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TOMOYO Linux Cross Reference
Linux/fs/xfs/xfs_aops.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * Copyright (c) 2000-2005 Silicon Graphics, Inc.
  4  * Copyright (c) 2016-2018 Christoph Hellwig.
  5  * All Rights Reserved.
  6  */
  7 #include "xfs.h"
  8 #include "xfs_shared.h"
  9 #include "xfs_format.h"
 10 #include "xfs_log_format.h"
 11 #include "xfs_trans_resv.h"
 12 #include "xfs_mount.h"
 13 #include "xfs_inode.h"
 14 #include "xfs_trans.h"
 15 #include "xfs_inode_item.h"
 16 #include "xfs_alloc.h"
 17 #include "xfs_error.h"
 18 #include "xfs_iomap.h"
 19 #include "xfs_trace.h"
 20 #include "xfs_bmap.h"
 21 #include "xfs_bmap_util.h"
 22 #include "xfs_bmap_btree.h"
 23 #include "xfs_reflink.h"
 24 #include <linux/writeback.h>
 25 
 26 /*
 27  * structure owned by writepages passed to individual writepage calls
 28  */
 29 struct xfs_writepage_ctx {
 30         struct xfs_bmbt_irec    imap;
 31         unsigned int            io_type;
 32         unsigned int            cow_seq;
 33         struct xfs_ioend        *ioend;
 34 };
 35 
 36 struct block_device *
 37 xfs_find_bdev_for_inode(
 38         struct inode            *inode)
 39 {
 40         struct xfs_inode        *ip = XFS_I(inode);
 41         struct xfs_mount        *mp = ip->i_mount;
 42 
 43         if (XFS_IS_REALTIME_INODE(ip))
 44                 return mp->m_rtdev_targp->bt_bdev;
 45         else
 46                 return mp->m_ddev_targp->bt_bdev;
 47 }
 48 
 49 struct dax_device *
 50 xfs_find_daxdev_for_inode(
 51         struct inode            *inode)
 52 {
 53         struct xfs_inode        *ip = XFS_I(inode);
 54         struct xfs_mount        *mp = ip->i_mount;
 55 
 56         if (XFS_IS_REALTIME_INODE(ip))
 57                 return mp->m_rtdev_targp->bt_daxdev;
 58         else
 59                 return mp->m_ddev_targp->bt_daxdev;
 60 }
 61 
 62 static void
 63 xfs_finish_page_writeback(
 64         struct inode            *inode,
 65         struct bio_vec          *bvec,
 66         int                     error)
 67 {
 68         struct iomap_page       *iop = to_iomap_page(bvec->bv_page);
 69 
 70         if (error) {
 71                 SetPageError(bvec->bv_page);
 72                 mapping_set_error(inode->i_mapping, -EIO);
 73         }
 74 
 75         ASSERT(iop || i_blocksize(inode) == PAGE_SIZE);
 76         ASSERT(!iop || atomic_read(&iop->write_count) > 0);
 77 
 78         if (!iop || atomic_dec_and_test(&iop->write_count))
 79                 end_page_writeback(bvec->bv_page);
 80 }
 81 
 82 /*
 83  * We're now finished for good with this ioend structure.  Update the page
 84  * state, release holds on bios, and finally free up memory.  Do not use the
 85  * ioend after this.
 86  */
 87 STATIC void
 88 xfs_destroy_ioend(
 89         struct xfs_ioend        *ioend,
 90         int                     error)
 91 {
 92         struct inode            *inode = ioend->io_inode;
 93         struct bio              *bio = &ioend->io_inline_bio;
 94         struct bio              *last = ioend->io_bio, *next;
 95         u64                     start = bio->bi_iter.bi_sector;
 96         bool                    quiet = bio_flagged(bio, BIO_QUIET);
 97 
 98         for (bio = &ioend->io_inline_bio; bio; bio = next) {
 99                 struct bio_vec  *bvec;
100                 int             i;
101 
102                 /*
103                  * For the last bio, bi_private points to the ioend, so we
104                  * need to explicitly end the iteration here.
