ocfs2: harden buffer check during mapping of page blocks
[linux-2.6] / fs / ocfs2 / aops.c
1 /* -*- mode: c; c-basic-offset: 8; -*-
2  * vim: noexpandtab sw=8 ts=8 sts=0:
3  *
4  * Copyright (C) 2002, 2004 Oracle.  All rights reserved.
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public
8  * License as published by the Free Software Foundation; either
9  * version 2 of the License, or (at your option) any later version.
10  *
11  * This program is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14  * General Public License for more details.
15  *
16  * You should have received a copy of the GNU General Public
17  * License along with this program; if not, write to the
18  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
19  * Boston, MA 021110-1307, USA.
20  */
21
22 #include <linux/fs.h>
23 #include <linux/slab.h>
24 #include <linux/highmem.h>
25 #include <linux/pagemap.h>
26 #include <asm/byteorder.h>
27 #include <linux/swap.h>
28 #include <linux/pipe_fs_i.h>
29
30 #define MLOG_MASK_PREFIX ML_FILE_IO
31 #include <cluster/masklog.h>
32
33 #include "ocfs2.h"
34
35 #include "alloc.h"
36 #include "aops.h"
37 #include "dlmglue.h"
38 #include "extent_map.h"
39 #include "file.h"
40 #include "inode.h"
41 #include "journal.h"
42 #include "suballoc.h"
43 #include "super.h"
44 #include "symlink.h"
45
46 #include "buffer_head_io.h"
47
48 static int ocfs2_symlink_get_block(struct inode *inode, sector_t iblock,
49                                    struct buffer_head *bh_result, int create)
50 {
51         int err = -EIO;
52         int status;
53         struct ocfs2_dinode *fe = NULL;
54         struct buffer_head *bh = NULL;
55         struct buffer_head *buffer_cache_bh = NULL;
56         struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
57         void *kaddr;
58
59         mlog_entry("(0x%p, %llu, 0x%p, %d)\n", inode,
60                    (unsigned long long)iblock, bh_result, create);
61
62         BUG_ON(ocfs2_inode_is_fast_symlink(inode));
63
64         if ((iblock << inode->i_sb->s_blocksize_bits) > PATH_MAX + 1) {
65                 mlog(ML_ERROR, "block offset > PATH_MAX: %llu",
66                      (unsigned long long)iblock);
67                 goto bail;
68         }
69
70         status = ocfs2_read_block(OCFS2_SB(inode->i_sb),
71                                   OCFS2_I(inode)->ip_blkno,
72                                   &bh, OCFS2_BH_CACHED, inode);
73         if (status < 0) {
74                 mlog_errno(status);
75                 goto bail;
76         }
77         fe = (struct ocfs2_dinode *) bh->b_data;
78
79         if (!OCFS2_IS_VALID_DINODE(fe)) {
80                 mlog(ML_ERROR, "Invalid dinode #%llu: signature = %.*s\n",
81                      (unsigned long long)le64_to_cpu(fe->i_blkno), 7,
82                      fe->i_signature);
83                 goto bail;
84         }
85
86         if ((u64)iblock >= ocfs2_clusters_to_blocks(inode->i_sb,
87                                                     le32_to_cpu(fe->i_clusters))) {
88                 mlog(ML_ERROR, "block offset is outside the allocated size: "
89                      "%llu\n", (unsigned long long)iblock);
90                 goto bail;
91         }
92
93         /* We don't use the page cache to create symlink data, so if
94          * need be, copy it over from the buffer cache. */
95         if (!buffer_uptodate(bh_result) && ocfs2_inode_is_new(inode)) {
96                 u64 blkno = le64_to_cpu(fe->id2.i_list.l_recs[0].e_blkno) +
97                             iblock;
98                 buffer_cache_bh = sb_getblk(osb->sb, blkno);
99                 if (!buffer_cache_bh) {
100                         mlog(ML_ERROR, "couldn't getblock for symlink!\n");
101                         goto bail;
102                 }
103
104                 /* we haven't locked out transactions, so a commit
105                  * could've happened. Since we've got a reference on
106                  * the bh, even if it commits while we're doing the
107                  * copy, the data is still good. */
108                 if (buffer_jbd(buffer_cache_bh)
109                     && ocfs2_inode_is_new(inode)) {
110                         kaddr = kmap_atomic(bh_result->b_page, KM_USER0);
111                         if (!kaddr) {
112                                 mlog(ML_ERROR, "couldn't kmap!\n");
113                                 goto bail;
114                         }
115                         memcpy(kaddr + (bh_result->b_size * iblock),
116                                buffer_cache_bh->b_data,
117                                bh_result->b_size);
118                         kunmap_atomic(kaddr, KM_USER0);
119                         set_buffer_uptodate(bh_result);
120                 }
121                 brelse(buffer_cache_bh);
122         }
123
124         map_bh(bh_result, inode->i_sb,
125                le64_to_cpu(fe->id2.i_list.l_recs[0].e_blkno) + iblock);
126
127         err = 0;
128
129 bail:
130         if (bh)
131                 brelse(bh);
132
133         mlog_exit(err);
134         return err;
135 }
136
137 static int ocfs2_get_block(struct inode *inode, sector_t iblock,
138                            struct buffer_head *bh_result, int create)
139 {
140         int err = 0;
141         unsigned int ext_flags;
142         u64 p_blkno, past_eof;
143         struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
144
145         mlog_entry("(0x%p, %llu, 0x%p, %d)\n", inode,
146                    (unsigned long long)iblock, bh_result, create);
147
148         if (OCFS2_I(inode)->ip_flags & OCFS2_INODE_SYSTEM_FILE)
149                 mlog(ML_NOTICE, "get_block on system inode 0x%p (%lu)\n",
150                      inode, inode->i_ino);
151
152         if (S_ISLNK(inode->i_mode)) {
153                 /* this always does I/O for some reason. */
154                 err = ocfs2_symlink_get_block(inode, iblock, bh_result, create);
155                 goto bail;
156         }
157
158         err = ocfs2_extent_map_get_blocks(inode, iblock, &p_blkno, NULL,
159                                           &ext_flags);
160         if (err) {
161                 mlog(ML_ERROR, "Error %d from get_blocks(0x%p, %llu, 1, "
162                      "%llu, NULL)\n", err, inode, (unsigned long long)iblock,
163                      (unsigned long long)p_blkno);
164                 goto bail;
165         }
166
167         /*
168          * ocfs2 never allocates in this function - the only time we
169          * need to use BH_New is when we're extending i_size on a file
170          * system which doesn't support holes, in which case BH_New
171          * allows block_prepare_write() to zero.
