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Linux/fs/ext4/page-io.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * linux/fs/ext4/page-io.c
  4  *
  5  * This contains the new page_io functions for ext4
  6  *
  7  * Written by Theodore Ts'o, 2010.
  8  */
  9 
 10 #include <linux/fs.h>
 11 #include <linux/time.h>
 12 #include <linux/highuid.h>
 13 #include <linux/pagemap.h>
 14 #include <linux/quotaops.h>
 15 #include <linux/string.h>
 16 #include <linux/buffer_head.h>
 17 #include <linux/writeback.h>
 18 #include <linux/pagevec.h>
 19 #include <linux/mpage.h>
 20 #include <linux/namei.h>
 21 #include <linux/uio.h>
 22 #include <linux/bio.h>
 23 #include <linux/workqueue.h>
 24 #include <linux/kernel.h>
 25 #include <linux/slab.h>
 26 #include <linux/mm.h>
 27 #include <linux/backing-dev.h>
 28 
 29 #include "ext4_jbd2.h"
 30 #include "xattr.h"
 31 #include "acl.h"
 32 
 33 static struct kmem_cache *io_end_cachep;
 34 
 35 int __init ext4_init_pageio(void)
 36 {
 37         io_end_cachep = KMEM_CACHE(ext4_io_end, SLAB_RECLAIM_ACCOUNT);
 38         if (io_end_cachep == NULL)
 39                 return -ENOMEM;
 40         return 0;
 41 }
 42 
 43 void ext4_exit_pageio(void)
 44 {
 45         kmem_cache_destroy(io_end_cachep);
 46 }
 47 
 48 /*
 49  * Print an buffer I/O error compatible with the fs/buffer.c.  This
 50  * provides compatibility with dmesg scrapers that look for a specific
 51  * buffer I/O error message.  We really need a unified error reporting
 52  * structure to userspace ala Digital Unix's uerf system, but it's
 53  * probably not going to happen in my lifetime, due to LKML politics...
 54  */
 55 static void buffer_io_error(struct buffer_head *bh)
 56 {
 57         printk_ratelimited(KERN_ERR "Buffer I/O error on device %pg, logical block %llu\n",
 58                        bh->b_bdev,
 59                         (unsigned long long)bh->b_blocknr);
 60 }
 61 
 62 static void ext4_finish_bio(struct bio *bio)
 63 {
 64         int i;
 65         struct bio_vec *bvec;
 66 
 67         bio_for_each_segment_all(bvec, bio, i) {
 68                 struct page *page = bvec->bv_page;
 69 #ifdef CONFIG_EXT4_FS_ENCRYPTION
 70                 struct page *data_page = NULL;
 71 #endif
 72                 struct buffer_head *bh, *head;
 73                 unsigned bio_start = bvec->bv_offset;
 74                 unsigned bio_end = bio_start + bvec->bv_len;
 75                 unsigned under_io = 0;
 76                 unsigned long flags;
 77 
 78                 if (!page)
 79                         continue;
 80 
 81 #ifdef CONFIG_EXT4_FS_ENCRYPTION
 82                 if (!page->mapping) {
 83                         /* The bounce data pages are unmapped. */
 84                         data_page = page;
 85                         fscrypt_pullback_bio_page(&page, false);
 86                 }
 87 #endif
 88 
 89                 if (bio->bi_status) {
 90                         SetPageError(page);
 91                         mapping_set_error(page->mapping, -EIO);
 92                 }
 93                 bh = head = page_buffers(page);
 94                 /*
 95                  * We check all buffers in the page under BH_Uptodate_Lock
 96                  * to avoid races with other end io clearing async_write flags
 97                  */
 98                 local_irq_save(flags);
 99                 bit_spin_lock(BH_Uptodate_Lock, &head->b_state);
100                 do {
101                         if (bh_offset(bh) < bio_start ||
102                             bh_offset(bh) + bh->b_size > bio_end) {
103                                 if (buffer_async_write(bh))
104                                         under_io++;
105                                 continue;
106                         }
107                         clear_buffer_async_write(bh);
108                         if (bio->bi_status)
109                                 buffer_io_error(bh);
110                 } while ((bh = bh->b_this_page) != head);
111                 bit_spin_unlock(BH_Uptodate_Lock, &head->b_state);
112                 local_irq_restore(flags);
113                 if (!under_io) {
114 #ifdef CONFIG_EXT4_FS_ENCRYPTION
115                         if (data_page)
116                                 fscrypt_restore_control_page(data_page);
