Merge ../linux-2.6/
[linux-2.6] / fs / nfs / direct.c
1 /*
2  * linux/fs/nfs/direct.c
3  *
4  * Copyright (C) 2003 by Chuck Lever <cel@netapp.com>
5  *
6  * High-performance uncached I/O for the Linux NFS client
7  *
8  * There are important applications whose performance or correctness
9  * depends on uncached access to file data.  Database clusters
10  * (multiple copies of the same instance running on separate hosts)
11  * implement their own cache coherency protocol that subsumes file
12  * system cache protocols.  Applications that process datasets
13  * considerably larger than the client's memory do not always benefit
14  * from a local cache.  A streaming video server, for instance, has no
15  * need to cache the contents of a file.
16  *
17  * When an application requests uncached I/O, all read and write requests
18  * are made directly to the server; data stored or fetched via these
19  * requests is not cached in the Linux page cache.  The client does not
20  * correct unaligned requests from applications.  All requested bytes are
21  * held on permanent storage before a direct write system call returns to
22  * an application.
23  *
24  * Solaris implements an uncached I/O facility called directio() that
25  * is used for backups and sequential I/O to very large files.  Solaris
26  * also supports uncaching whole NFS partitions with "-o forcedirectio,"
27  * an undocumented mount option.
28  *
29  * Designed by Jeff Kimmel, Chuck Lever, and Trond Myklebust, with
30  * help from Andrew Morton.
31  *
32  * 18 Dec 2001  Initial implementation for 2.4  --cel
33  * 08 Jul 2002  Version for 2.4.19, with bug fixes --trondmy
34  * 08 Jun 2003  Port to 2.5 APIs  --cel
35  * 31 Mar 2004  Handle direct I/O without VFS support  --cel
36  * 15 Sep 2004  Parallel async reads  --cel
37  * 04 May 2005  support O_DIRECT with aio  --cel
38  *
39  */
40
41 #include <linux/config.h>
42 #include <linux/errno.h>
43 #include <linux/sched.h>
44 #include <linux/kernel.h>
45 #include <linux/smp_lock.h>
46 #include <linux/file.h>
47 #include <linux/pagemap.h>
48 #include <linux/kref.h>
49
50 #include <linux/nfs_fs.h>
51 #include <linux/nfs_page.h>
52 #include <linux/sunrpc/clnt.h>
53
54 #include <asm/system.h>
55 #include <asm/uaccess.h>
56 #include <asm/atomic.h>
57
58 #include "iostat.h"
59
60 #define NFSDBG_FACILITY         NFSDBG_VFS
61
62 static kmem_cache_t *nfs_direct_cachep;
63
64 /*
65  * This represents a set of asynchronous requests that we're waiting on
66  */
67 struct nfs_direct_req {
68         struct kref             kref;           /* release manager */
69
70         /* I/O parameters */
71         struct list_head        list,           /* nfs_read/write_data structs */
72                                 rewrite_list;   /* saved nfs_write_data structs */
73         struct nfs_open_context *ctx;           /* file open context info */
74         struct kiocb *          iocb;           /* controlling i/o request */
75         struct inode *          inode;          /* target file of i/o */
76         unsigned long           user_addr;      /* location of user's buffer */
77         size_t                  user_count;     /* total bytes to move */
78         loff_t                  pos;            /* starting offset in file */
79         struct page **          pages;          /* pages in our buffer */
80         unsigned int            npages;         /* count of pages */
81
82         /* completion state */
83         spinlock_t              lock;           /* protect completion state */
84         int                     outstanding;    /* i/os we're waiting for */
85         ssize_t                 count,          /* bytes actually processed */
86                                 error;          /* any reported error */
87         struct completion       completion;     /* wait for i/o completion */
88
89         /* commit state */
90         struct nfs_write_data * commit_data;    /* special write_data for commits */
91         int                     flags;
92 #define NFS_ODIRECT_DO_COMMIT           (1)     /* an unstable reply was received */
93 #define NFS_ODIRECT_RESCHED_WRITES      (2)     /* write verification failed */
94         struct nfs_writeverf    verf;           /* unstable write verifier */
95 };
96
97 static void nfs_direct_write_schedule(struct nfs_direct_req *dreq, int sync);
98 static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode);
99
100 /**
101  * nfs_direct_IO - NFS address space operation for direct I/O
102  * @rw: direction (read or write)
103  * @iocb: target I/O control block
104  * @iov: array of vectors that define I/O buffer
105  * @pos: offset in file to begin the operation
106  * @nr_segs: size of iovec array
107  *
108  * The presence of this routine in the address space ops vector means
109  * the NFS client supports direct I/O.  However, we shunt off direct
110  * read and write requests before the VFS gets them, so this method
111  * should never be called.
