lock must be held
2645  */
2646 void __blk_put_request(request_queue_t *q, struct request *req)
2647 {
2648         struct request_list *rl = req->rl;
2649
2650         if (unlikely(!q))
2651                 return;
2652         if (unlikely(--req->ref_count))
2653                 return;
2654
2655         elv_completed_request(q, req);
2656
2657         req->rq_status = RQ_INACTIVE;
2658         req->rl = NULL;
2659
2660         /*
2661          * Request may not have originated from ll_rw_blk. if not,
2662          * it didn't come out of our reserved rq pools
2663          */
2664         if (rl) {
2665                 int rw = rq_data_dir(req);
2666                 int priv = req->flags & REQ_ELVPRIV;
2667
2668                 BUG_ON(!list_empty(&req->queuelist));
2669
2670                 blk_free_request(q, req);
2671                 freed_request(q, rw, priv);
2672         }
2673 }
2674
2675 EXPORT_SYMBOL_GPL(__blk_put_request);
2676
2677 void blk_put_request(struct request *req)
2678 {
2679         unsigned long flags;
2680         request_queue_t *q = req->q;
2681
2682         /*
2683          * Gee, IDE calls in w/ NULL q.  Fix IDE and remove the
2684          * following if (q) test.
2685          */
2686         if (q) {
2687                 spin_lock_irqsave(q->queue_lock, flags);
2688                 __blk_put_request(q, req);
2689                 spin_unlock_irqrestore(q->queue_lock, flags);
2690         }
2691 }
2692
2693 EXPORT_SYMBOL(blk_put_request);
2694
2695 /**
2696  * blk_end_sync_rq - executes a completion event on a request
2697  * @rq: request to complete
2698  * @error: end io status of the request
2699  */
2700 void blk_end_sync_rq(struct request *rq, int error)
2701 {
2702         struct completion *waiting = rq->waiting;
2703
2704         rq->waiting = NULL;
2705         __blk_put_request(rq->q, rq);
2706
2707         /*
2708          * complete last, if this is a stack request the process (and thus
2709          * the rq pointer) could be invalid right after this complete()
2710          */
2711         complete(waiting);
2712 }
2713 EXPORT_SYMBOL(blk_end_sync_rq);
2714
2715 /**
2716  * blk_congestion_wait - wait for a queue to become uncongested
2717  * @rw: READ or WRITE
2718  * @timeout: timeout in jiffies
2719  *
2720  * Waits for up to @timeout jiffies for a queue (any queue) to exit congestion.
2721  * If no queues are congested then just wait for the next request to be
2722  * returned.
2723  */
2724 long blk_congestion_wait(int rw, long timeout)
2725 {
2726         long ret;
2727         DEFINE_WAIT(wait);
2728         wait_queue_head_t *wqh = &congestion_wqh[rw];
2729
2730         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
2731         ret = io_schedule_timeout(timeout);
2732         finish_wait(wqh, &wait);
2733         return ret;
2734 }
2735
2736 EXPORT_SYMBOL(blk_congestion_wait);
2737
2738 /*
2739  * Has to be called with the request spinlock acquired
2740  */
2741 static int attempt_merge(request_queue_t *q, struct request *req,
2742                           struct request *next)
2743 {
2744         if (!rq_mergeable(req) || !rq_mergeable(next))
2745                 return 0;
2746
2747         /*
2748          * not contiguous
2749          */
2750         if (req->sector + req->nr_sectors != next->sector)
2751                 return 0;
2752
2753         if (rq_data_dir(req) != rq_data_dir(next)
2754             || req->rq_disk != next->rq_disk
2755             || next->waiting || next->special)
2756                 return 0;
2757
2758         /*
2759          * If we are allowed to merge, then append bio list
2760          * from next to rq and release next. merge_requests_fn
2761          * will have updated segment counts, update sector
2762          * counts here.
2763          */
2764         if (!q->merge_requests_fn(q, req, next))
2765                 return 0;
2766
2767         /*
2768          * At this point we have either done a back merge
2769          * or front merge. We need the smaller start_time of
2770          * the merged requests to be the current request
2771          * for accounting purposes.
2772          */
2773         if (time_after(req->start_time, next->start_time))
2774                 req->start_time = next->start_time;
2775
2776         req->biotail->bi_next = next->bio;
2777         req->biotail = next->biotail;
2778
2779         req->nr_sectors = req->hard_nr_sectors += next->hard_nr_sectors;
2780
2781         elv_merge_requests(q, req, next);
2782
2783         if (req->rq_disk) {
2784                 disk_round_stats(req->rq_disk);
2785                 req->rq_disk->in_flight--;
2786         }
2787
2788         req->ioprio = ioprio_best(req->ioprio, next->ioprio);
2789
2790         __blk_put_request(q, next);
2791         return 1;
2792 }
2793
2794 static inline int attempt_back_merge(request_queue_t *q, struct request *rq)
2795 {
2796         struct request *next = elv_latter_request(q, rq);
2797
2798         if (next)
2799                 return attempt_merge(q, rq, next);
2800
2801         return 0;
2802 }
2803
2804 static inline int attempt_front_merge(request_queue_t *q, struct request *rq)
2805 {
2806         struct request *prev = elv_former_request(q, rq);
2807
2808         if (prev)
2809                 return attempt_merge(q, prev, rq);
2810
2811         return 0;
2812 }
2813
2814 static void init_request_from_bio(struct request *req, struct bio *bio)
2815 {
2816         req->flags |= REQ_CMD;
2817
2818         /*
2819          * inherit FAILFAST from bio (for read-ahead, and explicit FAILFAST)
2820          */
2821         if (bio_rw_ahead(bio) || bio_failfast(bio))
2822                 req->flags |= REQ_FAILFAST;
2823
2824         /*
2825          * REQ_BARRIER implies no merging, but lets make it explicit
2826          */
2827         if (unlikely(bio_barrier(bio)))
2828                 req->flags |= (REQ_HARDBARRIER | REQ_NOMERGE);
2829
2830         if (bio_sync(bio))
2831                 req->flags |= REQ_RW_SYNC;
2832
2833         req->errors = 0;
2834         req->hard_sector = req->sector = bio->bi_sector;
2835         req->hard_nr_sectors = req->nr_sectors = bio_sectors(bio);
2836         req->current_nr_sectors = req->hard_cur_sectors = bio_cur_sectors(bio);
2837         req->nr_phys_segments = bio_phys_segments(req->q, bio);