117 #endif
118                         end_page_writeback(page);
119                 }
120         }
121 }
122 
123 static void ext4_release_io_end(ext4_io_end_t *io_end)
124 {
125         struct bio *bio, *next_bio;
126 
127         BUG_ON(!list_empty(&io_end->list));
128         BUG_ON(io_end->flag & EXT4_IO_END_UNWRITTEN);
129         WARN_ON(io_end->handle);
130 
131         for (bio = io_end->bio; bio; bio = next_bio) {
132                 next_bio = bio->bi_private;
133                 ext4_finish_bio(bio);
134                 bio_put(bio);
135         }
136         kmem_cache_free(io_end_cachep, io_end);
137 }
138 
139 /*
140  * Check a range of space and convert unwritten extents to written. Note that
141  * we are protected from truncate touching same part of extent tree by the
142  * fact that truncate code waits for all DIO to finish (thus exclusion from
143  * direct IO is achieved) and also waits for PageWriteback bits. Thus we
144  * cannot get to ext4_ext_truncate() before all IOs overlapping that range are
145  * completed (happens from ext4_free_ioend()).
146  */
147 static int ext4_end_io(ext4_io_end_t *io)
148 {
149         struct inode *inode = io->inode;
150         loff_t offset = io->offset;
151         ssize_t size = io->size;
152         handle_t *handle = io->handle;
153         int ret = 0;
154 
155         ext4_debug("ext4_end_io_nolock: io 0x%p from inode %lu,list->next 0x%p,"
156                    "list->prev 0x%p\n",
157                    io, inode->i_ino, io->list.next, io->list.prev);
158 
159         io->handle = NULL;      /* Following call will use up the handle */
160         ret = ext4_convert_unwritten_extents(handle, inode, offset, size);
161         if (ret < 0 && !ext4_forced_shutdown(EXT4_SB(inode->i_sb))) {
162                 ext4_msg(inode->i_sb, KERN_EMERG,
163                          "failed to convert unwritten extents to written "
164                          "extents -- potential data loss!  "
165                          "(inode %lu, offset %llu, size %zd, error %d)",
166                          inode->i_ino, offset, size, ret);
167         }
168         ext4_clear_io_unwritten_flag(io);
169         ext4_release_io_end(io);
170         return ret;
171 }
172 
173 static void dump_completed_IO(struct inode *inode, struct list_head *head)
174 {
175 #ifdef  EXT4FS_DEBUG
176         struct list_head *cur, *before, *after;
177         ext4_io_end_t *io, *io0, *io1;
178 
179         if (list_empty(head))
180                 return;
181 
182         ext4_debug("Dump inode %lu completed io list\n", inode->i_ino);
183         list_for_each_entry(io, head, list) {
184                 cur = &io->list;
185                 before = cur->prev;
186                 io0 = container_of(before, ext4_io_end_t, list);
187                 after = cur->next;
188                 io1 = container_of(after, ext4_io_end_t, list);
189 
190                 ext4_debug("io 0x%p from inode %lu,prev 0x%p,next 0x%p\n",
191                             io, inode->i_ino, io0, io1);
192         }
193 #endif
194 }
195 
196 /* Add the io_end to per-inode completed end_io list. */
197 static void ext4_add_complete_io(ext4_io_end_t *io_end)
198 {
199         struct ext4_inode_info *ei = EXT4_I(io_end->inode);
200         struct ext4_sb_info *sbi = EXT4_SB(io_end->inode->i_sb);
201         struct workqueue_struct *wq;
202         unsigned long flags;
203 
204         /* Only reserved conversions from writeback should enter here */
205         WARN_ON(!(io_end->flag & EXT4_IO_END_UNWRITTEN));
206         WARN_ON(!io_end->handle && sbi->s_journal);
207         spin_lock_irqsave(&ei->i_completed_io_lock, flags);
208         wq = sbi->rsv_conversion_wq;
209         if (list_empty(&ei->i_rsv_conversion_list))
210                 queue_work(wq, &ei->i_rsv_conversion_work);
211         list_add_tail(&io_end->list, &ei->i_rsv_conversion_list);
212         spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
213 }
214 
215 static int ext4_do_flush_completed_IO(struct inode *inode,
216                                       struct list_head *head)
217 {
218         ext4_io_end_t *io;
219         struct list_head unwritten;
220         unsigned long flags;
221         struct ext4_inode_info *ei = EXT4_I(inode);
222         int err, ret = 0;