112  */
113 ssize_t nfs_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, loff_t pos, unsigned long nr_segs)
114 {
115         dprintk("NFS: nfs_direct_IO (%s) off/no(%Ld/%lu) EINVAL\n",
116                         iocb->ki_filp->f_dentry->d_name.name,
117                         (long long) pos, nr_segs);
118
119         return -EINVAL;
120 }
121
122 static void nfs_free_user_pages(struct page **pages, int npages, int do_dirty)
123 {
124         int i;
125         for (i = 0; i < npages; i++) {
126                 struct page *page = pages[i];
127                 if (do_dirty && !PageCompound(page))
128                         set_page_dirty_lock(page);
129                 page_cache_release(page);
130         }
131         kfree(pages);
132 }
133
134 static inline int nfs_get_user_pages(int rw, unsigned long user_addr, size_t size, struct page ***pages)
135 {
136         int result = -ENOMEM;
137         unsigned long page_count;
138         size_t array_size;
139
140         page_count = (user_addr + size + PAGE_SIZE - 1) >> PAGE_SHIFT;
141         page_count -= user_addr >> PAGE_SHIFT;
142
143         array_size = (page_count * sizeof(struct page *));
144         *pages = kmalloc(array_size, GFP_KERNEL);
145         if (*pages) {
146                 down_read(&current->mm->mmap_sem);
147                 result = get_user_pages(current, current->mm, user_addr,
148                                         page_count, (rw == READ), 0,
149                                         *pages, NULL);
150                 up_read(&current->mm->mmap_sem);
151                 if (result != page_count) {
152                         /*
153                          * If we got fewer pages than expected from
154                          * get_user_pages(), the user buffer runs off the
155                          * end of a mapping; return EFAULT.
156                          */
157                         if (result >= 0) {
158                                 nfs_free_user_pages(*pages, result, 0);
159                                 result = -EFAULT;
160                         } else
161                                 kfree(*pages);
162                         *pages = NULL;
163                 }
164         }
165         return result;
166 }
167
168 static inline struct nfs_direct_req *nfs_direct_req_alloc(void)
169 {
170         struct nfs_direct_req *dreq;
171
172         dreq = kmem_cache_alloc(nfs_direct_cachep, SLAB_KERNEL);
173         if (!dreq)
174                 return NULL;
175
176         kref_init(&dreq->kref);
177         init_completion(&dreq->completion);
178         INIT_LIST_HEAD(&dreq->list);
179         INIT_LIST_HEAD(&dreq->rewrite_list);
180         dreq->iocb = NULL;
181         dreq->ctx = NULL;
182         spin_lock_init(&dreq->lock);
183         dreq->outstanding = 0;
184         dreq->count = 0;
185         dreq->error = 0;
186         dreq->flags = 0;
187
188         return dreq;
189 }
190
191 static void nfs_direct_req_release(struct kref *kref)
192 {
193         struct nfs_direct_req *dreq = container_of(kref, struct nfs_direct_req, kref);
194
195         if (dreq->ctx != NULL)
196                 put_nfs_open_context(dreq->ctx);
197         kmem_cache_free(nfs_direct_cachep, dreq);
198 }
199
200 /*
201  * Collects and returns the final error value/byte-count.
202  */
203 static ssize_t nfs_direct_wait(struct nfs_direct_req *dreq)
204 {
205         ssize_t result = -EIOCBQUEUED;
206
207         /* Async requests don't wait here */
208         if (dreq->iocb)
209                 goto out;
210
211         result = wait_for_completion_interruptible(&dreq->completion);
212
213         if (!result)
214                 result = dreq->error;
215         if (!result)
216                 result = dreq->count;
217
218 out:
219         kref_put(&dreq->kref, nfs_direct_req_release);
220         return (ssize_t) result;
221 }
222
223 /*
224  * We must hold a reference to all the pages in this direct read request
225  * until the RPCs complete.  This could be long *after* we are woken up in
226  * nfs_direct_wait (for instance, if someone hits ^C on a slow server).
