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TOMOYO Linux Cross Reference
Linux/fs/ubifs/file.c

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  1 /*
  2  * This file is part of UBIFS.
  3  *
  4  * Copyright (C) 2006-2008 Nokia Corporation.
  5  *
  6  * This program is free software; you can redistribute it and/or modify it
  7  * under the terms of the GNU General Public License version 2 as published by
  8  * the Free Software Foundation.
  9  *
 10  * This program is distributed in the hope that it will be useful, but WITHOUT
 11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 13  * more details.
 14  *
 15  * You should have received a copy of the GNU General Public License along with
 16  * this program; if not, write to the Free Software Foundation, Inc., 51
 17  * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 18  *
 19  * Authors: Artem Bityutskiy (Битюцкий Артём)
 20  *          Adrian Hunter
 21  */
 22 
 23 /*
 24  * This file implements VFS file and inode operations for regular files, device
 25  * nodes and symlinks as well as address space operations.
 26  *
 27  * UBIFS uses 2 page flags: @PG_private and @PG_checked. @PG_private is set if
 28  * the page is dirty and is used for optimization purposes - dirty pages are
 29  * not budgeted so the flag shows that 'ubifs_write_end()' should not release
 30  * the budget for this page. The @PG_checked flag is set if full budgeting is
 31  * required for the page e.g., when it corresponds to a file hole or it is
 32  * beyond the file size. The budgeting is done in 'ubifs_write_begin()', because
 33  * it is OK to fail in this function, and the budget is released in
 34  * 'ubifs_write_end()'. So the @PG_private and @PG_checked flags carry
 35  * information about how the page was budgeted, to make it possible to release
 36  * the budget properly.
 37  *
 38  * A thing to keep in mind: inode @i_mutex is locked in most VFS operations we
 39  * implement. However, this is not true for 'ubifs_writepage()', which may be
 40  * called with @i_mutex unlocked. For example, when pdflush is doing background
 41  * write-back, it calls 'ubifs_writepage()' with unlocked @i_mutex. At "normal"
 42  * work-paths the @i_mutex is locked in 'ubifs_writepage()', e.g. in the
 43  * "sys_write -> alloc_pages -> direct reclaim path". So, in 'ubifs_writepage()'
 44  * we are only guaranteed that the page is locked.
 45  *
 46  * Similarly, @i_mutex is not always locked in 'ubifs_readpage()', e.g., the
 47  * read-ahead path does not lock it ("sys_read -> generic_file_aio_read ->
 48  * ondemand_readahead -> readpage"). In case of readahead, @I_SYNC flag is not
 49  * set as well. However, UBIFS disables readahead.
 50  */
 51 
 52 #include "ubifs.h"
 53 #include <linux/mount.h>
 54 #include <linux/namei.h>
 55 #include <linux/slab.h>
 56 #include <linux/migrate.h>
 57 
 58 static int read_block(struct inode *inode, void *addr, unsigned int block,
 59                       struct ubifs_data_node *dn)
 60 {
 61         struct ubifs_info *c = inode->i_sb->s_fs_info;
 62         int err, len, out_len;
 63         union ubifs_key key;
 64         unsigned int dlen;
 65 
 66         data_key_init(c, &key, inode->i_ino, block);
 67         err = ubifs_tnc_lookup(c, &key, dn);
 68         if (err) {
 69                 if (err == -ENOENT)
 70                         /* Not found, so it must be a hole */
 71                         memset(addr, 0, UBIFS_BLOCK_SIZE);
 72                 return err;
 73         }
 74 
 75         ubifs_assert(le64_to_cpu(dn->ch.sqnum) >
 76                      ubifs_inode(inode)->creat_sqnum);
 77         len = le32_to_cpu(dn->size);
 78         if (len <= 0 || len > UBIFS_BLOCK_SIZE)
 79                 goto dump;
 80 
 81         dlen = le32_to_cpu(dn->ch.len) - UBIFS_DATA_NODE_SZ;
 82         out_len = UBIFS_BLOCK_SIZE;
 83         err = ubifs_decompress(&dn->data, dlen, addr, &out_len,
 84                                le16_to_cpu(dn->compr_type));
 85         if (err || len != out_len)
 86                 goto dump;
 87 
 88         /*
 89          * Data length can be less than a full block, even for blocks that are
 90          * not the last in the file (e.g., as a result of making a hole and
 91          * appending data). Ensure that the remainder is zeroed out.
 92          */
 93         if (len < UBIFS_BLOCK_SIZE)
 94                 memset(addr + len, 0, UBIFS_BLOCK_SIZE - len);
 95 
 96         return 0;
 97 
 98 dump:
 99         ubifs_err("bad data node (block %u, inode %lu)",
100                   block, inode->i_ino);
101         dbg_dump_node(c, dn);
102         return -EINVAL;
103 }
104 
105 static int do_readpage(struct page *page)
106 {
107         void *addr;
108         int err = 0, i;
109         unsigned int block, beyond;
110         struct ubifs_data_node *dn;
111         struct inode *inode = page->mapping->host;
112         loff_t i_size = i_size_read(inode);
113 
114         dbg_gen("ino %lu, pg %lu, i_size %lld, flags %#lx",
115                 inode->i_ino, page->index, i_size, page->flags);
116         ubifs_assert(!PageChecked(page));
117         ubifs_assert(!PagePrivate(page));
118 
119         addr = kmap(page);
120 
121         block = page->index << UBIFS_BLOCKS_PER_PAGE_SHIFT;
122         beyond = (i_size + UBIFS_BLOCK_SIZE - 1) >> UBIFS_BLOCK_SHIFT;
123         if (block >= beyond) {
124                 /* Reading beyond inode */
125                 SetPageChecked(page);
126                 memset(addr, 0, PAGE_CACHE_SIZE);
127                 goto out;
128         }
129 
130         dn = kmalloc(UBIFS_MAX_DATA_NODE_SZ, GFP_NOFS);
131         if (!dn) {
132                 err = -ENOMEM;
133                 goto error;
134         }
135 
136         i = 0;
137         while (1) {
138                 int ret;
139 
140                 if (block >= beyond) {
141                         /* Reading beyond inode */
142                         err = -ENOENT;
143                         memset(addr, 0, UBIFS_BLOCK_SIZE);
144                 } else {
145                         ret = read_block(inode, addr, block, dn);
146                         if (ret) {
147                                 err = ret;
148                                 if (err != -ENOENT)
149                                         break;
150                         } else if (block + 1 == beyond) {
151                                 int dlen = le32_to_cpu(dn->size);
152                                 int ilen = i_size & (UBIFS_BLOCK_SIZE - 1);
153 
154                                 if (ilen && ilen < dlen)
155                                         memset(addr + ilen, 0, dlen - ilen);
156                         }
157                 }
158                 if (++i >= UBIFS_BLOCKS_PER_PAGE)
159                         break;
160                 block += 1;
161                 addr += UBIFS_BLOCK_SIZE;
162         }
163         if (err) {
164                 if (err == -ENOENT) {
165                         /* Not found, so it must be a hole */
166                         SetPageChecked(page);
167                         dbg_gen("hole");
168                         goto out_free;
169                 }
170                 ubifs_err("cannot read page %lu of inode %lu, error %d",
171                           page->index, inode->i_ino, err);
172                 goto error;
173         }
174 
175 out_free:
176         kfree(dn);
177 out:
178         SetPageUptodate(page);
179         ClearPageError(page);
180         flush_dcache_page(page);
181         kunmap(page);
182         return 0;
183 
184 error:
185         kfree(dn);
186         ClearPageUptodate(page);
187         SetPageError(page);
188         flush_dcache_page(page);
189         kunmap(page);
190         return err;
191 }
192 
193 /**
194  * release_new_page_budget - release budget of a new page.
