Merge branch 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...
[linux-2.6] / fs / buffer.c
1 /*
2  *  linux/fs/buffer.c
3  *
4  *  Copyright (C) 1991, 1992, 2002  Linus Torvalds
5  */
6
7 /*
8  * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95
9  *
10  * Removed a lot of unnecessary code and simplified things now that
11  * the buffer cache isn't our primary cache - Andrew Tridgell 12/96
12  *
13  * Speed up hash, lru, and free list operations.  Use gfp() for allocating
14  * hash table, use SLAB cache for buffer heads. SMP threading.  -DaveM
15  *
16  * Added 32k buffer block sizes - these are required older ARM systems. - RMK
17  *
18  * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de>
19  */
20
21 #include <linux/kernel.h>
22 #include <linux/syscalls.h>
23 #include <linux/fs.h>
24 #include <linux/mm.h>
25 #include <linux/percpu.h>
26 #include <linux/slab.h>
27 #include <linux/capability.h>
28 #include <linux/blkdev.h>
29 #include <linux/file.h>
30 #include <linux/quotaops.h>
31 #include <linux/highmem.h>
32 #include <linux/module.h>
33 #include <linux/writeback.h>
34 #include <linux/hash.h>
35 #include <linux/suspend.h>
36 #include <linux/buffer_head.h>
37 #include <linux/task_io_accounting_ops.h>
38 #include <linux/bio.h>
39 #include <linux/notifier.h>
40 #include <linux/cpu.h>
41 #include <linux/bitops.h>
42 #include <linux/mpage.h>
43 #include <linux/bit_spinlock.h>
44
45 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
46
47 #define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
48
49 inline void
50 init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
51 {
52         bh->b_end_io = handler;
53         bh->b_private = private;
54 }
55
56 static int sync_buffer(void *word)
57 {
58         struct block_device *bd;
59         struct buffer_head *bh
60                 = container_of(word, struct buffer_head, b_state);
61
62         smp_mb();
63         bd = bh->b_bdev;
64         if (bd)
65                 blk_run_address_space(bd->bd_inode->i_mapping);
66         io_schedule();
67         return 0;
68 }
69
70 void __lock_buffer(struct buffer_head *bh)
71 {
72         wait_on_bit_lock(&bh->b_state, BH_Lock, sync_buffer,
73                                                         TASK_UNINTERRUPTIBLE);
74 }
75 EXPORT_SYMBOL(__lock_buffer);
76
77 void unlock_buffer(struct buffer_head *bh)
78 {
79         clear_bit_unlock(BH_Lock, &bh->b_state);
80         smp_mb__after_clear_bit();
81         wake_up_bit(&bh->b_state, BH_Lock);
82 }
83
84 /*
85  * Block until a buffer comes unlocked.  This doesn't stop it
86  * from becoming locked again - you have to lock it yourself
87  * if you want to preserve its state.
88  */
89 void __wait_on_buffer(struct buffer_head * bh)
90 {
91         wait_on_bit(&bh->b_state, BH_Lock, sync_buffer, TASK_UNINTERRUPTIBLE);
92 }
93
94 static void
95 __clear_page_buffers(struct page *page)
96 {
97         ClearPagePrivate(page);
98         set_page_private(page, 0);
99         page_cache_release(page);
100 }
101
102 static void buffer_io_error(struct buffer_head *bh)
103 {
104         char b[BDEVNAME_SIZE];
105
106         printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
107                         bdevname(bh->b_bdev, b),
108                         (unsigned long long)bh->b_blocknr);
109 }
110
111 /*
112  * End-of-IO handler helper function which does not touch the bh after
113  * unlocking it.
114  * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
115  * a race there is benign: unlock_buffer() only use the bh's address for
116  * hashing after unlocking the buffer, so it doesn't actually touch the bh
117  * itself.
118  */
119 static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
120 {
121         if (uptodate) {
122                 set_buffer_uptodate(bh);
123         } else {
124                 /* This happens, due to failed READA attempts. */
125                 clear_buffer_uptodate(bh);
126         }
127         unlock_buffer(bh);
128 }
129
130 /*
131  * Default synchronous end-of-IO handler..  Just mark it up-to-date and
132  * unlock the buffer. This is what ll_rw_block uses too.
133  */
134 void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
135 {
136         __end_buffer_read_notouch(bh, uptodate);
137         put_bh(bh);
138 }
139
140 void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
141 {
142         char b[BDEVNAME_SIZE];
143
144         if (uptodate) {
145                 set_buffer_uptodate(bh);
146         } else {
147                 if (!buffer_eopnotsupp(bh) && printk_ratelimit()) {
148                         buffer_io_error(bh);
149                         printk(KERN_WARNING "lost page write due to "
150                                         "I/O error on %s\n",
151                                        bdevname(bh->b_bdev, b));
152                 }
153                 set_buffer_write_io_error(bh);
154                 clear_buffer_uptodate(bh);
155         }
156         unlock_buffer(bh);
157         put_bh(bh);
158 }
159
160 /*
161  * Write out and wait upon all the dirty data associated with a block
162  * device via its mapping.  Does not take the superblock lock.
163  */
164 int sync_blockdev(struct block_device *bdev)
165 {
166         int ret = 0;
167
168         if (bdev)
169                 ret = filemap_write_and_wait(bdev->bd_inode->i_mapping);
170         return ret;
171 }
172 EXPORT_SYMBOL(sync_blockdev);
173
174 /*
175  * Write out and wait upon all dirty data associated with this
176  * device.   Filesystem data as well as the underlying block
177  * device.  Takes the superblock lock.
178  */
179 int fsync_bdev(struct block_device *bdev)
180 {
181         struct super_block *sb = get_super(bdev);
182         if (sb) {
183                 int res = fsync_super(sb);
184                 drop_super(sb);
185                 return res;
186         }
187         return sync_blockdev(bdev);
188 }
189
190 /**
191  * freeze_bdev  --  lock a filesystem and force it into a consistent state
192  * @bdev:       blockdevice to lock
193  *
194  * This takes the block device bd_mount_sem to make sure no new mounts
195  * happen on bdev until thaw_bdev() is called.
196  * If a superblock is found on this device, we take the s_umount semaphore
197  * on it to make sure nobody unmounts until the snapshot creation is done.
198  */
199 struct super_block *freeze_bdev(struct block_device *bdev)
200 {
201         struct super_block *sb;
202
203         down(&bdev->bd_mount_sem);
204         sb = get_super(bdev);
205         if (sb && !(sb->s_flags & MS_RDONLY)) {
206                 sb->s_frozen = SB_FREEZE_WRITE;
207                 smp_wmb();
208
209                 __fsync_super(sb);
210
211                 sb->s_frozen = SB_FREEZE_TRANS;
212                 smp_wmb();
213
214                 sync_blockdev(sb->s_bdev);
215
216                 if (sb->s_op->write_super_lockfs)
217                         sb->s_op->write_super_lockfs(sb);
218         }
219
220         sync_blockdev(bdev);
221         return sb;      /* thaw_bdev releases s->s_umount and bd_mount_sem */
222 }
223 EXPORT_SYMBOL(freeze_bdev);
224
225 /**
226  * thaw_bdev  -- unlock filesystem
227  * @bdev:       blockdevice to unlock
228  * @sb:         associated superblock
229  *
230  * Unlocks the filesystem and marks it writeable again after freeze_bdev().
231  */
232 void thaw_bdev(struct block_device *bdev, struct super_block *sb)
233 {
234         if (sb) {
235                 BUG_ON(sb->s_bdev != bdev);
236
237                 if (sb->s_op->unlockfs)
238                         sb->s_op->unlockfs(sb);
239                 sb->s_frozen = SB_UNFROZEN;
240                 smp_wmb();
241                 wake_up(&sb->s_wait_unfrozen);
242                 drop_super(sb);
243         }
244
245         up(&bdev->bd_mount_sem);
246 }
247 EXPORT_SYMBOL(thaw_bdev);
248
249 /*
250  * Various filesystems appear to want __find_get_block to be non-blocking.
251  * But it's the page lock which protects the buffers.  To get around this,
252  * we get exclusion from try_to_free_buffers with the blockdev mapping's
253  * private_lock.
254  *
255  * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
256  * may be quite high.  This code could TryLock the page, and if that
257  * succeeds, there is no need to take private_lock. (But if
258  * private_lock is contended then so is mapping->tree_lock).
259  */
260 static struct buffer_head *
261 __find_get_block_slow(struct block_device *bdev, sector_t block)
262 {
263         struct inode *bd_inode = bdev->bd_inode;
264         struct address_space *bd_mapping = bd_inode->i_mapping;
265         struct buffer_head *ret = NULL;
266         pgoff_t index;
267         struct buffer_head *bh;
268         struct buffer_head *head;
269         struct page *page;
270         int all_mapped = 1;
271
272         index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
273         page = find_get_page(bd_mapping, index);
274         if (!page)
275                 goto out;
276
277         spin_lock(&bd_mapping->private_lock);
278         if (!page_has_buffers(page))
279                 goto out_unlock;
280         head = page_buffers(page);
281         bh = head;
282         do {
283                 if (bh->b_blocknr == block) {
284                         ret = bh;
285                         get_bh(bh);
286                         goto out_unlock;
287                 }
288                 if (!buffer_mapped(bh))
289                         all_mapped = 0;
290                 bh = bh->b_this_page;
291         } while (bh != head);
292
293         /* we might be here because some of the buffers on this page are
294          * not mapped.  This is due to various races between
295          * file io on the block device and getblk.  It gets dealt with
296          * elsewhere, don't buffer_error if we had some unmapped buffers
297          */
298         if (all_mapped) {
299                 printk("__find_get_block_slow() failed. "
300                         "block=%llu, b_blocknr=%llu\n",
301                         (unsigned long long)block,
302                         (unsigned long long)bh->b_blocknr);
303                 printk("b_state=0x%08lx, b_size=%zu\n",
304                         bh->b_state, bh->b_size);
305                 printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits);
306         }
307 out_unlock:
308         spin_unlock(&bd_mapping->private_lock);
309         page_cache_release(page);
310 out:
311         return ret;
312 }
313
314 /* If invalidate_buffers() will trash dirty buffers, it means some kind
315    of fs corruption is going on. Trashing dirty data always imply losing
316    information that was supposed to be just stored on the physical layer
317    by the user.
318
319    Thus invalidate_buffers in general usage is not allwowed to trash
320    dirty buffers. For example ioctl(FLSBLKBUF) expects dirty data to
321    be preserved.  These buffers are simply skipped.
322   
323    We also skip buffers which are still in use.  For example this can
324    happen if a userspace program is reading the block device.
325
326    NOTE: In the case where the user removed a removable-media-disk even if
327    there's still dirty data not synced on disk (due a bug in the device driver
328    or due an error of the user), by not destroying the dirty buffers we could
329    generate corruption also on the next media inserted, thus a parameter is
330    necessary to handle this case in the most safe way possible (trying
331    to not corrupt also the new disk inserted with the data belonging to
332    the old now corrupted disk). Also for the ramdisk the natural thing
333    to do in order to release the ramdisk memory is to destroy dirty buffers.
334
335    These are two special cases. Normal usage imply the device driver
336    to issue a sync on the device (without waiting I/O completion) and
337    then an invalidate_buffers call that doesn't trash dirty buffers.
338
339    For handling cache coherency with the blkdev pagecache the 'update' case
340    is been introduced. It is needed to re-read from disk any pinned
341    buffer. NOTE: re-reading from disk is destructive so we can do it only
342    when we assume nobody is changing the buffercache under our I/O and when
343    we think the disk contains more recent information than the buffercache.
344    The update == 1 pass marks the buffers we need to update, the update == 2
345    pass does the actual I/O. */
346 void invalidate_bdev(struct block_device *bdev)
347 {
348         struct address_space *mapping = bdev->bd_inode->i_mapping;
349
350         if (mapping->nrpages == 0)
351                 return;
352
353         invalidate_bh_lrus();
354         invalidate_mapping_pages(mapping, 0, -1);
355 }
356
357 /*
358  * Kick pdflush then try to free up some ZONE_NORMAL memory.
359  */
360 static void free_more_memory(void)
361 {
362         struct zone *zone;
363         int nid;
364
365         wakeup_pdflush(1024);
366         yield();
367
368         for_each_online_node(nid) {
369                 (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS),
370                                                 gfp_zone(GFP_NOFS), NULL,
371                                                 &zone);
372                 if (zone)
373                         try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0,
374                                                 GFP_NOFS);
375         }
376 }
377
378 /*
379  * I/O completion handler for block_read_full_page() - pages
380  * which come unlocked at the end of I/O.
381  */
382 static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
383 {
384         unsigned long flags;
385         struct buffer_head *first;
386         struct buffer_head *tmp;
387         struct page *page;
388         int page_uptodate = 1;
389
390         BUG_ON(!buffer_async_read(bh));
391
392         page = bh->b_page;
393         if (uptodate) {
394                 set_buffer_uptodate(bh);
395         } else {
396                 clear_buffer_uptodate(bh);
397                 if (printk_ratelimit())
398                         buffer_io_error(bh);
399                 SetPageError(page);
400         }
401
402         /*
403          * Be _very_ careful from here on. Bad things can happen if
404          * two buffer heads end IO at almost the same time and both
405          * decide that the page is now completely done.
406          */
407         first = page_buffers(page);
408         local_irq_save(flags);
409         bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
410         clear_buffer_async_read(bh);
411         unlock_buffer(bh);
412         tmp = bh;
413         do {
414                 if (!buffer_uptodate(tmp))
415                         page_uptodate = 0;
416                 if (buffer_async_read(tmp)) {
417                         BUG_ON(!buffer_locked(tmp));
418                         goto still_busy;
419                 }
420                 tmp = tmp->b_this_page;
421         } while (tmp != bh);
422         bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
423         local_irq_restore(flags);
424
425         /*
426          * If none of the buffers had errors and they are all
427          * uptodate then we can set the page uptodate.
428          */
429         if (page_uptodate && !PageError(page))
430                 SetPageUptodate(page);
431         unlock_page(page);
432         return;
433
434 still_busy:
435         bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
436         local_irq_restore(flags);
437         return;
438 }
439
440 /*
441  * Completion handler for block_write_full_page() - pages which are unlocked
442  * during I/O, and which have PageWriteback cleared upon I/O completion.