172          */
173         mlog_bug_on_msg(create && p_blkno == 0 && ocfs2_sparse_alloc(osb),
174                         "ino %lu, iblock %llu\n", inode->i_ino,
175                         (unsigned long long)iblock);
176
177         /* Treat the unwritten extent as a hole for zeroing purposes. */
178         if (p_blkno && !(ext_flags & OCFS2_EXT_UNWRITTEN))
179                 map_bh(bh_result, inode->i_sb, p_blkno);
180
181         if (!ocfs2_sparse_alloc(osb)) {
182                 if (p_blkno == 0) {
183                         err = -EIO;
184                         mlog(ML_ERROR,
185                              "iblock = %llu p_blkno = %llu blkno=(%llu)\n",
186                              (unsigned long long)iblock,
187                              (unsigned long long)p_blkno,
188                              (unsigned long long)OCFS2_I(inode)->ip_blkno);
189                         mlog(ML_ERROR, "Size %llu, clusters %u\n", (unsigned long long)i_size_read(inode), OCFS2_I(inode)->ip_clusters);
190                         dump_stack();
191                 }
192
193                 past_eof = ocfs2_blocks_for_bytes(inode->i_sb, i_size_read(inode));
194                 mlog(0, "Inode %lu, past_eof = %llu\n", inode->i_ino,
195                      (unsigned long long)past_eof);
196
197                 if (create && (iblock >= past_eof))
198                         set_buffer_new(bh_result);
199         }
200
201 bail:
202         if (err < 0)
203                 err = -EIO;
204
205         mlog_exit(err);
206         return err;
207 }
208
209 static int ocfs2_readpage(struct file *file, struct page *page)
210 {
211         struct inode *inode = page->mapping->host;
212         loff_t start = (loff_t)page->index << PAGE_CACHE_SHIFT;
213         int ret, unlock = 1;
214
215         mlog_entry("(0x%p, %lu)\n", file, (page ? page->index : 0));
216
217         ret = ocfs2_meta_lock_with_page(inode, NULL, 0, page);
218         if (ret != 0) {
219                 if (ret == AOP_TRUNCATED_PAGE)
220                         unlock = 0;
221                 mlog_errno(ret);
222                 goto out;
223         }
224
225         if (down_read_trylock(&OCFS2_I(inode)->ip_alloc_sem) == 0) {
226                 ret = AOP_TRUNCATED_PAGE;
227                 goto out_meta_unlock;
228         }
229
230         /*
231          * i_size might have just been updated as we grabed the meta lock.  We
232          * might now be discovering a truncate that hit on another node.
233          * block_read_full_page->get_block freaks out if it is asked to read
234          * beyond the end of a file, so we check here.  Callers
235          * (generic_file_read, fault->nopage) are clever enough to check i_size
236          * and notice that the page they just read isn't needed.
237          *
238          * XXX sys_readahead() seems to get that wrong?
239          */
240         if (start >= i_size_read(inode)) {
241                 zero_user_page(page, 0, PAGE_SIZE, KM_USER0);
242                 SetPageUptodate(page);
243                 ret = 0;
244                 goto out_alloc;
245         }
246
247         ret = ocfs2_data_lock_with_page(inode, 0, page);
248         if (ret != 0) {
249                 if (ret == AOP_TRUNCATED_PAGE)
250                         unlock = 0;
251                 mlog_errno(ret);
252                 goto out_alloc;
253         }
254
255         ret = block_read_full_page(page, ocfs2_get_block);
256         unlock = 0;
257
258         ocfs2_data_unlock(inode, 0);
259 out_alloc:
260         up_read(&OCFS2_I(inode)->ip_alloc_sem);
261 out_meta_unlock:
262         ocfs2_meta_unlock(inode, 0);
263 out:
264         if (unlock)
265                 unlock_page(page);
266         mlog_exit(ret);
267         return ret;
268 }
269
270 /* Note: Because we don't support holes, our allocation has
271  * already happened (allocation writes zeros to the file data)
272  * so we don't have to worry about ordered writes in
273  * ocfs2_writepage.
274  *
275  * ->writepage is called during the process of invalidating the page cache
276  * during blocked lock processing.  It can't block on any cluster locks
277  * to during block mapping.  It's relying on the fact that the block
278  * mapping can't have disappeared under the dirty pages that it is
279  * being asked to write back.
280  */
281 static int ocfs2_writepage(struct page *page, struct writeback_control *wbc)
282 {
283         int ret;
284
285         mlog_entry("(0x%p)\n", page);
286
287         ret = block_write_full_page(page, ocfs2_get_block, wbc);
288
289         mlog_exit(ret);
290
291         return ret;
292 }
293
294 /*
295  * This is called from ocfs2_write_zero_page() which has handled it's
296  * own cluster locking and has ensured allocation exists for those
297  * blocks to be written.
298  */
299 int ocfs2_prepare_write_nolock(struct inode *inode, struct page *page,
300                                unsigned from, unsigned to)
301 {
302         int ret;
303
304         down_read(&OCFS2_I(inode)->ip_alloc_sem);
305
306         ret = block_prepare_write(page, from, to, ocfs2_get_block);
307
308         up_read(&OCFS2_I(inode)->ip_alloc_sem);
309
310         return ret;
311 }
312
313 /* Taken from ext3. We don't necessarily need the full blown
314  * functionality yet, but IMHO it's better to cut and paste the whole
315  * thing so we can avoid introducing our own bugs (and easily pick up
316  * their fixes when they happen) --Mark */
317 int walk_page_buffers(  handle_t *handle,
318                         struct buffer_head *head,
319                         unsigned from,
320                         unsigned to,
321                         int *partial,
322                         int (*fn)(      handle_t *handle,
323                                         struct buffer_head *bh))
324 {
325         struct buffer_head *bh;
326         unsigned block_start, block_end;
327         unsigned blocksize = head->b_size;
328         int err, ret = 0;
329         struct buffer_head *next;
330
331         for (   bh = head, block_start = 0;
332                 ret == 0 && (bh != head || !block_start);
333                 block_start = block_end, bh = next)
334         {
335                 next = bh->b_this_page;
336                 block_end = block_start + blocksize;
337                 if (block_end <= from || block_start >= to) {
338                         if (partial && !buffer_uptodate(bh))
339                                 *partial = 1;
340                         continue;
341                 }
342                 err = (*fn)(handle, bh);
343                 if (!ret)
344                         ret = err;
345         }
346         return ret;
347 }
348
349 handle_t *ocfs2_start_walk_page_trans(struct inode *inode,
350                                                          struct page *page,
351                                                          unsigned from,
352                                                          unsigned to)
353 {
354         struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
355         handle_t *handle = NULL;
356         int ret = 0;
357
358         handle = ocfs2_start_trans(osb, OCFS2_INODE_UPDATE_CREDITS);
359         if (!handle) {
360                 ret = -ENOMEM;
361                 mlog_errno(ret);
362                 goto out;
363         }
364
365         if (ocfs2_should_order_data(inode)) {
366                 ret = walk_page_buffers(handle,
367                                         page_buffers(page),
368                                         from, to, NULL,
369                                         ocfs2_journal_dirty_data);
370                 if (ret < 0) 
371                         mlog_errno(ret);
372         }
373 out:
374         if (ret) {
375                 if (handle)
376                         ocfs2_commit_trans(osb, handle);
377                 handle = ERR_PTR(ret);
378         }
379         return handle;
380 }
381
382 static sector_t ocfs2_bmap(struct address_space *mapping, sector_t block)
383 {
384         sector_t status;
385         u64 p_blkno = 0;
386         int err = 0;
387         struct inode *inode = mapping->host;
388
389         mlog_entry("(block = %llu)\n", (unsigned long long)block);
390
391         /* We don't need to lock journal system files, since they aren't
392          * accessed concurrently from multiple nodes.