195  * @c: UBIFS file-system description object
196  *
197  * This is a helper function which releases budget corresponding to the budget
198  * of one new page of data.
199  */
200 static void release_new_page_budget(struct ubifs_info *c)
201 {
202         struct ubifs_budget_req req = { .recalculate = 1, .new_page = 1 };
203 
204         ubifs_release_budget(c, &req);
205 }
206 
207 /**
208  * release_existing_page_budget - release budget of an existing page.
209  * @c: UBIFS file-system description object
210  *
211  * This is a helper function which releases budget corresponding to the budget
212  * of changing one one page of data which already exists on the flash media.
213  */
214 static void release_existing_page_budget(struct ubifs_info *c)
215 {
216         struct ubifs_budget_req req = { .dd_growth = c->bi.page_budget};
217 
218         ubifs_release_budget(c, &req);
219 }
220 
221 static int write_begin_slow(struct address_space *mapping,
222                             loff_t pos, unsigned len, struct page **pagep,
223                             unsigned flags)
224 {
225         struct inode *inode = mapping->host;
226         struct ubifs_info *c = inode->i_sb->s_fs_info;
227         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
228         struct ubifs_budget_req req = { .new_page = 1 };
229         int uninitialized_var(err), appending = !!(pos + len > inode->i_size);
230         struct page *page;
231 
232         dbg_gen("ino %lu, pos %llu, len %u, i_size %lld",
233                 inode->i_ino, pos, len, inode->i_size);
234 
235         /*
236          * At the slow path we have to budget before locking the page, because
237          * budgeting may force write-back, which would wait on locked pages and
238          * deadlock if we had the page locked. At this point we do not know
239          * anything about the page, so assume that this is a new page which is
240          * written to a hole. This corresponds to largest budget. Later the
241          * budget will be amended if this is not true.
242          */
243         if (appending)
244                 /* We are appending data, budget for inode change */
245                 req.dirtied_ino = 1;
246 
247         err = ubifs_budget_space(c, &req);
248         if (unlikely(err))
249                 return err;
250 
251         page = grab_cache_page_write_begin(mapping, index, flags);
252         if (unlikely(!page)) {
253                 ubifs_release_budget(c, &req);
254                 return -ENOMEM;
255         }
256 
257         if (!PageUptodate(page)) {
258                 if (!(pos & ~PAGE_CACHE_MASK) && len == PAGE_CACHE_SIZE)
259                         SetPageChecked(page);
260                 else {
261                         err = do_readpage(page);
262                         if (err) {
263                                 unlock_page(page);
264                                 page_cache_release(page);
265                                 return err;
266                         }
267                 }
268 
269                 SetPageUptodate(page);
270                 ClearPageError(page);
271         }
272 
273         if (PagePrivate(page))
274                 /*
275                  * The page is dirty, which means it was budgeted twice:
276                  *   o first time the budget was allocated by the task which
277                  *     made the page dirty and set the PG_private flag;
278                  *   o and then we budgeted for it for the second time at the
279                  *     very beginning of this function.
280                  *
281                  * So what we have to do is to release the page budget we
282                  * allocated.
283                  */
284                 release_new_page_budget(c);
285         else if (!PageChecked(page))
286                 /*
287                  * We are changing a page which already exists on the media.
288                  * This means that changing the page does not make the amount
289                  * of indexing information larger, and this part of the budget
290                  * which we have already acquired may be released.
291                  */
292                 ubifs_convert_page_budget(c);
293 
294         if (appending) {
295                 struct ubifs_inode *ui = ubifs_inode(inode);
296 
297                 /*
298                  * 'ubifs_write_end()' is optimized from the fast-path part of
299                  * 'ubifs_write_begin()' and expects the @ui_mutex to be locked
300                  * if data is appended.
301                  */
302                 mutex_lock(&ui->ui_mutex);
303                 if (ui->dirty)
304                         /*
305                          * The inode is dirty already, so we may free the
306                          * budget we allocated.
307                          */
308                         ubifs_release_dirty_inode_budget(c, ui);
309         }
310 
311         *pagep = page;
312         return 0;
313 }
314 
315 /**
316  * allocate_budget - allocate budget for 'ubifs_write_begin()'.
317  * @c: UBIFS file-system description object
318  * @page: page to allocate budget for
319  * @ui: UBIFS inode object the page belongs to
320  * @appending: non-zero if the page is appended
321  *
322  * This is a helper function for 'ubifs_write_begin()' which allocates budget
323  * for the operation. The budget is allocated differently depending on whether
324  * this is appending, whether the page is dirty or not, and so on. This
325  * function leaves the @ui->ui_mutex locked in case of appending. Returns zero
326  * in case of success and %-ENOSPC in case of failure.
327  */
328 static int allocate_budget(struct ubifs_info *c, struct page *page,
329                            struct ubifs_inode *ui, int appending)
330 {
331         struct ubifs_budget_req req = { .fast = 1 };
332 
333         if (PagePrivate(page)) {
334                 if (!appending)
335                         /*
336                          * The page is dirty and we are not appending, which
337                          * means no budget is needed at all.
338                          */
339                         return 0;
340 
341                 mutex_lock(&ui->ui_mutex);
342                 if (ui->dirty)
343                         /*
344                          * The page is dirty and we are appending, so the inode
345                          * has to be marked as dirty. However, it is already
346                          * dirty, so we do not need any budget. We may return,
347                          * but @ui->ui_mutex hast to be left locked because we
348                          * should prevent write-back from flushing the inode
349                          * and freeing the budget. The lock will be released in
350                          * 'ubifs_write_end()'.
351                          */
352                         return 0;
353 
354                 /*
355                  * The page is dirty, we are appending, the inode is clean, so
356                  * we need to budget the inode change.
357                  */
358                 req.dirtied_ino = 1;
359         } else {
360                 if (PageChecked(page))
361                         /*
362                          * The page corresponds to a hole and does not
363                          * exist on the media. So changing it makes
364                          * make the amount of indexing information
365                          * larger, and we have to budget for a new
366                          * page.
367                          */
368                         req.new_page = 1;
369                 else
370                         /*
371                          * Not a hole, the change will not add any new
372                          * indexing information, budget for page
373                          * change.
374                          */
375                         req.dirtied_page = 1;
376 
377                 if (appending) {
378                         mutex_lock(&ui->ui_mutex);
379                         if (!ui->dirty)
380                                 /*
381                                  * The inode is clean but we will have to mark
382                                  * it as dirty because we are appending. This
383                                  * needs a budget.
384                                  */
385                                 req.dirtied_ino = 1;
386                 }
387         }
388 
389         return ubifs_budget_space(c, &req);
390 }
391 
392 /*
393  * This function is called when a page of data is going to be written. Since
394  * the page of data will not necessarily go to the flash straight away, UBIFS
395  * has to reserve space on the media for it, which is done by means of
396  * budgeting.
397  *
398  * This is the hot-path of the file-system and we are trying to optimize it as
399  * much as possible. For this reasons it is split on 2 parts - slow and fast.
400  *
401  * There many budgeting cases:
402  *     o a new page is appended - we have to budget for a new page and for
403  *       changing the inode; however, if the inode is already dirty, there is
404  *       no need to budget for it;
405  *     o an existing clean page is changed - we have budget for it; if the page
406  *       does not exist on the media (a hole), we have to budget for a new
407  *       page; otherwise, we may budget for changing an existing page; the
408  *       difference between these cases is that changing an existing page does
409  *       not introduce anything new to the FS indexing information, so it does
410  *       not grow, and smaller budget is acquired in this case;
411  *     o an existing dirty page is changed - no need to budget at all, because
412  *       the page budget has been acquired by earlier, when the page has been
413  *       marked dirty.