443  */
444 static void end_buffer_async_write(struct buffer_head *bh, int uptodate)
445 {
446         char b[BDEVNAME_SIZE];
447         unsigned long flags;
448         struct buffer_head *first;
449         struct buffer_head *tmp;
450         struct page *page;
451
452         BUG_ON(!buffer_async_write(bh));
453
454         page = bh->b_page;
455         if (uptodate) {
456                 set_buffer_uptodate(bh);
457         } else {
458                 if (printk_ratelimit()) {
459                         buffer_io_error(bh);
460                         printk(KERN_WARNING "lost page write due to "
461                                         "I/O error on %s\n",
462                                bdevname(bh->b_bdev, b));
463                 }
464                 set_bit(AS_EIO, &page->mapping->flags);
465                 set_buffer_write_io_error(bh);
466                 clear_buffer_uptodate(bh);
467                 SetPageError(page);
468         }
469
470         first = page_buffers(page);
471         local_irq_save(flags);
472         bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
473
474         clear_buffer_async_write(bh);
475         unlock_buffer(bh);
476         tmp = bh->b_this_page;
477         while (tmp != bh) {
478                 if (buffer_async_write(tmp)) {
479                         BUG_ON(!buffer_locked(tmp));
480                         goto still_busy;
481                 }
482                 tmp = tmp->b_this_page;
483         }
484         bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
485         local_irq_restore(flags);
486         end_page_writeback(page);
487         return;
488
489 still_busy:
490         bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
491         local_irq_restore(flags);
492         return;
493 }
494
495 /*
496  * If a page's buffers are under async readin (end_buffer_async_read
497  * completion) then there is a possibility that another thread of
498  * control could lock one of the buffers after it has completed
499  * but while some of the other buffers have not completed.  This
500  * locked buffer would confuse end_buffer_async_read() into not unlocking
501  * the page.  So the absence of BH_Async_Read tells end_buffer_async_read()
502  * that this buffer is not under async I/O.
503  *
504  * The page comes unlocked when it has no locked buffer_async buffers
505  * left.
506  *
507  * PageLocked prevents anyone starting new async I/O reads any of
508  * the buffers.
509  *
510  * PageWriteback is used to prevent simultaneous writeout of the same
511  * page.
512  *
513  * PageLocked prevents anyone from starting writeback of a page which is
514  * under read I/O (PageWriteback is only ever set against a locked page).
515  */
516 static void mark_buffer_async_read(struct buffer_head *bh)
517 {
518         bh->b_end_io = end_buffer_async_read;
519         set_buffer_async_read(bh);
520 }
521
522 void mark_buffer_async_write(struct buffer_head *bh)
523 {
524         bh->b_end_io = end_buffer_async_write;
525         set_buffer_async_write(bh);
526 }
527 EXPORT_SYMBOL(mark_buffer_async_write);
528
529
530 /*
531  * fs/buffer.c contains helper functions for buffer-backed address space's
532  * fsync functions.  A common requirement for buffer-based filesystems is
533  * that certain data from the backing blockdev needs to be written out for
534  * a successful fsync().  For example, ext2 indirect blocks need to be
535  * written back and waited upon before fsync() returns.
536  *
537  * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
538  * inode_has_buffers() and invalidate_inode_buffers() are provided for the
539  * management of a list of dependent buffers at ->i_mapping->private_list.
540  *
541  * Locking is a little subtle: try_to_free_buffers() will remove buffers
542  * from their controlling inode's queue when they are being freed.  But
543  * try_to_free_buffers() will be operating against the *blockdev* mapping
544  * at the time, not against the S_ISREG file which depends on those buffers.
545  * So the locking for private_list is via the private_lock in the address_space
546  * which backs the buffers.  Which is different from the address_space 
547  * against which the buffers are listed.  So for a particular address_space,
548  * mapping->private_lock does *not* protect mapping->private_list!  In fact,
549  * mapping->private_list will always be protected by the backing blockdev's
550  * ->private_lock.
551  *
552  * Which introduces a requirement: all buffers on an address_space's
553  * ->private_list must be from the same address_space: the blockdev's.
554  *
555  * address_spaces which do not place buffers at ->private_list via these
556  * utility functions are free to use private_lock and private_list for
557  * whatever they want.  The only requirement is that list_empty(private_list)
558  * be true at clear_inode() time.
559  *
560  * FIXME: clear_inode should not call invalidate_inode_buffers().  The
561  * filesystems should do that.  invalidate_inode_buffers() should just go
562  * BUG_ON(!list_empty).
563  *
564  * FIXME: mark_buffer_dirty_inode() is a data-plane operation.  It should
565  * take an address_space, not an inode.  And it should be called
566  * mark_buffer_dirty_fsync() to clearly define why those buffers are being
567  * queued up.
568  *
569  * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
570  * list if it is already on a list.  Because if the buffer is on a list,
571  * it *must* already be on the right one.  If not, the filesystem is being
572  * silly.  This will save a ton of locking.  But first we have to ensure
573  * that buffers are taken *off* the old inode's list when they are freed
574  * (presumably in truncate).  That requires careful auditing of all
575  * filesystems (do it inside bforget()).  It could also be done by bringing
576  * b_inode back.
577  */
578
579 /*
580  * The buffer's backing address_space's private_lock must be held
581  */
582 static void __remove_assoc_queue(struct buffer_head *bh)
583 {
584         list_del_init(&bh->b_assoc_buffers);
585         WARN_ON(!bh->b_assoc_map);
586         if (buffer_write_io_error(bh))
587                 set_bit(AS_EIO, &bh->b_assoc_map->flags);
588         bh->b_assoc_map = NULL;
589 }
590
591 int inode_has_buffers(struct inode *inode)
592 {
593         return !list_empty(&inode->i_data.private_list);
594 }
595
596 /*
597  * osync is designed to support O_SYNC io.  It waits synchronously for
598  * all already-submitted IO to complete, but does not queue any new
599  * writes to the disk.
600  *
601  * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
602  * you dirty the buffers, and then use osync_inode_buffers to wait for
603  * completion.  Any other dirty buffers which are not yet queued for
604  * write will not be flushed to disk by the osync.
605  */
606 static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
607 {
608         struct buffer_head *bh;
609         struct list_head *p;
610         int err = 0;
611
612         spin_lock(lock);
613 repeat:
614         list_for_each_prev(p, list) {
615                 bh = BH_ENTRY(p);
616                 if (buffer_locked(bh)) {
617                         get_bh(bh);
618                         spin_unlock(lock);
619                         wait_on_buffer(bh);
620                         if (!buffer_uptodate(bh))
621                                 err = -EIO;
622                         brelse(bh);
623                         spin_lock(lock);
624                         goto repeat;
625                 }
626         }
627         spin_unlock(lock);
628         return err;
629 }
630
631 /**
632  * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
633  * @mapping: the mapping which wants those buffers written
634  *
635  * Starts I/O against the buffers at mapping->private_list, and waits upon
636  * that I/O.
637  *
638  * Basically, this is a convenience function for fsync().
639  * @mapping is a file or directory which needs those buffers to be written for
640  * a successful fsync().
641  */
642 int sync_mapping_buffers(struct address_space *mapping)
643 {
644         struct address_space *buffer_mapping = mapping->assoc_mapping;
645
646         if (buffer_mapping == NULL || list_empty(&mapping->private_list))
647                 return 0;
648
649         return fsync_buffers_list(&buffer_mapping->private_lock,
650                                         &mapping->private_list);
651 }
652 EXPORT_SYMBOL(sync_mapping_buffers);
653
654 /*
655  * Called when we've recently written block `bblock', and it is known that
656  * `bblock' was for a buffer_boundary() buffer.  This means that the block at
657  * `bblock + 1' is probably a dirty indirect block.  Hunt it down and, if it's
658  * dirty, schedule it for IO.  So that indirects merge nicely with their data.
659  */
660 void write_boundary_block(struct block_device *bdev,
661                         sector_t bblock, unsigned blocksize)
662 {
663         struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
664         if (bh) {
665                 if (buffer_dirty(bh))
666                         ll_rw_block(WRITE, 1, &bh);
667                 put_bh(bh);
668         }
669 }
670
671 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
672 {
673         struct address_space *mapping = inode->i_mapping;
674         struct address_space *buffer_mapping = bh->b_page->mapping;
675
676         mark_buffer_dirty(bh);
677         if (!mapping->assoc_mapping) {
678                 mapping->assoc_mapping = buffer_mapping;
679         } else {
680                 BUG_ON(mapping->assoc_mapping != buffer_mapping);
681         }
682         if (!bh->b_assoc_map) {
683                 spin_lock(&buffer_mapping->private_lock);
684                 list_move_tail(&bh->b_assoc_buffers,
685                                 &mapping->private_list);
686                 bh->b_assoc_map = mapping;
687                 spin_unlock(&buffer_mapping->private_lock);
688         }
689 }
690 EXPORT_SYMBOL(mark_buffer_dirty_inode);
691
692 /*
693  * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
694  * dirty.
695  *
696  * If warn is true, then emit a warning if the page is not uptodate and has
697  * not been truncated.
698  */
699 static int __set_page_dirty(struct page *page,
700                 struct address_space *mapping, int warn)
701 {
702         if (unlikely(!mapping))
703                 return !TestSetPageDirty(page);
704
705         if (TestSetPageDirty(page))
706                 return 0;
707
708         spin_lock_irq(&mapping->tree_lock);
709         if (page->mapping) {    /* Race with truncate? */
710                 WARN_ON_ONCE(warn && !PageUptodate(page));
711
712                 if (mapping_cap_account_dirty(mapping)) {
713                         __inc_zone_page_state(page, NR_FILE_DIRTY);
714                         __inc_bdi_stat(mapping->backing_dev_info,
715                                         BDI_RECLAIMABLE);
716                         task_io_account_write(PAGE_CACHE_SIZE);
717                 }
718                 radix_tree_tag_set(&mapping->page_tree,
719                                 page_index(page), PAGECACHE_TAG_DIRTY);
720         }
721         spin_unlock_irq(&mapping->tree_lock);
722         __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
723
724         return 1;
725 }
726
727 /*
728  * Add a page to the dirty page list.
729  *
730  * It is a sad fact of life that this function is called from several places
731  * deeply under spinlocking.  It may not sleep.
732  *
733  * If the page has buffers, the uptodate buffers are set dirty, to preserve
734  * dirty-state coherency between the page and the buffers.  It the page does
735  * not have buffers then when they are later attached they will all be set
736  * dirty.
737  *
738  * The buffers are dirtied before the page is dirtied.  There's a small race
739  * window in which a writepage caller may see the page cleanness but not the
740  * buffer dirtiness.  That's fine.  If this code were to set the page dirty
741  * before the buffers, a concurrent writepage caller could clear the page dirty
742  * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
743  * page on the dirty page list.
744  *
745  * We use private_lock to lock against try_to_free_buffers while using the
746  * page's buffer list.  Also use this to protect against clean buffers being
747  * added to the page after it was set dirty.
748  *
749  * FIXME: may need to call ->reservepage here as well.  That's rather up to the
750  * address_space though.
751  */
752 int __set_page_dirty_buffers(struct page *page)
753 {
754         struct address_space *mapping = page_mapping(page);
755
756         if (unlikely(!mapping))
757                 return !TestSetPageDirty(page);
758
759         spin_lock(&mapping->private_lock);
760         if (page_has_buffers(page)) {
761                 struct buffer_head *head = page_buffers(page);
762                 struct buffer_head *bh = head;
763
764                 do {
765                         set_buffer_dirty(bh);
766                         bh = bh->b_this_page;
767                 } while (bh != head);
768         }
769         spin_unlock(&mapping->private_lock);
770
771         return __set_page_dirty(page, mapping, 1);
772 }
773 EXPORT_SYMBOL(__set_page_dirty_buffers);
774
775 /*
776  * Write out and wait upon a list of buffers.
777  *
778  * We have conflicting pressures: we want to make sure that all
779  * initially dirty buffers get waited on, but that any subsequently
780  * dirtied buffers don't.  After all, we don't want fsync to last
781  * forever if somebody is actively writing to the file.
782  *
783  * Do this in two main stages: first we copy dirty buffers to a
784  * temporary inode list, queueing the writes as we go.  Then we clean
785  * up, waiting for those writes to complete.
786  * 
787  * During this second stage, any subsequent updates to the file may end
788  * up refiling the buffer on the original inode's dirty list again, so
789  * there is a chance we will end up with a buffer queued for write but
790  * not yet completed on that list.  So, as a final cleanup we go through
791  * the osync code to catch these locked, dirty buffers without requeuing
792  * any newly dirty buffers for write.
793  */
794 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
795 {
796         struct buffer_head *bh;
797         struct list_head tmp;
798         struct address_space *mapping;
799         int err = 0, err2;
800
801         INIT_LIST_HEAD(&tmp);
802
803         spin_lock(lock);
804         while (!list_empty(list)) {
805                 bh = BH_ENTRY(list->next);
806                 mapping = bh->b_assoc_map;
807                 __remove_assoc_queue(bh);
808                 /* Avoid race with mark_buffer_dirty_inode() which does
809                  * a lockless check and we rely on seeing the dirty bit */
810                 smp_mb();
811                 if (buffer_dirty(bh) || buffer_locked(bh)) {
812                         list_add(&bh->b_assoc_buffers, &tmp);
813                         bh->b_assoc_map = mapping;
814                         if (buffer_dirty(bh)) {
815                                 get_bh(bh);
816                                 spin_unlock(lock);
817                                 /*
818                                  * Ensure any pending I/O completes so that
819                                  * ll_rw_block() actually writes the current
820                                  * contents - it is a noop if I/O is still in
821                                  * flight on potentially older contents.
822                                  */
823                                 ll_rw_block(SWRITE_SYNC, 1, &bh);
824                                 brelse(bh);
825                                 spin_lock(lock);
826                         }
827                 }
828         }
829
830         while (!list_empty(&tmp)) {
831                 bh = BH_ENTRY(tmp.prev);
832                 get_bh(bh);
833                 mapping = bh->b_assoc_map;
834                 __remove_assoc_queue(bh);
835                 /* Avoid race with mark_buffer_dirty_inode() which does
836                  * a lockless check and we rely on seeing the dirty bit */
837                 smp_mb();
838                 if (buffer_dirty(bh)) {
839                         list_add(&bh->b_assoc_buffers,
840                                  &mapping->private_list);
841                         bh->b_assoc_map = mapping;
842                 }
843                 spin_unlock(lock);
844                 wait_on_buffer(bh);
845                 if (!buffer_uptodate(bh))
846                         err = -EIO;
847                 brelse(bh);
848                 spin_lock(lock);
849         }
850         
851         spin_unlock(lock);
852         err2 = osync_buffers_list(lock, list);
853         if (err)
854                 return err;
855         else
856                 return err2;
857 }
858
859 /*
860  * Invalidate any and all dirty buffers on a given inode.  We are
861  * probably unmounting the fs, but that doesn't mean we have already
862  * done a sync().  Just drop the buffers from the inode list.