393          */
394         if (!INODE_JOURNAL(inode)) {
395                 err = ocfs2_meta_lock(inode, NULL, 0);
396                 if (err) {
397                         if (err != -ENOENT)
398                                 mlog_errno(err);
399                         goto bail;
400                 }
401                 down_read(&OCFS2_I(inode)->ip_alloc_sem);
402         }
403
404         err = ocfs2_extent_map_get_blocks(inode, block, &p_blkno, NULL, NULL);
405
406         if (!INODE_JOURNAL(inode)) {
407                 up_read(&OCFS2_I(inode)->ip_alloc_sem);
408                 ocfs2_meta_unlock(inode, 0);
409         }
410
411         if (err) {
412                 mlog(ML_ERROR, "get_blocks() failed, block = %llu\n",
413                      (unsigned long long)block);
414                 mlog_errno(err);
415                 goto bail;
416         }
417
418
419 bail:
420         status = err ? 0 : p_blkno;
421
422         mlog_exit((int)status);
423
424         return status;
425 }
426
427 /*
428  * TODO: Make this into a generic get_blocks function.
429  *
430  * From do_direct_io in direct-io.c:
431  *  "So what we do is to permit the ->get_blocks function to populate
432  *   bh.b_size with the size of IO which is permitted at this offset and
433  *   this i_blkbits."
434  *
435  * This function is called directly from get_more_blocks in direct-io.c.
436  *
437  * called like this: dio->get_blocks(dio->inode, fs_startblk,
438  *                                      fs_count, map_bh, dio->rw == WRITE);
439  */
440 static int ocfs2_direct_IO_get_blocks(struct inode *inode, sector_t iblock,
441                                      struct buffer_head *bh_result, int create)
442 {
443         int ret;
444         u64 p_blkno, inode_blocks, contig_blocks;
445         unsigned int ext_flags;
446         unsigned char blocksize_bits = inode->i_sb->s_blocksize_bits;
447         unsigned long max_blocks = bh_result->b_size >> inode->i_blkbits;
448
449         /* This function won't even be called if the request isn't all
450          * nicely aligned and of the right size, so there's no need
451          * for us to check any of that. */
452
453         inode_blocks = ocfs2_blocks_for_bytes(inode->i_sb, i_size_read(inode));
454
455         /*
456          * Any write past EOF is not allowed because we'd be extending.
457          */
458         if (create && (iblock + max_blocks) > inode_blocks) {
459                 ret = -EIO;
460                 goto bail;
461         }
462
463         /* This figures out the size of the next contiguous block, and
464          * our logical offset */
465         ret = ocfs2_extent_map_get_blocks(inode, iblock, &p_blkno,
466                                           &contig_blocks, &ext_flags);
467         if (ret) {
468                 mlog(ML_ERROR, "get_blocks() failed iblock=%llu\n",
469                      (unsigned long long)iblock);
470                 ret = -EIO;
471                 goto bail;
472         }
473
474         if (!ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)) && !p_blkno) {
475                 ocfs2_error(inode->i_sb,
476                             "Inode %llu has a hole at block %llu\n",
477                             (unsigned long long)OCFS2_I(inode)->ip_blkno,
478                             (unsigned long long)iblock);
479                 ret = -EROFS;
480                 goto bail;
481         }
482
483         /*
484          * get_more_blocks() expects us to describe a hole by clearing
485          * the mapped bit on bh_result().
486          *
487          * Consider an unwritten extent as a hole.
488          */
489         if (p_blkno && !(ext_flags & OCFS2_EXT_UNWRITTEN))
490                 map_bh(bh_result, inode->i_sb, p_blkno);
491         else {
492                 /*
493                  * ocfs2_prepare_inode_for_write() should have caught
494                  * the case where we'd be filling a hole and triggered
495                  * a buffered write instead.
496                  */
497                 if (create) {
498                         ret = -EIO;
499                         mlog_errno(ret);
500                         goto bail;
501                 }
502
503                 clear_buffer_mapped(bh_result);
504         }
505
506         /* make sure we don't map more than max_blocks blocks here as
507            that's all the kernel will handle at this point. */
508         if (max_blocks < contig_blocks)
509                 contig_blocks = max_blocks;
510         bh_result->b_size = contig_blocks << blocksize_bits;
511 bail:
512         return ret;
513 }
514
515 /* 
516  * ocfs2_dio_end_io is called by the dio core when a dio is finished.  We're
517  * particularly interested in the aio/dio case.  Like the core uses
518  * i_alloc_sem, we use the rw_lock DLM lock to protect io on one node from
519  * truncation on another.
520  */
521 static void ocfs2_dio_end_io(struct kiocb *iocb,
522                              loff_t offset,
523                              ssize_t bytes,
524                              void *private)
525 {
526         struct inode *inode = iocb->ki_filp->f_path.dentry->d_inode;
527         int level;
528
529         /* this io's submitter should not have unlocked this before we could */
530         BUG_ON(!ocfs2_iocb_is_rw_locked(iocb));
531
532         ocfs2_iocb_clear_rw_locked(iocb);
533
534         level = ocfs2_iocb_rw_locked_level(iocb);
535         if (!level)
536                 up_read(&inode->i_alloc_sem);
537         ocfs2_rw_unlock(inode, level);
538 }
539
540 /*
541  * ocfs2_invalidatepage() and ocfs2_releasepage() are shamelessly stolen
542  * from ext3.  PageChecked() bits have been removed as OCFS2 does not
543  * do journalled data.