414  *
415  * UBIFS budgeting sub-system may force write-back if it thinks there is no
416  * space to reserve. This imposes some locking restrictions and makes it
417  * impossible to take into account the above cases, and makes it impossible to
418  * optimize budgeting.
419  *
420  * The solution for this is that the fast path of 'ubifs_write_begin()' assumes
421  * there is a plenty of flash space and the budget will be acquired quickly,
422  * without forcing write-back. The slow path does not make this assumption.
423  */
424 static int ubifs_write_begin(struct file *file, struct address_space *mapping,
425                              loff_t pos, unsigned len, unsigned flags,
426                              struct page **pagep, void **fsdata)
427 {
428         struct inode *inode = mapping->host;
429         struct ubifs_info *c = inode->i_sb->s_fs_info;
430         struct ubifs_inode *ui = ubifs_inode(inode);
431         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
432         int uninitialized_var(err), appending = !!(pos + len > inode->i_size);
433         int skipped_read = 0;
434         struct page *page;
435 
436         ubifs_assert(ubifs_inode(inode)->ui_size == inode->i_size);
437         ubifs_assert(!c->ro_media && !c->ro_mount);
438 
439         if (unlikely(c->ro_error))
440                 return -EROFS;
441 
442         /* Try out the fast-path part first */
443         page = grab_cache_page_write_begin(mapping, index, flags);
444         if (unlikely(!page))
445                 return -ENOMEM;
446 
447         if (!PageUptodate(page)) {
448                 /* The page is not loaded from the flash */
449                 if (!(pos & ~PAGE_CACHE_MASK) && len == PAGE_CACHE_SIZE) {
450                         /*
451                          * We change whole page so no need to load it. But we
452                          * do not know whether this page exists on the media or
453                          * not, so we assume the latter because it requires
454                          * larger budget. The assumption is that it is better
455                          * to budget a bit more than to read the page from the
456                          * media. Thus, we are setting the @PG_checked flag
457                          * here.
458                          */
459                         SetPageChecked(page);
460                         skipped_read = 1;
461                 } else {
462                         err = do_readpage(page);
463                         if (err) {
464                                 unlock_page(page);
465                                 page_cache_release(page);
466                                 return err;
467                         }
468                 }
469 
470                 SetPageUptodate(page);
471                 ClearPageError(page);
472         }
473 
474         err = allocate_budget(c, page, ui, appending);
475         if (unlikely(err)) {
476                 ubifs_assert(err == -ENOSPC);
477                 /*
478                  * If we skipped reading the page because we were going to
479                  * write all of it, then it is not up to date.
480                  */
481                 if (skipped_read) {
482                         ClearPageChecked(page);
483                         ClearPageUptodate(page);
484                 }
485                 /*
486                  * Budgeting failed which means it would have to force
487                  * write-back but didn't, because we set the @fast flag in the
488                  * request. Write-back cannot be done now, while we have the
489                  * page locked, because it would deadlock. Unlock and free
490                  * everything and fall-back to slow-path.
491                  */
492                 if (appending) {
493                         ubifs_assert(mutex_is_locked(&ui->ui_mutex));
494                         mutex_unlock(&ui->ui_mutex);
495                 }
496                 unlock_page(page);
497                 page_cache_release(page);
498 
499                 return write_begin_slow(mapping, pos, len, pagep, flags);
500         }
501 
502         /*
503          * Whee, we acquired budgeting quickly - without involving
504          * garbage-collection, committing or forcing write-back. We return
505          * with @ui->ui_mutex locked if we are appending pages, and unlocked
506          * otherwise. This is an optimization (slightly hacky though).
507          */
508         *pagep = page;
509         return 0;
510 
511 }
512 
513 /**
514  * cancel_budget - cancel budget.
515  * @c: UBIFS file-system description object
516  * @page: page to cancel budget for
517  * @ui: UBIFS inode object the page belongs to
518  * @appending: non-zero if the page is appended
519  *
520  * This is a helper function for a page write operation. It unlocks the
521  * @ui->ui_mutex in case of appending.
522  */
523 static void cancel_budget(struct ubifs_info *c, struct page *page,
524                           struct ubifs_inode *ui, int appending)
525 {
526         if (appending) {
527                 if (!ui->dirty)
528                         ubifs_release_dirty_inode_budget(c, ui);
529                 mutex_unlock(&ui->ui_mutex);
530         }
531         if (!PagePrivate(page)) {
532                 if (PageChecked(page))
533                         release_new_page_budget(c);
534                 else
535                         release_existing_page_budget(c);
536         }
537 }
538 
539 static int ubifs_write_end(struct file *file, struct address_space *mapping,
540                            loff_t pos, unsigned len, unsigned copied,
541                            struct page *page, void *fsdata)
542 {
543         struct inode *inode = mapping->host;
544         struct ubifs_inode *ui = ubifs_inode(inode);
545         struct ubifs_info *c = inode->i_sb->s_fs_info;
546         loff_t end_pos = pos + len;
547         int appending = !!(end_pos > inode->i_size);
548 
549         dbg_gen("ino %lu, pos %llu, pg %lu, len %u, copied %d, i_size %lld",
550                 inode->i_ino, pos, page->index, len, copied, inode->i_size);
551 
552         if (unlikely(copied < len && len == PAGE_CACHE_SIZE)) {
553                 /*
554                  * VFS copied less data to the page that it intended and
555                  * declared in its '->write_begin()' call via the @len
556                  * argument. If the page was not up-to-date, and @len was
557                  * @PAGE_CACHE_SIZE, the 'ubifs_write_begin()' function did
558                  * not load it from the media (for optimization reasons). This
559                  * means that part of the page contains garbage. So read the
560                  * page now.
561                  */
562                 dbg_gen("copied %d instead of %d, read page and repeat",
563                         copied, len);
564                 cancel_budget(c, page, ui, appending);
565                 ClearPageChecked(page);
566 
567                 /*
568                  * Return 0 to force VFS to repeat the whole operation, or the
569                  * error code if 'do_readpage()' fails.
570                  */
571                 copied = do_readpage(page);
572                 goto out;
573         }
574 
575         if (!PagePrivate(page)) {
576                 SetPagePrivate(page);
577                 atomic_long_inc(&c->dirty_pg_cnt);
578                 __set_page_dirty_nobuffers(page);
579         }
580 
581         if (appending) {
582                 i_size_write(inode, end_pos);
583                 ui->ui_size = end_pos;
584                 /*
585                  * Note, we do not set @I_DIRTY_PAGES (which means that the
586                  * inode has dirty pages), this has been done in
587                  * '__set_page_dirty_nobuffers()'.
588                  */
589                 __mark_inode_dirty(inode, I_DIRTY_DATASYNC);
590                 ubifs_assert(mutex_is_locked(&ui->ui_mutex));
591                 mutex_unlock(&ui->ui_mutex);
592         }
593 
594 out:
595         unlock_page(page);
596         page_cache_release(page);
597         return copied;
598 }
599 
600 /**
601  * populate_page - copy data nodes into a page for bulk-read.
602  * @c: UBIFS file-system description object
603  * @page: page
604  * @bu: bulk-read information
605  * @n: next zbranch slot
606  *
607  * This function returns %0 on success and a negative error code on failure.