223 
224         spin_lock_irqsave(&ei->i_completed_io_lock, flags);
225         dump_completed_IO(inode, head);
226         list_replace_init(head, &unwritten);
227         spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
228 
229         while (!list_empty(&unwritten)) {
230                 io = list_entry(unwritten.next, ext4_io_end_t, list);
231                 BUG_ON(!(io->flag & EXT4_IO_END_UNWRITTEN));
232                 list_del_init(&io->list);
233 
234                 err = ext4_end_io(io);
235                 if (unlikely(!ret && err))
236                         ret = err;
237         }
238         return ret;
239 }
240 
241 /*
242  * work on completed IO, to convert unwritten extents to extents
243  */
244 void ext4_end_io_rsv_work(struct work_struct *work)
245 {
246         struct ext4_inode_info *ei = container_of(work, struct ext4_inode_info,
247                                                   i_rsv_conversion_work);
248         ext4_do_flush_completed_IO(&ei->vfs_inode, &ei->i_rsv_conversion_list);
249 }
250 
251 ext4_io_end_t *ext4_init_io_end(struct inode *inode, gfp_t flags)
252 {
253         ext4_io_end_t *io = kmem_cache_zalloc(io_end_cachep, flags);
254         if (io) {
255                 io->inode = inode;
256                 INIT_LIST_HEAD(&io->list);
257                 atomic_set(&io->count, 1);
258         }
259         return io;
260 }
261 
262 void ext4_put_io_end_defer(ext4_io_end_t *io_end)
263 {
264         if (atomic_dec_and_test(&io_end->count)) {
265                 if (!(io_end->flag & EXT4_IO_END_UNWRITTEN) || !io_end->size) {
266                         ext4_release_io_end(io_end);
267                         return;
268                 }
269                 ext4_add_complete_io(io_end);
270         }
271 }
272 
273 int ext4_put_io_end(ext4_io_end_t *io_end)
274 {
275         int err = 0;
276 
277         if (atomic_dec_and_test(&io_end->count)) {
278                 if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
279                         err = ext4_convert_unwritten_extents(io_end->handle,
280                                                 io_end->inode, io_end->offset,
281                                                 io_end->size);
282                         io_end->handle = NULL;
283                         ext4_clear_io_unwritten_flag(io_end);
284                 }
285                 ext4_release_io_end(io_end);
286         }
287         return err;
288 }
289 
290 ext4_io_end_t *ext4_get_io_end(ext4_io_end_t *io_end)
291 {
292         atomic_inc(&io_end->count);
293         return io_end;
294 }
295 
296 /* BIO completion function for page writeback */
297 static void ext4_end_bio(struct bio *bio)
298 {
299         ext4_io_end_t *io_end = bio->bi_private;
300         sector_t bi_sector = bio->bi_iter.bi_sector;
301         char b[BDEVNAME_SIZE];
302 
303         if (WARN_ONCE(!io_end, "io_end is NULL: %s: sector %Lu len %u err %d\n",
304                       bio_devname(bio, b),
305                       (long long) bio->bi_iter.bi_sector,
306                       (unsigned) bio_sectors(bio),
307                       bio->bi_status)) {
308                 ext4_finish_bio(bio);
309                 bio_put(bio);
310                 return;
311         }
312         bio->bi_end_io = NULL;
313 
314         if (bio->bi_status) {
315                 struct inode *inode = io_end->inode;
316 
317                 ext4_warning(inode->i_sb, "I/O error %d writing to inode %lu "
318                              "(offset %llu size %ld starting block %llu)",
319                              bio->bi_status, inode->i_ino,
320                              (unsigned long long) io_end->offset,
321                              (long) io_end->size,
322                              (unsigned long long)
323                              bi_sector >> (inode->i_blkbits - 9));
324                 mapping_set_error(inode->i_mapping,
325                                 blk_status_to_errno(bio->bi_status));
326         }
327 
328         if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
329                 /*
330                  * Link bio into list hanging from io_end. We have to do it
331                  * atomically as bio completions can be racing against each
332                  * other.