227  *
228  * In addition, synchronous I/O uses a stack-allocated iocb.  Thus we
229  * can't trust the iocb is still valid here if this is a synchronous
230  * request.  If the waiter is woken prematurely, the iocb is long gone.
231  */
232 static void nfs_direct_complete(struct nfs_direct_req *dreq)
233 {
234         nfs_free_user_pages(dreq->pages, dreq->npages, 1);
235
236         if (dreq->iocb) {
237                 long res = (long) dreq->error;
238                 if (!res)
239                         res = (long) dreq->count;
240                 aio_complete(dreq->iocb, res, 0);
241         }
242         complete_all(&dreq->completion);
243
244         kref_put(&dreq->kref, nfs_direct_req_release);
245 }
246
247 /*
248  * Note we also set the number of requests we have in the dreq when we are
249  * done.  This prevents races with I/O completion so we will always wait
250  * until all requests have been dispatched and completed.
251  */
252 static struct nfs_direct_req *nfs_direct_read_alloc(size_t nbytes, size_t rsize)
253 {
254         struct list_head *list;
255         struct nfs_direct_req *dreq;
256         unsigned int rpages = (rsize + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
257
258         dreq = nfs_direct_req_alloc();
259         if (!dreq)
260                 return NULL;
261
262         list = &dreq->list;
263         for(;;) {
264                 struct nfs_read_data *data = nfs_readdata_alloc(rpages);
265
266                 if (unlikely(!data)) {
267                         while (!list_empty(list)) {
268                                 data = list_entry(list->next,
269                                                   struct nfs_read_data, pages);
270                                 list_del(&data->pages);
271                                 nfs_readdata_free(data);
272                         }
273                         kref_put(&dreq->kref, nfs_direct_req_release);
274                         return NULL;
275                 }
276
277                 INIT_LIST_HEAD(&data->pages);
278                 list_add(&data->pages, list);
279
280                 data->req = (struct nfs_page *) dreq;
281                 dreq->outstanding++;
282                 if (nbytes <= rsize)
283                         break;
284                 nbytes -= rsize;
285         }
286         kref_get(&dreq->kref);
287         return dreq;
288 }
289
290 static void nfs_direct_read_result(struct rpc_task *task, void *calldata)
291 {
292         struct nfs_read_data *data = calldata;
293         struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;
294
295         if (nfs_readpage_result(task, data) != 0)
296                 return;
297
298         spin_lock(&dreq->lock);
299
300         if (likely(task->tk_status >= 0))
301                 dreq->count += data->res.count;
302         else
303                 dreq->error = task->tk_status;
304
305         if (--dreq->outstanding) {
306                 spin_unlock(&dreq->lock);
307                 return;
308         }
309
310         spin_unlock(&dreq->lock);
311         nfs_direct_complete(dreq);
312 }
313
314 static const struct rpc_call_ops nfs_read_direct_ops = {
315         .rpc_call_done = nfs_direct_read_result,
316         .rpc_release = nfs_readdata_release,
317 };
318
319 /*
320  * For each nfs_read_data struct that was allocated on the list, dispatch
321  * an NFS READ operation
322  */
323 static void nfs_direct_read_schedule(struct nfs_direct_req *dreq)
324 {
325         struct nfs_open_context *ctx = dreq->ctx;
326         struct inode *inode = ctx->dentry->d_inode;
327         struct list_head *list = &dreq->list;
328         struct page **pages = dreq->pages;
329         size_t count = dreq->user_count;
330         loff_t pos = dreq->pos;
331         size_t rsize = NFS_SERVER(inode)->rsize;
332         unsigned int curpage, pgbase;
333
334         curpage = 0;
335         pgbase = dreq->user_addr & ~PAGE_MASK;
336         do {
337                 struct nfs_read_data *data;
338                 size_t bytes;
339
340                 bytes = rsize;
341                 if (count < rsize)
342                         bytes = count;
343
344                 BUG_ON(list_empty(list));
345                 data = list_entry(list->next, struct nfs_read_data, pages);
346                 list_del_init(&data->pages);
347
348                 data->inode = inode;
349                 data->cred = ctx->cred;
350                 data->args.fh = NFS_FH(inode);
351                 data->args.context = ctx;