544  */
545 static void ocfs2_invalidatepage(struct page *page, unsigned long offset)
546 {
547         journal_t *journal = OCFS2_SB(page->mapping->host->i_sb)->journal->j_journal;
548
549         journal_invalidatepage(journal, page, offset);
550 }
551
552 static int ocfs2_releasepage(struct page *page, gfp_t wait)
553 {
554         journal_t *journal = OCFS2_SB(page->mapping->host->i_sb)->journal->j_journal;
555
556         if (!page_has_buffers(page))
557                 return 0;
558         return journal_try_to_free_buffers(journal, page, wait);
559 }
560
561 static ssize_t ocfs2_direct_IO(int rw,
562                                struct kiocb *iocb,
563                                const struct iovec *iov,
564                                loff_t offset,
565                                unsigned long nr_segs)
566 {
567         struct file *file = iocb->ki_filp;
568         struct inode *inode = file->f_path.dentry->d_inode->i_mapping->host;
569         int ret;
570
571         mlog_entry_void();
572
573         if (!ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb))) {
574                 /*
575                  * We get PR data locks even for O_DIRECT.  This
576                  * allows concurrent O_DIRECT I/O but doesn't let
577                  * O_DIRECT with extending and buffered zeroing writes
578                  * race.  If they did race then the buffered zeroing
579                  * could be written back after the O_DIRECT I/O.  It's
580                  * one thing to tell people not to mix buffered and
581                  * O_DIRECT writes, but expecting them to understand
582                  * that file extension is also an implicit buffered
583                  * write is too much.  By getting the PR we force
584                  * writeback of the buffered zeroing before
585                  * proceeding.
586                  */
587                 ret = ocfs2_data_lock(inode, 0);
588                 if (ret < 0) {
589                         mlog_errno(ret);
590                         goto out;
591                 }
592                 ocfs2_data_unlock(inode, 0);
593         }
594
595         ret = blockdev_direct_IO_no_locking(rw, iocb, inode,
596                                             inode->i_sb->s_bdev, iov, offset,
597                                             nr_segs, 
598                                             ocfs2_direct_IO_get_blocks,
599                                             ocfs2_dio_end_io);
600 out:
601         mlog_exit(ret);
602         return ret;
603 }
604
605 static void ocfs2_figure_cluster_boundaries(struct ocfs2_super *osb,
606                                             u32 cpos,
607                                             unsigned int *start,
608                                             unsigned int *end)
609 {
610         unsigned int cluster_start = 0, cluster_end = PAGE_CACHE_SIZE;
611
612         if (unlikely(PAGE_CACHE_SHIFT > osb->s_clustersize_bits)) {
613                 unsigned int cpp;
614
615                 cpp = 1 << (PAGE_CACHE_SHIFT - osb->s_clustersize_bits);
616
617                 cluster_start = cpos % cpp;
618                 cluster_start = cluster_start << osb->s_clustersize_bits;
619
620                 cluster_end = cluster_start + osb->s_clustersize;
621         }
622
623         BUG_ON(cluster_start > PAGE_SIZE);
624         BUG_ON(cluster_end > PAGE_SIZE);
625
626         if (start)
627                 *start = cluster_start;
628         if (end)
629                 *end = cluster_end;
630 }
631
632 /*
633  * 'from' and 'to' are the region in the page to avoid zeroing.
634  *
635  * If pagesize > clustersize, this function will avoid zeroing outside
636  * of the cluster boundary.
637  *
638  * from == to == 0 is code for "zero the entire cluster region"
639  */
640 static void ocfs2_clear_page_regions(struct page *page,
641                                      struct ocfs2_super *osb, u32 cpos,
642                                      unsigned from, unsigned to)
643 {
644         void *kaddr;
645         unsigned int cluster_start, cluster_end;
646
647         ocfs2_figure_cluster_boundaries(osb, cpos, &cluster_start, &cluster_end);
648
649         kaddr = kmap_atomic(page, KM_USER0);
650
651         if (from || to) {
652                 if (from > cluster_start)
653                         memset(kaddr + cluster_start, 0, from - cluster_start);
654                 if (to < cluster_end)
655                         memset(kaddr + to, 0, cluster_end - to);
656         } else {
657                 memset(kaddr + cluster_start, 0, cluster_end - cluster_start);
658         }
659
660         kunmap_atomic(kaddr, KM_USER0);
661 }
662
663 /*
664  * Some of this taken from block_prepare_write(). We already have our
665  * mapping by now though, and the entire write will be allocating or
666  * it won't, so not much need to use BH_New.
667  *
668  * This will also skip zeroing, which is handled externally.
669  */
670 int ocfs2_map_page_blocks(struct page *page, u64 *p_blkno,
671                           struct inode *inode, unsigned int from,
672                           unsigned int to, int new)
673 {
674         int ret = 0;
675         struct buffer_head *head, *bh, *wait[2], **wait_bh = wait;
676         unsigned int block_end, block_start;
677         unsigned int bsize = 1 << inode->i_blkbits;
678
679         if (!page_has_buffers(page))
680                 create_empty_buffers(page, bsize, 0);
681
682         head = page_buffers(page);
683         for (bh = head, block_start = 0; bh != head || !block_start;
684              bh = bh->b_this_page, block_start += bsize) {
685                 block_end = block_start + bsize;
686
687                 clear_buffer_new(bh);
688
689                 /*
690                  * Ignore blocks outside of our i/o range -
691                  * they may belong to unallocated clusters.
692                  */
693                 if (block_start >= to || block_end <= from) {
694                         if (PageUptodate(page))
695                                 set_buffer_uptodate(bh);
696                         continue;
697                 }
698
699                 /*
700                  * For an allocating write with cluster size >= page
701                  * size, we always write the entire page.
702                  */
703                 if (new)
704                         set_buffer_new(bh);
705
706                 if (!buffer_mapped(bh)) {
707                         map_bh(bh, inode->i_sb, *p_blkno);
708                         unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
709                 }
710
711                 if (PageUptodate(page)) {
712                         if (!buffer_uptodate(bh))
713                                 set_buffer_uptodate(bh);
714                 } else if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
715                            !buffer_new(bh) &&
716                            (block_start < from || block_end > to)) {
717                         ll_rw_block(READ, 1, &bh);
718                         *wait_bh++=bh;
719                 }
720
721                 *p_blkno = *p_blkno + 1;
722         }
723
724         /*
725          * If we issued read requests - let them complete.
726          */
727         while(wait_bh > wait) {
728                 wait_on_buffer(*--wait_bh);
729                 if (!buffer_uptodate(*wait_bh))
730                         ret = -EIO;
731         }
732
733         if (ret == 0 || !new)
734                 return ret;
735
736         /*
737          * If we get -EIO above, zero out any newly allocated blocks
738          * to avoid exposing stale data.
739          */
740         bh = head;
741         block_start = 0;
742         do {
743                 void *kaddr;
744
745                 block_end = block_start + bsize;
746                 if (block_end <= from)
747                         goto next_bh;
748                 if (block_start >= to)
749                         break;
750
751                 kaddr = kmap_atomic(page, KM_USER0);
752                 memset(kaddr+block_start, 0, bh->b_size);
753                 flush_dcache_page(page);
754                 kunmap_atomic(kaddr, KM_USER0);
755                 set_buffer_uptodate(bh);
756                 mark_buffer_dirty(bh);
757
758 next_bh:
759                 block_start = block_end;
760                 bh = bh->b_this_page;
761         } while (bh != head);
762
763         return ret;
764 }
765
766 #if (PAGE_CACHE_SIZE >= OCFS2_MAX_CLUSTERSIZE)
767 #define OCFS2_MAX_CTXT_PAGES    1
768 #else
769 #define OCFS2_MAX_CTXT_PAGES    (OCFS2_MAX_CLUSTERSIZE / PAGE_CACHE_SIZE)
770 #endif
771
772 #define OCFS2_MAX_CLUSTERS_PER_PAGE     (PAGE_CACHE_SIZE / OCFS2_MIN_CLUSTERSIZE)
773
774 /*
775  * Describe the state of a single cluster to be written to.