105                  */
106                 if (bio == last)
107                         next = NULL;
108                 else
109                         next = bio->bi_private;
110 
111                 /* walk each page on bio, ending page IO on them */
112                 bio_for_each_segment_all(bvec, bio, i)
113                         xfs_finish_page_writeback(inode, bvec, error);
114                 bio_put(bio);
115         }
116 
117         if (unlikely(error && !quiet)) {
118                 xfs_err_ratelimited(XFS_I(inode)->i_mount,
119                         "writeback error on sector %llu", start);
120         }
121 }
122 
123 /*
124  * Fast and loose check if this write could update the on-disk inode size.
125  */
126 static inline bool xfs_ioend_is_append(struct xfs_ioend *ioend)
127 {
128         return ioend->io_offset + ioend->io_size >
129                 XFS_I(ioend->io_inode)->i_d.di_size;
130 }
131 
132 STATIC int
133 xfs_setfilesize_trans_alloc(
134         struct xfs_ioend        *ioend)
135 {
136         struct xfs_mount        *mp = XFS_I(ioend->io_inode)->i_mount;
137         struct xfs_trans        *tp;
138         int                     error;
139 
140         error = xfs_trans_alloc(mp, &M_RES(mp)->tr_fsyncts, 0, 0,
141                                 XFS_TRANS_NOFS, &tp);
142         if (error)
143                 return error;
144 
145         ioend->io_append_trans = tp;
146 
147         /*
148          * We may pass freeze protection with a transaction.  So tell lockdep
149          * we released it.
150          */
151         __sb_writers_release(ioend->io_inode->i_sb, SB_FREEZE_FS);
152         /*
153          * We hand off the transaction to the completion thread now, so
154          * clear the flag here.
155          */
156         current_restore_flags_nested(&tp->t_pflags, PF_MEMALLOC_NOFS);
157         return 0;
158 }
159 
160 /*
161  * Update on-disk file size now that data has been written to disk.
162  */
163 STATIC int
164 __xfs_setfilesize(
165         struct xfs_inode        *ip,
166         struct xfs_trans        *tp,
167         xfs_off_t               offset,
168         size_t                  size)
169 {
170         xfs_fsize_t             isize;
171 
172         xfs_ilock(ip, XFS_ILOCK_EXCL);
173         isize = xfs_new_eof(ip, offset + size);
174         if (!isize) {
175                 xfs_iunlock(ip, XFS_ILOCK_EXCL);
176                 xfs_trans_cancel(tp);
177                 return 0;
178         }
179 
180         trace_xfs_setfilesize(ip, offset, size);
181 
182         ip->i_d.di_size = isize;
183         xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
184         xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
185 
186         return xfs_trans_commit(tp);
187 }
188 
189 int
190 xfs_setfilesize(
191         struct xfs_inode        *ip,
192         xfs_off_t               offset,
193         size_t                  size)
194 {
195         struct xfs_mount        *mp = ip->i_mount;
196         struct xfs_trans        *tp;
197         int                     error;
198 
199         error = xfs_trans_alloc(mp, &M_RES(mp)->tr_fsyncts, 0, 0, 0, &tp);
200         if (error)
201                 return error;
202 
203         return __xfs_setfilesize(ip, tp, offset, size);
204 }
205 
206 STATIC int
207 xfs_setfilesize_ioend(
208         struct xfs_ioend        *ioend,
209         int                     error)
210 {
211         struct xfs_inode        *ip = XFS_I(ioend->io_inode);
212         struct xfs_trans        *tp = ioend->io_append_trans;
213 
214         /*
215          * The transaction may have been allocated in the I/O submission thread,
216          * thus we need to mark ourselves as being in a transaction manually.
217          * Similarly for freeze protection.
218          */
219         current_set_flags_nested(&tp->t_pflags, PF_MEMALLOC_NOFS);
220         __sb_writers_acquired(VFS_I(ip)->i_sb, SB_FREEZE_FS);
221 
222         /* we abort the update if there was an IO error */
223         if (error) {
224                 xfs_trans_cancel(tp);
225                 return error;
226         }
227 
228         return __xfs_setfilesize(ip, tp, ioend->io_offset, ioend->io_size);
229 }
230 
231 /*
232  * IO write completion.