608  */
609 static int populate_page(struct ubifs_info *c, struct page *page,
610                          struct bu_info *bu, int *n)
611 {
612         int i = 0, nn = *n, offs = bu->zbranch[0].offs, hole = 0, read = 0;
613         struct inode *inode = page->mapping->host;
614         loff_t i_size = i_size_read(inode);
615         unsigned int page_block;
616         void *addr, *zaddr;
617         pgoff_t end_index;
618 
619         dbg_gen("ino %lu, pg %lu, i_size %lld, flags %#lx",
620                 inode->i_ino, page->index, i_size, page->flags);
621 
622         addr = zaddr = kmap(page);
623 
624         end_index = (i_size - 1) >> PAGE_CACHE_SHIFT;
625         if (!i_size || page->index > end_index) {
626                 hole = 1;
627                 memset(addr, 0, PAGE_CACHE_SIZE);
628                 goto out_hole;
629         }
630 
631         page_block = page->index << UBIFS_BLOCKS_PER_PAGE_SHIFT;
632         while (1) {
633                 int err, len, out_len, dlen;
634 
635                 if (nn >= bu->cnt) {
636                         hole = 1;
637                         memset(addr, 0, UBIFS_BLOCK_SIZE);
638                 } else if (key_block(c, &bu->zbranch[nn].key) == page_block) {
639                         struct ubifs_data_node *dn;
640 
641                         dn = bu->buf + (bu->zbranch[nn].offs - offs);
642 
643                         ubifs_assert(le64_to_cpu(dn->ch.sqnum) >
644                                      ubifs_inode(inode)->creat_sqnum);
645 
646                         len = le32_to_cpu(dn->size);
647                         if (len <= 0 || len > UBIFS_BLOCK_SIZE)
648                                 goto out_err;
649 
650                         dlen = le32_to_cpu(dn->ch.len) - UBIFS_DATA_NODE_SZ;
651                         out_len = UBIFS_BLOCK_SIZE;
652                         err = ubifs_decompress(&dn->data, dlen, addr, &out_len,
653                                                le16_to_cpu(dn->compr_type));
654                         if (err || len != out_len)
655                                 goto out_err;
656 
657                         if (len < UBIFS_BLOCK_SIZE)
658                                 memset(addr + len, 0, UBIFS_BLOCK_SIZE - len);
659 
660                         nn += 1;
661                         read = (i << UBIFS_BLOCK_SHIFT) + len;
662                 } else if (key_block(c, &bu->zbranch[nn].key) < page_block) {
663                         nn += 1;
664                         continue;
665                 } else {
666                         hole = 1;
667                         memset(addr, 0, UBIFS_BLOCK_SIZE);
668                 }
669                 if (++i >= UBIFS_BLOCKS_PER_PAGE)
670                         break;
671                 addr += UBIFS_BLOCK_SIZE;
672                 page_block += 1;
673         }
674 
675         if (end_index == page->index) {
676                 int len = i_size & (PAGE_CACHE_SIZE - 1);
677 
678                 if (len && len < read)
679                         memset(zaddr + len, 0, read - len);
680         }
681 
682 out_hole:
683         if (hole) {
684                 SetPageChecked(page);
685                 dbg_gen("hole");
686         }
687 
688         SetPageUptodate(page);
689         ClearPageError(page);
690         flush_dcache_page(page);
691         kunmap(page);
692         *n = nn;
693         return 0;
694 
695 out_err:
696         ClearPageUptodate(page);
697         SetPageError(page);
698         flush_dcache_page(page);
699         kunmap(page);
700         ubifs_err("bad data node (block %u, inode %lu)",
701                   page_block, inode->i_ino);
702         return -EINVAL;
703 }
704 
705 /**
706  * ubifs_do_bulk_read - do bulk-read.
707  * @c: UBIFS file-system description object
708  * @bu: bulk-read information
709  * @page1: first page to read
710  *
711  * This function returns %1 if the bulk-read is done, otherwise %0 is returned.
712  */
713 static int ubifs_do_bulk_read(struct ubifs_info *c, struct bu_info *bu,
714                               struct page *page1)
715 {
716         pgoff_t offset = page1->index, end_index;
717         struct address_space *mapping = page1->mapping;
718         struct inode *inode = mapping->host;
719         struct ubifs_inode *ui = ubifs_inode(inode);
720         int err, page_idx, page_cnt, ret = 0, n = 0;
721         int allocate = bu->buf ? 0 : 1;
722         loff_t isize;
723 
724         err = ubifs_tnc_get_bu_keys(c, bu);
725         if (err)
726                 goto out_warn;
727 
728         if (bu->eof) {
729                 /* Turn off bulk-read at the end of the file */
730                 ui->read_in_a_row = 1;
731                 ui->bulk_read = 0;
732         }
733 
734         page_cnt = bu->blk_cnt >> UBIFS_BLOCKS_PER_PAGE_SHIFT;
735         if (!page_cnt) {
736                 /*
737                  * This happens when there are multiple blocks per page and the
738                  * blocks for the first page we are looking for, are not
739                  * together. If all the pages were like this, bulk-read would
740                  * reduce performance, so we turn it off for a while.
741                  */
742                 goto out_bu_off;
743         }
744 
745         if (bu->cnt) {
746                 if (allocate) {
747                         /*
748                          * Allocate bulk-read buffer depending on how many data
749                          * nodes we are going to read.
750                          */
751                         bu->buf_len = bu->zbranch[bu->cnt - 1].offs +
752                                       bu->zbranch[bu->cnt - 1].len -
753                                       bu->zbranch[0].offs;
754                         ubifs_assert(bu->buf_len > 0);
755                         ubifs_assert(bu->buf_len <= c->leb_size);
756                         bu->buf = kmalloc(bu->buf_len, GFP_NOFS | __GFP_NOWARN);
757                         if (!bu->buf)
758                                 goto out_bu_off;
759                 }
760 
761                 err = ubifs_tnc_bulk_read(c, bu);
762                 if (err)
763                         goto out_warn;
764         }
765 
766         err = populate_page(c, page1, bu, &n);
767         if (err)
768                 goto out_warn;
769 
770         unlock_page(page1);
771         ret = 1;
772 
773         isize = i_size_read(inode);
774         if (isize == 0)
775                 goto out_free;
776         end_index = ((isize - 1) >> PAGE_CACHE_SHIFT);
777 
778         for (page_idx = 1; page_idx < page_cnt; page_idx++) {
779                 pgoff_t page_offset = offset + page_idx;
780                 struct page *page;
781 
782                 if (page_offset > end_index)
783                         break;
784                 page = find_or_create_page(mapping, page_offset,
785                                            GFP_NOFS | __GFP_COLD);
786                 if (!page)
787                         break;
788                 if (!PageUptodate(page))
789                         err = populate_page(c, page, bu, &n);
790                 unlock_page(page);
791                 page_cache_release(page);
792                 if (err)
793                         break;
794         }
795 
796         ui->last_page_read = offset + page_idx - 1;
797 
798 out_free:
799         if (allocate)
800                 kfree(bu->buf);
801         return ret;
802 
803 out_warn:
804         ubifs_warn("ignoring error %d and skipping bulk-read", err);
805         goto out_free;
806 
807 out_bu_off:
808         ui->read_in_a_row = ui->bulk_read = 0;
809         goto out_free;
810 }
811 
812 /**
813  * ubifs_bulk_read - determine whether to bulk-read and, if so, do it.
814  * @page: page from which to start bulk-read.
815  *
816  * Some flash media are capable of reading sequentially at faster rates. UBIFS
817  * bulk-read facility is designed to take advantage of that, by reading in one
818  * go consecutive data nodes that are also located consecutively in the same
819  * LEB. This function returns %1 if a bulk-read is done and %0 otherwise.
820  */
821 static int ubifs_bulk_read(struct page *page)
822 {
823         struct inode *inode = page->mapping->host;
824         struct ubifs_info *c = inode->i_sb->s_fs_info;
825         struct ubifs_inode *ui = ubifs_inode(inode);
826         pgoff_t index = page->index, last_page_read = ui->last_page_read;
827         struct bu_info *bu;
828         int err = 0, allocated = 0;
829 
830         ui->last_page_read = index;
831         if (!c->bulk_read)
832                 return 0;
833 
834         /*
835          * Bulk-read is protected by @ui->ui_mutex, but it is an optimization,
836          * so don't bother if we cannot lock the mutex.