776  */
777 struct ocfs2_write_cluster_desc {
778         u32             c_cpos;
779         u32             c_phys;
780         /*
781          * Give this a unique field because c_phys eventually gets
782          * filled.
783          */
784         unsigned        c_new;
785 };
786
787 struct ocfs2_write_ctxt {
788         /* Logical cluster position / len of write */
789         u32                             w_cpos;
790         u32                             w_clen;
791
792         struct ocfs2_write_cluster_desc w_desc[OCFS2_MAX_CLUSTERS_PER_PAGE];
793
794         /*
795          * This is true if page_size > cluster_size.
796          *
797          * It triggers a set of special cases during write which might
798          * have to deal with allocating writes to partial pages.
799          */
800         unsigned int                    w_large_pages;
801
802         /*
803          * Pages involved in this write.
804          *
805          * w_target_page is the page being written to by the user.
806          *
807          * w_pages is an array of pages which always contains
808          * w_target_page, and in the case of an allocating write with
809          * page_size < cluster size, it will contain zero'd and mapped
810          * pages adjacent to w_target_page which need to be written
811          * out in so that future reads from that region will get
812          * zero's.
813          */
814         struct page                     *w_pages[OCFS2_MAX_CTXT_PAGES];
815         unsigned int                    w_num_pages;
816         struct page                     *w_target_page;
817
818         /*
819          * ocfs2_write_end() uses this to know what the real range to
820          * write in the target should be.
821          */
822         unsigned int                    w_target_from;
823         unsigned int                    w_target_to;
824
825         /*
826          * We could use journal_current_handle() but this is cleaner,
827          * IMHO -Mark
828          */
829         handle_t                        *w_handle;
830
831         struct buffer_head              *w_di_bh;
832 };
833
834 static void ocfs2_free_write_ctxt(struct ocfs2_write_ctxt *wc)
835 {
836         int i;
837
838         for(i = 0; i < wc->w_num_pages; i++) {
839                 if (wc->w_pages[i] == NULL)
840                         continue;
841
842                 unlock_page(wc->w_pages[i]);
843                 mark_page_accessed(wc->w_pages[i]);
844                 page_cache_release(wc->w_pages[i]);
845         }
846
847         brelse(wc->w_di_bh);
848         kfree(wc);
849 }
850
851 static int ocfs2_alloc_write_ctxt(struct ocfs2_write_ctxt **wcp,
852                                   struct ocfs2_super *osb, loff_t pos,
853                                   unsigned len, struct buffer_head *di_bh)
854 {
855         struct ocfs2_write_ctxt *wc;
856
857         wc = kzalloc(sizeof(struct ocfs2_write_ctxt), GFP_NOFS);
858         if (!wc)
859                 return -ENOMEM;
860
861         wc->w_cpos = pos >> osb->s_clustersize_bits;
862         wc->w_clen = ocfs2_clusters_for_bytes(osb->sb, len);
863         get_bh(di_bh);
864         wc->w_di_bh = di_bh;
865
866         if (unlikely(PAGE_CACHE_SHIFT > osb->s_clustersize_bits))
867                 wc->w_large_pages = 1;
868         else
869                 wc->w_large_pages = 0;
870
871         *wcp = wc;
872
873         return 0;
874 }
875
876 /*
877  * If a page has any new buffers, zero them out here, and mark them uptodate
878  * and dirty so they'll be written out (in order to prevent uninitialised
879  * block data from leaking). And clear the new bit.
880  */
881 static void ocfs2_zero_new_buffers(struct page *page, unsigned from, unsigned to)
882 {
883         unsigned int block_start, block_end;
884         struct buffer_head *head, *bh;
885
886         BUG_ON(!PageLocked(page));
887         if (!page_has_buffers(page))
888                 return;
889
890         bh = head = page_buffers(page);
891         block_start = 0;
892         do {
893                 block_end = block_start + bh->b_size;
894
895                 if (buffer_new(bh)) {
896                         if (block_end > from && block_start < to) {
897                                 if (!PageUptodate(page)) {
898                                         unsigned start, end;
899                                         void *kaddr;
900
901                                         start = max(from, block_start);
902                                         end = min(to, block_end);
903
904                                         kaddr = kmap_atomic(page, KM_USER0);
905                                         memset(kaddr+start, 0, end - start);
906                                         flush_dcache_page(page);
907                                         kunmap_atomic(kaddr, KM_USER0);
908                                         set_buffer_uptodate(bh);
909                                 }
910
911                                 clear_buffer_new(bh);
912                                 mark_buffer_dirty(bh);
913                         }
914                 }
915
916                 block_start = block_end;
917                 bh = bh->b_this_page;
918         } while (bh != head);
919 }
920
921 /*
922  * Only called when we have a failure during allocating write to write
923  * zero's to the newly allocated region.
924  */
925 static void ocfs2_write_failure(struct inode *inode,
926                                 struct ocfs2_write_ctxt *wc,
927                                 loff_t user_pos, unsigned user_len)
928 {
929         int i;
930         unsigned from, to;
931         struct page *tmppage;
932
933         ocfs2_zero_new_buffers(wc->w_target_page, user_pos, user_len);
934
935         if (wc->w_large_pages) {
936                 from = wc->w_target_from;
937                 to = wc->w_target_to;
938         } else {
939                 from = 0;
940                 to = PAGE_CACHE_SIZE;
941         }
942
943         for(i = 0; i < wc->w_num_pages; i++) {
944                 tmppage = wc->w_pages[i];
945
946                 if (ocfs2_should_order_data(inode))
947                         walk_page_buffers(wc->w_handle, page_buffers(tmppage),
948                                           from, to, NULL,
949                                           ocfs2_journal_dirty_data);
950
951                 block_commit_write(tmppage, from, to);
952         }
953 }
954
955 static int ocfs2_prepare_page_for_write(struct inode *inode, u64 *p_blkno,
956                                         struct ocfs2_write_ctxt *wc,
957                                         struct page *page, u32 cpos,
958                                         loff_t user_pos, unsigned user_len,
959                                         int new)
960 {
961         int ret;
962         unsigned int map_from = 0, map_to = 0;
963         unsigned int cluster_start, cluster_end;
964         unsigned int user_data_from = 0, user_data_to = 0;
965
966         ocfs2_figure_cluster_boundaries(OCFS2_SB(inode->i_sb), cpos,
967                                         &cluster_start, &cluster_end);
968
969         if (page == wc->w_target_page) {
970                 map_from = user_pos & (PAGE_CACHE_SIZE - 1);
971                 map_to = map_from + user_len;
972
973                 if (new)
974                         ret = ocfs2_map_page_blocks(page, p_blkno, inode,
975                                                     cluster_start, cluster_end,
976                                                     new);
977                 else
978                         ret = ocfs2_map_page_blocks(page, p_blkno, inode,
979                                                     map_from, map_to, new);
980                 if (ret) {
981                         mlog_errno(ret);
982                         goto out;
983                 }
984
985                 user_data_from = map_from;
986                 user_data_to = map_to;
987                 if (new) {
988                         map_from = cluster_start;
989                         map_to = cluster_end;
990                 }
991
992                 wc->w_target_from = map_from;
993                 wc->w_target_to = map_to;
994         } else {
995                 /*
996                  * If we haven't allocated the new page yet, we
997                  * shouldn't be writing it out without copying user
998                  * data. This is likely a math error from the caller.