2838         req->nr_hw_segments = bio_hw_segments(req->q, bio);
2839         req->buffer = bio_data(bio);    /* see ->buffer comment above */
2840         req->waiting = NULL;
2841         req->bio = req->biotail = bio;
2842         req->ioprio = bio_prio(bio);
2843         req->rq_disk = bio->bi_bdev->bd_disk;
2844         req->start_time = jiffies;
2845 }
2846
2847 static int __make_request(request_queue_t *q, struct bio *bio)
2848 {
2849         struct request *req;
2850         int el_ret, rw, nr_sectors, cur_nr_sectors, barrier, err, sync;
2851         unsigned short prio;
2852         sector_t sector;
2853
2854         sector = bio->bi_sector;
2855         nr_sectors = bio_sectors(bio);
2856         cur_nr_sectors = bio_cur_sectors(bio);
2857         prio = bio_prio(bio);
2858
2859         rw = bio_data_dir(bio);
2860         sync = bio_sync(bio);
2861
2862         /*
2863          * low level driver can indicate that it wants pages above a
2864          * certain limit bounced to low memory (ie for highmem, or even
2865          * ISA dma in theory)
2866          */
2867         blk_queue_bounce(q, &bio);
2868
2869         spin_lock_prefetch(q->queue_lock);
2870
2871         barrier = bio_barrier(bio);
2872         if (unlikely(barrier) && (q->next_ordered == QUEUE_ORDERED_NONE)) {
2873                 err = -EOPNOTSUPP;
2874                 goto end_io;
2875         }
2876
2877         spin_lock_irq(q->queue_lock);
2878
2879         if (unlikely(barrier) || elv_queue_empty(q))
2880                 goto get_rq;
2881
2882         el_ret = elv_merge(q, &req, bio);
2883         switch (el_ret) {
2884                 case ELEVATOR_BACK_MERGE:
2885                         BUG_ON(!rq_mergeable(req));
2886
2887                         if (!q->back_merge_fn(q, req, bio))
2888                                 break;
2889
2890                         blk_add_trace_bio(q, bio, BLK_TA_BACKMERGE);
2891
2892                         req->biotail->bi_next = bio;
2893                         req->biotail = bio;
2894                         req->nr_sectors = req->hard_nr_sectors += nr_sectors;
2895                         req->ioprio = ioprio_best(req->ioprio, prio);
2896                         drive_stat_acct(req, nr_sectors, 0);
2897                         if (!attempt_back_merge(q, req))
2898                                 elv_merged_request(q, req);
2899                         goto out;
2900
2901                 case ELEVATOR_FRONT_MERGE:
2902                         BUG_ON(!rq_mergeable(req));
2903
2904                         if (!q->front_merge_fn(q, req, bio))
2905                                 break;
2906
2907                         blk_add_trace_bio(q, bio, BLK_TA_FRONTMERGE);
2908
2909                         bio->bi_next = req->bio;
2910                         req->bio = bio;
2911
2912                         /*
2913                          * may not be valid. if the low level driver said
2914                          * it didn't need a bounce buffer then it better
2915                          * not touch req->buffer either...
2916                          */
2917                         req->buffer = bio_data(bio);
2918                         req->current_nr_sectors = cur_nr_sectors;
2919                         req->hard_cur_sectors = cur_nr_sectors;
2920                         req->sector = req->hard_sector = sector;
2921                         req->nr_sectors = req->hard_nr_sectors += nr_sectors;
2922                         req->ioprio = ioprio_best(req->ioprio, prio);
2923                         drive_stat_acct(req, nr_sectors, 0);
2924                         if (!attempt_front_merge(q, req))
2925                                 elv_merged_request(q, req);
2926                         goto out;
2927
2928                 /* ELV_NO_MERGE: elevator says don't/can't merge. */
2929                 default:
2930                         ;
2931         }
2932
2933 get_rq:
2934         /*
2935          * Grab a free request. This is might sleep but can not fail.
2936          * Returns with the queue unlocked.
2937          */
2938         req = get_request_wait(q, rw, bio);
2939
2940         /*
2941          * After dropping the lock and possibly sleeping here, our request
2942          * may now be mergeable after it had proven unmergeable (above).
2943          * We don't worry about that case for efficiency. It won't happen
2944          * often, and the elevators are able to handle it.
2945          */
2946         init_request_from_bio(req, bio);
2947
2948         spin_lock_irq(q->queue_lock);
2949         if (elv_queue_empty(q))
2950                 blk_plug_device(q);
2951         add_request(q, req);
2952 out:
2953         if (sync)
2954                 __generic_unplug_device(q);
2955
2956         spin_unlock_irq(q->queue_lock);
2957         return 0;
2958
2959 end_io:
2960         bio_endio(bio, nr_sectors << 9, err);
2961         return 0;
2962 }
2963
2964 /*
2965  * If bio->bi_dev is a partition, remap the location
2966  */
2967 static inline void blk_partition_remap(struct bio *bio)
2968 {
2969         struct block_device *bdev = bio->bi_bdev;
2970
2971         if (bdev != bdev->bd_contains) {
2972                 struct hd_struct *p = bdev->bd_part;
2973                 const int rw = bio_data_dir(bio);
2974
2975                 p->sectors[rw] += bio_sectors(bio);
2976                 p->ios[rw]++;
2977
2978                 bio->bi_sector += p->start_sect;
2979                 bio->bi_bdev = bdev->bd_contains;
2980         }
2981 }
2982
2983 static void handle_bad_sector(struct bio *bio)
2984 {
2985         char b[BDEVNAME_SIZE];
2986
2987         printk(KERN_INFO "attempt to access beyond end of device\n");
2988         printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n",
2989                         bdevname(bio->bi_bdev, b),
2990                         bio->bi_rw,
2991                         (unsigned long long)bio->bi_sector + bio_sectors(bio),
2992                         (long long)(bio->bi_bdev->bd_inode->i_size >> 9));
2993
2994         set_bit(BIO_EOF, &bio->bi_flags);
2995 }
2996
2997 /**
2998  * generic_make_request: hand a buffer to its device driver for I/O
2999  * @bio:  The bio describing the location in memory and on the device.