837          */
838         if (!mutex_trylock(&ui->ui_mutex))
839                 return 0;
840 
841         if (index != last_page_read + 1) {
842                 /* Turn off bulk-read if we stop reading sequentially */
843                 ui->read_in_a_row = 1;
844                 if (ui->bulk_read)
845                         ui->bulk_read = 0;
846                 goto out_unlock;
847         }
848 
849         if (!ui->bulk_read) {
850                 ui->read_in_a_row += 1;
851                 if (ui->read_in_a_row < 3)
852                         goto out_unlock;
853                 /* Three reads in a row, so switch on bulk-read */
854                 ui->bulk_read = 1;
855         }
856 
857         /*
858          * If possible, try to use pre-allocated bulk-read information, which
859          * is protected by @c->bu_mutex.
860          */
861         if (mutex_trylock(&c->bu_mutex))
862                 bu = &c->bu;
863         else {
864                 bu = kmalloc(sizeof(struct bu_info), GFP_NOFS | __GFP_NOWARN);
865                 if (!bu)
866                         goto out_unlock;
867 
868                 bu->buf = NULL;
869                 allocated = 1;
870         }
871 
872         bu->buf_len = c->max_bu_buf_len;
873         data_key_init(c, &bu->key, inode->i_ino,
874                       page->index << UBIFS_BLOCKS_PER_PAGE_SHIFT);
875         err = ubifs_do_bulk_read(c, bu, page);
876 
877         if (!allocated)
878                 mutex_unlock(&c->bu_mutex);
879         else
880                 kfree(bu);
881 
882 out_unlock:
883         mutex_unlock(&ui->ui_mutex);
884         return err;
885 }
886 
887 static int ubifs_readpage(struct file *file, struct page *page)
888 {
889         if (ubifs_bulk_read(page))
890                 return 0;
891         do_readpage(page);
892         unlock_page(page);
893         return 0;
894 }
895 
896 static int do_writepage(struct page *page, int len)
897 {
898         int err = 0, i, blen;
899         unsigned int block;
900         void *addr;
901         union ubifs_key key;
902         struct inode *inode = page->mapping->host;
903         struct ubifs_info *c = inode->i_sb->s_fs_info;
904 
905 #ifdef UBIFS_DEBUG
906         spin_lock(&ui->ui_lock);
907         ubifs_assert(page->index <= ui->synced_i_size << PAGE_CACHE_SIZE);
908         spin_unlock(&ui->ui_lock);
909 #endif
910 
911         /* Update radix tree tags */
912         set_page_writeback(page);
913 
914         addr = kmap(page);
915         block = page->index << UBIFS_BLOCKS_PER_PAGE_SHIFT;
916         i = 0;
917         while (len) {
918                 blen = min_t(int, len, UBIFS_BLOCK_SIZE);
919                 data_key_init(c, &key, inode->i_ino, block);
920                 err = ubifs_jnl_write_data(c, inode, &key, addr, blen);
921                 if (err)
922                         break;
923                 if (++i >= UBIFS_BLOCKS_PER_PAGE)
924                         break;
925                 block += 1;
926                 addr += blen;
927                 len -= blen;
928         }
929         if (err) {
930                 SetPageError(page);
931                 ubifs_err("cannot write page %lu of inode %lu, error %d",
932                           page->index, inode->i_ino, err);
933                 ubifs_ro_mode(c, err);
934         }
935 
936         ubifs_assert(PagePrivate(page));
937         if (PageChecked(page))
938                 release_new_page_budget(c);
939         else
940                 release_existing_page_budget(c);
941 
942         atomic_long_dec(&c->dirty_pg_cnt);
943         ClearPagePrivate(page);
944         ClearPageChecked(page);
945 
946         kunmap(page);
947         unlock_page(page);
948         end_page_writeback(page);
949         return err;
950 }
951 
952 /*
953  * When writing-back dirty inodes, VFS first writes-back pages belonging to the
954  * inode, then the inode itself. For UBIFS this may cause a problem. Consider a
955  * situation when a we have an inode with size 0, then a megabyte of data is
956  * appended to the inode, then write-back starts and flushes some amount of the
957  * dirty pages, the journal becomes full, commit happens and finishes, and then
958  * an unclean reboot happens. When the file system is mounted next time, the
959  * inode size would still be 0, but there would be many pages which are beyond
960  * the inode size, they would be indexed and consume flash space. Because the
961  * journal has been committed, the replay would not be able to detect this
962  * situation and correct the inode size. This means UBIFS would have to scan
963  * whole index and correct all inode sizes, which is long an unacceptable.
964  *
965  * To prevent situations like this, UBIFS writes pages back only if they are
966  * within the last synchronized inode size, i.e. the size which has been
967  * written to the flash media last time. Otherwise, UBIFS forces inode
968  * write-back, thus making sure the on-flash inode contains current inode size,
969  * and then keeps writing pages back.
970  *
971  * Some locking issues explanation. 'ubifs_writepage()' first is called with
972  * the page locked, and it locks @ui_mutex. However, write-back does take inode
973  * @i_mutex, which means other VFS operations may be run on this inode at the
974  * same time. And the problematic one is truncation to smaller size, from where
975  * we have to call 'truncate_setsize()', which first changes @inode->i_size,
976  * then drops the truncated pages. And while dropping the pages, it takes the
977  * page lock. This means that 'do_truncation()' cannot call 'truncate_setsize()'
978  * with @ui_mutex locked, because it would deadlock with 'ubifs_writepage()'.
979  * This means that @inode->i_size is changed while @ui_mutex is unlocked.
980  *
981  * XXX(truncate): with the new truncate sequence this is not true anymore,
982  * and the calls to truncate_setsize can be move around freely.  They should
983  * be moved to the very end of the truncate sequence.
984  *
985  * But in 'ubifs_writepage()' we have to guarantee that we do not write beyond
986  * inode size. How do we do this if @inode->i_size may became smaller while we
987  * are in the middle of 'ubifs_writepage()'? The UBIFS solution is the
988  * @ui->ui_isize "shadow" field which UBIFS uses instead of @inode->i_size
989  * internally and updates it under @ui_mutex.
990  *
991  * Q: why we do not worry that if we race with truncation, we may end up with a
992  * situation when the inode is truncated while we are in the middle of
993  * 'do_writepage()', so we do write beyond inode size?
994  * A: If we are in the middle of 'do_writepage()', truncation would be locked
995  * on the page lock and it would not write the truncated inode node to the
996  * journal before we have finished.
997  */
998 static int ubifs_writepage(struct page *page, struct writeback_control *wbc)
999 {
1000         struct inode *inode = page->mapping->host;
1001         struct ubifs_inode *ui = ubifs_inode(inode);
1002         loff_t i_size =  i_size_read(inode), synced_i_size;
1003         pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
1004         int err, len = i_size & (PAGE_CACHE_SIZE - 1);
1005         void *kaddr;
1006 
1007         dbg_gen("ino %lu, pg %lu, pg flags %#lx",
1008                 inode->i_ino, page->index, page->flags);
1009         ubifs_assert(PagePrivate(page));
1010 
1011         /* Is the page fully outside @i_size? (truncate in progress) */
1012         if (page->index > end_index || (page->index == end_index && !len)) {
1013                 err = 0;
1014                 goto out_unlock;
1015         }
1016 
1017         spin_lock(&ui->ui_lock);
1018         synced_i_size = ui->synced_i_size;
1019         spin_unlock(&ui->ui_lock);
1020 
1021         /* Is the page fully inside @i_size? */
1022         if (page->index < end_index) {
1023                 if (page->index >= synced_i_size >> PAGE_CACHE_SHIFT) {
1024                         err = inode->i_sb->s_op->write_inode(inode, NULL);
1025                         if (err)
1026                                 goto out_unlock;
1027                         /*
1028                          * The inode has been written, but the write-buffer has
1029                          * not been synchronized, so in case of an unclean
1030                          * reboot we may end up with some pages beyond inode
1031                          * size, but they would be in the journal (because
1032                          * commit flushes write buffers) and recovery would deal
1033                          * with this.