863  *
864  * NOTE: we take the inode's blockdev's mapping's private_lock.  Which
865  * assumes that all the buffers are against the blockdev.  Not true
866  * for reiserfs.
867  */
868 void invalidate_inode_buffers(struct inode *inode)
869 {
870         if (inode_has_buffers(inode)) {
871                 struct address_space *mapping = &inode->i_data;
872                 struct list_head *list = &mapping->private_list;
873                 struct address_space *buffer_mapping = mapping->assoc_mapping;
874
875                 spin_lock(&buffer_mapping->private_lock);
876                 while (!list_empty(list))
877                         __remove_assoc_queue(BH_ENTRY(list->next));
878                 spin_unlock(&buffer_mapping->private_lock);
879         }
880 }
881 EXPORT_SYMBOL(invalidate_inode_buffers);
882
883 /*
884  * Remove any clean buffers from the inode's buffer list.  This is called
885  * when we're trying to free the inode itself.  Those buffers can pin it.
886  *
887  * Returns true if all buffers were removed.
888  */
889 int remove_inode_buffers(struct inode *inode)
890 {
891         int ret = 1;
892
893         if (inode_has_buffers(inode)) {
894                 struct address_space *mapping = &inode->i_data;
895                 struct list_head *list = &mapping->private_list;
896                 struct address_space *buffer_mapping = mapping->assoc_mapping;
897
898                 spin_lock(&buffer_mapping->private_lock);
899                 while (!list_empty(list)) {
900                         struct buffer_head *bh = BH_ENTRY(list->next);
901                         if (buffer_dirty(bh)) {
902                                 ret = 0;
903                                 break;
904                         }
905                         __remove_assoc_queue(bh);
906                 }
907                 spin_unlock(&buffer_mapping->private_lock);
908         }
909         return ret;
910 }
911
912 /*
913  * Create the appropriate buffers when given a page for data area and
914  * the size of each buffer.. Use the bh->b_this_page linked list to
915  * follow the buffers created.  Return NULL if unable to create more
916  * buffers.
917  *
918  * The retry flag is used to differentiate async IO (paging, swapping)
919  * which may not fail from ordinary buffer allocations.
920  */
921 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
922                 int retry)
923 {
924         struct buffer_head *bh, *head;
925         long offset;
926
927 try_again:
928         head = NULL;
929         offset = PAGE_SIZE;
930         while ((offset -= size) >= 0) {
931                 bh = alloc_buffer_head(GFP_NOFS);
932                 if (!bh)
933                         goto no_grow;
934
935                 bh->b_bdev = NULL;
936                 bh->b_this_page = head;
937                 bh->b_blocknr = -1;
938                 head = bh;
939
940                 bh->b_state = 0;
941                 atomic_set(&bh->b_count, 0);
942                 bh->b_private = NULL;
943                 bh->b_size = size;
944
945                 /* Link the buffer to its page */
946                 set_bh_page(bh, page, offset);
947
948                 init_buffer(bh, NULL, NULL);
949         }
950         return head;
951 /*
952  * In case anything failed, we just free everything we got.
953  */
954 no_grow:
955         if (head) {
956                 do {
957                         bh = head;
958                         head = head->b_this_page;
959                         free_buffer_head(bh);
960                 } while (head);
961         }
962
963         /*
964          * Return failure for non-async IO requests.  Async IO requests
965          * are not allowed to fail, so we have to wait until buffer heads
966          * become available.  But we don't want tasks sleeping with 
967          * partially complete buffers, so all were released above.
968          */
969         if (!retry)
970                 return NULL;
971
972         /* We're _really_ low on memory. Now we just
973          * wait for old buffer heads to become free due to
974          * finishing IO.  Since this is an async request and
975          * the reserve list is empty, we're sure there are 
976          * async buffer heads in use.
977          */
978         free_more_memory();
979         goto try_again;
980 }
981 EXPORT_SYMBOL_GPL(alloc_page_buffers);
982
983 static inline void
984 link_dev_buffers(struct page *page, struct buffer_head *head)
985 {
986         struct buffer_head *bh, *tail;
987
988         bh = head;
989         do {
990                 tail = bh;
991                 bh = bh->b_this_page;
992         } while (bh);
993         tail->b_this_page = head;
994         attach_page_buffers(page, head);
995 }
996
997 /*
998  * Initialise the state of a blockdev page's buffers.
999  */ 
1000 static void
1001 init_page_buffers(struct page *page, struct block_device *bdev,
1002                         sector_t block, int size)
1003 {
1004         struct buffer_head *head = page_buffers(page);
1005         struct buffer_head *bh = head;
1006         int uptodate = PageUptodate(page);
1007
1008         do {
1009                 if (!buffer_mapped(bh)) {
1010                         init_buffer(bh, NULL, NULL);
1011                         bh->b_bdev = bdev;
1012                         bh->b_blocknr = block;
1013                         if (uptodate)
1014                                 set_buffer_uptodate(bh);
1015                         set_buffer_mapped(bh);
1016                 }
1017                 block++;
1018                 bh = bh->b_this_page;
1019         } while (bh != head);
1020 }
1021
1022 /*
1023  * Create the page-cache page that contains the requested block.
1024  *
1025  * This is user purely for blockdev mappings.
1026  */
1027 static struct page *
1028 grow_dev_page(struct block_device *bdev, sector_t block,
1029                 pgoff_t index, int size)
1030 {
1031         struct inode *inode = bdev->bd_inode;
1032         struct page *page;
1033         struct buffer_head *bh;
1034
1035         page = find_or_create_page(inode->i_mapping, index,
1036                 (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE);
1037         if (!page)
1038                 return NULL;
1039
1040         BUG_ON(!PageLocked(page));
1041
1042         if (page_has_buffers(page)) {
1043                 bh = page_buffers(page);
1044                 if (bh->b_size == size) {
1045                         init_page_buffers(page, bdev, block, size);
1046                         return page;
1047                 }
1048                 if (!try_to_free_buffers(page))
1049                         goto failed;
1050         }
1051
1052         /*
1053          * Allocate some buffers for this page
1054          */
1055         bh = alloc_page_buffers(page, size, 0);
1056         if (!bh)
1057                 goto failed;
1058
1059         /*
1060          * Link the page to the buffers and initialise them.  Take the
1061          * lock to be atomic wrt __find_get_block(), which does not
1062          * run under the page lock.
1063          */
1064         spin_lock(&inode->i_mapping->private_lock);
1065         link_dev_buffers(page, bh);
1066         init_page_buffers(page, bdev, block, size);
1067         spin_unlock(&inode->i_mapping->private_lock);
1068         return page;
1069
1070 failed:
1071         BUG();
1072         unlock_page(page);
1073         page_cache_release(page);
1074         return NULL;
1075 }
1076
1077 /*
1078  * Create buffers for the specified block device block's page.  If
1079  * that page was dirty, the buffers are set dirty also.
1080  */
1081 static int
1082 grow_buffers(struct block_device *bdev, sector_t block, int size)
1083 {
1084         struct page *page;
1085         pgoff_t index;
1086         int sizebits;
1087
1088         sizebits = -1;
1089         do {
1090                 sizebits++;
1091         } while ((size << sizebits) < PAGE_SIZE);
1092
1093         index = block >> sizebits;
1094
1095         /*
1096          * Check for a block which wants to lie outside our maximum possible
1097          * pagecache index.  (this comparison is done using sector_t types).
1098          */
1099         if (unlikely(index != block >> sizebits)) {
1100                 char b[BDEVNAME_SIZE];
1101
1102                 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1103                         "device %s\n",
1104                         __func__, (unsigned long long)block,
1105                         bdevname(bdev, b));
1106                 return -EIO;
1107         }
1108         block = index << sizebits;
1109         /* Create a page with the proper size buffers.. */
1110         page = grow_dev_page(bdev, block, index, size);
1111         if (!page)
1112                 return 0;
1113         unlock_page(page);
1114         page_cache_release(page);
1115         return 1;
1116 }
1117
1118 static struct buffer_head *
1119 __getblk_slow(struct block_device *bdev, sector_t block, int size)
1120 {
1121         /* Size must be multiple of hard sectorsize */
1122         if (unlikely(size & (bdev_hardsect_size(bdev)-1) ||
1123                         (size < 512 || size > PAGE_SIZE))) {
1124                 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1125                                         size);
1126                 printk(KERN_ERR "hardsect size: %d\n",
1127                                         bdev_hardsect_size(bdev));
1128
1129                 dump_stack();
1130                 return NULL;
1131         }
1132
1133         for (;;) {
1134                 struct buffer_head * bh;
1135                 int ret;
1136
1137                 bh = __find_get_block(bdev, block, size);
1138                 if (bh)
1139                         return bh;
1140
1141                 ret = grow_buffers(bdev, block, size);
1142                 if (ret < 0)
1143                         return NULL;
1144                 if (ret == 0)
1145                         free_more_memory();
1146         }
1147 }
1148
1149 /*
1150  * The relationship between dirty buffers and dirty pages:
1151  *
1152  * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1153  * the page is tagged dirty in its radix tree.
1154  *
1155  * At all times, the dirtiness of the buffers represents the dirtiness of
1156  * subsections of the page.  If the page has buffers, the page dirty bit is
1157  * merely a hint about the true dirty state.
1158  *
1159  * When a page is set dirty in its entirety, all its buffers are marked dirty
1160  * (if the page has buffers).
1161  *
1162  * When a buffer is marked dirty, its page is dirtied, but the page's other
1163  * buffers are not.
1164  *
1165  * Also.  When blockdev buffers are explicitly read with bread(), they
1166  * individually become uptodate.  But their backing page remains not
1167  * uptodate - even if all of its buffers are uptodate.  A subsequent
1168  * block_read_full_page() against that page will discover all the uptodate
1169  * buffers, will set the page uptodate and will perform no I/O.
1170  */
1171
1172 /**
1173  * mark_buffer_dirty - mark a buffer_head as needing writeout
1174  * @bh: the buffer_head to mark dirty
1175  *
1176  * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1177  * backing page dirty, then tag the page as dirty in its address_space's radix
1178  * tree and then attach the address_space's inode to its superblock's dirty
1179  * inode list.
1180  *
1181  * mark_buffer_dirty() is atomic.  It takes bh->b_page->mapping->private_lock,
1182  * mapping->tree_lock and the global inode_lock.
1183  */
1184 void mark_buffer_dirty(struct buffer_head *bh)
1185 {
1186         WARN_ON_ONCE(!buffer_uptodate(bh));
1187
1188         /*
1189          * Very *carefully* optimize the it-is-already-dirty case.
1190          *
1191          * Don't let the final "is it dirty" escape to before we
1192          * perhaps modified the buffer.
1193          */
1194         if (buffer_dirty(bh)) {
1195                 smp_mb();
1196                 if (buffer_dirty(bh))
1197                         return;
1198         }
1199
1200         if (!test_set_buffer_dirty(bh))
1201                 __set_page_dirty(bh->b_page, page_mapping(bh->b_page), 0);
1202 }
1203
1204 /*
1205  * Decrement a buffer_head's reference count.  If all buffers against a page
1206  * have zero reference count, are clean and unlocked, and if the page is clean
1207  * and unlocked then try_to_free_buffers() may strip the buffers from the page
1208  * in preparation for freeing it (sometimes, rarely, buffers are removed from
1209  * a page but it ends up not being freed, and buffers may later be reattached).
1210  */
1211 void __brelse(struct buffer_head * buf)
1212 {
1213         if (atomic_read(&buf->b_count)) {
1214                 put_bh(buf);
1215                 return;
1216         }
1217         WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1218 }
1219
1220 /*
1221  * bforget() is like brelse(), except it discards any
1222  * potentially dirty data.
1223  */
1224 void __bforget(struct buffer_head *bh)
1225 {
1226         clear_buffer_dirty(bh);
1227         if (bh->b_assoc_map) {
1228                 struct address_space *buffer_mapping = bh->b_page->mapping;
1229
1230                 spin_lock(&buffer_mapping->private_lock);
1231                 list_del_init(&bh->b_assoc_buffers);
1232                 bh->b_assoc_map = NULL;
1233                 spin_unlock(&buffer_mapping->private_lock);
1234         }
1235         __brelse(bh);
1236 }
1237
1238 static struct buffer_head *__bread_slow(struct buffer_head *bh)
1239 {
1240         lock_buffer(bh);
1241         if (buffer_uptodate(bh)) {
1242                 unlock_buffer(bh);
1243                 return bh;
1244         } else {
1245                 get_bh(bh);
1246                 bh->b_end_io = end_buffer_read_sync;
1247                 submit_bh(READ, bh);
1248                 wait_on_buffer(bh);
1249                 if (buffer_uptodate(bh))
1250                         return bh;
1251         }
1252         brelse(bh);
1253         return NULL;
1254 }
1255
1256 /*
1257  * Per-cpu buffer LRU implementation.  To reduce the cost of __find_get_block().
1258  * The bhs[] array is sorted - newest buffer is at bhs[0].  Buffers have their
1259  * refcount elevated by one when they're in an LRU.  A buffer can only appear
1260  * once in a particular CPU's LRU.  A single buffer can be present in multiple
1261  * CPU's LRUs at the same time.
1262  *
1263  * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1264  * sb_find_get_block().
1265  *
1266  * The LRUs themselves only need locking against invalidate_bh_lrus.  We use
1267  * a local interrupt disable for that.
1268  */
1269
1270 #define BH_LRU_SIZE     8
1271
1272 struct bh_lru {
1273         struct buffer_head *bhs[BH_LRU_SIZE];
1274 };
1275
1276 static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1277
1278 #ifdef CONFIG_SMP
1279 #define bh_lru_lock()   local_irq_disable()
1280 #define bh_lru_unlock() local_irq_enable()
1281 #else
1282 #define bh_lru_lock()   preempt_disable()
1283 #define bh_lru_unlock() preempt_enable()
1284 #endif
1285
1286 static inline void check_irqs_on(void)
1287 {
1288 #ifdef irqs_disabled
1289         BUG_ON(irqs_disabled());
1290 #endif
1291 }
1292
1293 /*
1294  * The LRU management algorithm is dopey-but-simple.  Sorry.