3000  *
3001  * generic_make_request() is used to make I/O requests of block
3002  * devices. It is passed a &struct bio, which describes the I/O that needs
3003  * to be done.
3004  *
3005  * generic_make_request() does not return any status.  The
3006  * success/failure status of the request, along with notification of
3007  * completion, is delivered asynchronously through the bio->bi_end_io
3008  * function described (one day) else where.
3009  *
3010  * The caller of generic_make_request must make sure that bi_io_vec
3011  * are set to describe the memory buffer, and that bi_dev and bi_sector are
3012  * set to describe the device address, and the
3013  * bi_end_io and optionally bi_private are set to describe how
3014  * completion notification should be signaled.
3015  *
3016  * generic_make_request and the drivers it calls may use bi_next if this
3017  * bio happens to be merged with someone else, and may change bi_dev and
3018  * bi_sector for remaps as it sees fit.  So the values of these fields
3019  * should NOT be depended on after the call to generic_make_request.
3020  */
3021 void generic_make_request(struct bio *bio)
3022 {
3023         request_queue_t *q;
3024         sector_t maxsector;
3025         int ret, nr_sectors = bio_sectors(bio);
3026         dev_t old_dev;
3027
3028         might_sleep();
3029         /* Test device or partition size, when known. */
3030         maxsector = bio->bi_bdev->bd_inode->i_size >> 9;
3031         if (maxsector) {
3032                 sector_t sector = bio->bi_sector;
3033
3034                 if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
3035                         /*
3036                          * This may well happen - the kernel calls bread()
3037                          * without checking the size of the device, e.g., when
3038                          * mounting a device.
3039                          */
3040                         handle_bad_sector(bio);
3041                         goto end_io;
3042                 }
3043         }
3044
3045         /*
3046          * Resolve the mapping until finished. (drivers are
3047          * still free to implement/resolve their own stacking
3048          * by explicitly returning 0)
3049          *
3050          * NOTE: we don't repeat the blk_size check for each new device.
3051          * Stacking drivers are expected to know what they are doing.
3052          */
3053         maxsector = -1;
3054         old_dev = 0;
3055         do {
3056                 char b[BDEVNAME_SIZE];
3057
3058                 q = bdev_get_queue(bio->bi_bdev);
3059                 if (!q) {
3060                         printk(KERN_ERR
3061                                "generic_make_request: Trying to access "
3062                                 "nonexistent block-device %s (%Lu)\n",
3063                                 bdevname(bio->bi_bdev, b),
3064                                 (long long) bio->bi_sector);
3065 end_io:
3066                         bio_endio(bio, bio->bi_size, -EIO);
3067                         break;
3068                 }
3069
3070                 if (unlikely(bio_sectors(bio) > q->max_hw_sectors)) {
3071                         printk("bio too big device %s (%u > %u)\n", 
3072                                 bdevname(bio->bi_bdev, b),
3073                                 bio_sectors(bio),
3074                                 q->max_hw_sectors);
3075                         goto end_io;
3076                 }
3077
3078                 if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)))
3079                         goto end_io;
3080
3081                 /*
3082                  * If this device has partitions, remap block n
3083                  * of partition p to block n+start(p) of the disk.
3084                  */
3085                 blk_partition_remap(bio);
3086
3087                 if (maxsector != -1)
3088                         blk_add_trace_remap(q, bio, old_dev, bio->bi_sector, 
3089                                             maxsector);
3090
3091                 blk_add_trace_bio(q, bio, BLK_TA_QUEUE);
3092
3093                 maxsector = bio->bi_sector;
3094                 old_dev = bio->bi_bdev->bd_dev;
3095
3096                 ret = q->make_request_fn(q, bio);
3097         } while (ret);
3098 }
3099
3100 EXPORT_SYMBOL(generic_make_request);
3101
3102 /**
3103  * submit_bio: submit a bio to the block device layer for I/O
3104  * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
3105  * @bio: The &struct bio which describes the I/O
3106  *
3107  * submit_bio() is very similar in purpose to generic_make_request(), and
3108  * uses that function to do most of the work. Both are fairly rough
3109  * interfaces, @bio must be presetup and ready for I/O.