1034                          */
1035                 }
1036                 return do_writepage(page, PAGE_CACHE_SIZE);
1037         }
1038 
1039         /*
1040          * The page straddles @i_size. It must be zeroed out on each and every
1041          * writepage invocation because it may be mmapped. "A file is mapped
1042          * in multiples of the page size. For a file that is not a multiple of
1043          * the page size, the remaining memory is zeroed when mapped, and
1044          * writes to that region are not written out to the file."
1045          */
1046         kaddr = kmap_atomic(page, KM_USER0);
1047         memset(kaddr + len, 0, PAGE_CACHE_SIZE - len);
1048         flush_dcache_page(page);
1049         kunmap_atomic(kaddr, KM_USER0);
1050 
1051         if (i_size > synced_i_size) {
1052                 err = inode->i_sb->s_op->write_inode(inode, NULL);
1053                 if (err)
1054                         goto out_unlock;
1055         }
1056 
1057         return do_writepage(page, len);
1058 
1059 out_unlock:
1060         unlock_page(page);
1061         return err;
1062 }
1063 
1064 /**
1065  * do_attr_changes - change inode attributes.
1066  * @inode: inode to change attributes for
1067  * @attr: describes attributes to change
1068  */
1069 static void do_attr_changes(struct inode *inode, const struct iattr *attr)
1070 {
1071         if (attr->ia_valid & ATTR_UID)
1072                 inode->i_uid = attr->ia_uid;
1073         if (attr->ia_valid & ATTR_GID)
1074                 inode->i_gid = attr->ia_gid;
1075         if (attr->ia_valid & ATTR_ATIME)
1076                 inode->i_atime = timespec_trunc(attr->ia_atime,
1077                                                 inode->i_sb->s_time_gran);
1078         if (attr->ia_valid & ATTR_MTIME)
1079                 inode->i_mtime = timespec_trunc(attr->ia_mtime,
1080                                                 inode->i_sb->s_time_gran);
1081         if (attr->ia_valid & ATTR_CTIME)
1082                 inode->i_ctime = timespec_trunc(attr->ia_ctime,
1083                                                 inode->i_sb->s_time_gran);
1084         if (attr->ia_valid & ATTR_MODE) {
1085                 umode_t mode = attr->ia_mode;
1086 
1087                 if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
1088                         mode &= ~S_ISGID;
1089                 inode->i_mode = mode;
1090         }
1091 }
1092 
1093 /**
1094  * do_truncation - truncate an inode.
1095  * @c: UBIFS file-system description object
1096  * @inode: inode to truncate
1097  * @attr: inode attribute changes description
1098  *
1099  * This function implements VFS '->setattr()' call when the inode is truncated
1100  * to a smaller size. Returns zero in case of success and a negative error code
1101  * in case of failure.
1102  */
1103 static int do_truncation(struct ubifs_info *c, struct inode *inode,
1104                          const struct iattr *attr)
1105 {
1106         int err;
1107         struct ubifs_budget_req req;
1108         loff_t old_size = inode->i_size, new_size = attr->ia_size;
1109         int offset = new_size & (UBIFS_BLOCK_SIZE - 1), budgeted = 1;
1110         struct ubifs_inode *ui = ubifs_inode(inode);
1111 
1112         dbg_gen("ino %lu, size %lld -> %lld", inode->i_ino, old_size, new_size);
1113         memset(&req, 0, sizeof(struct ubifs_budget_req));
1114 
1115         /*
1116          * If this is truncation to a smaller size, and we do not truncate on a
1117          * block boundary, budget for changing one data block, because the last
1118          * block will be re-written.
1119          */
1120         if (new_size & (UBIFS_BLOCK_SIZE - 1))
1121                 req.dirtied_page = 1;
1122 
1123         req.dirtied_ino = 1;
1124         /* A funny way to budget for truncation node */
1125         req.dirtied_ino_d = UBIFS_TRUN_NODE_SZ;
1126         err = ubifs_budget_space(c, &req);
1127         if (err) {
1128                 /*
1129                  * Treat truncations to zero as deletion and always allow them,
1130                  * just like we do for '->unlink()'.
1131                  */
1132                 if (new_size || err != -ENOSPC)
1133                         return err;
1134                 budgeted = 0;
1135         }
1136 
1137         truncate_setsize(inode, new_size);
1138 
1139         if (offset) {
1140                 pgoff_t index = new_size >> PAGE_CACHE_SHIFT;
1141                 struct page *page;
1142 
1143                 page = find_lock_page(inode->i_mapping, index);
1144                 if (page) {
1145                         if (PageDirty(page)) {
1146                                 /*
1147                                  * 'ubifs_jnl_truncate()' will try to truncate
1148                                  * the last data node, but it contains
1149                                  * out-of-date data because the page is dirty.
1150                                  * Write the page now, so that
1151                                  * 'ubifs_jnl_truncate()' will see an already
1152                                  * truncated (and up to date) data node.
1153                                  */
1154                                 ubifs_assert(PagePrivate(page));
1155 
1156                                 clear_page_dirty_for_io(page);
1157                                 if (UBIFS_BLOCKS_PER_PAGE_SHIFT)
1158                                         offset = new_size &
1159                                                  (PAGE_CACHE_SIZE - 1);
1160                                 err = do_writepage(page, offset);
1161                                 page_cache_release(page);
1162                                 if (err)
1163                                         goto out_budg;
1164                                 /*
1165                                  * We could now tell 'ubifs_jnl_truncate()' not
1166                                  * to read the last block.
1167                                  */
1168                         } else {
1169                                 /*
1170                                  * We could 'kmap()' the page and pass the data
1171                                  * to 'ubifs_jnl_truncate()' to save it from
1172                                  * having to read it.
1173                                  */
1174                                 unlock_page(page);
1175                                 page_cache_release(page);
1176                         }
1177                 }
1178         }
1179 
1180         mutex_lock(&ui->ui_mutex);
1181         ui->ui_size = inode->i_size;
1182         /* Truncation changes inode [mc]time */
1183         inode->i_mtime = inode->i_ctime = ubifs_current_time(inode);
1184         /* Other attributes may be changed at the same time as well */
1185         do_attr_changes(inode, attr);
1186         err = ubifs_jnl_truncate(c, inode, old_size, new_size);
1187         mutex_unlock(&ui->ui_mutex);
1188 
1189 out_budg:
1190         if (budgeted)
1191                 ubifs_release_budget(c, &req);
1192         else {
1193                 c->bi.nospace = c->bi.nospace_rp = 0;
1194                 smp_wmb();
1195         }
1196         return err;
1197 }
1198 
1199 /**
1200  * do_setattr - change inode attributes.
1201  * @c: UBIFS file-system description object
1202  * @inode: inode to change attributes for
1203  * @attr: inode attribute changes description
1204  *
1205  * This function implements VFS '->setattr()' call for all cases except
1206  * truncations to smaller size. Returns zero in case of success and a negative
1207  * error code in case of failure.