352                 data->args.offset = pos;
353                 data->args.pgbase = pgbase;
354                 data->args.pages = &pages[curpage];
355                 data->args.count = bytes;
356                 data->res.fattr = &data->fattr;
357                 data->res.eof = 0;
358                 data->res.count = bytes;
359
360                 rpc_init_task(&data->task, NFS_CLIENT(inode), RPC_TASK_ASYNC,
361                                 &nfs_read_direct_ops, data);
362                 NFS_PROTO(inode)->read_setup(data);
363
364                 data->task.tk_cookie = (unsigned long) inode;
365
366                 lock_kernel();
367                 rpc_execute(&data->task);
368                 unlock_kernel();
369
370                 dfprintk(VFS, "NFS: %5u initiated direct read call (req %s/%Ld, %zu bytes @ offset %Lu)\n",
371                                 data->task.tk_pid,
372                                 inode->i_sb->s_id,
373                                 (long long)NFS_FILEID(inode),
374                                 bytes,
375                                 (unsigned long long)data->args.offset);
376
377                 pos += bytes;
378                 pgbase += bytes;
379                 curpage += pgbase >> PAGE_SHIFT;
380                 pgbase &= ~PAGE_MASK;
381
382                 count -= bytes;
383         } while (count != 0);
384         BUG_ON(!list_empty(list));
385 }
386
387 static ssize_t nfs_direct_read(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t pos, struct page **pages, unsigned int nr_pages)
388 {
389         ssize_t result;
390         sigset_t oldset;
391         struct inode *inode = iocb->ki_filp->f_mapping->host;
392         struct rpc_clnt *clnt = NFS_CLIENT(inode);
393         struct nfs_direct_req *dreq;
394
395         dreq = nfs_direct_read_alloc(count, NFS_SERVER(inode)->rsize);
396         if (!dreq)
397                 return -ENOMEM;
398
399         dreq->user_addr = user_addr;
400         dreq->user_count = count;
401         dreq->pos = pos;
402         dreq->pages = pages;
403         dreq->npages = nr_pages;
404         dreq->inode = inode;
405         dreq->ctx = get_nfs_open_context((struct nfs_open_context *)iocb->ki_filp->private_data);
406         if (!is_sync_kiocb(iocb))
407                 dreq->iocb = iocb;
408
409         nfs_add_stats(inode, NFSIOS_DIRECTREADBYTES, count);
410         rpc_clnt_sigmask(clnt, &oldset);
411         nfs_direct_read_schedule(dreq);
412         result = nfs_direct_wait(dreq);
413         rpc_clnt_sigunmask(clnt, &oldset);
414
415         return result;
416 }
417
418 static void nfs_direct_free_writedata(struct nfs_direct_req *dreq)
419 {
420         list_splice_init(&dreq->rewrite_list, &dreq->list);
421         while (!list_empty(&dreq->list)) {
422                 struct nfs_write_data *data = list_entry(dreq->list.next, struct nfs_write_data, pages);
423                 list_del(&data->pages);
424                 nfs_writedata_release(data);
425         }
426 }
427
428 #if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4)
429 static void nfs_direct_write_reschedule(struct nfs_direct_req *dreq)
430 {
431         struct list_head *pos;
432
433         list_splice_init(&dreq->rewrite_list, &dreq->list);
434         list_for_each(pos, &dreq->list)
435                 dreq->outstanding++;
436         dreq->count = 0;
437
438         nfs_direct_write_schedule(dreq, FLUSH_STABLE);
439 }
440
441 static void nfs_direct_commit_result(struct rpc_task *task, void *calldata)
442 {
443         struct nfs_write_data *data = calldata;
444         struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;
445
446         /* Call the NFS version-specific code */
447         if (NFS_PROTO(data->inode)->commit_done(task, data) != 0)
448                 return;
449         if (unlikely(task->tk_status < 0)) {
450                 dreq->error = task->tk_status;
451                 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
452         }
453         if (memcmp(&dreq->verf, &data->verf, sizeof(data->verf))) {
454                 dprintk("NFS: %5u commit verify failed\n", task->tk_pid);
455                 dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
456         }
457
458         dprintk("NFS: %5u commit returned %d\n", task->tk_pid, task->tk_status);
459         nfs_direct_write_complete(dreq, data->inode);
460 }
461
462 static const struct rpc_call_ops nfs_commit_direct_ops = {
463         .rpc_call_done = nfs_direct_commit_result,
464         .rpc_release = nfs_commit_release,