1295  */
1296 static void bh_lru_install(struct buffer_head *bh)
1297 {
1298         struct buffer_head *evictee = NULL;
1299         struct bh_lru *lru;
1300
1301         check_irqs_on();
1302         bh_lru_lock();
1303         lru = &__get_cpu_var(bh_lrus);
1304         if (lru->bhs[0] != bh) {
1305                 struct buffer_head *bhs[BH_LRU_SIZE];
1306                 int in;
1307                 int out = 0;
1308
1309                 get_bh(bh);
1310                 bhs[out++] = bh;
1311                 for (in = 0; in < BH_LRU_SIZE; in++) {
1312                         struct buffer_head *bh2 = lru->bhs[in];
1313
1314                         if (bh2 == bh) {
1315                                 __brelse(bh2);
1316                         } else {
1317                                 if (out >= BH_LRU_SIZE) {
1318                                         BUG_ON(evictee != NULL);
1319                                         evictee = bh2;
1320                                 } else {
1321                                         bhs[out++] = bh2;
1322                                 }
1323                         }
1324                 }
1325                 while (out < BH_LRU_SIZE)
1326                         bhs[out++] = NULL;
1327                 memcpy(lru->bhs, bhs, sizeof(bhs));
1328         }
1329         bh_lru_unlock();
1330
1331         if (evictee)
1332                 __brelse(evictee);
1333 }
1334
1335 /*
1336  * Look up the bh in this cpu's LRU.  If it's there, move it to the head.
1337  */
1338 static struct buffer_head *
1339 lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1340 {
1341         struct buffer_head *ret = NULL;
1342         struct bh_lru *lru;
1343         unsigned int i;
1344
1345         check_irqs_on();
1346         bh_lru_lock();
1347         lru = &__get_cpu_var(bh_lrus);
1348         for (i = 0; i < BH_LRU_SIZE; i++) {
1349                 struct buffer_head *bh = lru->bhs[i];
1350
1351                 if (bh && bh->b_bdev == bdev &&
1352                                 bh->b_blocknr == block && bh->b_size == size) {
1353                         if (i) {
1354                                 while (i) {
1355                                         lru->bhs[i] = lru->bhs[i - 1];
1356                                         i--;
1357                                 }
1358                                 lru->bhs[0] = bh;
1359                         }
1360                         get_bh(bh);
1361                         ret = bh;
1362                         break;
1363                 }
1364         }
1365         bh_lru_unlock();
1366         return ret;
1367 }
1368
1369 /*
1370  * Perform a pagecache lookup for the matching buffer.  If it's there, refresh
1371  * it in the LRU and mark it as accessed.  If it is not present then return
1372  * NULL
1373  */
1374 struct buffer_head *
1375 __find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1376 {
1377         struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1378
1379         if (bh == NULL) {
1380                 bh = __find_get_block_slow(bdev, block);
1381                 if (bh)
1382                         bh_lru_install(bh);
1383         }
1384         if (bh)
1385                 touch_buffer(bh);
1386         return bh;
1387 }
1388 EXPORT_SYMBOL(__find_get_block);
1389
1390 /*
1391  * __getblk will locate (and, if necessary, create) the buffer_head
1392  * which corresponds to the passed block_device, block and size. The
1393  * returned buffer has its reference count incremented.
1394  *
1395  * __getblk() cannot fail - it just keeps trying.  If you pass it an
1396  * illegal block number, __getblk() will happily return a buffer_head
1397  * which represents the non-existent block.  Very weird.
1398  *
1399  * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1400  * attempt is failing.  FIXME, perhaps?
1401  */
1402 struct buffer_head *
1403 __getblk(struct block_device *bdev, sector_t block, unsigned size)
1404 {
1405         struct buffer_head *bh = __find_get_block(bdev, block, size);
1406
1407         might_sleep();
1408         if (bh == NULL)
1409                 bh = __getblk_slow(bdev, block, size);
1410         return bh;
1411 }
1412 EXPORT_SYMBOL(__getblk);
1413
1414 /*
1415  * Do async read-ahead on a buffer..
1416  */
1417 void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1418 {
1419         struct buffer_head *bh = __getblk(bdev, block, size);
1420         if (likely(bh)) {
1421                 ll_rw_block(READA, 1, &bh);
1422                 brelse(bh);
1423         }
1424 }
1425 EXPORT_SYMBOL(__breadahead);
1426
1427 /**
1428  *  __bread() - reads a specified block and returns the bh
1429  *  @bdev: the block_device to read from
1430  *  @block: number of block
1431  *  @size: size (in bytes) to read
1432  * 
1433  *  Reads a specified block, and returns buffer head that contains it.
1434  *  It returns NULL if the block was unreadable.
1435  */
1436 struct buffer_head *
1437 __bread(struct block_device *bdev, sector_t block, unsigned size)
1438 {
1439         struct buffer_head *bh = __getblk(bdev, block, size);
1440
1441         if (likely(bh) && !buffer_uptodate(bh))
1442                 bh = __bread_slow(bh);
1443         return bh;
1444 }
1445 EXPORT_SYMBOL(__bread);
1446
1447 /*
1448  * invalidate_bh_lrus() is called rarely - but not only at unmount.
1449  * This doesn't race because it runs in each cpu either in irq
1450  * or with preempt disabled.
1451  */
1452 static void invalidate_bh_lru(void *arg)
1453 {
1454         struct bh_lru *b = &get_cpu_var(bh_lrus);
1455         int i;
1456
1457         for (i = 0; i < BH_LRU_SIZE; i++) {
1458                 brelse(b->bhs[i]);
1459                 b->bhs[i] = NULL;
1460         }
1461         put_cpu_var(bh_lrus);
1462 }
1463         
1464 void invalidate_bh_lrus(void)
1465 {
1466         on_each_cpu(invalidate_bh_lru, NULL, 1);
1467 }
1468 EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1469
1470 void set_bh_page(struct buffer_head *bh,
1471                 struct page *page, unsigned long offset)
1472 {
1473         bh->b_page = page;
1474         BUG_ON(offset >= PAGE_SIZE);
1475         if (PageHighMem(page))
1476                 /*
1477                  * This catches illegal uses and preserves the offset:
1478                  */
1479                 bh->b_data = (char *)(0 + offset);
1480         else
1481                 bh->b_data = page_address(page) + offset;
1482 }
1483 EXPORT_SYMBOL(set_bh_page);
1484
1485 /*
1486  * Called when truncating a buffer on a page completely.
1487  */
1488 static void discard_buffer(struct buffer_head * bh)
1489 {
1490         lock_buffer(bh);
1491         clear_buffer_dirty(bh);
1492         bh->b_bdev = NULL;
1493         clear_buffer_mapped(bh);
1494         clear_buffer_req(bh);
1495         clear_buffer_new(bh);
1496         clear_buffer_delay(bh);
1497         clear_buffer_unwritten(bh);
1498         unlock_buffer(bh);
1499 }
1500
1501 /**
1502  * block_invalidatepage - invalidate part of all of a buffer-backed page
1503  *
1504  * @page: the page which is affected
1505  * @offset: the index of the truncation point
1506  *
1507  * block_invalidatepage() is called when all or part of the page has become
1508  * invalidatedby a truncate operation.
1509  *
1510  * block_invalidatepage() does not have to release all buffers, but it must
1511  * ensure that no dirty buffer is left outside @offset and that no I/O
1512  * is underway against any of the blocks which are outside the truncation
1513  * point.  Because the caller is about to free (and possibly reuse) those
1514  * blocks on-disk.
1515  */
1516 void block_invalidatepage(struct page *page, unsigned long offset)
1517 {
1518         struct buffer_head *head, *bh, *next;
1519         unsigned int curr_off = 0;
1520
1521         BUG_ON(!PageLocked(page));
1522         if (!page_has_buffers(page))
1523                 goto out;
1524
1525         head = page_buffers(page);
1526         bh = head;
1527         do {
1528                 unsigned int next_off = curr_off + bh->b_size;
1529                 next = bh->b_this_page;
1530
1531                 /*
1532                  * is this block fully invalidated?
1533                  */
1534                 if (offset <= curr_off)
1535                         discard_buffer(bh);
1536                 curr_off = next_off;
1537                 bh = next;
1538         } while (bh != head);
1539
1540         /*
1541          * We release buffers only if the entire page is being invalidated.
1542          * The get_block cached value has been unconditionally invalidated,
1543          * so real IO is not possible anymore.
1544          */
1545         if (offset == 0)
1546                 try_to_release_page(page, 0);
1547 out:
1548         return;
1549 }
1550 EXPORT_SYMBOL(block_invalidatepage);
1551
1552 /*
1553  * We attach and possibly dirty the buffers atomically wrt
1554  * __set_page_dirty_buffers() via private_lock.  try_to_free_buffers
1555  * is already excluded via the page lock.
1556  */
1557 void create_empty_buffers(struct page *page,
1558                         unsigned long blocksize, unsigned long b_state)
1559 {
1560         struct buffer_head *bh, *head, *tail;
1561
1562         head = alloc_page_buffers(page, blocksize, 1);
1563         bh = head;
1564         do {
1565                 bh->b_state |= b_state;
1566                 tail = bh;
1567                 bh = bh->b_this_page;
1568         } while (bh);
1569         tail->b_this_page = head;
1570
1571         spin_lock(&page->mapping->private_lock);
1572         if (PageUptodate(page) || PageDirty(page)) {
1573                 bh = head;
1574                 do {
1575                         if (PageDirty(page))
1576                                 set_buffer_dirty(bh);
1577                         if (PageUptodate(page))
1578                                 set_buffer_uptodate(bh);
1579                         bh = bh->b_this_page;
1580                 } while (bh != head);
1581         }
1582         attach_page_buffers(page, head);
1583         spin_unlock(&page->mapping->private_lock);
1584 }
1585 EXPORT_SYMBOL(create_empty_buffers);
1586
1587 /*
1588  * We are taking a block for data and we don't want any output from any
1589  * buffer-cache aliases starting from return from that function and
1590  * until the moment when something will explicitly mark the buffer
1591  * dirty (hopefully that will not happen until we will free that block ;-)
1592  * We don't even need to mark it not-uptodate - nobody can expect
1593  * anything from a newly allocated buffer anyway. We used to used
1594  * unmap_buffer() for such invalidation, but that was wrong. We definitely
1595  * don't want to mark the alias unmapped, for example - it would confuse
1596  * anyone who might pick it with bread() afterwards...
1597  *
1598  * Also..  Note that bforget() doesn't lock the buffer.  So there can
1599  * be writeout I/O going on against recently-freed buffers.  We don't
1600  * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1601  * only if we really need to.  That happens here.
1602  */
1603 void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1604 {
1605         struct buffer_head *old_bh;
1606
1607         might_sleep();
1608
1609         old_bh = __find_get_block_slow(bdev, block);
1610         if (old_bh) {
1611                 clear_buffer_dirty(old_bh);
1612                 wait_on_buffer(old_bh);
1613                 clear_buffer_req(old_bh);
1614                 __brelse(old_bh);
1615         }
1616 }
1617 EXPORT_SYMBOL(unmap_underlying_metadata);
1618
1619 /*
1620  * NOTE! All mapped/uptodate combinations are valid:
1621  *
1622  *      Mapped  Uptodate        Meaning
1623  *
1624  *      No      No              "unknown" - must do get_block()
1625  *      No      Yes             "hole" - zero-filled
1626  *      Yes     No              "allocated" - allocated on disk, not read in
1627  *      Yes     Yes             "valid" - allocated and up-to-date in memory.
1628  *
1629  * "Dirty" is valid only with the last case (mapped+uptodate).
1630  */
1631
1632 /*
1633  * While block_write_full_page is writing back the dirty buffers under
1634  * the page lock, whoever dirtied the buffers may decide to clean them
1635  * again at any time.  We handle that by only looking at the buffer
1636  * state inside lock_buffer().
1637  *
1638  * If block_write_full_page() is called for regular writeback
1639  * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1640  * locked buffer.   This only can happen if someone has written the buffer
1641  * directly, with submit_bh().  At the address_space level PageWriteback
1642  * prevents this contention from occurring.
1643  */
1644 static int __block_write_full_page(struct inode *inode, struct page *page,
1645                         get_block_t *get_block, struct writeback_control *wbc)
1646 {
1647         int err;
1648         sector_t block;
1649         sector_t last_block;
1650         struct buffer_head *bh, *head;
1651         const unsigned blocksize = 1 << inode->i_blkbits;
1652         int nr_underway = 0;
1653
1654         BUG_ON(!PageLocked(page));
1655
1656         last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
1657
1658         if (!page_has_buffers(page)) {
1659                 create_empty_buffers(page, blocksize,
1660                                         (1 << BH_Dirty)|(1 << BH_Uptodate));
1661         }
1662
1663         /*
1664          * Be very careful.  We have no exclusion from __set_page_dirty_buffers
1665          * here, and the (potentially unmapped) buffers may become dirty at
1666          * any time.  If a buffer becomes dirty here after we've inspected it
1667          * then we just miss that fact, and the page stays dirty.
1668          *
1669          * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1670          * handle that here by just cleaning them.
1671          */
1672
1673         block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
1674         head = page_buffers(page);
1675         bh = head;
1676
1677         /*
1678          * Get all the dirty buffers mapped to disk addresses and
1679          * handle any aliases from the underlying blockdev's mapping.
1680          */
1681         do {
1682                 if (block > last_block) {
1683                         /*
1684                          * mapped buffers outside i_size will occur, because
1685                          * this page can be outside i_size when there is a
1686                          * truncate in progress.