1208  */
1209 static int do_setattr(struct ubifs_info *c, struct inode *inode,
1210                       const struct iattr *attr)
1211 {
1212         int err, release;
1213         loff_t new_size = attr->ia_size;
1214         struct ubifs_inode *ui = ubifs_inode(inode);
1215         struct ubifs_budget_req req = { .dirtied_ino = 1,
1216                                 .dirtied_ino_d = ALIGN(ui->data_len, 8) };
1217 
1218         err = ubifs_budget_space(c, &req);
1219         if (err)
1220                 return err;
1221 
1222         if (attr->ia_valid & ATTR_SIZE) {
1223                 dbg_gen("size %lld -> %lld", inode->i_size, new_size);
1224                 truncate_setsize(inode, new_size);
1225         }
1226 
1227         mutex_lock(&ui->ui_mutex);
1228         if (attr->ia_valid & ATTR_SIZE) {
1229                 /* Truncation changes inode [mc]time */
1230                 inode->i_mtime = inode->i_ctime = ubifs_current_time(inode);
1231                 /* 'truncate_setsize()' changed @i_size, update @ui_size */
1232                 ui->ui_size = inode->i_size;
1233         }
1234 
1235         do_attr_changes(inode, attr);
1236 
1237         release = ui->dirty;
1238         if (attr->ia_valid & ATTR_SIZE)
1239                 /*
1240                  * Inode length changed, so we have to make sure
1241                  * @I_DIRTY_DATASYNC is set.
1242                  */
1243                  __mark_inode_dirty(inode, I_DIRTY_SYNC | I_DIRTY_DATASYNC);
1244         else
1245                 mark_inode_dirty_sync(inode);
1246         mutex_unlock(&ui->ui_mutex);
1247 
1248         if (release)
1249                 ubifs_release_budget(c, &req);
1250         if (IS_SYNC(inode))
1251                 err = inode->i_sb->s_op->write_inode(inode, NULL);
1252         return err;
1253 }
1254 
1255 int ubifs_setattr(struct dentry *dentry, struct iattr *attr)
1256 {
1257         int err;
1258         struct inode *inode = dentry->d_inode;
1259         struct ubifs_info *c = inode->i_sb->s_fs_info;
1260 
1261         dbg_gen("ino %lu, mode %#x, ia_valid %#x",
1262                 inode->i_ino, inode->i_mode, attr->ia_valid);
1263         err = setattr_prepare(dentry, attr);
1264         if (err)
1265                 return err;
1266 
1267         err = dbg_check_synced_i_size(c, inode);
1268         if (err)
1269                 return err;
1270 
1271         if ((attr->ia_valid & ATTR_SIZE) && attr->ia_size < inode->i_size)
1272                 /* Truncation to a smaller size */
1273                 err = do_truncation(c, inode, attr);
1274         else
1275                 err = do_setattr(c, inode, attr);
1276 
1277         return err;
1278 }
1279 
1280 static void ubifs_invalidatepage(struct page *page, unsigned long offset)
1281 {
1282         struct inode *inode = page->mapping->host;
1283         struct ubifs_info *c = inode->i_sb->s_fs_info;
1284 
1285         ubifs_assert(PagePrivate(page));
1286         if (offset)
1287                 /* Partial page remains dirty */
1288                 return;
1289 
1290         if (PageChecked(page))
1291                 release_new_page_budget(c);
1292         else
1293                 release_existing_page_budget(c);
1294 
1295         atomic_long_dec(&c->dirty_pg_cnt);
1296         ClearPagePrivate(page);
1297         ClearPageChecked(page);
1298 }
1299 
1300 static void *ubifs_follow_link(struct dentry *dentry, struct nameidata *nd)
1301 {
1302         struct ubifs_inode *ui = ubifs_inode(dentry->d_inode);
1303 
1304         nd_set_link(nd, ui->data);
1305         return NULL;
1306 }
1307 
1308 int ubifs_fsync(struct file *file, loff_t start, loff_t end, int datasync)
1309 {
1310         struct inode *inode = file->f_mapping->host;
1311         struct ubifs_info *c = inode->i_sb->s_fs_info;
1312         int err;
1313 
1314         dbg_gen("syncing inode %lu", inode->i_ino);
1315 
1316         if (c->ro_mount)
1317                 /*
1318                  * For some really strange reasons VFS does not filter out
1319                  * 'fsync()' for R/O mounted file-systems as per 2.6.39.
1320                  */
1321                 return 0;
1322 
1323         err = filemap_write_and_wait_range(inode->i_mapping, start, end);
1324         if (err)
1325                 return err;
1326         mutex_lock(&inode->i_mutex);
1327 
1328         /* Synchronize the inode unless this is a 'datasync()' call. */
1329         if (!datasync || (inode->i_state & I_DIRTY_DATASYNC)) {
1330                 err = inode->i_sb->s_op->write_inode(inode, NULL);
1331                 if (err)
1332                         goto out;
1333         }
1334 
1335         /*
1336          * Nodes related to this inode may still sit in a write-buffer. Flush
1337          * them.
1338          */
1339         err = ubifs_sync_wbufs_by_inode(c, inode);
1340 out:
1341         mutex_unlock(&inode->i_mutex);
1342         return err;
1343 }
1344 
1345 /**
1346  * mctime_update_needed - check if mtime or ctime update is needed.
1347  * @inode: the inode to do the check for
1348  * @now: current time
1349  *
1350  * This helper function checks if the inode mtime/ctime should be updated or
1351  * not. If current values of the time-stamps are within the UBIFS inode time
1352  * granularity, they are not updated. This is an optimization.
1353  */
1354 static inline int mctime_update_needed(const struct inode *inode,
1355                                        const struct timespec *now)
1356 {
1357         if (!timespec_equal(&inode->i_mtime, now) ||
1358             !timespec_equal(&inode->i_ctime, now))
1359                 return 1;
1360         return 0;
1361 }
1362 
1363 /**
1364  * update_ctime - update mtime and ctime of an inode.
1365  * @c: UBIFS file-system description object
1366  * @inode: inode to update
1367  *
1368  * This function updates mtime and ctime of the inode if it is not equivalent to
1369  * current time. Returns zero in case of success and a negative error code in
1370  * case of failure.
1371  */
1372 static int update_mctime(struct ubifs_info *c, struct inode *inode)
1373 {
1374         struct timespec now = ubifs_current_time(inode);
1375         struct ubifs_inode *ui = ubifs_inode(inode);
1376 
1377         if (mctime_update_needed(inode, &now)) {
1378                 int err, release;
1379                 struct ubifs_budget_req req = { .dirtied_ino = 1,
1380                                 .dirtied_ino_d = ALIGN(ui->data_len, 8) };
1381 
1382                 err = ubifs_budget_space(c, &req);
1383                 if (err)
1384                         return err;
1385 
1386                 mutex_lock(&ui->ui_mutex);
1387                 inode->i_mtime = inode->i_ctime = ubifs_current_time(inode);
1388                 release = ui->dirty;
1389                 mark_inode_dirty_sync(inode);
1390                 mutex_unlock(&ui->ui_mutex);
1391                 if (release)
1392                         ubifs_release_budget(c, &req);
1393         }
1394 
1395         return 0;
1396 }
1397 
1398 static ssize_t ubifs_aio_write(struct kiocb *iocb, const struct iovec *iov,
1399                                unsigned long nr_segs, loff_t pos)
1400 {
1401         int err;
1402         struct inode *inode = iocb->ki_filp->f_mapping->host;
1403         struct ubifs_info *c = inode->i_sb->s_fs_info;
1404 
1405         err = update_mctime(c, inode);
1406         if (err)
1407                 return err;
1408 
1409         return generic_file_aio_write(iocb, iov, nr_segs, pos);
1410 }
1411 
1412 static int ubifs_set_page_dirty(struct page *page)
1413 {
1414         int ret;
1415 
1416         ret = __set_page_dirty_nobuffers(page);
1417         /*
1418          * An attempt to dirty a page without budgeting for it - should not
1419          * happen.