3110  *
3111  */
3112 void submit_bio(int rw, struct bio *bio)
3113 {
3114         int count = bio_sectors(bio);
3115
3116         BIO_BUG_ON(!bio->bi_size);
3117         BIO_BUG_ON(!bio->bi_io_vec);
3118         bio->bi_rw |= rw;
3119         if (rw & WRITE)
3120                 mod_page_state(pgpgout, count);
3121         else
3122                 mod_page_state(pgpgin, count);
3123
3124         if (unlikely(block_dump)) {
3125                 char b[BDEVNAME_SIZE];
3126                 printk(KERN_DEBUG "%s(%d): %s block %Lu on %s\n",
3127                         current->comm, current->pid,
3128                         (rw & WRITE) ? "WRITE" : "READ",
3129                         (unsigned long long)bio->bi_sector,
3130                         bdevname(bio->bi_bdev,b));
3131         }
3132
3133         generic_make_request(bio);
3134 }
3135
3136 EXPORT_SYMBOL(submit_bio);
3137
3138 static void blk_recalc_rq_segments(struct request *rq)
3139 {
3140         struct bio *bio, *prevbio = NULL;
3141         int nr_phys_segs, nr_hw_segs;
3142         unsigned int phys_size, hw_size;
3143         request_queue_t *q = rq->q;
3144
3145         if (!rq->bio)
3146                 return;
3147
3148         phys_size = hw_size = nr_phys_segs = nr_hw_segs = 0;
3149         rq_for_each_bio(bio, rq) {
3150                 /* Force bio hw/phys segs to be recalculated. */
3151                 bio->bi_flags &= ~(1 << BIO_SEG_VALID);
3152
3153                 nr_phys_segs += bio_phys_segments(q, bio);
3154                 nr_hw_segs += bio_hw_segments(q, bio);
3155                 if (prevbio) {
3156                         int pseg = phys_size + prevbio->bi_size + bio->bi_size;
3157                         int hseg = hw_size + prevbio->bi_size + bio->bi_size;
3158
3159                         if (blk_phys_contig_segment(q, prevbio, bio) &&
3160                             pseg <= q->max_segment_size) {
3161                                 nr_phys_segs--;
3162                                 phys_size += prevbio->bi_size + bio->bi_size;
3163                         } else
3164                                 phys_size = 0;
3165
3166                         if (blk_hw_contig_segment(q, prevbio, bio) &&
3167                             hseg <= q->max_segment_size) {
3168                                 nr_hw_segs--;
3169                                 hw_size += prevbio->bi_size + bio->bi_size;
3170                         } else
3171                                 hw_size = 0;
3172                 }
3173                 prevbio = bio;
3174         }
3175
3176         rq->nr_phys_segments = nr_phys_segs;
3177         rq->nr_hw_segments = nr_hw_segs;
3178 }
3179
3180 static void blk_recalc_rq_sectors(struct request *rq, int nsect)
3181 {
3182         if (blk_fs_request(rq)) {
3183                 rq->hard_sector += nsect;
3184                 rq->hard_nr_sectors -= nsect;
3185
3186                 /*
3187                  * Move the I/O submission pointers ahead if required.
3188                  */
3189                 if ((rq->nr_sectors >= rq->hard_nr_sectors) &&
3190                     (rq->sector <= rq->hard_sector)) {
3191                         rq->sector = rq->hard_sector;
3192                         rq->nr_sectors = rq->hard_nr_sectors;
3193                         rq->hard_cur_sectors = bio_cur_sectors(rq->bio);
3194                         rq->current_nr_sectors = rq->hard_cur_sectors;
3195                         rq->buffer = bio_data(rq->bio);
3196                 }
3197
3198                 /*
3199                  * if total number of sectors is less than the first segment
3200                  * size, something has gone terribly wrong
3201                  */
3202                 if (rq->nr_sectors < rq->current_nr_sectors) {
3203                         printk("blk: request botched\n");
3204                         rq->nr_sectors = rq->current_nr_sectors;
3205                 }
3206         }
3207 }
3208
3209 static int __end_that_request_first(struct request *req, int uptodate,
3210                                     int nr_bytes)
3211 {
3212         int total_bytes, bio_nbytes, error, next_idx = 0;
3213         struct bio *bio;
3214
3215         blk_add_trace_rq(req->q, req, BLK_TA_COMPLETE);
3216
3217         /*
3218          * extend uptodate bool to allow < 0 value to be direct io error
3219          */
3220         error = 0;
3221         if (end_io_error(uptodate))
3222                 error = !uptodate ? -EIO : uptodate;
3223
3224         /*
3225          * for a REQ_BLOCK_PC request, we want to carry any eventual
3226          * sense key with us all the way through
3227          */
3228         if (!blk_pc_request(req))
3229                 req->errors = 0;
3230
3231         if (!uptodate) {
3232                 if (blk_fs_request(req) && !(req->flags & REQ_QUIET))
3233                         printk("end_request: I/O error, dev %s, sector %llu\n",
3234                                 req->rq_disk ? req->rq_disk->disk_name : "?",
3235                                 (unsigned long long)req->sector);
3236         }
3237
3238         if (blk_fs_request(req) && req->rq_disk) {
3239                 const int rw = rq_data_dir(req);
3240
3241                 disk_stat_add(req->rq_disk, sectors[rw], nr_bytes >> 9);
3242         }
3243
3244         total_bytes = bio_nbytes = 0;
3245         while ((bio = req->bio) != NULL) {
3246                 int nbytes;
3247
3248                 if (nr_bytes >= bio->bi_size) {
3249                         req->bio = bio->bi_next;
3250                         nbytes = bio->bi_size;
3251                         if (!ordered_bio_endio(req, bio, nbytes, error))
3252                                 bio_endio(bio, nbytes, error);
3253                         next_idx = 0;
3254                         bio_nbytes = 0;
3255                 } else {
3256                         int idx = bio->bi_idx + next_idx;
3257
3258                         if (unlikely(bio->bi_idx >= bio->bi_vcnt)) {
3259                                 blk_dump_rq_flags(req, "__end_that");
3260                                 printk("%s: bio idx %d >= vcnt %d\n",
3261                                                 __FUNCTION__,
3262                                                 bio->bi_idx, bio->bi_vcnt);
3263                                 break;
3264                         }
3265
3266                         nbytes = bio_iovec_idx(bio, idx)->bv_len;
3267                         BIO_BUG_ON(nbytes > bio->bi_size);
3268
3269                         /*
3270                          * not a complete bvec done
3271                          */
3272                         if (unlikely(nbytes > nr_bytes)) {
3273                                 bio_nbytes += nr_bytes;
3274                                 total_bytes += nr_bytes;
3275                                 break;
3276                         }
3277
3278                         /*
3279                          * advance to the next vector
3280                          */
3281                         next_idx++;
3282                         bio_nbytes += nbytes;
3283                 }
3284
3285                 total_bytes += nbytes;
3286                 nr_bytes -= nbytes;
3287
3288                 if ((bio = req->bio)) {
3289                         /*
3290                          * end more in this run, or just return 'not-done'
3291                          */
3292                         if (unlikely(nr_bytes <= 0))
3293                                 break;
3294                 }
3295         }
3296
3297         /*
3298          * completely done
3299          */
3300         if (!req->bio)
3301                 return 0;
3302
3303         /*
3304          * if the request wasn't completed, update state
3305          */
3306         if (bio_nbytes) {
3307                 if (!ordered_bio_endio(req, bio, bio_nbytes, error))
3308                         bio_endio(bio, bio_nbytes, error);
3309                 bio->bi_idx += next_idx;
3310                 bio_iovec(bio)->bv_offset += nr_bytes;
3311                 bio_iovec(bio)->bv_len -= nr_bytes;
3312         }
3313
3314         blk_recalc_rq_sectors(req, total_bytes >> 9);
3315         blk_recalc_rq_segments(req);
3316         return 1;
3317 }
3318
3319 /**
3320  * end_that_request_first - end I/O on a request
3321  * @req:      the request being processed
3322  * @uptodate: 1 for success, 0 for I/O error, < 0 for specific error
3323  * @nr_sectors: number of sectors to end I/O on
3324  *
3325  * Description:
3326  *     Ends I/O on a number of sectors attached to @req, and sets it up
3327  *     for the next range of segments (if any) in the cluster.