999                  */
1000                 BUG_ON(!new);
1001
1002                 map_from = cluster_start;
1003                 map_to = cluster_end;
1004
1005                 ret = ocfs2_map_page_blocks(page, p_blkno, inode,
1006                                             cluster_start, cluster_end, new);
1007                 if (ret) {
1008                         mlog_errno(ret);
1009                         goto out;
1010                 }
1011         }
1012
1013         /*
1014          * Parts of newly allocated pages need to be zero'd.
1015          *
1016          * Above, we have also rewritten 'to' and 'from' - as far as
1017          * the rest of the function is concerned, the entire cluster
1018          * range inside of a page needs to be written.
1019          *
1020          * We can skip this if the page is up to date - it's already
1021          * been zero'd from being read in as a hole.
1022          */
1023         if (new && !PageUptodate(page))
1024                 ocfs2_clear_page_regions(page, OCFS2_SB(inode->i_sb),
1025                                          cpos, user_data_from, user_data_to);
1026
1027         flush_dcache_page(page);
1028
1029 out:
1030         return ret;
1031 }
1032
1033 /*
1034  * This function will only grab one clusters worth of pages.
1035  */
1036 static int ocfs2_grab_pages_for_write(struct address_space *mapping,
1037                                       struct ocfs2_write_ctxt *wc,
1038                                       u32 cpos, loff_t user_pos, int new,
1039                                       struct page *mmap_page)
1040 {
1041         int ret = 0, i;
1042         unsigned long start, target_index, index;
1043         struct inode *inode = mapping->host;
1044
1045         target_index = user_pos >> PAGE_CACHE_SHIFT;
1046
1047         /*
1048          * Figure out how many pages we'll be manipulating here. For
1049          * non allocating write, we just change the one
1050          * page. Otherwise, we'll need a whole clusters worth.
1051          */
1052         if (new) {
1053                 wc->w_num_pages = ocfs2_pages_per_cluster(inode->i_sb);
1054                 start = ocfs2_align_clusters_to_page_index(inode->i_sb, cpos);
1055         } else {
1056                 wc->w_num_pages = 1;
1057                 start = target_index;
1058         }
1059
1060         for(i = 0; i < wc->w_num_pages; i++) {
1061                 index = start + i;
1062
1063                 if (index == target_index && mmap_page) {
1064                         /*
1065                          * ocfs2_pagemkwrite() is a little different
1066                          * and wants us to directly use the page
1067                          * passed in.
1068                          */
1069                         lock_page(mmap_page);
1070
1071                         if (mmap_page->mapping != mapping) {
1072                                 unlock_page(mmap_page);
1073                                 /*
1074                                  * Sanity check - the locking in
1075                                  * ocfs2_pagemkwrite() should ensure
1076                                  * that this code doesn't trigger.
1077                                  */
1078                                 ret = -EINVAL;
1079                                 mlog_errno(ret);
1080                                 goto out;
1081                         }
1082
1083                         page_cache_get(mmap_page);
1084                         wc->w_pages[i] = mmap_page;
1085                 } else {
1086                         wc->w_pages[i] = find_or_create_page(mapping, index,
1087                                                              GFP_NOFS);
1088                         if (!wc->w_pages[i]) {
1089                                 ret = -ENOMEM;
1090                                 mlog_errno(ret);
1091                                 goto out;
1092                         }
1093                 }
1094
1095                 if (index == target_index)
1096                         wc->w_target_page = wc->w_pages[i];
1097         }
1098 out:
1099         return ret;
1100 }
1101
1102 /*
1103  * Prepare a single cluster for write one cluster into the file.
1104  */
1105 static int ocfs2_write_cluster(struct address_space *mapping,
1106                                u32 phys, struct ocfs2_alloc_context *data_ac,
1107                                struct ocfs2_alloc_context *meta_ac,
1108                                struct ocfs2_write_ctxt *wc, u32 cpos,
1109                                loff_t user_pos, unsigned user_len)
1110 {
1111         int ret, i, new;
1112         u64 v_blkno, p_blkno;
1113         struct inode *inode = mapping->host;
1114
1115         new = phys == 0 ? 1 : 0;
1116
1117         if (new) {
1118                 u32 tmp_pos;
1119
1120                 /*
1121                  * This is safe to call with the page locks - it won't take
1122                  * any additional semaphores or cluster locks.
1123                  */
1124                 tmp_pos = cpos;
1125                 ret = ocfs2_do_extend_allocation(OCFS2_SB(inode->i_sb), inode,
1126                                                  &tmp_pos, 1, wc->w_di_bh,
1127                                                  wc->w_handle, data_ac,
1128                                                  meta_ac, NULL);
1129                 /*
1130                  * This shouldn't happen because we must have already
1131                  * calculated the correct meta data allocation required. The
1132                  * internal tree allocation code should know how to increase
1133                  * transaction credits itself.
1134                  *
1135                  * If need be, we could handle -EAGAIN for a
1136                  * RESTART_TRANS here.
1137                  */
1138                 mlog_bug_on_msg(ret == -EAGAIN,
1139                                 "Inode %llu: EAGAIN return during allocation.\n",
1140                                 (unsigned long long)OCFS2_I(inode)->ip_blkno);
1141                 if (ret < 0) {
1142                         mlog_errno(ret);
1143                         goto out;
1144                 }
1145
1146                 v_blkno = ocfs2_clusters_to_blocks(inode->i_sb, cpos);
1147         } else {
1148                 v_blkno = user_pos >> inode->i_sb->s_blocksize_bits;
1149         }
1150
1151         /*
1152          * The only reason this should fail is due to an inability to
1153          * find the extent added.