465 };
466
467 static void nfs_direct_commit_schedule(struct nfs_direct_req *dreq)
468 {
469         struct nfs_write_data *data = dreq->commit_data;
470
471         data->inode = dreq->inode;
472         data->cred = dreq->ctx->cred;
473
474         data->args.fh = NFS_FH(data->inode);
475         data->args.offset = dreq->pos;
476         data->args.count = dreq->user_count;
477         data->res.count = 0;
478         data->res.fattr = &data->fattr;
479         data->res.verf = &data->verf;
480
481         rpc_init_task(&data->task, NFS_CLIENT(dreq->inode), RPC_TASK_ASYNC,
482                                 &nfs_commit_direct_ops, data);
483         NFS_PROTO(data->inode)->commit_setup(data, 0);
484
485         data->task.tk_priority = RPC_PRIORITY_NORMAL;
486         data->task.tk_cookie = (unsigned long)data->inode;
487         /* Note: task.tk_ops->rpc_release will free dreq->commit_data */
488         dreq->commit_data = NULL;
489
490         dprintk("NFS: %5u initiated commit call\n", data->task.tk_pid);
491
492         lock_kernel();
493         rpc_execute(&data->task);
494         unlock_kernel();
495 }
496
497 static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode)
498 {
499         int flags = dreq->flags;
500
501         dreq->flags = 0;
502         switch (flags) {
503                 case NFS_ODIRECT_DO_COMMIT:
504                         nfs_direct_commit_schedule(dreq);
505                         break;
506                 case NFS_ODIRECT_RESCHED_WRITES:
507                         nfs_direct_write_reschedule(dreq);
508                         break;
509                 default:
510                         nfs_end_data_update(inode);
511                         if (dreq->commit_data != NULL)
512                                 nfs_commit_free(dreq->commit_data);
513                         nfs_direct_free_writedata(dreq);
514                         nfs_direct_complete(dreq);
515         }
516 }
517
518 static void nfs_alloc_commit_data(struct nfs_direct_req *dreq)
519 {
520         dreq->commit_data = nfs_commit_alloc(0);
521         if (dreq->commit_data != NULL)
522                 dreq->commit_data->req = (struct nfs_page *) dreq;
523 }
524 #else
525 static inline void nfs_alloc_commit_data(struct nfs_direct_req *dreq)
526 {
527         dreq->commit_data = NULL;
528 }
529
530 static void nfs_direct_write_complete(struct nfs_direct_req *dreq, struct inode *inode)
531 {
532         nfs_end_data_update(inode);
533         nfs_direct_free_writedata(dreq);
534         nfs_direct_complete(dreq);
535 }
536 #endif
537
538 static struct nfs_direct_req *nfs_direct_write_alloc(size_t nbytes, size_t wsize)
539 {
540         struct list_head *list;
541         struct nfs_direct_req *dreq;
542         unsigned int wpages = (wsize + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
543
544         dreq = nfs_direct_req_alloc();
545         if (!dreq)
546                 return NULL;
547
548         list = &dreq->list;
549         for(;;) {
550                 struct nfs_write_data *data = nfs_writedata_alloc(wpages);
551
552                 if (unlikely(!data)) {
553                         while (!list_empty(list)) {
554                                 data = list_entry(list->next,
555                                                   struct nfs_write_data, pages);
556                                 list_del(&data->pages);
557                                 nfs_writedata_free(data);
558                         }
559                         kref_put(&dreq->kref, nfs_direct_req_release);
560                         return NULL;
561                 }
562
563                 INIT_LIST_HEAD(&data->pages);
564                 list_add(&data->pages, list);
565
566                 data->req = (struct nfs_page *) dreq;
567                 dreq->outstanding++;
568                 if (nbytes <= wsize)
569                         break;
570                 nbytes -= wsize;
571         }
572
573         nfs_alloc_commit_data(dreq);
574
575         kref_get(&dreq->kref);
576         return dreq;
577 }
578
579 static void nfs_direct_write_result(struct rpc_task *task, void *calldata)
580 {
581         struct nfs_write_data *data = calldata;
582         struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;
583         int status = task->tk_status;
584
585         if (nfs_writeback_done(task, data) != 0)
586                 return;
587
588         spin_lock(&dreq->lock);
589
590         if (likely(status >= 0))