1420          */
1421         ubifs_assert(ret == 0);
1422         return ret;
1423 }
1424 
1425 #ifdef CONFIG_MIGRATION
1426 static int ubifs_migrate_page(struct address_space *mapping,
1427                 struct page *newpage, struct page *page, enum migrate_mode mode)
1428 {
1429         int rc;
1430 
1431         rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode);
1432         if (rc != 0)
1433                 return rc;
1434 
1435         if (PagePrivate(page)) {
1436                 ClearPagePrivate(page);
1437                 SetPagePrivate(newpage);
1438         }
1439 
1440         migrate_page_copy(newpage, page);
1441         return 0;
1442 }
1443 #endif
1444 
1445 static int ubifs_releasepage(struct page *page, gfp_t unused_gfp_flags)
1446 {
1447         /*
1448          * An attempt to release a dirty page without budgeting for it - should
1449          * not happen.
1450          */
1451         if (PageWriteback(page))
1452                 return 0;
1453         ubifs_assert(PagePrivate(page));
1454         ubifs_assert(0);
1455         ClearPagePrivate(page);
1456         ClearPageChecked(page);
1457         return 1;
1458 }
1459 
1460 /*
1461  * mmap()d file has taken write protection fault and is being made writable.
1462  * UBIFS must ensure page is budgeted for.
1463  */
1464 static int ubifs_vm_page_mkwrite(struct vm_area_struct *vma,
1465                                  struct vm_fault *vmf)
1466 {
1467         struct page *page = vmf->page;
1468         struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
1469         struct ubifs_info *c = inode->i_sb->s_fs_info;
1470         struct timespec now = ubifs_current_time(inode);
1471         struct ubifs_budget_req req = { .new_page = 1 };
1472         int err, update_time;
1473 
1474         dbg_gen("ino %lu, pg %lu, i_size %lld", inode->i_ino, page->index,
1475                 i_size_read(inode));
1476         ubifs_assert(!c->ro_media && !c->ro_mount);
1477 
1478         if (unlikely(c->ro_error))
1479                 return VM_FAULT_SIGBUS; /* -EROFS */
1480 
1481         /*
1482          * We have not locked @page so far so we may budget for changing the
1483          * page. Note, we cannot do this after we locked the page, because
1484          * budgeting may cause write-back which would cause deadlock.
1485          *
1486          * At the moment we do not know whether the page is dirty or not, so we
1487          * assume that it is not and budget for a new page. We could look at
1488          * the @PG_private flag and figure this out, but we may race with write
1489          * back and the page state may change by the time we lock it, so this
1490          * would need additional care. We do not bother with this at the
1491          * moment, although it might be good idea to do. Instead, we allocate
1492          * budget for a new page and amend it later on if the page was in fact
1493          * dirty.
1494          *
1495          * The budgeting-related logic of this function is similar to what we
1496          * do in 'ubifs_write_begin()' and 'ubifs_write_end()'. Glance there
1497          * for more comments.
1498          */
1499         update_time = mctime_update_needed(inode, &now);
1500         if (update_time)
1501                 /*
1502                  * We have to change inode time stamp which requires extra
1503                  * budgeting.
1504                  */
1505                 req.dirtied_ino = 1;
1506 
1507         err = ubifs_budget_space(c, &req);
1508         if (unlikely(err)) {
1509                 if (err == -ENOSPC)
1510                         ubifs_warn("out of space for mmapped file "
1511                                    "(inode number %lu)", inode->i_ino);
1512                 return VM_FAULT_SIGBUS;
1513         }
1514 
1515         lock_page(page);
1516         if (unlikely(page->mapping != inode->i_mapping ||
1517                      page_offset(page) > i_size_read(inode))) {
1518                 /* Page got truncated out from underneath us */
1519                 err = -EINVAL;
1520                 goto out_unlock;
1521         }
1522 
1523         if (PagePrivate(page))
1524                 release_new_page_budget(c);
1525         else {
1526                 if (!PageChecked(page))
1527                         ubifs_convert_page_budget(c);
1528                 SetPagePrivate(page);
1529                 atomic_long_inc(&c->dirty_pg_cnt);
1530                 __set_page_dirty_nobuffers(page);
1531         }
1532 
1533         if (update_time) {
1534                 int release;
1535                 struct ubifs_inode *ui = ubifs_inode(inode);
1536 
1537                 mutex_lock(&ui->ui_mutex);
1538                 inode->i_mtime = inode->i_ctime = ubifs_current_time(inode);
1539                 release = ui->dirty;
1540                 mark_inode_dirty_sync(inode);
1541                 mutex_unlock(&ui->ui_mutex);
1542                 if (release)
1543                         ubifs_release_dirty_inode_budget(c, ui);
1544         }
1545 
1546         return VM_FAULT_LOCKED;
1547 
1548 out_unlock:
1549         unlock_page(page);
1550         ubifs_release_budget(c, &req);
1551         if (err)
1552                 err = VM_FAULT_SIGBUS;
1553         return err;
1554 }
1555 
1556 static const struct vm_operations_struct ubifs_file_vm_ops = {
1557         .fault        = filemap_fault,
1558         .page_mkwrite = ubifs_vm_page_mkwrite,
1559 };
1560 
1561 static int ubifs_file_mmap(struct file *file, struct vm_area_struct *vma)
1562 {
1563         int err;
1564 
1565         err = generic_file_mmap(file, vma);
1566         if (err)
1567                 return err;
1568         vma->vm_ops = &ubifs_file_vm_ops;
1569         return 0;
1570 }
1571 
1572 const struct address_space_operations ubifs_file_address_operations = {
1573         .readpage       = ubifs_readpage,
1574         .writepage      = ubifs_writepage,
1575         .write_begin    = ubifs_write_begin,
1576         .write_end      = ubifs_write_end,
1577         .invalidatepage = ubifs_invalidatepage,
1578         .set_page_dirty = ubifs_set_page_dirty,
1579 #ifdef CONFIG_MIGRATION
1580         .migratepage    = ubifs_migrate_page,
1581 #endif
1582         .releasepage    = ubifs_releasepage,
1583 };
1584 
1585 const struct inode_operations ubifs_file_inode_operations = {
1586         .setattr     = ubifs_setattr,
1587         .getattr     = ubifs_getattr,
1588 #ifdef CONFIG_UBIFS_FS_XATTR
1589         .setxattr    = ubifs_setxattr,
1590         .getxattr    = ubifs_getxattr,
1591         .listxattr   = ubifs_listxattr,
1592         .removexattr = ubifs_removexattr,
1593 #endif
1594 };
1595 
1596 const struct inode_operations ubifs_symlink_inode_operations = {
1597         .readlink    = generic_readlink,
1598         .follow_link = ubifs_follow_link,
1599         .setattr     = ubifs_setattr,
1600         .getattr     = ubifs_getattr,
1601 };
1602 
1603 const struct file_operations ubifs_file_operations = {
1604         .llseek         = generic_file_llseek,
1605         .read           = do_sync_read,
1606         .write          = do_sync_write,
1607         .aio_read       = generic_file_aio_read,
1608         .aio_write      = ubifs_aio_write,
1609         .mmap           = ubifs_file_mmap,
1610         .fsync          = ubifs_fsync,
1611         .unlocked_ioctl = ubifs_ioctl,
1612         .splice_read    = generic_file_splice_read,
1613         .splice_write   = generic_file_splice_write,
1614 #ifdef CONFIG_COMPAT
1615         .compat_ioctl   = ubifs_compat_ioctl,
1616 #endif
1617 };
1618 

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