333                  */
334                 bio->bi_private = xchg(&io_end->bio, bio);
335                 ext4_put_io_end_defer(io_end);
336         } else {
337                 /*
338                  * Drop io_end reference early. Inode can get freed once
339                  * we finish the bio.
340                  */
341                 ext4_put_io_end_defer(io_end);
342                 ext4_finish_bio(bio);
343                 bio_put(bio);
344         }
345 }
346 
347 void ext4_io_submit(struct ext4_io_submit *io)
348 {
349         struct bio *bio = io->io_bio;
350 
351         if (bio) {
352                 int io_op_flags = io->io_wbc->sync_mode == WB_SYNC_ALL ?
353                                   REQ_SYNC : 0;
354                 io->io_bio->bi_write_hint = io->io_end->inode->i_write_hint;
355                 bio_set_op_attrs(io->io_bio, REQ_OP_WRITE, io_op_flags);
356                 submit_bio(io->io_bio);
357         }
358         io->io_bio = NULL;
359 }
360 
361 void ext4_io_submit_init(struct ext4_io_submit *io,
362                          struct writeback_control *wbc)
363 {
364         io->io_wbc = wbc;
365         io->io_bio = NULL;
366         io->io_end = NULL;
367 }
368 
369 static int io_submit_init_bio(struct ext4_io_submit *io,
370                               struct buffer_head *bh)
371 {
372         struct bio *bio;
373 
374         bio = bio_alloc(GFP_NOIO, BIO_MAX_PAGES);
375         if (!bio)
376                 return -ENOMEM;
377         wbc_init_bio(io->io_wbc, bio);
378         bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
379         bio_set_dev(bio, bh->b_bdev);
380         bio->bi_end_io = ext4_end_bio;
381         bio->bi_private = ext4_get_io_end(io->io_end);
382         io->io_bio = bio;
383         io->io_next_block = bh->b_blocknr;
384         return 0;
385 }
386 
387 static int io_submit_add_bh(struct ext4_io_submit *io,
388                             struct inode *inode,
389                             struct page *page,
390                             struct buffer_head *bh)
391 {
392         int ret;
393 
394         if (io->io_bio && bh->b_blocknr != io->io_next_block) {
395 submit_and_retry:
396                 ext4_io_submit(io);
397         }
398         if (io->io_bio == NULL) {
399                 ret = io_submit_init_bio(io, bh);
400                 if (ret)
401                         return ret;
402                 io->io_bio->bi_write_hint = inode->i_write_hint;
403         }
404         ret = bio_add_page(io->io_bio, page, bh->b_size, bh_offset(bh));
405         if (ret != bh->b_size)
406                 goto submit_and_retry;
407         wbc_account_io(io->io_wbc, page, bh->b_size);
408         io->io_next_block++;
409         return 0;
410 }
411 
412 int ext4_bio_write_page(struct ext4_io_submit *io,
413                         struct page *page,
414                         int len,
415                         struct writeback_control *wbc,
416                         bool keep_towrite)
417 {
418         struct page *data_page = NULL;
419         struct inode *inode = page->mapping->host;
420         unsigned block_start;
421         struct buffer_head *bh, *head;
422         int ret = 0;
423         int nr_submitted = 0;
424         int nr_to_submit = 0;
425 
426         BUG_ON(!PageLocked(page));
427         BUG_ON(PageWriteback(page));
428 
429         if (keep_towrite)
430                 set_page_writeback_keepwrite(page);
431         else
432                 set_page_writeback(page);
433         ClearPageError(page);
434 
435         /*
436          * Comments copied from block_write_full_page:
437          *
438          * The page straddles i_size.  It must be zeroed out on each and every
439          * writepage invocation because it may be mmapped.  "A file is mapped
440          * in multiples of the page size.  For a file that is not a multiple of
441          * the page size, the remaining memory is zeroed when mapped, and
442          * writes to that region are not written out to the file."