3328  *
3329  * Return:
3330  *     0 - we are done with this request, call end_that_request_last()
3331  *     1 - still buffers pending for this request
3332  **/
3333 int end_that_request_first(struct request *req, int uptodate, int nr_sectors)
3334 {
3335         return __end_that_request_first(req, uptodate, nr_sectors << 9);
3336 }
3337
3338 EXPORT_SYMBOL(end_that_request_first);
3339
3340 /**
3341  * end_that_request_chunk - end I/O on a request
3342  * @req:      the request being processed
3343  * @uptodate: 1 for success, 0 for I/O error, < 0 for specific error
3344  * @nr_bytes: number of bytes to complete
3345  *
3346  * Description:
3347  *     Ends I/O on a number of bytes attached to @req, and sets it up
3348  *     for the next range of segments (if any). Like end_that_request_first(),
3349  *     but deals with bytes instead of sectors.
3350  *
3351  * Return:
3352  *     0 - we are done with this request, call end_that_request_last()
3353  *     1 - still buffers pending for this request
3354  **/
3355 int end_that_request_chunk(struct request *req, int uptodate, int nr_bytes)
3356 {
3357         return __end_that_request_first(req, uptodate, nr_bytes);
3358 }
3359
3360 EXPORT_SYMBOL(end_that_request_chunk);
3361
3362 /*
3363  * splice the completion data to a local structure and hand off to
3364  * process_completion_queue() to complete the requests
3365  */
3366 static void blk_done_softirq(struct softirq_action *h)
3367 {
3368         struct list_head *cpu_list, local_list;
3369
3370         local_irq_disable();
3371         cpu_list = &__get_cpu_var(blk_cpu_done);
3372         list_replace_init(cpu_list, &local_list);
3373         local_irq_enable();
3374
3375         while (!list_empty(&local_list)) {
3376                 struct request *rq = list_entry(local_list.next, struct request, donelist);
3377
3378                 list_del_init(&rq->donelist);
3379                 rq->q->softirq_done_fn(rq);
3380         }
3381 }
3382
3383 #ifdef CONFIG_HOTPLUG_CPU
3384
3385 static int blk_cpu_notify(struct notifier_block *self, unsigned long action,
3386                           void *hcpu)
3387 {
3388         /*
3389          * If a CPU goes away, splice its entries to the current CPU
3390          * and trigger a run of the softirq
3391          */
3392         if (action == CPU_DEAD) {
3393                 int cpu = (unsigned long) hcpu;
3394
3395                 local_irq_disable();
3396                 list_splice_init(&per_cpu(blk_cpu_done, cpu),
3397                                  &__get_cpu_var(blk_cpu_done));
3398                 raise_softirq_irqoff(BLOCK_SOFTIRQ);
3399                 local_irq_enable();
3400         }
3401
3402         return NOTIFY_OK;
3403 }
3404
3405
3406 static struct notifier_block __devinitdata blk_cpu_notifier = {
3407         .notifier_call  = blk_cpu_notify,
3408 };
3409
3410 #endif /* CONFIG_HOTPLUG_CPU */
3411
3412 /**
3413  * blk_complete_request - end I/O on a request
3414  * @req:      the request being processed
3415  *
3416  * Description:
3417  *     Ends all I/O on a request. It does not handle partial completions,
3418  *     unless the driver actually implements this in its completion callback
3419  *     through requeueing. Theh actual completion happens out-of-order,
3420  *     through a softirq handler. The user must have registered a completion
3421  *     callback through blk_queue_softirq_done().
3422  **/
3423
3424 void blk_complete_request(struct request *req)
3425 {
3426         struct list_head *cpu_list;
3427         unsigned long flags;
3428
3429         BUG_ON(!req->q->softirq_done_fn);
3430                 
3431         local_irq_save(flags);
3432
3433         cpu_list = &__get_cpu_var(blk_cpu_done);
3434         list_add_tail(&req->donelist, cpu_list);
3435         raise_softirq_irqoff(BLOCK_SOFTIRQ);
3436
3437         local_irq_restore(flags);
3438 }
3439
3440 EXPORT_SYMBOL(blk_complete_request);
3441         
3442 /*
3443  * queue lock must be held
3444  */
3445 void end_that_request_last(struct request *req, int uptodate)
3446 {
3447         struct gendisk *disk = req->rq_disk;
3448         int error;
3449
3450         /*
3451          * extend uptodate bool to allow < 0 value to be direct io error
3452          */
3453         error = 0;
3454         if (end_io_error(uptodate))
3455                 error = !uptodate ? -EIO : uptodate;
3456
3457         if (unlikely(laptop_mode) && blk_fs_request(req))
3458                 laptop_io_completion();
3459
3460         /*
3461          * Account IO completion.  bar_rq isn't accounted as a normal
3462          * IO on queueing nor completion.  Accounting the containing
3463          * request is enough.