1687                          */
1688                         /*
1689                          * The buffer was zeroed by block_write_full_page()
1690                          */
1691                         clear_buffer_dirty(bh);
1692                         set_buffer_uptodate(bh);
1693                 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1694                            buffer_dirty(bh)) {
1695                         WARN_ON(bh->b_size != blocksize);
1696                         err = get_block(inode, block, bh, 1);
1697                         if (err)
1698                                 goto recover;
1699                         clear_buffer_delay(bh);
1700                         if (buffer_new(bh)) {
1701                                 /* blockdev mappings never come here */
1702                                 clear_buffer_new(bh);
1703                                 unmap_underlying_metadata(bh->b_bdev,
1704                                                         bh->b_blocknr);
1705                         }
1706                 }
1707                 bh = bh->b_this_page;
1708                 block++;
1709         } while (bh != head);
1710
1711         do {
1712                 if (!buffer_mapped(bh))
1713                         continue;
1714                 /*
1715                  * If it's a fully non-blocking write attempt and we cannot
1716                  * lock the buffer then redirty the page.  Note that this can
1717                  * potentially cause a busy-wait loop from pdflush and kswapd
1718                  * activity, but those code paths have their own higher-level
1719                  * throttling.
1720                  */
1721                 if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
1722                         lock_buffer(bh);
1723                 } else if (!trylock_buffer(bh)) {
1724                         redirty_page_for_writepage(wbc, page);
1725                         continue;
1726                 }
1727                 if (test_clear_buffer_dirty(bh)) {
1728                         mark_buffer_async_write(bh);
1729                 } else {
1730                         unlock_buffer(bh);
1731                 }
1732         } while ((bh = bh->b_this_page) != head);
1733
1734         /*
1735          * The page and its buffers are protected by PageWriteback(), so we can
1736          * drop the bh refcounts early.
1737          */
1738         BUG_ON(PageWriteback(page));
1739         set_page_writeback(page);
1740
1741         do {
1742                 struct buffer_head *next = bh->b_this_page;
1743                 if (buffer_async_write(bh)) {
1744                         submit_bh(WRITE, bh);
1745                         nr_underway++;
1746                 }
1747                 bh = next;
1748         } while (bh != head);
1749         unlock_page(page);
1750
1751         err = 0;
1752 done:
1753         if (nr_underway == 0) {
1754                 /*
1755                  * The page was marked dirty, but the buffers were
1756                  * clean.  Someone wrote them back by hand with
1757                  * ll_rw_block/submit_bh.  A rare case.
1758                  */
1759                 end_page_writeback(page);
1760
1761                 /*
1762                  * The page and buffer_heads can be released at any time from
1763                  * here on.
1764                  */
1765         }
1766         return err;
1767
1768 recover:
1769         /*
1770          * ENOSPC, or some other error.  We may already have added some
1771          * blocks to the file, so we need to write these out to avoid
1772          * exposing stale data.
1773          * The page is currently locked and not marked for writeback
1774          */
1775         bh = head;
1776         /* Recovery: lock and submit the mapped buffers */
1777         do {
1778                 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1779                     !buffer_delay(bh)) {
1780                         lock_buffer(bh);
1781                         mark_buffer_async_write(bh);
1782                 } else {
1783                         /*
1784                          * The buffer may have been set dirty during
1785                          * attachment to a dirty page.
1786                          */
1787                         clear_buffer_dirty(bh);
1788                 }
1789         } while ((bh = bh->b_this_page) != head);
1790         SetPageError(page);
1791         BUG_ON(PageWriteback(page));
1792         mapping_set_error(page->mapping, err);
1793         set_page_writeback(page);
1794         do {
1795                 struct buffer_head *next = bh->b_this_page;
1796                 if (buffer_async_write(bh)) {
1797                         clear_buffer_dirty(bh);
1798                         submit_bh(WRITE, bh);
1799                         nr_underway++;
1800                 }
1801                 bh = next;
1802         } while (bh != head);
1803         unlock_page(page);
1804         goto done;
1805 }
1806
1807 /*
1808  * If a page has any new buffers, zero them out here, and mark them uptodate
1809  * and dirty so they'll be written out (in order to prevent uninitialised
1810  * block data from leaking). And clear the new bit.
1811  */
1812 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1813 {
1814         unsigned int block_start, block_end;
1815         struct buffer_head *head, *bh;
1816
1817         BUG_ON(!PageLocked(page));
1818         if (!page_has_buffers(page))
1819                 return;
1820
1821         bh = head = page_buffers(page);
1822         block_start = 0;
1823         do {
1824                 block_end = block_start + bh->b_size;
1825
1826                 if (buffer_new(bh)) {
1827                         if (block_end > from && block_start < to) {
1828                                 if (!PageUptodate(page)) {
1829                                         unsigned start, size;
1830
1831                                         start = max(from, block_start);
1832                                         size = min(to, block_end) - start;
1833
1834                                         zero_user(page, start, size);
1835                                         set_buffer_uptodate(bh);
1836                                 }
1837
1838                                 clear_buffer_new(bh);
1839                                 mark_buffer_dirty(bh);
1840                         }
1841                 }
1842
1843                 block_start = block_end;
1844                 bh = bh->b_this_page;
1845         } while (bh != head);
1846 }
1847 EXPORT_SYMBOL(page_zero_new_buffers);
1848
1849 static int __block_prepare_write(struct inode *inode, struct page *page,
1850                 unsigned from, unsigned to, get_block_t *get_block)
1851 {
1852         unsigned block_start, block_end;
1853         sector_t block;
1854         int err = 0;
1855         unsigned blocksize, bbits;
1856         struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1857
1858         BUG_ON(!PageLocked(page));
1859         BUG_ON(from > PAGE_CACHE_SIZE);
1860         BUG_ON(to > PAGE_CACHE_SIZE);
1861         BUG_ON(from > to);
1862
1863         blocksize = 1 << inode->i_blkbits;
1864         if (!page_has_buffers(page))
1865                 create_empty_buffers(page, blocksize, 0);
1866         head = page_buffers(page);
1867
1868         bbits = inode->i_blkbits;
1869         block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1870
1871         for(bh = head, block_start = 0; bh != head || !block_start;
1872             block++, block_start=block_end, bh = bh->b_this_page) {
1873                 block_end = block_start + blocksize;
1874                 if (block_end <= from || block_start >= to) {
1875                         if (PageUptodate(page)) {
1876                                 if (!buffer_uptodate(bh))
1877                                         set_buffer_uptodate(bh);
1878                         }
1879                         continue;
1880                 }
1881                 if (buffer_new(bh))
1882                         clear_buffer_new(bh);
1883                 if (!buffer_mapped(bh)) {
1884                         WARN_ON(bh->b_size != blocksize);
1885                         err = get_block(inode, block, bh, 1);
1886                         if (err)
1887                                 break;
1888                         if (buffer_new(bh)) {
1889                                 unmap_underlying_metadata(bh->b_bdev,
1890                                                         bh->b_blocknr);
1891                                 if (PageUptodate(page)) {
1892                                         clear_buffer_new(bh);
1893                                         set_buffer_uptodate(bh);
1894                                         mark_buffer_dirty(bh);
1895                                         continue;
1896                                 }
1897                                 if (block_end > to || block_start < from)
1898                                         zero_user_segments(page,
1899                                                 to, block_end,
1900                                                 block_start, from);
1901                                 continue;
1902                         }
1903                 }
1904                 if (PageUptodate(page)) {
1905                         if (!buffer_uptodate(bh))
1906                                 set_buffer_uptodate(bh);
1907                         continue; 
1908                 }
1909                 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
1910                     !buffer_unwritten(bh) &&
1911                      (block_start < from || block_end > to)) {
1912                         ll_rw_block(READ, 1, &bh);
1913                         *wait_bh++=bh;
1914                 }
1915         }
1916         /*
1917          * If we issued read requests - let them complete.
1918          */
1919         while(wait_bh > wait) {
1920                 wait_on_buffer(*--wait_bh);
1921                 if (!buffer_uptodate(*wait_bh))
1922                         err = -EIO;
1923         }
1924         if (unlikely(err))
1925                 page_zero_new_buffers(page, from, to);
1926         return err;
1927 }
1928
1929 static int __block_commit_write(struct inode *inode, struct page *page,
1930                 unsigned from, unsigned to)
1931 {
1932         unsigned block_start, block_end;
1933         int partial = 0;
1934         unsigned blocksize;
1935         struct buffer_head *bh, *head;
1936
1937         blocksize = 1 << inode->i_blkbits;
1938
1939         for(bh = head = page_buffers(page), block_start = 0;
1940             bh != head || !block_start;
1941             block_start=block_end, bh = bh->b_this_page) {
1942                 block_end = block_start + blocksize;
1943                 if (block_end <= from || block_start >= to) {
1944                         if (!buffer_uptodate(bh))
1945                                 partial = 1;
1946                 } else {
1947                         set_buffer_uptodate(bh);
1948                         mark_buffer_dirty(bh);
1949                 }
1950                 clear_buffer_new(bh);
1951         }
1952
1953         /*
1954          * If this is a partial write which happened to make all buffers
1955          * uptodate then we can optimize away a bogus readpage() for
1956          * the next read(). Here we 'discover' whether the page went
1957          * uptodate as a result of this (potentially partial) write.
1958          */
1959         if (!partial)
1960                 SetPageUptodate(page);
1961         return 0;
1962 }
1963
1964 /*
1965  * block_write_begin takes care of the basic task of block allocation and
1966  * bringing partial write blocks uptodate first.
1967  *
1968  * If *pagep is not NULL, then block_write_begin uses the locked page
1969  * at *pagep rather than allocating its own. In this case, the page will
1970  * not be unlocked or deallocated on failure.
1971  */
1972 int block_write_begin(struct file *file, struct address_space *mapping,
1973                         loff_t pos, unsigned len, unsigned flags,
1974                         struct page **pagep, void **fsdata,
1975                         get_block_t *get_block)
1976 {
1977         struct inode *inode = mapping->host;
1978         int status = 0;
1979         struct page *page;
1980         pgoff_t index;
1981         unsigned start, end;
1982         int ownpage = 0;
1983
1984         index = pos >> PAGE_CACHE_SHIFT;
1985         start = pos & (PAGE_CACHE_SIZE - 1);
1986         end = start + len;
1987
1988         page = *pagep;
1989         if (page == NULL) {
1990                 ownpage = 1;
1991                 page = __grab_cache_page(mapping, index);
1992                 if (!page) {
1993                         status = -ENOMEM;
1994                         goto out;
1995                 }
1996                 *pagep = page;
1997         } else
1998                 BUG_ON(!PageLocked(page));
1999
2000         status = __block_prepare_write(inode, page, start, end, get_block);
2001         if (unlikely(status)) {
2002                 ClearPageUptodate(page);
2003
2004                 if (ownpage) {
2005                         unlock_page(page);
2006                         page_cache_release(page);
2007                         *pagep = NULL;
2008
2009                         /*
2010                          * prepare_write() may have instantiated a few blocks
2011                          * outside i_size.  Trim these off again. Don't need
2012                          * i_size_read because we hold i_mutex.
2013                          */
2014                         if (pos + len > inode->i_size)
2015                                 vmtruncate(inode, inode->i_size);
2016                 }
2017                 goto out;
2018         }
2019
2020 out:
2021         return status;
2022 }
2023 EXPORT_SYMBOL(block_write_begin);
2024
2025 int block_write_end(struct file *file, struct address_space *mapping,
2026                         loff_t pos, unsigned len, unsigned copied,
2027                         struct page *page, void *fsdata)
2028 {
2029         struct inode *inode = mapping->host;
2030         unsigned start;
2031
2032         start = pos & (PAGE_CACHE_SIZE - 1);
2033
2034         if (unlikely(copied < len)) {
2035                 /*
2036                  * The buffers that were written will now be uptodate, so we
2037                  * don't have to worry about a readpage reading them and
2038                  * overwriting a partial write. However if we have encountered
2039                  * a short write and only partially written into a buffer, it
2040                  * will not be marked uptodate, so a readpage might come in and
2041                  * destroy our partial write.
2042                  *
2043                  * Do the simplest thing, and just treat any short write to a
2044                  * non uptodate page as a zero-length write, and force the
2045                  * caller to redo the whole thing.
2046                  */
2047                 if (!PageUptodate(page))
2048                         copied = 0;
2049
2050                 page_zero_new_buffers(page, start+copied, start+len);
2051         }
2052         flush_dcache_page(page);
2053
2054         /* This could be a short (even 0-length) commit */
2055         __block_commit_write(inode, page, start, start+copied);
2056
2057         return copied;
2058 }
2059 EXPORT_SYMBOL(block_write_end);
2060
2061 int generic_write_end(struct file *file, struct address_space *mapping,
2062                         loff_t pos, unsigned len, unsigned copied,
2063                         struct page *page, void *fsdata)
2064 {
2065         struct inode *inode = mapping->host;
2066         int i_size_changed = 0;
2067
2068         copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2069
2070         /*
2071          * No need to use i_size_read() here, the i_size
2072          * cannot change under us because we hold i_mutex.
2073          *
2074          * But it's important to update i_size while still holding page lock:
2075          * page writeout could otherwise come in and zero beyond i_size.
2076          */
2077         if (pos+copied > inode->i_size) {
2078                 i_size_write(inode, pos+copied);
2079                 i_size_changed = 1;
2080         }
2081
2082         unlock_page(page);
2083         page_cache_release(page);
2084
2085         /*
2086          * Don't mark the inode dirty under page lock. First, it unnecessarily
2087          * makes the holding time of page lock longer. Second, it forces lock
2088          * ordering of page lock and transaction start for journaling
2089          * filesystems.
2090          */
2091         if (i_size_changed)
2092                 mark_inode_dirty(inode);
2093
2094         return copied;
2095 }
2096 EXPORT_SYMBOL(generic_write_end);
2097
2098 /*
2099  * block_is_partially_uptodate checks whether buffers within a page are
2100  * uptodate or not.
2101  *
2102  * Returns true if all buffers which correspond to a file portion
2103  * we want to read are uptodate.
2104  */
2105 int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
2106                                         unsigned long from)
2107 {
2108         struct inode *inode = page->mapping->host;
2109         unsigned block_start, block_end, blocksize;
2110         unsigned to;
2111         struct buffer_head *bh, *head;
2112         int ret = 1;
2113
2114         if (!page_has_buffers(page))
2115                 return 0;
2116
2117         blocksize = 1 << inode->i_blkbits;
2118         to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count);
2119         to = from + to;
2120         if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
2121                 return 0;
2122
2123         head = page_buffers(page);
2124         bh = head;
2125         block_start = 0;
2126         do {
2127                 block_end = block_start + blocksize;
2128                 if (block_end > from && block_start < to) {
2129                         if (!buffer_uptodate(bh)) {
2130                                 ret = 0;
2131                                 break;
2132                         }
2133                         if (block_end >= to)
2134                                 break;
2135                 }
2136                 block_start = block_end;
2137                 bh = bh->b_this_page;
2138         } while (bh != head);
2139
2140         return ret;
2141 }
2142 EXPORT_SYMBOL(block_is_partially_uptodate);
2143
2144 /*
2145  * Generic "read page" function for block devices that have the normal
2146  * get_block functionality. This is most of the block device filesystems.