591                 dreq->count += data->res.count;
592         else
593                 dreq->error = task->tk_status;
594
595         if (data->res.verf->committed != NFS_FILE_SYNC) {
596                 switch (dreq->flags) {
597                         case 0:
598                                 memcpy(&dreq->verf, &data->verf, sizeof(dreq->verf));
599                                 dreq->flags = NFS_ODIRECT_DO_COMMIT;
600                                 break;
601                         case NFS_ODIRECT_DO_COMMIT:
602                                 if (memcmp(&dreq->verf, &data->verf, sizeof(dreq->verf))) {
603                                         dprintk("NFS: %5u write verify failed\n", task->tk_pid);
604                                         dreq->flags = NFS_ODIRECT_RESCHED_WRITES;
605                                 }
606                 }
607         }
608         /* In case we have to resend */
609         data->args.stable = NFS_FILE_SYNC;
610
611         spin_unlock(&dreq->lock);
612 }
613
614 /*
615  * NB: Return the value of the first error return code.  Subsequent
616  *     errors after the first one are ignored.
617  */
618 static void nfs_direct_write_release(void *calldata)
619 {
620         struct nfs_write_data *data = calldata;
621         struct nfs_direct_req *dreq = (struct nfs_direct_req *) data->req;
622
623         spin_lock(&dreq->lock);
624         if (--dreq->outstanding) {
625                 spin_unlock(&dreq->lock);
626                 return;
627         }
628         spin_unlock(&dreq->lock);
629
630         nfs_direct_write_complete(dreq, data->inode);
631 }
632
633 static const struct rpc_call_ops nfs_write_direct_ops = {
634         .rpc_call_done = nfs_direct_write_result,
635         .rpc_release = nfs_direct_write_release,
636 };
637
638 /*
639  * For each nfs_write_data struct that was allocated on the list, dispatch
640  * an NFS WRITE operation
641  */
642 static void nfs_direct_write_schedule(struct nfs_direct_req *dreq, int sync)
643 {
644         struct nfs_open_context *ctx = dreq->ctx;
645         struct inode *inode = ctx->dentry->d_inode;
646         struct list_head *list = &dreq->list;
647         struct page **pages = dreq->pages;
648         size_t count = dreq->user_count;
649         loff_t pos = dreq->pos;
650         size_t wsize = NFS_SERVER(inode)->wsize;
651         unsigned int curpage, pgbase;
652
653         curpage = 0;
654         pgbase = dreq->user_addr & ~PAGE_MASK;
655         do {
656                 struct nfs_write_data *data;
657                 size_t bytes;
658
659                 bytes = wsize;
660                 if (count < wsize)
661                         bytes = count;
662
663                 BUG_ON(list_empty(list));
664                 data = list_entry(list->next, struct nfs_write_data, pages);
665                 list_move_tail(&data->pages, &dreq->rewrite_list);
666
667                 data->inode = inode;
668                 data->cred = ctx->cred;
669                 data->args.fh = NFS_FH(inode);
670                 data->args.context = ctx;
671                 data->args.offset = pos;
672                 data->args.pgbase = pgbase;
673                 data->args.pages = &pages[curpage];
674                 data->args.count = bytes;
675                 data->res.fattr = &data->fattr;
676                 data->res.count = bytes;
677                 data->res.verf = &data->verf;
678
679                 rpc_init_task(&data->task, NFS_CLIENT(inode), RPC_TASK_ASYNC,
680                                 &nfs_write_direct_ops, data);
681                 NFS_PROTO(inode)->write_setup(data, sync);
682
683                 data->task.tk_priority = RPC_PRIORITY_NORMAL;
684                 data->task.tk_cookie = (unsigned long) inode;
685
686                 lock_kernel();
687                 rpc_execute(&data->task);
688                 unlock_kernel();
689
690                 dfprintk(VFS, "NFS: %5u initiated direct write call (req %s/%Ld, %zu bytes @ offset %Lu)\n",
691                                 data->task.tk_pid,
692                                 inode->i_sb->s_id,
693                                 (long long)NFS_FILEID(inode),
694                                 bytes,
695                                 (unsigned long long)data->args.offset);
696
697                 pos += bytes;
698                 pgbase += bytes;
699                 curpage += pgbase >> PAGE_SHIFT;
700                 pgbase &= ~PAGE_MASK;
701
702                 count -= bytes;
703         } while (count != 0);