3464          */
3465         if (disk && blk_fs_request(req) && req != &req->q->bar_rq) {
3466                 unsigned long duration = jiffies - req->start_time;
3467                 const int rw = rq_data_dir(req);
3468
3469                 __disk_stat_inc(disk, ios[rw]);
3470                 __disk_stat_add(disk, ticks[rw], duration);
3471                 disk_round_stats(disk);
3472                 disk->in_flight--;
3473         }
3474         if (req->end_io)
3475                 req->end_io(req, error);
3476         else
3477                 __blk_put_request(req->q, req);
3478 }
3479
3480 EXPORT_SYMBOL(end_that_request_last);
3481
3482 void end_request(struct request *req, int uptodate)
3483 {
3484         if (!end_that_request_first(req, uptodate, req->hard_cur_sectors)) {
3485                 add_disk_randomness(req->rq_disk);
3486                 blkdev_dequeue_request(req);
3487                 end_that_request_last(req, uptodate);
3488         }
3489 }
3490
3491 EXPORT_SYMBOL(end_request);
3492
3493 void blk_rq_bio_prep(request_queue_t *q, struct request *rq, struct bio *bio)
3494 {
3495         /* first three bits are identical in rq->flags and bio->bi_rw */
3496         rq->flags |= (bio->bi_rw & 7);
3497
3498         rq->nr_phys_segments = bio_phys_segments(q, bio);
3499         rq->nr_hw_segments = bio_hw_segments(q, bio);
3500         rq->current_nr_sectors = bio_cur_sectors(bio);
3501         rq->hard_cur_sectors = rq->current_nr_sectors;
3502         rq->hard_nr_sectors = rq->nr_sectors = bio_sectors(bio);
3503         rq->buffer = bio_data(bio);
3504
3505         rq->bio = rq->biotail = bio;
3506 }
3507
3508 EXPORT_SYMBOL(blk_rq_bio_prep);
3509
3510 int kblockd_schedule_work(struct work_struct *work)
3511 {
3512         return queue_work(kblockd_workqueue, work);
3513 }
3514
3515 EXPORT_SYMBOL(kblockd_schedule_work);
3516
3517 void kblockd_flush(void)
3518 {
3519         flush_workqueue(kblockd_workqueue);
3520 }
3521 EXPORT_SYMBOL(kblockd_flush);
3522
3523 int __init blk_dev_init(void)
3524 {
3525         int i;
3526
3527         kblockd_workqueue = create_workqueue("kblockd");
3528         if (!kblockd_workqueue)
3529                 panic("Failed to create kblockd\n");
3530
3531         request_cachep = kmem_cache_create("blkdev_requests",
3532                         sizeof(struct request), 0, SLAB_PANIC, NULL, NULL);
3533
3534         requestq_cachep = kmem_cache_create("blkdev_queue",
3535                         sizeof(request_queue_t), 0, SLAB_PANIC, NULL, NULL);
3536
3537         iocontext_cachep = kmem_cache_create("blkdev_ioc",
3538                         sizeof(struct io_context), 0, SLAB_PANIC, NULL, NULL);
3539
3540         for_each_possible_cpu(i)
3541                 INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i));
3542
3543         open_softirq(BLOCK_SOFTIRQ, blk_done_softirq, NULL);
3544         register_hotcpu_notifier(&blk_cpu_notifier);
3545
3546         blk_max_low_pfn = max_low_pfn;
3547         blk_max_pfn = max_pfn;
3548
3549         return 0;
3550 }
3551
3552 /*
3553  * IO Context helper functions
3554  */
3555 void put_io_context(struct io_context *ioc)
3556 {
3557         if (ioc == NULL)
3558                 return;
3559
3560         BUG_ON(atomic_read(&ioc->refcount) == 0);
3561
3562         if (atomic_dec_and_test(&ioc->refcount)) {
3563                 struct cfq_io_context *cic;
3564
3565                 rcu_read_lock();
3566                 if (ioc->aic && ioc->aic->dtor)
3567                         ioc->aic->dtor(ioc->aic);
3568                 if (ioc->cic_root.rb_node != NULL) {
3569                         struct rb_node *n = rb_first(&ioc->cic_root);
3570
3571                         cic = rb_entry(n, struct cfq_io_context, rb_node);
3572                         cic->dtor(ioc);
3573                 }
3574                 rcu_read_unlock();
3575
3576                 kmem_cache_free(iocontext_cachep, ioc);
3577         }
3578 }
3579 EXPORT_SYMBOL(put_io_context);
3580
3581 /* Called by the exitting task */
3582 void exit_io_context(void)
3583 {
3584         unsigned long flags;
3585         struct io_context *ioc;
3586         struct cfq_io_context *cic;
3587
3588         local_irq_save(flags);
3589         task_lock(current);
3590         ioc = current->io_context;
3591         current->io_context = NULL;
3592         ioc->task = NULL;
3593         task_unlock(current);
3594         local_irq_restore(flags);
3595
3596         if (ioc->aic && ioc->aic->exit)
3597                 ioc->aic->exit(ioc->aic);
3598         if (ioc->cic_root.rb_node != NULL) {
3599                 cic = rb_entry(rb_first(&ioc->cic_root), struct cfq_io_context, rb_node);
3600                 cic->exit(ioc);
3601         }
3602  
3603         put_io_context(ioc);
3604 }
3605
3606 /*
3607  * If the current task has no IO context then create one and initialise it.
3608  * Otherwise, return its existing IO context.
3609  *
3610  * This returned IO context doesn't have a specifically elevated refcount,
3611  * but since the current task itself holds a reference, the context can be
3612  * used in general code, so long as it stays within `current` context.