2147  * Reads the page asynchronously --- the unlock_buffer() and
2148  * set/clear_buffer_uptodate() functions propagate buffer state into the
2149  * page struct once IO has completed.
2150  */
2151 int block_read_full_page(struct page *page, get_block_t *get_block)
2152 {
2153         struct inode *inode = page->mapping->host;
2154         sector_t iblock, lblock;
2155         struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2156         unsigned int blocksize;
2157         int nr, i;
2158         int fully_mapped = 1;
2159
2160         BUG_ON(!PageLocked(page));
2161         blocksize = 1 << inode->i_blkbits;
2162         if (!page_has_buffers(page))
2163                 create_empty_buffers(page, blocksize, 0);
2164         head = page_buffers(page);
2165
2166         iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2167         lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
2168         bh = head;
2169         nr = 0;
2170         i = 0;
2171
2172         do {
2173                 if (buffer_uptodate(bh))
2174                         continue;
2175
2176                 if (!buffer_mapped(bh)) {
2177                         int err = 0;
2178
2179                         fully_mapped = 0;
2180                         if (iblock < lblock) {
2181                                 WARN_ON(bh->b_size != blocksize);
2182                                 err = get_block(inode, iblock, bh, 0);
2183                                 if (err)
2184                                         SetPageError(page);
2185                         }
2186                         if (!buffer_mapped(bh)) {
2187                                 zero_user(page, i * blocksize, blocksize);
2188                                 if (!err)
2189                                         set_buffer_uptodate(bh);
2190                                 continue;
2191                         }
2192                         /*
2193                          * get_block() might have updated the buffer
2194                          * synchronously
2195                          */
2196                         if (buffer_uptodate(bh))
2197                                 continue;
2198                 }
2199                 arr[nr++] = bh;
2200         } while (i++, iblock++, (bh = bh->b_this_page) != head);
2201
2202         if (fully_mapped)
2203                 SetPageMappedToDisk(page);
2204
2205         if (!nr) {
2206                 /*
2207                  * All buffers are uptodate - we can set the page uptodate
2208                  * as well. But not if get_block() returned an error.
2209                  */
2210                 if (!PageError(page))
2211                         SetPageUptodate(page);
2212                 unlock_page(page);
2213                 return 0;
2214         }
2215
2216         /* Stage two: lock the buffers */
2217         for (i = 0; i < nr; i++) {
2218                 bh = arr[i];
2219                 lock_buffer(bh);
2220                 mark_buffer_async_read(bh);
2221         }
2222
2223         /*
2224          * Stage 3: start the IO.  Check for uptodateness
2225          * inside the buffer lock in case another process reading
2226          * the underlying blockdev brought it uptodate (the sct fix).
2227          */
2228         for (i = 0; i < nr; i++) {
2229                 bh = arr[i];
2230                 if (buffer_uptodate(bh))
2231                         end_buffer_async_read(bh, 1);
2232                 else
2233                         submit_bh(READ, bh);
2234         }
2235         return 0;
2236 }
2237
2238 /* utility function for filesystems that need to do work on expanding
2239  * truncates.  Uses filesystem pagecache writes to allow the filesystem to
2240  * deal with the hole.  
2241  */
2242 int generic_cont_expand_simple(struct inode *inode, loff_t size)
2243 {
2244         struct address_space *mapping = inode->i_mapping;
2245         struct page *page;
2246         void *fsdata;
2247         unsigned long limit;
2248         int err;
2249
2250         err = -EFBIG;
2251         limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
2252         if (limit != RLIM_INFINITY && size > (loff_t)limit) {
2253                 send_sig(SIGXFSZ, current, 0);
2254                 goto out;
2255         }
2256         if (size > inode->i_sb->s_maxbytes)
2257                 goto out;
2258
2259         err = pagecache_write_begin(NULL, mapping, size, 0,
2260                                 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
2261                                 &page, &fsdata);
2262         if (err)
2263                 goto out;
2264
2265         err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2266         BUG_ON(err > 0);
2267
2268 out:
2269         return err;
2270 }
2271
2272 static int cont_expand_zero(struct file *file, struct address_space *mapping,
2273                             loff_t pos, loff_t *bytes)
2274 {
2275         struct inode *inode = mapping->host;
2276         unsigned blocksize = 1 << inode->i_blkbits;
2277         struct page *page;
2278         void *fsdata;
2279         pgoff_t index, curidx;
2280         loff_t curpos;
2281         unsigned zerofrom, offset, len;
2282         int err = 0;
2283
2284         index = pos >> PAGE_CACHE_SHIFT;
2285         offset = pos & ~PAGE_CACHE_MASK;
2286
2287         while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
2288                 zerofrom = curpos & ~PAGE_CACHE_MASK;
2289                 if (zerofrom & (blocksize-1)) {
2290                         *bytes |= (blocksize-1);
2291                         (*bytes)++;
2292                 }
2293                 len = PAGE_CACHE_SIZE - zerofrom;
2294
2295                 err = pagecache_write_begin(file, mapping, curpos, len,
2296                                                 AOP_FLAG_UNINTERRUPTIBLE,
2297                                                 &page, &fsdata);
2298                 if (err)
2299                         goto out;
2300                 zero_user(page, zerofrom, len);
2301                 err = pagecache_write_end(file, mapping, curpos, len, len,
2302                                                 page, fsdata);
2303                 if (err < 0)
2304                         goto out;
2305                 BUG_ON(err != len);
2306                 err = 0;
2307
2308                 balance_dirty_pages_ratelimited(mapping);
2309         }
2310
2311         /* page covers the boundary, find the boundary offset */
2312         if (index == curidx) {
2313                 zerofrom = curpos & ~PAGE_CACHE_MASK;
2314                 /* if we will expand the thing last block will be filled */
2315                 if (offset <= zerofrom) {
2316                         goto out;
2317                 }
2318                 if (zerofrom & (blocksize-1)) {
2319                         *bytes |= (blocksize-1);
2320                         (*bytes)++;
2321                 }
2322                 len = offset - zerofrom;
2323
2324                 err = pagecache_write_begin(file, mapping, curpos, len,
2325                                                 AOP_FLAG_UNINTERRUPTIBLE,
2326                                                 &page, &fsdata);
2327                 if (err)
2328                         goto out;
2329                 zero_user(page, zerofrom, len);
2330                 err = pagecache_write_end(file, mapping, curpos, len, len,
2331                                                 page, fsdata);
2332                 if (err < 0)
2333                         goto out;
2334                 BUG_ON(err != len);
2335                 err = 0;
2336         }
2337 out:
2338         return err;
2339 }
2340
2341 /*
2342  * For moronic filesystems that do not allow holes in file.
2343  * We may have to extend the file.
2344  */
2345 int cont_write_begin(struct file *file, struct address_space *mapping,
2346                         loff_t pos, unsigned len, unsigned flags,
2347                         struct page **pagep, void **fsdata,
2348                         get_block_t *get_block, loff_t *bytes)
2349 {
2350         struct inode *inode = mapping->host;
2351         unsigned blocksize = 1 << inode->i_blkbits;
2352         unsigned zerofrom;
2353         int err;
2354
2355         err = cont_expand_zero(file, mapping, pos, bytes);
2356         if (err)
2357                 goto out;
2358
2359         zerofrom = *bytes & ~PAGE_CACHE_MASK;
2360         if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2361                 *bytes |= (blocksize-1);
2362                 (*bytes)++;
2363         }
2364
2365         *pagep = NULL;
2366         err = block_write_begin(file, mapping, pos, len,
2367                                 flags, pagep, fsdata, get_block);
2368 out:
2369         return err;
2370 }
2371
2372 int block_prepare_write(struct page *page, unsigned from, unsigned to,
2373                         get_block_t *get_block)
2374 {
2375         struct inode *inode = page->mapping->host;
2376         int err = __block_prepare_write(inode, page, from, to, get_block);
2377         if (err)
2378                 ClearPageUptodate(page);
2379         return err;
2380 }
2381
2382 int block_commit_write(struct page *page, unsigned from, unsigned to)
2383 {
2384         struct inode *inode = page->mapping->host;
2385         __block_commit_write(inode,page,from,to);
2386         return 0;
2387 }
2388
2389 /*
2390  * block_page_mkwrite() is not allowed to change the file size as it gets
2391  * called from a page fault handler when a page is first dirtied. Hence we must
2392  * be careful to check for EOF conditions here. We set the page up correctly
2393  * for a written page which means we get ENOSPC checking when writing into
2394  * holes and correct delalloc and unwritten extent mapping on filesystems that
2395  * support these features.
2396  *
2397  * We are not allowed to take the i_mutex here so we have to play games to
2398  * protect against truncate races as the page could now be beyond EOF.  Because
2399  * vmtruncate() writes the inode size before removing pages, once we have the
2400  * page lock we can determine safely if the page is beyond EOF. If it is not
2401  * beyond EOF, then the page is guaranteed safe against truncation until we
2402  * unlock the page.
2403  */
2404 int
2405 block_page_mkwrite(struct vm_area_struct *vma, struct page *page,
2406                    get_block_t get_block)
2407 {
2408         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
2409         unsigned long end;
2410         loff_t size;
2411         int ret = -EINVAL;
2412
2413         lock_page(page);
2414         size = i_size_read(inode);
2415         if ((page->mapping != inode->i_mapping) ||
2416             (page_offset(page) > size)) {
2417                 /* page got truncated out from underneath us */
2418                 goto out_unlock;
2419         }
2420
2421         /* page is wholly or partially inside EOF */
2422         if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
2423                 end = size & ~PAGE_CACHE_MASK;
2424         else
2425                 end = PAGE_CACHE_SIZE;
2426
2427         ret = block_prepare_write(page, 0, end, get_block);
2428         if (!ret)
2429                 ret = block_commit_write(page, 0, end);
2430
2431 out_unlock:
2432         unlock_page(page);
2433         return ret;
2434 }
2435
2436 /*
2437  * nobh_write_begin()'s prereads are special: the buffer_heads are freed
2438  * immediately, while under the page lock.  So it needs a special end_io
2439  * handler which does not touch the bh after unlocking it.
2440  */
2441 static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2442 {
2443         __end_buffer_read_notouch(bh, uptodate);
2444 }
2445
2446 /*
2447  * Attach the singly-linked list of buffers created by nobh_write_begin, to
2448  * the page (converting it to circular linked list and taking care of page
2449  * dirty races).
2450  */
2451 static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2452 {
2453         struct buffer_head *bh;
2454
2455         BUG_ON(!PageLocked(page));
2456
2457         spin_lock(&page->mapping->private_lock);
2458         bh = head;
2459         do {
2460                 if (PageDirty(page))
2461                         set_buffer_dirty(bh);
2462                 if (!bh->b_this_page)
2463                         bh->b_this_page = head;
2464                 bh = bh->b_this_page;
2465         } while (bh != head);
2466         attach_page_buffers(page, head);
2467         spin_unlock(&page->mapping->private_lock);
2468 }
2469
2470 /*
2471  * On entry, the page is fully not uptodate.
2472  * On exit the page is fully uptodate in the areas outside (from,to)
2473  */
2474 int nobh_write_begin(struct file *file, struct address_space *mapping,
2475                         loff_t pos, unsigned len, unsigned flags,
2476                         struct page **pagep, void **fsdata,
2477                         get_block_t *get_block)
2478 {
2479         struct inode *inode = mapping->host;
2480         const unsigned blkbits = inode->i_blkbits;
2481         const unsigned blocksize = 1 << blkbits;
2482         struct buffer_head *head, *bh;
2483         struct page *page;
2484         pgoff_t index;
2485         unsigned from, to;
2486         unsigned block_in_page;
2487         unsigned block_start, block_end;
2488         sector_t block_in_file;
2489         int nr_reads = 0;
2490         int ret = 0;
2491         int is_mapped_to_disk = 1;
2492
2493         index = pos >> PAGE_CACHE_SHIFT;
2494         from = pos & (PAGE_CACHE_SIZE - 1);
2495         to = from + len;
2496
2497         page = __grab_cache_page(mapping, index);
2498         if (!page)
2499                 return -ENOMEM;
2500         *pagep = page;
2501         *fsdata = NULL;
2502
2503         if (page_has_buffers(page)) {
2504                 unlock_page(page);
2505                 page_cache_release(page);
2506                 *pagep = NULL;
2507                 return block_write_begin(file, mapping, pos, len, flags, pagep,
2508                                         fsdata, get_block);
2509         }
2510
2511         if (PageMappedToDisk(page))
2512                 return 0;
2513
2514         /*
2515          * Allocate buffers so that we can keep track of state, and potentially
2516          * attach them to the page if an error occurs. In the common case of
2517          * no error, they will just be freed again without ever being attached
2518          * to the page (which is all OK, because we're under the page lock).
2519          *
2520          * Be careful: the buffer linked list is a NULL terminated one, rather
2521          * than the circular one we're used to.
2522          */
2523         head = alloc_page_buffers(page, blocksize, 0);
2524         if (!head) {
2525                 ret = -ENOMEM;
2526                 goto out_release;
2527         }
2528
2529         block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
2530
2531         /*
2532          * We loop across all blocks in the page, whether or not they are
2533          * part of the affected region.  This is so we can discover if the
2534          * page is fully mapped-to-disk.
2535          */
2536         for (block_start = 0, block_in_page = 0, bh = head;
2537                   block_start < PAGE_CACHE_SIZE;
2538                   block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
2539                 int create;
2540
2541                 block_end = block_start + blocksize;
2542                 bh->b_state = 0;
2543                 create = 1;
2544                 if (block_start >= to)
2545                         create = 0;
2546                 ret = get_block(inode, block_in_file + block_in_page,
2547                                         bh, create);
2548                 if (ret)
2549                         goto failed;
2550                 if (!buffer_mapped(bh))
2551                         is_mapped_to_disk = 0;
2552                 if (buffer_new(bh))
2553                         unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
2554                 if (PageUptodate(page)) {
2555                         set_buffer_uptodate(bh);
2556                         continue;
2557                 }
2558                 if (buffer_new(bh) || !buffer_mapped(bh)) {
2559                         zero_user_segments(page, block_start, from,
2560                                                         to, block_end);
2561                         continue;
2562                 }
2563                 if (buffer_uptodate(bh))
2564                         continue;       /* reiserfs does this */
2565                 if (block_start < from || block_end > to) {
2566                         lock_buffer(bh);
2567                         bh->b_end_io = end_buffer_read_nobh;
2568                         submit_bh(READ, bh);
2569                         nr_reads++;
2570                 }
2571         }
2572
2573         if (nr_reads) {
2574                 /*
2575                  * The page is locked, so these buffers are protected from
2576                  * any VM or truncate activity.  Hence we don't need to care
2577                  * for the buffer_head refcounts.