1154          */
1155         ret = ocfs2_extent_map_get_blocks(inode, v_blkno, &p_blkno, NULL,
1156                                           NULL);
1157         if (ret < 0) {
1158                 ocfs2_error(inode->i_sb, "Corrupting extend for inode %llu, "
1159                             "at logical block %llu",
1160                             (unsigned long long)OCFS2_I(inode)->ip_blkno,
1161                             (unsigned long long)v_blkno);
1162                 goto out;
1163         }
1164
1165         BUG_ON(p_blkno == 0);
1166
1167         for(i = 0; i < wc->w_num_pages; i++) {
1168                 int tmpret;
1169
1170                 tmpret = ocfs2_prepare_page_for_write(inode, &p_blkno, wc,
1171                                                       wc->w_pages[i], cpos,
1172                                                       user_pos, user_len, new);
1173                 if (tmpret) {
1174                         mlog_errno(tmpret);
1175                         if (ret == 0)
1176                                 tmpret = ret;
1177                 }
1178         }
1179
1180         /*
1181          * We only have cleanup to do in case of allocating write.
1182          */
1183         if (ret && new)
1184                 ocfs2_write_failure(inode, wc, user_pos, user_len);
1185
1186 out:
1187
1188         return ret;
1189 }
1190
1191 /*
1192  * ocfs2_write_end() wants to know which parts of the target page it
1193  * should complete the write on. It's easiest to compute them ahead of
1194  * time when a more complete view of the write is available.
1195  */
1196 static void ocfs2_set_target_boundaries(struct ocfs2_super *osb,
1197                                         struct ocfs2_write_ctxt *wc,
1198                                         loff_t pos, unsigned len, int alloc)
1199 {
1200         struct ocfs2_write_cluster_desc *desc;
1201
1202         wc->w_target_from = pos & (PAGE_CACHE_SIZE - 1);
1203         wc->w_target_to = wc->w_target_from + len;
1204
1205         if (alloc == 0)
1206                 return;
1207
1208         /*
1209          * Allocating write - we may have different boundaries based
1210          * on page size and cluster size.
1211          *
1212          * NOTE: We can no longer compute one value from the other as
1213          * the actual write length and user provided length may be
1214          * different.
1215          */
1216
1217         if (wc->w_large_pages) {
1218                 /*
1219                  * We only care about the 1st and last cluster within
1220                  * our range and whether they are holes or not. Either
1221                  * value may be extended out to the start/end of a
1222                  * newly allocated cluster.
1223                  */
1224                 desc = &wc->w_desc[0];
1225                 if (desc->c_new)
1226                         ocfs2_figure_cluster_boundaries(osb,
1227                                                         desc->c_cpos,
1228                                                         &wc->w_target_from,
1229                                                         NULL);
1230
1231                 desc = &wc->w_desc[wc->w_clen - 1];
1232                 if (desc->c_new)
1233                         ocfs2_figure_cluster_boundaries(osb,
1234                                                         desc->c_cpos,
1235                                                         NULL,
1236                                                         &wc->w_target_to);
1237         } else {
1238                 wc->w_target_from = 0;
1239                 wc->w_target_to = PAGE_CACHE_SIZE;
1240         }
1241 }
1242
1243 int ocfs2_write_begin_nolock(struct address_space *mapping,
1244                              loff_t pos, unsigned len, unsigned flags,
1245                              struct page **pagep, void **fsdata,
1246                              struct buffer_head *di_bh, struct page *mmap_page)
1247 {
1248         int ret, i, credits = OCFS2_INODE_UPDATE_CREDITS;
1249         unsigned int num_clusters = 0, clusters_to_alloc = 0;
1250         u32 phys = 0;
1251         struct ocfs2_write_ctxt *wc;
1252         struct inode *inode = mapping->host;
1253         struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
1254         struct ocfs2_dinode *di;
1255         struct ocfs2_alloc_context *data_ac = NULL;
1256         struct ocfs2_alloc_context *meta_ac = NULL;
1257         handle_t *handle;
1258         struct ocfs2_write_cluster_desc *desc;
1259
1260         ret = ocfs2_alloc_write_ctxt(&wc, osb, pos, len, di_bh);
1261         if (ret) {
1262                 mlog_errno(ret);
1263                 return ret;
1264         }
1265
1266         di = (struct ocfs2_dinode *)wc->w_di_bh->b_data;
1267
1268         for (i = 0; i < wc->w_clen; i++) {
1269                 desc = &wc->w_desc[i];
1270                 desc->c_cpos = wc->w_cpos + i;
1271
1272                 if (num_clusters == 0) {
1273                         ret = ocfs2_get_clusters(inode, desc->c_cpos, &phys,
1274                                                  &num_clusters, NULL);
1275                         if (ret) {
1276                                 mlog_errno(ret);
1277                                 goto out;
1278                         }
1279                 } else if (phys) {
1280                         /*
1281                          * Only increment phys if it doesn't describe
1282                          * a hole.
1283                          */
1284                         phys++;
1285                 }
1286
1287                 desc->c_phys = phys;
1288                 if (phys == 0) {
1289                         desc->c_new = 1;
1290                         clusters_to_alloc++;
1291                 }
1292
1293                 num_clusters--;
1294         }
1295
1296         /*
1297          * We set w_target_from, w_target_to here so that
1298          * ocfs2_write_end() knows which range in the target page to
1299          * write out. An allocation requires that we write the entire
1300          * cluster range.
1301          */
1302         if (clusters_to_alloc > 0) {
1303                 /*
1304                  * XXX: We are stretching the limits of
1305                  * ocfs2_lock_allocators(). It greately over-estimates
1306                  * the work to be done.
1307                  */
1308                 ret = ocfs2_lock_allocators(inode, di, clusters_to_alloc,
1309                                             &data_ac, &meta_ac);
1310                 if (ret) {
1311                         mlog_errno(ret);
1312                         goto out;
1313                 }
1314
1315                 credits = ocfs2_calc_extend_credits(inode->i_sb, di,
1316                                                     clusters_to_alloc);
1317
1318         }
1319
1320         ocfs2_set_target_boundaries(osb, wc, pos, len, clusters_to_alloc);
1321
1322         handle = ocfs2_start_trans(osb, credits);
1323         if (IS_ERR(handle)) {
1324                 ret = PTR_ERR(handle);
1325                 mlog_errno(ret);
1326                 goto out;
1327         }
1328
1329         wc->w_handle = handle;
1330
1331         /*
1332          * We don't want this to fail in ocfs2_write_end(), so do it
1333          * here.
1334          */
1335         ret = ocfs2_journal_access(handle, inode, wc->w_di_bh,
1336                                    OCFS2_JOURNAL_ACCESS_WRITE);
1337         if (ret) {
1338                 mlog_errno(ret);
1339                 goto out_commit;
1340         }
1341
1342         /*
1343          * Fill our page array first. That way we've grabbed enough so
1344          * that we can zero and flush if we error after adding the
1345          * extent.