704         BUG_ON(!list_empty(list));
705 }
706
707 static ssize_t nfs_direct_write(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t pos, struct page **pages, int nr_pages)
708 {
709         ssize_t result;
710         sigset_t oldset;
711         struct inode *inode = iocb->ki_filp->f_mapping->host;
712         struct rpc_clnt *clnt = NFS_CLIENT(inode);
713         struct nfs_direct_req *dreq;
714         size_t wsize = NFS_SERVER(inode)->wsize;
715         int sync = 0;
716
717         dreq = nfs_direct_write_alloc(count, wsize);
718         if (!dreq)
719                 return -ENOMEM;
720         if (dreq->commit_data == NULL || count < wsize)
721                 sync = FLUSH_STABLE;
722
723         dreq->user_addr = user_addr;
724         dreq->user_count = count;
725         dreq->pos = pos;
726         dreq->pages = pages;
727         dreq->npages = nr_pages;
728         dreq->inode = inode;
729         dreq->ctx = get_nfs_open_context((struct nfs_open_context *)iocb->ki_filp->private_data);
730         if (!is_sync_kiocb(iocb))
731                 dreq->iocb = iocb;
732
733         nfs_add_stats(inode, NFSIOS_DIRECTWRITTENBYTES, count);
734
735         nfs_begin_data_update(inode);
736
737         rpc_clnt_sigmask(clnt, &oldset);
738         nfs_direct_write_schedule(dreq, sync);
739         result = nfs_direct_wait(dreq);
740         rpc_clnt_sigunmask(clnt, &oldset);
741
742         return result;
743 }
744
745 /**
746  * nfs_file_direct_read - file direct read operation for NFS files
747  * @iocb: target I/O control block
748  * @buf: user's buffer into which to read data
749  * @count: number of bytes to read
750  * @pos: byte offset in file where reading starts
751  *
752  * We use this function for direct reads instead of calling
753  * generic_file_aio_read() in order to avoid gfar's check to see if
754  * the request starts before the end of the file.  For that check
755  * to work, we must generate a GETATTR before each direct read, and
756  * even then there is a window between the GETATTR and the subsequent
757  * READ where the file size could change.  Our preference is simply
758  * to do all reads the application wants, and the server will take
759  * care of managing the end of file boundary.
760  *
761  * This function also eliminates unnecessarily updating the file's
762  * atime locally, as the NFS server sets the file's atime, and this
763  * client must read the updated atime from the server back into its
764  * cache.
765  */
766 ssize_t nfs_file_direct_read(struct kiocb *iocb, char __user *buf, size_t count, loff_t pos)
767 {
768         ssize_t retval = -EINVAL;
769         int page_count;
770         struct page **pages;
771         struct file *file = iocb->ki_filp;
772         struct address_space *mapping = file->f_mapping;
773
774         dprintk("nfs: direct read(%s/%s, %lu@%Ld)\n",
775                 file->f_dentry->d_parent->d_name.name,
776                 file->f_dentry->d_name.name,
777                 (unsigned long) count, (long long) pos);
778
779         if (count < 0)
780                 goto out;
781         retval = -EFAULT;
782         if (!access_ok(VERIFY_WRITE, buf, count))
783                 goto out;
784         retval = 0;
785         if (!count)
786                 goto out;
787
788         retval = nfs_sync_mapping(mapping);
789         if (retval)
790                 goto out;
791
792         retval = nfs_get_user_pages(READ, (unsigned long) buf,
793                                                 count, &pages);
794         if (retval < 0)
795                 goto out;
796         page_count = retval;
797
798         retval = nfs_direct_read(iocb, (unsigned long) buf, count, pos,
799                                                 pages, page_count);
800         if (retval > 0)
801                 iocb->ki_pos = pos + retval;
802
803 out:
804         return retval;
805 }
806
807 /**
808  * nfs_file_direct_write - file direct write operation for NFS files
809  * @iocb: target I/O control block
810  * @buf: user's buffer from which to write data
811  * @count: number of bytes to write
812  * @pos: byte offset in file where writing starts
813  *
814  * We use this function for direct writes instead of calling
815  * generic_file_aio_write() in order to avoid taking the inode
816  * semaphore and updating the i_size.  The NFS server will set
817  * the new i_size and this client must read the updated size
818  * back into its cache.  We let the server do generic write
819  * parameter checking and report problems.