2578                  */
2579                 for (bh = head; bh; bh = bh->b_this_page) {
2580                         wait_on_buffer(bh);
2581                         if (!buffer_uptodate(bh))
2582                                 ret = -EIO;
2583                 }
2584                 if (ret)
2585                         goto failed;
2586         }
2587
2588         if (is_mapped_to_disk)
2589                 SetPageMappedToDisk(page);
2590
2591         *fsdata = head; /* to be released by nobh_write_end */
2592
2593         return 0;
2594
2595 failed:
2596         BUG_ON(!ret);
2597         /*
2598          * Error recovery is a bit difficult. We need to zero out blocks that
2599          * were newly allocated, and dirty them to ensure they get written out.
2600          * Buffers need to be attached to the page at this point, otherwise
2601          * the handling of potential IO errors during writeout would be hard
2602          * (could try doing synchronous writeout, but what if that fails too?)
2603          */
2604         attach_nobh_buffers(page, head);
2605         page_zero_new_buffers(page, from, to);
2606
2607 out_release:
2608         unlock_page(page);
2609         page_cache_release(page);
2610         *pagep = NULL;
2611
2612         if (pos + len > inode->i_size)
2613                 vmtruncate(inode, inode->i_size);
2614
2615         return ret;
2616 }
2617 EXPORT_SYMBOL(nobh_write_begin);
2618
2619 int nobh_write_end(struct file *file, struct address_space *mapping,
2620                         loff_t pos, unsigned len, unsigned copied,
2621                         struct page *page, void *fsdata)
2622 {
2623         struct inode *inode = page->mapping->host;
2624         struct buffer_head *head = fsdata;
2625         struct buffer_head *bh;
2626         BUG_ON(fsdata != NULL && page_has_buffers(page));
2627
2628         if (unlikely(copied < len) && !page_has_buffers(page))
2629                 attach_nobh_buffers(page, head);
2630         if (page_has_buffers(page))
2631                 return generic_write_end(file, mapping, pos, len,
2632                                         copied, page, fsdata);
2633
2634         SetPageUptodate(page);
2635         set_page_dirty(page);
2636         if (pos+copied > inode->i_size) {
2637                 i_size_write(inode, pos+copied);
2638                 mark_inode_dirty(inode);
2639         }
2640
2641         unlock_page(page);
2642         page_cache_release(page);
2643
2644         while (head) {
2645                 bh = head;
2646                 head = head->b_this_page;
2647                 free_buffer_head(bh);
2648         }
2649
2650         return copied;
2651 }
2652 EXPORT_SYMBOL(nobh_write_end);
2653
2654 /*
2655  * nobh_writepage() - based on block_full_write_page() except
2656  * that it tries to operate without attaching bufferheads to
2657  * the page.
2658  */
2659 int nobh_writepage(struct page *page, get_block_t *get_block,
2660                         struct writeback_control *wbc)
2661 {
2662         struct inode * const inode = page->mapping->host;
2663         loff_t i_size = i_size_read(inode);
2664         const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2665         unsigned offset;
2666         int ret;
2667
2668         /* Is the page fully inside i_size? */
2669         if (page->index < end_index)
2670                 goto out;
2671
2672         /* Is the page fully outside i_size? (truncate in progress) */
2673         offset = i_size & (PAGE_CACHE_SIZE-1);
2674         if (page->index >= end_index+1 || !offset) {
2675                 /*
2676                  * The page may have dirty, unmapped buffers.  For example,
2677                  * they may have been added in ext3_writepage().  Make them
2678                  * freeable here, so the page does not leak.
2679                  */
2680 #if 0
2681                 /* Not really sure about this  - do we need this ? */
2682                 if (page->mapping->a_ops->invalidatepage)
2683                         page->mapping->a_ops->invalidatepage(page, offset);
2684 #endif
2685                 unlock_page(page);
2686                 return 0; /* don't care */
2687         }
2688
2689         /*
2690          * The page straddles i_size.  It must be zeroed out on each and every
2691          * writepage invocation because it may be mmapped.  "A file is mapped
2692          * in multiples of the page size.  For a file that is not a multiple of
2693          * the  page size, the remaining memory is zeroed when mapped, and
2694          * writes to that region are not written out to the file."
2695          */
2696         zero_user_segment(page, offset, PAGE_CACHE_SIZE);
2697 out:
2698         ret = mpage_writepage(page, get_block, wbc);
2699         if (ret == -EAGAIN)
2700                 ret = __block_write_full_page(inode, page, get_block, wbc);
2701         return ret;
2702 }
2703 EXPORT_SYMBOL(nobh_writepage);
2704
2705 int nobh_truncate_page(struct address_space *mapping,
2706                         loff_t from, get_block_t *get_block)
2707 {
2708         pgoff_t index = from >> PAGE_CACHE_SHIFT;
2709         unsigned offset = from & (PAGE_CACHE_SIZE-1);
2710         unsigned blocksize;
2711         sector_t iblock;
2712         unsigned length, pos;
2713         struct inode *inode = mapping->host;
2714         struct page *page;
2715         struct buffer_head map_bh;
2716         int err;
2717
2718         blocksize = 1 << inode->i_blkbits;
2719         length = offset & (blocksize - 1);
2720
2721         /* Block boundary? Nothing to do */
2722         if (!length)
2723                 return 0;
2724
2725         length = blocksize - length;
2726         iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2727
2728         page = grab_cache_page(mapping, index);
2729         err = -ENOMEM;
2730         if (!page)
2731                 goto out;
2732
2733         if (page_has_buffers(page)) {
2734 has_buffers:
2735                 unlock_page(page);
2736                 page_cache_release(page);
2737                 return block_truncate_page(mapping, from, get_block);
2738         }
2739
2740         /* Find the buffer that contains "offset" */
2741         pos = blocksize;
2742         while (offset >= pos) {
2743                 iblock++;
2744                 pos += blocksize;
2745         }
2746
2747         err = get_block(inode, iblock, &map_bh, 0);
2748         if (err)
2749                 goto unlock;
2750         /* unmapped? It's a hole - nothing to do */
2751         if (!buffer_mapped(&map_bh))
2752                 goto unlock;
2753
2754         /* Ok, it's mapped. Make sure it's up-to-date */
2755         if (!PageUptodate(page)) {
2756                 err = mapping->a_ops->readpage(NULL, page);
2757                 if (err) {
2758                         page_cache_release(page);
2759                         goto out;
2760                 }
2761                 lock_page(page);
2762                 if (!PageUptodate(page)) {
2763                         err = -EIO;
2764                         goto unlock;
2765                 }
2766                 if (page_has_buffers(page))
2767                         goto has_buffers;
2768         }
2769         zero_user(page, offset, length);
2770         set_page_dirty(page);
2771         err = 0;
2772
2773 unlock:
2774         unlock_page(page);
2775         page_cache_release(page);
2776 out:
2777         return err;
2778 }
2779 EXPORT_SYMBOL(nobh_truncate_page);
2780
2781 int block_truncate_page(struct address_space *mapping,
2782                         loff_t from, get_block_t *get_block)
2783 {
2784         pgoff_t index = from >> PAGE_CACHE_SHIFT;
2785         unsigned offset = from & (PAGE_CACHE_SIZE-1);
2786         unsigned blocksize;
2787         sector_t iblock;
2788         unsigned length, pos;
2789         struct inode *inode = mapping->host;
2790         struct page *page;
2791         struct buffer_head *bh;
2792         int err;
2793
2794         blocksize = 1 << inode->i_blkbits;
2795         length = offset & (blocksize - 1);
2796
2797         /* Block boundary? Nothing to do */
2798         if (!length)
2799                 return 0;
2800
2801         length = blocksize - length;
2802         iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2803         
2804         page = grab_cache_page(mapping, index);
2805         err = -ENOMEM;
2806         if (!page)
2807                 goto out;
2808
2809         if (!page_has_buffers(page))
2810                 create_empty_buffers(page, blocksize, 0);
2811
2812         /* Find the buffer that contains "offset" */
2813         bh = page_buffers(page);
2814         pos = blocksize;
2815         while (offset >= pos) {
2816                 bh = bh->b_this_page;
2817                 iblock++;
2818                 pos += blocksize;
2819         }
2820
2821         err = 0;
2822         if (!buffer_mapped(bh)) {
2823                 WARN_ON(bh->b_size != blocksize);
2824                 err = get_block(inode, iblock, bh, 0);
2825                 if (err)
2826                         goto unlock;
2827                 /* unmapped? It's a hole - nothing to do */
2828                 if (!buffer_mapped(bh))
2829                         goto unlock;
2830         }
2831
2832         /* Ok, it's mapped. Make sure it's up-to-date */
2833         if (PageUptodate(page))
2834                 set_buffer_uptodate(bh);
2835
2836         if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2837                 err = -EIO;
2838                 ll_rw_block(READ, 1, &bh);
2839                 wait_on_buffer(bh);
2840                 /* Uhhuh. Read error. Complain and punt. */
2841                 if (!buffer_uptodate(bh))
2842                         goto unlock;
2843         }
2844
2845         zero_user(page, offset, length);
2846         mark_buffer_dirty(bh);
2847         err = 0;
2848
2849 unlock:
2850         unlock_page(page);
2851         page_cache_release(page);
2852 out:
2853         return err;
2854 }
2855
2856 /*
2857  * The generic ->writepage function for buffer-backed address_spaces
2858  */
2859 int block_write_full_page(struct page *page, get_block_t *get_block,
2860                         struct writeback_control *wbc)
2861 {
2862         struct inode * const inode = page->mapping->host;
2863         loff_t i_size = i_size_read(inode);
2864         const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2865         unsigned offset;
2866
2867         /* Is the page fully inside i_size? */
2868         if (page->index < end_index)
2869                 return __block_write_full_page(inode, page, get_block, wbc);
2870
2871         /* Is the page fully outside i_size? (truncate in progress) */
2872         offset = i_size & (PAGE_CACHE_SIZE-1);
2873         if (page->index >= end_index+1 || !offset) {
2874                 /*
2875                  * The page may have dirty, unmapped buffers.  For example,
2876                  * they may have been added in ext3_writepage().  Make them
2877                  * freeable here, so the page does not leak.
2878                  */
2879                 do_invalidatepage(page, 0);
2880                 unlock_page(page);
2881                 return 0; /* don't care */
2882         }
2883
2884         /*
2885          * The page straddles i_size.  It must be zeroed out on each and every
2886          * writepage invokation because it may be mmapped.  "A file is mapped
2887          * in multiples of the page size.  For a file that is not a multiple of
2888          * the  page size, the remaining memory is zeroed when mapped, and
2889          * writes to that region are not written out to the file."
2890          */
2891         zero_user_segment(page, offset, PAGE_CACHE_SIZE);
2892         return __block_write_full_page(inode, page, get_block, wbc);
2893 }
2894
2895 sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2896                             get_block_t *get_block)
2897 {
2898         struct buffer_head tmp;
2899         struct inode *inode = mapping->host;
2900         tmp.b_state = 0;
2901         tmp.b_blocknr = 0;
2902         tmp.b_size = 1 << inode->i_blkbits;
2903         get_block(inode, block, &tmp, 0);
2904         return tmp.b_blocknr;
2905 }
2906
2907 static void end_bio_bh_io_sync(struct bio *bio, int err)
2908 {
2909         struct buffer_head *bh = bio->bi_private;
2910
2911         if (err == -EOPNOTSUPP) {
2912                 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
2913                 set_bit(BH_Eopnotsupp, &bh->b_state);
2914         }
2915
2916         bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2917         bio_put(bio);
2918 }
2919
2920 int submit_bh(int rw, struct buffer_head * bh)
2921 {
2922         struct bio *bio;
2923         int ret = 0;
2924
2925         BUG_ON(!buffer_locked(bh));
2926         BUG_ON(!buffer_mapped(bh));
2927         BUG_ON(!bh->b_end_io);
2928
2929         /*
2930          * Mask in barrier bit for a write (could be either a WRITE or a
2931          * WRITE_SYNC
2932          */
2933         if (buffer_ordered(bh) && (rw & WRITE))
2934                 rw |= WRITE_BARRIER;
2935
2936         /*
2937          * Only clear out a write error when rewriting
2938          */
2939         if (test_set_buffer_req(bh) && (rw & WRITE))
2940                 clear_buffer_write_io_error(bh);
2941
2942         /*
2943          * from here on down, it's all bio -- do the initial mapping,
2944          * submit_bio -> generic_make_request may further map this bio around
2945          */
2946         bio = bio_alloc(GFP_NOIO, 1);
2947
2948         bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2949         bio->bi_bdev = bh->b_bdev;
2950         bio->bi_io_vec[0].bv_page = bh->b_page;
2951         bio->bi_io_vec[0].bv_len = bh->b_size;
2952         bio->bi_io_vec[0].bv_offset = bh_offset(bh);
2953
2954         bio->bi_vcnt = 1;
2955         bio->bi_idx = 0;
2956         bio->bi_size = bh->b_size;
2957
2958         bio->bi_end_io = end_bio_bh_io_sync;
2959         bio->bi_private = bh;
2960
2961         bio_get(bio);
2962         submit_bio(rw, bio);
2963
2964         if (bio_flagged(bio, BIO_EOPNOTSUPP))
2965                 ret = -EOPNOTSUPP;
2966
2967         bio_put(bio);
2968         return ret;
2969 }
2970
2971 /**
2972  * ll_rw_block: low-level access to block devices (DEPRECATED)
2973  * @rw: whether to %READ or %WRITE or %SWRITE or maybe %READA (readahead)
2974  * @nr: number of &struct buffer_heads in the array
2975  * @bhs: array of pointers to &struct buffer_head
2976  *
2977  * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
2978  * requests an I/O operation on them, either a %READ or a %WRITE.  The third
2979  * %SWRITE is like %WRITE only we make sure that the *current* data in buffers
2980  * are sent to disk. The fourth %READA option is described in the documentation
2981  * for generic_make_request() which ll_rw_block() calls.