3613  */
3614 struct io_context *current_io_context(gfp_t gfp_flags)
3615 {
3616         struct task_struct *tsk = current;
3617         struct io_context *ret;
3618
3619         ret = tsk->io_context;
3620         if (likely(ret))
3621                 return ret;
3622
3623         ret = kmem_cache_alloc(iocontext_cachep, gfp_flags);
3624         if (ret) {
3625                 atomic_set(&ret->refcount, 1);
3626                 ret->task = current;
3627                 ret->set_ioprio = NULL;
3628                 ret->last_waited = jiffies; /* doesn't matter... */
3629                 ret->nr_batch_requests = 0; /* because this is 0 */
3630                 ret->aic = NULL;
3631                 ret->cic_root.rb_node = NULL;
3632                 tsk->io_context = ret;
3633         }
3634
3635         return ret;
3636 }
3637 EXPORT_SYMBOL(current_io_context);
3638
3639 /*
3640  * If the current task has no IO context then create one and initialise it.
3641  * If it does have a context, take a ref on it.
3642  *
3643  * This is always called in the context of the task which submitted the I/O.
3644  */
3645 struct io_context *get_io_context(gfp_t gfp_flags)
3646 {
3647         struct io_context *ret;
3648         ret = current_io_context(gfp_flags);
3649         if (likely(ret))
3650                 atomic_inc(&ret->refcount);
3651         return ret;
3652 }
3653 EXPORT_SYMBOL(get_io_context);
3654
3655 void copy_io_context(struct io_context **pdst, struct io_context **psrc)
3656 {
3657         struct io_context *src = *psrc;
3658         struct io_context *dst = *pdst;
3659
3660         if (src) {
3661                 BUG_ON(atomic_read(&src->refcount) == 0);
3662                 atomic_inc(&src->refcount);
3663                 put_io_context(dst);
3664                 *pdst = src;
3665         }
3666 }
3667 EXPORT_SYMBOL(copy_io_context);
3668
3669 void swap_io_context(struct io_context **ioc1, struct io_context **ioc2)
3670 {
3671         struct io_context *temp;
3672         temp = *ioc1;
3673         *ioc1 = *ioc2;
3674         *ioc2 = temp;
3675 }
3676 EXPORT_SYMBOL(swap_io_context);
3677
3678 /*
3679  * sysfs parts below
3680  */
3681 struct queue_sysfs_entry {
3682         struct attribute attr;
3683         ssize_t (*show)(struct request_queue *, char *);
3684         ssize_t (*store)(struct request_queue *, const char *, size_t);
3685 };
3686
3687 static ssize_t
3688 queue_var_show(unsigned int var, char *page)
3689 {
3690         return sprintf(page, "%d\n", var);
3691 }
3692
3693 static ssize_t
3694 queue_var_store(unsigned long *var, const char *page, size_t count)
3695 {
3696         char *p = (char *) page;
3697
3698         *var = simple_strtoul(p, &p, 10);
3699         return count;
3700 }
3701
3702 static ssize_t queue_requests_show(struct request_queue *q, char *page)
3703 {
3704         return queue_var_show(q->nr_requests, (page));
3705 }
3706
3707 static ssize_t
3708 queue_requests_store(struct request_queue *q, const char *page, size_t count)
3709 {
3710         struct request_list *rl = &q->rq;
3711         unsigned long nr;
3712         int ret = queue_var_store(&nr, page, count);
3713         if (nr < BLKDEV_MIN_RQ)
3714                 nr = BLKDEV_MIN_RQ;
3715
3716         spin_lock_irq(q->queue_lock);
3717         q->nr_requests = nr;
3718         blk_queue_congestion_threshold(q);
3719
3720         if (rl->count[READ] >= queue_congestion_on_threshold(q))
3721                 set_queue_congested(q, READ);
3722         else if (rl->count[READ] < queue_congestion_off_threshold(q))
3723                 clear_queue_congested(q, READ);
3724
3725         if (rl->count[WRITE] >= queue_congestion_on_threshold(q))
3726                 set_queue_congested(q, WRITE);
3727         else if (rl->count[WRITE] < queue_congestion_off_threshold(q))
3728                 clear_queue_congested(q, WRITE);
3729
3730         if (rl->count[READ] >= q->nr_requests) {
3731                 blk_set_queue_full(q, READ);
3732         } else if (rl->count[READ]+1 <= q->nr_requests) {
3733                 blk_clear_queue_full(q, READ);
3734                 wake_up(&rl->wait[READ]);
3735         }
3736
3737         if (rl->count[WRITE] >= q->nr_requests) {
3738                 blk_set_queue_full(q, WRITE);
3739         } else if (rl->count[WRITE]+1 <= q->nr_requests) {
3740                 blk_clear_queue_full(q, WRITE);
3741                 wake_up(&rl->wait[WRITE]);
3742         }
3743         spin_unlock_irq(q->queue_lock);
3744         return ret;
3745 }
3746
3747 static ssize_t queue_ra_show(struct request_queue *q, char *page)
3748 {
3749         int ra_kb = q->backing_dev_info.ra_pages << (PAGE_CACHE_SHIFT - 10);
3750
3751         return queue_var_show(ra_kb, (page));
3752 }
3753
3754 static ssize_t
3755 queue_ra_store(struct request_queue *q, const char *page, size_t count)
3756 {
3757         unsigned long ra_kb;
3758         ssize_t ret = queue_var_store(&ra_kb, page, count);
3759
3760         spin_lock_irq(q->queue_lock);
3761         if (ra_kb > (q->max_sectors >> 1))
3762                 ra_kb = (q->max_sectors >> 1);
3763
3764         q->backing_dev_info.ra_pages = ra_kb >> (PAGE_CACHE_SHIFT - 10);
3765         spin_unlock_irq(q->queue_lock);
3766
3767         return ret;
3768 }
3769
3770 static ssize_t queue_max_sectors_show(struct request_queue *q, char *page)
3771 {
3772         int max_sectors_kb = q->max_sectors >> 1;
3773
3774         return queue_var_show(max_sectors_kb, (page));
3775 }
3776
3777 static ssize_t
3778 queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
3779 {
3780         unsigned long max_sectors_kb,