1346          */
1347         ret = ocfs2_grab_pages_for_write(mapping, wc, wc->w_cpos, pos,
1348                                          clusters_to_alloc, mmap_page);
1349         if (ret) {
1350                 mlog_errno(ret);
1351                 goto out_commit;
1352         }
1353
1354         for (i = 0; i < wc->w_clen; i++) {
1355                 desc = &wc->w_desc[i];
1356
1357                 ret = ocfs2_write_cluster(mapping, desc->c_phys, data_ac,
1358                                           meta_ac, wc, desc->c_cpos, pos, len);
1359                 if (ret) {
1360                         mlog_errno(ret);
1361                         goto out_commit;
1362                 }
1363         }
1364
1365         if (data_ac)
1366                 ocfs2_free_alloc_context(data_ac);
1367         if (meta_ac)
1368                 ocfs2_free_alloc_context(meta_ac);
1369
1370         *pagep = wc->w_target_page;
1371         *fsdata = wc;
1372         return 0;
1373 out_commit:
1374         ocfs2_commit_trans(osb, handle);
1375
1376 out:
1377         ocfs2_free_write_ctxt(wc);
1378
1379         if (data_ac)
1380                 ocfs2_free_alloc_context(data_ac);
1381         if (meta_ac)
1382                 ocfs2_free_alloc_context(meta_ac);
1383         return ret;
1384 }
1385
1386 int ocfs2_write_begin(struct file *file, struct address_space *mapping,
1387                       loff_t pos, unsigned len, unsigned flags,
1388                       struct page **pagep, void **fsdata)
1389 {
1390         int ret;
1391         struct buffer_head *di_bh = NULL;
1392         struct inode *inode = mapping->host;
1393
1394         ret = ocfs2_meta_lock(inode, &di_bh, 1);
1395         if (ret) {
1396                 mlog_errno(ret);
1397                 return ret;
1398         }
1399
1400         /*
1401          * Take alloc sem here to prevent concurrent lookups. That way
1402          * the mapping, zeroing and tree manipulation within
1403          * ocfs2_write() will be safe against ->readpage(). This
1404          * should also serve to lock out allocation from a shared
1405          * writeable region.
1406          */
1407         down_write(&OCFS2_I(inode)->ip_alloc_sem);
1408
1409         ret = ocfs2_data_lock(inode, 1);
1410         if (ret) {
1411                 mlog_errno(ret);
1412                 goto out_fail;
1413         }
1414
1415         ret = ocfs2_write_begin_nolock(mapping, pos, len, flags, pagep,
1416                                        fsdata, di_bh, NULL);
1417         if (ret) {
1418                 mlog_errno(ret);
1419                 goto out_fail_data;
1420         }
1421
1422         brelse(di_bh);
1423
1424         return 0;
1425
1426 out_fail_data:
1427         ocfs2_data_unlock(inode, 1);
1428 out_fail:
1429         up_write(&OCFS2_I(inode)->ip_alloc_sem);
1430
1431         brelse(di_bh);
1432         ocfs2_meta_unlock(inode, 1);
1433
1434         return ret;
1435 }
1436
1437 int ocfs2_write_end_nolock(struct address_space *mapping,
1438                            loff_t pos, unsigned len, unsigned copied,
1439                            struct page *page, void *fsdata)
1440 {
1441         int i;
1442         unsigned from, to, start = pos & (PAGE_CACHE_SIZE - 1);
1443         struct inode *inode = mapping->host;
1444         struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
1445         struct ocfs2_write_ctxt *wc = fsdata;
1446         struct ocfs2_dinode *di = (struct ocfs2_dinode *)wc->w_di_bh->b_data;
1447         handle_t *handle = wc->w_handle;
1448         struct page *tmppage;
1449
1450         if (unlikely(copied < len)) {
1451                 if (!PageUptodate(wc->w_target_page))
1452                         copied = 0;
1453
1454                 ocfs2_zero_new_buffers(wc->w_target_page, start+copied,
1455                                        start+len);
1456         }
1457         flush_dcache_page(wc->w_target_page);
1458
1459         for(i = 0; i < wc->w_num_pages; i++) {
1460                 tmppage = wc->w_pages[i];
1461
1462                 if (tmppage == wc->w_target_page) {
1463                         from = wc->w_target_from;
1464                         to = wc->w_target_to;
1465
1466                         BUG_ON(from > PAGE_CACHE_SIZE ||
1467                                to > PAGE_CACHE_SIZE ||
1468                                to < from);
1469                 } else {
1470                         /*
1471                          * Pages adjacent to the target (if any) imply
1472                          * a hole-filling write in which case we want
1473                          * to flush their entire range.
1474                          */
1475                         from = 0;
1476                         to = PAGE_CACHE_SIZE;
1477                 }
1478
1479                 if (ocfs2_should_order_data(inode))
1480                         walk_page_buffers(wc->w_handle, page_buffers(tmppage),
1481                                           from, to, NULL,
1482                                           ocfs2_journal_dirty_data);
1483
1484                 block_commit_write(tmppage, from, to);
1485         }
1486
1487         pos += copied;
1488         if (pos > inode->i_size) {
1489                 i_size_write(inode, pos);
1490                 mark_inode_dirty(inode);
1491         }
1492         inode->i_blocks = ocfs2_inode_sector_count(inode);
1493         di->i_size = cpu_to_le64((u64)i_size_read(inode));
1494         inode->i_mtime = inode->i_ctime = CURRENT_TIME;
1495         di->i_mtime = di->i_ctime = cpu_to_le64(inode->i_mtime.tv_sec);
1496         di->i_mtime_nsec = di->i_ctime_nsec = cpu_to_le32(inode->i_mtime.tv_nsec);
1497
1498         ocfs2_journal_dirty(handle, wc->w_di_bh);
1499
1500         ocfs2_commit_trans(osb, handle);
1501         ocfs2_free_write_ctxt(wc);
1502
1503         return copied;
1504 }
1505
1506 int ocfs2_write_end(struct file *file, struct address_space *mapping,
1507                     loff_t pos, unsigned len, unsigned copied,
1508                     struct page *page, void *fsdata)
1509 {
1510         int ret;
1511         struct inode *inode = mapping->host;
1512
1513         ret = ocfs2_write_end_nolock(mapping, pos, len, copied, page, fsdata);
1514
1515         ocfs2_data_unlock(inode, 1);
1516         up_write(&OCFS2_I(inode)->ip_alloc_sem);
1517         ocfs2_meta_unlock(inode, 1);
1518
1519         return ret;
1520 }
1521
1522 const struct address_space_operations ocfs2_aops = {
1523         .readpage       = ocfs2_readpage,
1524         .writepage      = ocfs2_writepage,
1525         .bmap           = ocfs2_bmap,
1526         .sync_page      = block_sync_page,
1527         .direct_IO      = ocfs2_direct_IO,
1528         .invalidatepage = ocfs2_invalidatepage,
1529         .releasepage    = ocfs2_releasepage,
1530         .migratepage    = buffer_migrate_page,
1531 };