443          */
444         if (len < PAGE_SIZE)
445                 zero_user_segment(page, len, PAGE_SIZE);
446         /*
447          * In the first loop we prepare and mark buffers to submit. We have to
448          * mark all buffers in the page before submitting so that
449          * end_page_writeback() cannot be called from ext4_bio_end_io() when IO
450          * on the first buffer finishes and we are still working on submitting
451          * the second buffer.
452          */
453         bh = head = page_buffers(page);
454         do {
455                 block_start = bh_offset(bh);
456                 if (block_start >= len) {
457                         clear_buffer_dirty(bh);
458                         set_buffer_uptodate(bh);
459                         continue;
460                 }
461                 if (!buffer_dirty(bh) || buffer_delay(bh) ||
462                     !buffer_mapped(bh) || buffer_unwritten(bh)) {
463                         /* A hole? We can safely clear the dirty bit */
464                         if (!buffer_mapped(bh))
465                                 clear_buffer_dirty(bh);
466                         if (io->io_bio)
467                                 ext4_io_submit(io);
468                         continue;
469                 }
470                 if (buffer_new(bh)) {
471                         clear_buffer_new(bh);
472                         clean_bdev_bh_alias(bh);
473                 }
474                 set_buffer_async_write(bh);
475                 nr_to_submit++;
476         } while ((bh = bh->b_this_page) != head);
477 
478         bh = head = page_buffers(page);
479 
480         if (ext4_encrypted_inode(inode) && S_ISREG(inode->i_mode) &&
481             nr_to_submit) {
482                 gfp_t gfp_flags = GFP_NOFS;
483 
484         retry_encrypt:
485                 data_page = fscrypt_encrypt_page(inode, page, PAGE_SIZE, 0,
486                                                 page->index, gfp_flags);
487                 if (IS_ERR(data_page)) {
488                         ret = PTR_ERR(data_page);
489                         if (ret == -ENOMEM && wbc->sync_mode == WB_SYNC_ALL) {
490                                 if (io->io_bio) {
491                                         ext4_io_submit(io);
492                                         congestion_wait(BLK_RW_ASYNC, HZ/50);
493                                 }
494                                 gfp_flags |= __GFP_NOFAIL;
495                                 goto retry_encrypt;
496                         }
497                         data_page = NULL;
498                         goto out;
499                 }
500         }
501 
502         /* Now submit buffers to write */
503         do {
504                 if (!buffer_async_write(bh))
505                         continue;
506                 ret = io_submit_add_bh(io, inode,
507                                        data_page ? data_page : page, bh);
508                 if (ret) {
509                         /*
510                          * We only get here on ENOMEM.  Not much else
511                          * we can do but mark the page as dirty, and
512                          * better luck next time.
513                          */
514                         break;
515                 }
516                 nr_submitted++;
517                 clear_buffer_dirty(bh);
518         } while ((bh = bh->b_this_page) != head);
519 
520         /* Error stopped previous loop? Clean up buffers... */
521         if (ret) {
522         out:
523                 if (data_page)
524                         fscrypt_restore_control_page(data_page);
525                 printk_ratelimited(KERN_ERR "%s: ret = %d\n", __func__, ret);
526                 redirty_page_for_writepage(wbc, page);
527                 do {
528                         clear_buffer_async_write(bh);
529                         bh = bh->b_this_page;
530                 } while (bh != head);
531         }
532         unlock_page(page);
533         /* Nothing submitted - we have to end page writeback */
534         if (!nr_submitted)
535                 end_page_writeback(page);
536         return ret;
537 }
538 

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