820  *
821  * We also avoid an unnecessary invocation of generic_osync_inode(),
822  * as it is fairly meaningless to sync the metadata of an NFS file.
823  *
824  * We eliminate local atime updates, see direct read above.
825  *
826  * We avoid unnecessary page cache invalidations for normal cached
827  * readers of this file.
828  *
829  * Note that O_APPEND is not supported for NFS direct writes, as there
830  * is no atomic O_APPEND write facility in the NFS protocol.
831  */
832 ssize_t nfs_file_direct_write(struct kiocb *iocb, const char __user *buf, size_t count, loff_t pos)
833 {
834         ssize_t retval;
835         int page_count;
836         struct page **pages;
837         struct file *file = iocb->ki_filp;
838         struct address_space *mapping = file->f_mapping;
839
840         dfprintk(VFS, "nfs: direct write(%s/%s, %lu@%Ld)\n",
841                 file->f_dentry->d_parent->d_name.name,
842                 file->f_dentry->d_name.name,
843                 (unsigned long) count, (long long) pos);
844
845         retval = generic_write_checks(file, &pos, &count, 0);
846         if (retval)
847                 goto out;
848
849         retval = -EINVAL;
850         if ((ssize_t) count < 0)
851                 goto out;
852         retval = 0;
853         if (!count)
854                 goto out;
855
856         retval = -EFAULT;
857         if (!access_ok(VERIFY_READ, buf, count))
858                 goto out;
859
860         retval = nfs_sync_mapping(mapping);
861         if (retval)
862                 goto out;
863
864         retval = nfs_get_user_pages(WRITE, (unsigned long) buf,
865                                                 count, &pages);
866         if (retval < 0)
867                 goto out;
868         page_count = retval;
869
870         retval = nfs_direct_write(iocb, (unsigned long) buf, count,
871                                         pos, pages, page_count);
872
873         /*
874          * XXX: nfs_end_data_update() already ensures this file's
875          *      cached data is subsequently invalidated.  Do we really
876          *      need to call invalidate_inode_pages2() again here?
877          *
878          *      For aio writes, this invalidation will almost certainly
879          *      occur before the writes complete.  Kind of racey.
880          */
881         if (mapping->nrpages)
882                 invalidate_inode_pages2(mapping);
883
884         if (retval > 0)
885                 iocb->ki_pos = pos + retval;
886
887 out:
888         return retval;
889 }
890
891 /**
892  * nfs_init_directcache - create a slab cache for nfs_direct_req structures
893  *
894  */
895 int __init nfs_init_directcache(void)
896 {
897         nfs_direct_cachep = kmem_cache_create("nfs_direct_cache",
898                                                 sizeof(struct nfs_direct_req),
899                                                 0, (SLAB_RECLAIM_ACCOUNT|
900                                                         SLAB_MEM_SPREAD),
901                                                 NULL, NULL);
902         if (nfs_direct_cachep == NULL)
903                 return -ENOMEM;
904
905         return 0;
906 }
907
908 /**
909  * nfs_destroy_directcache - destroy the slab cache for nfs_direct_req structures
910  *
911  */
912 void nfs_destroy_directcache(void)
913 {
914         if (kmem_cache_destroy(nfs_direct_cachep))
915                 printk(KERN_INFO "nfs_direct_cache: not all structures were freed\n");
916 }