2982  *
2983  * This function drops any buffer that it cannot get a lock on (with the
2984  * BH_Lock state bit) unless SWRITE is required, any buffer that appears to be
2985  * clean when doing a write request, and any buffer that appears to be
2986  * up-to-date when doing read request.  Further it marks as clean buffers that
2987  * are processed for writing (the buffer cache won't assume that they are
2988  * actually clean until the buffer gets unlocked).
2989  *
2990  * ll_rw_block sets b_end_io to simple completion handler that marks
2991  * the buffer up-to-date (if approriate), unlocks the buffer and wakes
2992  * any waiters. 
2993  *
2994  * All of the buffers must be for the same device, and must also be a
2995  * multiple of the current approved size for the device.
2996  */
2997 void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
2998 {
2999         int i;
3000
3001         for (i = 0; i < nr; i++) {
3002                 struct buffer_head *bh = bhs[i];
3003
3004                 if (rw == SWRITE || rw == SWRITE_SYNC)
3005                         lock_buffer(bh);
3006                 else if (!trylock_buffer(bh))
3007                         continue;
3008
3009                 if (rw == WRITE || rw == SWRITE || rw == SWRITE_SYNC) {
3010                         if (test_clear_buffer_dirty(bh)) {
3011                                 bh->b_end_io = end_buffer_write_sync;
3012                                 get_bh(bh);
3013                                 if (rw == SWRITE_SYNC)
3014                                         submit_bh(WRITE_SYNC, bh);
3015                                 else
3016                                         submit_bh(WRITE, bh);
3017                                 continue;
3018                         }
3019                 } else {
3020                         if (!buffer_uptodate(bh)) {
3021                                 bh->b_end_io = end_buffer_read_sync;
3022                                 get_bh(bh);
3023                                 submit_bh(rw, bh);
3024                                 continue;
3025                         }
3026                 }
3027                 unlock_buffer(bh);
3028         }
3029 }
3030
3031 /*
3032  * For a data-integrity writeout, we need to wait upon any in-progress I/O
3033  * and then start new I/O and then wait upon it.  The caller must have a ref on
3034  * the buffer_head.
3035  */
3036 int sync_dirty_buffer(struct buffer_head *bh)
3037 {
3038         int ret = 0;
3039
3040         WARN_ON(atomic_read(&bh->b_count) < 1);
3041         lock_buffer(bh);
3042         if (test_clear_buffer_dirty(bh)) {
3043                 get_bh(bh);
3044                 bh->b_end_io = end_buffer_write_sync;
3045                 ret = submit_bh(WRITE_SYNC, bh);
3046                 wait_on_buffer(bh);
3047                 if (buffer_eopnotsupp(bh)) {
3048                         clear_buffer_eopnotsupp(bh);
3049                         ret = -EOPNOTSUPP;
3050                 }
3051                 if (!ret && !buffer_uptodate(bh))
3052                         ret = -EIO;
3053         } else {
3054                 unlock_buffer(bh);
3055         }
3056         return ret;
3057 }
3058
3059 /*
3060  * try_to_free_buffers() checks if all the buffers on this particular page
3061  * are unused, and releases them if so.
3062  *
3063  * Exclusion against try_to_free_buffers may be obtained by either
3064  * locking the page or by holding its mapping's private_lock.
3065  *
3066  * If the page is dirty but all the buffers are clean then we need to
3067  * be sure to mark the page clean as well.  This is because the page
3068  * may be against a block device, and a later reattachment of buffers
3069  * to a dirty page will set *all* buffers dirty.  Which would corrupt
3070  * filesystem data on the same device.
3071  *
3072  * The same applies to regular filesystem pages: if all the buffers are
3073  * clean then we set the page clean and proceed.  To do that, we require
3074  * total exclusion from __set_page_dirty_buffers().  That is obtained with
3075  * private_lock.
3076  *
3077  * try_to_free_buffers() is non-blocking.
3078  */
3079 static inline int buffer_busy(struct buffer_head *bh)
3080 {
3081         return atomic_read(&bh->b_count) |
3082                 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3083 }
3084
3085 static int
3086 drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3087 {
3088         struct buffer_head *head = page_buffers(page);
3089         struct buffer_head *bh;
3090
3091         bh = head;
3092         do {
3093                 if (buffer_write_io_error(bh) && page->mapping)
3094                         set_bit(AS_EIO, &page->mapping->flags);
3095                 if (buffer_busy(bh))
3096                         goto failed;
3097                 bh = bh->b_this_page;
3098         } while (bh != head);
3099
3100         do {
3101                 struct buffer_head *next = bh->b_this_page;
3102
3103                 if (bh->b_assoc_map)
3104                         __remove_assoc_queue(bh);
3105                 bh = next;
3106         } while (bh != head);
3107         *buffers_to_free = head;
3108         __clear_page_buffers(page);
3109         return 1;
3110 failed:
3111         return 0;
3112 }
3113
3114 int try_to_free_buffers(struct page *page)
3115 {
3116         struct address_space * const mapping = page->mapping;
3117         struct buffer_head *buffers_to_free = NULL;
3118         int ret = 0;
3119
3120         BUG_ON(!PageLocked(page));
3121         if (PageWriteback(page))
3122                 return 0;
3123
3124         if (mapping == NULL) {          /* can this still happen? */
3125                 ret = drop_buffers(page, &buffers_to_free);
3126                 goto out;
3127         }
3128
3129         spin_lock(&mapping->private_lock);
3130         ret = drop_buffers(page, &buffers_to_free);
3131
3132         /*
3133          * If the filesystem writes its buffers by hand (eg ext3)
3134          * then we can have clean buffers against a dirty page.  We
3135          * clean the page here; otherwise the VM will never notice
3136          * that the filesystem did any IO at all.
3137          *
3138          * Also, during truncate, discard_buffer will have marked all
3139          * the page's buffers clean.  We discover that here and clean
3140          * the page also.
3141          *
3142          * private_lock must be held over this entire operation in order
3143          * to synchronise against __set_page_dirty_buffers and prevent the
3144          * dirty bit from being lost.
3145          */
3146         if (ret)
3147                 cancel_dirty_page(page, PAGE_CACHE_SIZE);
3148         spin_unlock(&mapping->private_lock);
3149 out:
3150         if (buffers_to_free) {
3151                 struct buffer_head *bh = buffers_to_free;
3152
3153                 do {
3154                         struct buffer_head *next = bh->b_this_page;
3155                         free_buffer_head(bh);
3156                         bh = next;
3157                 } while (bh != buffers_to_free);
3158         }
3159         return ret;
3160 }
3161 EXPORT_SYMBOL(try_to_free_buffers);
3162
3163 void block_sync_page(struct page *page)
3164 {
3165         struct address_space *mapping;
3166
3167         smp_mb();
3168         mapping = page_mapping(page);
3169         if (mapping)
3170                 blk_run_backing_dev(mapping->backing_dev_info, page);
3171 }
3172
3173 /*
3174  * There are no bdflush tunables left.  But distributions are
3175  * still running obsolete flush daemons, so we terminate them here.
3176  *
3177  * Use of bdflush() is deprecated and will be removed in a future kernel.
3178  * The `pdflush' kernel threads fully replace bdflush daemons and this call.
3179  */
3180 asmlinkage long sys_bdflush(int func, long data)
3181 {
3182         static int msg_count;
3183
3184         if (!capable(CAP_SYS_ADMIN))
3185                 return -EPERM;
3186
3187         if (msg_count < 5) {
3188                 msg_count++;
3189                 printk(KERN_INFO
3190                         "warning: process `%s' used the obsolete bdflush"
3191                         " system call\n", current->comm);
3192                 printk(KERN_INFO "Fix your initscripts?\n");
3193         }
3194
3195         if (func == 1)
3196                 do_exit(0);
3197         return 0;
3198 }
3199
3200 /*
3201  * Buffer-head allocation
3202  */
3203 static struct kmem_cache *bh_cachep;
3204
3205 /*
3206  * Once the number of bh's in the machine exceeds this level, we start
3207  * stripping them in writeback.
3208  */
3209 static int max_buffer_heads;
3210
3211 int buffer_heads_over_limit;
3212
3213 struct bh_accounting {
3214         int nr;                 /* Number of live bh's */
3215         int ratelimit;          /* Limit cacheline bouncing */
3216 };
3217
3218 static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3219
3220 static void recalc_bh_state(void)
3221 {
3222         int i;
3223         int tot = 0;
3224
3225         if (__get_cpu_var(bh_accounting).ratelimit++ < 4096)
3226                 return;
3227         __get_cpu_var(bh_accounting).ratelimit = 0;
3228         for_each_online_cpu(i)
3229                 tot += per_cpu(bh_accounting, i).nr;
3230         buffer_heads_over_limit = (tot > max_buffer_heads);
3231 }
3232         
3233 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3234 {
3235         struct buffer_head *ret = kmem_cache_alloc(bh_cachep, gfp_flags);
3236         if (ret) {
3237                 INIT_LIST_HEAD(&ret->b_assoc_buffers);
3238                 get_cpu_var(bh_accounting).nr++;
3239                 recalc_bh_state();
3240                 put_cpu_var(bh_accounting);
3241         }
3242         return ret;
3243 }
3244 EXPORT_SYMBOL(alloc_buffer_head);
3245
3246 void free_buffer_head(struct buffer_head *bh)
3247 {
3248         BUG_ON(!list_empty(&bh->b_assoc_buffers));
3249         kmem_cache_free(bh_cachep, bh);
3250         get_cpu_var(bh_accounting).nr--;
3251         recalc_bh_state();
3252         put_cpu_var(bh_accounting);
3253 }
3254 EXPORT_SYMBOL(free_buffer_head);
3255
3256 static void buffer_exit_cpu(int cpu)
3257 {
3258         int i;
3259         struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3260
3261         for (i = 0; i < BH_LRU_SIZE; i++) {
3262                 brelse(b->bhs[i]);
3263                 b->bhs[i] = NULL;
3264         }
3265         get_cpu_var(bh_accounting).nr += per_cpu(bh_accounting, cpu).nr;
3266         per_cpu(bh_accounting, cpu).nr = 0;
3267         put_cpu_var(bh_accounting);
3268 }
3269
3270 static int buffer_cpu_notify(struct notifier_block *self,
3271                               unsigned long action, void *hcpu)
3272 {
3273         if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
3274                 buffer_exit_cpu((unsigned long)hcpu);
3275         return NOTIFY_OK;
3276 }
3277
3278 /**
3279  * bh_uptodate_or_lock - Test whether the buffer is uptodate
3280  * @bh: struct buffer_head
3281  *
3282  * Return true if the buffer is up-to-date and false,
3283  * with the buffer locked, if not.
3284  */
3285 int bh_uptodate_or_lock(struct buffer_head *bh)
3286 {
3287         if (!buffer_uptodate(bh)) {
3288                 lock_buffer(bh);
3289                 if (!buffer_uptodate(bh))
3290                         return 0;
3291                 unlock_buffer(bh);
3292         }
3293         return 1;
3294 }
3295 EXPORT_SYMBOL(bh_uptodate_or_lock);
3296
3297 /**
3298  * bh_submit_read - Submit a locked buffer for reading
3299  * @bh: struct buffer_head
3300  *
3301  * Returns zero on success and -EIO on error.
3302  */
3303 int bh_submit_read(struct buffer_head *bh)
3304 {
3305         BUG_ON(!buffer_locked(bh));
3306
3307         if (buffer_uptodate(bh)) {
3308                 unlock_buffer(bh);
3309                 return 0;
3310         }
3311
3312         get_bh(bh);
3313         bh->b_end_io = end_buffer_read_sync;
3314         submit_bh(READ, bh);
3315         wait_on_buffer(bh);
3316         if (buffer_uptodate(bh))
3317                 return 0;
3318         return -EIO;
3319 }
3320 EXPORT_SYMBOL(bh_submit_read);
3321
3322 static void
3323 init_buffer_head(void *data)
3324 {
3325         struct buffer_head *bh = data;
3326
3327         memset(bh, 0, sizeof(*bh));
3328         INIT_LIST_HEAD(&bh->b_assoc_buffers);
3329 }
3330
3331 void __init buffer_init(void)
3332 {
3333         int nrpages;
3334
3335         bh_cachep = kmem_cache_create("buffer_head",
3336                         sizeof(struct buffer_head), 0,
3337                                 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3338                                 SLAB_MEM_SPREAD),
3339                                 init_buffer_head);
3340
3341         /*
3342          * Limit the bh occupancy to 10% of ZONE_NORMAL
3343          */
3344         nrpages = (nr_free_buffer_pages() * 10) / 100;
3345         max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3346         hotcpu_notifier(buffer_cpu_notify, 0);
3347 }
3348
3349 EXPORT_SYMBOL(__bforget);
3350 EXPORT_SYMBOL(__brelse);
3351 EXPORT_SYMBOL(__wait_on_buffer);
3352 EXPORT_SYMBOL(block_commit_write);
3353 EXPORT_SYMBOL(block_prepare_write);
3354 EXPORT_SYMBOL(block_page_mkwrite);
3355 EXPORT_SYMBOL(block_read_full_page);
3356 EXPORT_SYMBOL(block_sync_page);
3357 EXPORT_SYMBOL(block_truncate_page);
3358 EXPORT_SYMBOL(block_write_full_page);
3359 EXPORT_SYMBOL(cont_write_begin);
3360 EXPORT_SYMBOL(end_buffer_read_sync);
3361 EXPORT_SYMBOL(end_buffer_write_sync);
3362 EXPORT_SYMBOL(file_fsync);
3363 EXPORT_SYMBOL(fsync_bdev);
3364 EXPORT_SYMBOL(generic_block_bmap);
3365 EXPORT_SYMBOL(generic_cont_expand_simple);
3366 EXPORT_SYMBOL(init_buffer);
3367 EXPORT_SYMBOL(invalidate_bdev);
3368 EXPORT_SYMBOL(ll_rw_block);
3369 EXPORT_SYMBOL(mark_buffer_dirty);
3370 EXPORT_SYMBOL(submit_bh);
3371 EXPORT_SYMBOL(sync_dirty_buffer);
3372 EXPORT_SYMBOL(unlock_buffer);