3781                         max_hw_sectors_kb = q->max_hw_sectors >> 1,
3782                         page_kb = 1 << (PAGE_CACHE_SHIFT - 10);
3783         ssize_t ret = queue_var_store(&max_sectors_kb, page, count);
3784         int ra_kb;
3785
3786         if (max_sectors_kb > max_hw_sectors_kb || max_sectors_kb < page_kb)
3787                 return -EINVAL;
3788         /*
3789          * Take the queue lock to update the readahead and max_sectors
3790          * values synchronously:
3791          */
3792         spin_lock_irq(q->queue_lock);
3793         /*
3794          * Trim readahead window as well, if necessary:
3795          */
3796         ra_kb = q->backing_dev_info.ra_pages << (PAGE_CACHE_SHIFT - 10);
3797         if (ra_kb > max_sectors_kb)
3798                 q->backing_dev_info.ra_pages =
3799                                 max_sectors_kb >> (PAGE_CACHE_SHIFT - 10);
3800
3801         q->max_sectors = max_sectors_kb << 1;
3802         spin_unlock_irq(q->queue_lock);
3803
3804         return ret;
3805 }
3806
3807 static ssize_t queue_max_hw_sectors_show(struct request_queue *q, char *page)
3808 {
3809         int max_hw_sectors_kb = q->max_hw_sectors >> 1;
3810
3811         return queue_var_show(max_hw_sectors_kb, (page));
3812 }
3813
3814
3815 static struct queue_sysfs_entry queue_requests_entry = {
3816         .attr = {.name = "nr_requests", .mode = S_IRUGO | S_IWUSR },
3817         .show = queue_requests_show,
3818         .store = queue_requests_store,
3819 };
3820
3821 static struct queue_sysfs_entry queue_ra_entry = {
3822         .attr = {.name = "read_ahead_kb", .mode = S_IRUGO | S_IWUSR },
3823         .show = queue_ra_show,
3824         .store = queue_ra_store,
3825 };
3826
3827 static struct queue_sysfs_entry queue_max_sectors_entry = {
3828         .attr = {.name = "max_sectors_kb", .mode = S_IRUGO | S_IWUSR },
3829         .show = queue_max_sectors_show,
3830         .store = queue_max_sectors_store,
3831 };
3832
3833 static struct queue_sysfs_entry queue_max_hw_sectors_entry = {
3834         .attr = {.name = "max_hw_sectors_kb", .mode = S_IRUGO },
3835         .show = queue_max_hw_sectors_show,
3836 };
3837
3838 static struct queue_sysfs_entry queue_iosched_entry = {
3839         .attr = {.name = "scheduler", .mode = S_IRUGO | S_IWUSR },
3840         .show = elv_iosched_show,
3841         .store = elv_iosched_store,
3842 };
3843
3844 static struct attribute *default_attrs[] = {
3845         &queue_requests_entry.attr,
3846         &queue_ra_entry.attr,
3847         &queue_max_hw_sectors_entry.attr,
3848         &queue_max_sectors_entry.attr,
3849         &queue_iosched_entry.attr,
3850         NULL,
3851 };
3852
3853 #define to_queue(atr) container_of((atr), struct queue_sysfs_entry, attr)
3854
3855 static ssize_t
3856 queue_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
3857 {
3858         struct queue_sysfs_entry *entry = to_queue(attr);
3859         request_queue_t *q = container_of(kobj, struct request_queue, kobj);
3860         ssize_t res;
3861
3862         if (!entry->show)
3863                 return -EIO;
3864         mutex_lock(&q->sysfs_lock);
3865         if (test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)) {
3866                 mutex_unlock(&q->sysfs_lock);
3867                 return -ENOENT;
3868         }
3869         res = entry->show(q, page);
3870         mutex_unlock(&q->sysfs_lock);
3871         return res;
3872 }
3873
3874 static ssize_t
3875 queue_attr_store(struct kobject *kobj, struct attribute *attr,
3876                     const char *page, size_t length)
3877 {
3878         struct queue_sysfs_entry *entry = to_queue(attr);
3879         request_queue_t *q = container_of(kobj, struct request_queue, kobj);
3880
3881         ssize_t res;
3882
3883         if (!entry->store)
3884                 return -EIO;
3885         mutex_lock(&q->sysfs_lock);
3886         if (test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)) {
3887                 mutex_unlock(&q->sysfs_lock);
3888                 return -ENOENT;
3889         }
3890         res = entry->store(q, page, length);
3891         mutex_unlock(&q->sysfs_lock);
3892         return res;
3893 }
3894
3895 static struct sysfs_ops queue_sysfs_ops = {
3896         .show   = queue_attr_show,
3897         .store  = queue_attr_store,
3898 };
3899
3900 static struct kobj_type queue_ktype = {
3901         .sysfs_ops      = &queue_sysfs_ops,
3902         .default_attrs  = default_attrs,
3903         .release        = blk_release_queue,
3904 };
3905
3906 int blk_register_queue(struct gendisk *disk)
3907 {
3908         int ret;
3909
3910         request_queue_t *q = disk->queue;
3911
3912         if (!q || !q->request_fn)
3913                 return -ENXIO;
3914
3915         q->kobj.parent = kobject_get(&disk->kobj);
3916
3917         ret = kobject_add(&q->kobj);
3918         if (ret < 0)
3919                 return ret;
3920
3921         kobject_uevent(&q->kobj, KOBJ_ADD);
3922
3923         ret = elv_register_queue(q);
3924         if (ret) {
3925                 kobject_uevent(&q->kobj, KOBJ_REMOVE);
3926                 kobject_del(&q->kobj);
3927                 return ret;
3928         }
3929
3930         return 0;
3931 }
3932
3933 void blk_unregister_queue(struct gendisk *disk)
3934 {
3935         request_queue_t *q = disk->queue;
3936
3937         if (q && q->request_fn) {
3938                 elv_unregister_queue(q);
3939
3940                 kobject_uevent(&q->kobj, KOBJ_REMOVE);
3941                 kobject_del(&q->kobj);
3942                 kobject_put(&disk->kobj);
3943         }
3944 }