233  */
234 STATIC void
235 xfs_end_io(
236         struct work_struct *work)
237 {
238         struct xfs_ioend        *ioend =
239                 container_of(work, struct xfs_ioend, io_work);
240         struct xfs_inode        *ip = XFS_I(ioend->io_inode);
241         xfs_off_t               offset = ioend->io_offset;
242         size_t                  size = ioend->io_size;
243         int                     error;
244 
245         /*
246          * Just clean up the in-memory strutures if the fs has been shut down.
247          */
248         if (XFS_FORCED_SHUTDOWN(ip->i_mount)) {
249                 error = -EIO;
250                 goto done;
251         }
252 
253         /*
254          * Clean up any COW blocks on an I/O error.
255          */
256         error = blk_status_to_errno(ioend->io_bio->bi_status);
257         if (unlikely(error)) {
258                 switch (ioend->io_type) {
259                 case XFS_IO_COW:
260                         xfs_reflink_cancel_cow_range(ip, offset, size, true);
261                         break;
262                 }
263 
264                 goto done;
265         }
266 
267         /*
268          * Success:  commit the COW or unwritten blocks if needed.
269          */
270         switch (ioend->io_type) {
271         case XFS_IO_COW:
272                 error = xfs_reflink_end_cow(ip, offset, size);
273                 break;
274         case XFS_IO_UNWRITTEN:
275                 /* writeback should never update isize */
276                 error = xfs_iomap_write_unwritten(ip, offset, size, false);
277                 break;
278         default:
279                 ASSERT(!xfs_ioend_is_append(ioend) || ioend->io_append_trans);
280                 break;
281         }
282 
283 done:
284         if (ioend->io_append_trans)
285                 error = xfs_setfilesize_ioend(ioend, error);
286         xfs_destroy_ioend(ioend, error);
287 }
288 
289 STATIC void
290 xfs_end_bio(
291         struct bio              *bio)
292 {
293         struct xfs_ioend        *ioend = bio->bi_private;
294         struct xfs_mount        *mp = XFS_I(ioend->io_inode)->i_mount;
295 
296         if (ioend->io_type == XFS_IO_UNWRITTEN || ioend->io_type == XFS_IO_COW)
297                 queue_work(mp->m_unwritten_workqueue, &ioend->io_work);
298         else if (ioend->io_append_trans)
299                 queue_work(mp->m_data_workqueue, &ioend->io_work);
300         else
301                 xfs_destroy_ioend(ioend, blk_status_to_errno(bio->bi_status));
302 }
303 
304 STATIC int
305 xfs_map_blocks(
306         struct xfs_writepage_ctx *wpc,
307         struct inode            *inode,
308         loff_t                  offset)
309 {
310         struct xfs_inode        *ip = XFS_I(inode);
311         struct xfs_mount        *mp = ip->i_mount;
312         ssize_t                 count = i_blocksize(inode);
313         xfs_fileoff_t           offset_fsb = XFS_B_TO_FSBT(mp, offset), end_fsb;
314         xfs_fileoff_t           cow_fsb = NULLFILEOFF;
315         struct xfs_bmbt_irec    imap;
316         int                     whichfork = XFS_DATA_FORK;
317         struct xfs_iext_cursor  icur;
318         bool                    imap_valid;
319         int                     error = 0;
320 
321         /*
322          * We have to make sure the cached mapping is within EOF to protect
323          * against eofblocks trimming on file release leaving us with a stale
324          * mapping. Otherwise, a page for a subsequent file extending buffered
325          * write could get picked up by this writeback cycle and written to the
326          * wrong blocks.
327          *
328          * Note that what we really want here is a generic mapping invalidation
329          * mechanism to protect us from arbitrary extent modifying contexts, not
330          * just eofblocks.
331          */
332         xfs_trim_extent_eof(&wpc->imap, ip);
333 
334         /*
335          * COW fork blocks can overlap data fork blocks even if the blocks
336          * aren't shared.  COW I/O always takes precedent, so we must always
337          * check for overlap on reflink inodes unless the mapping is already a
338          * COW one, or the COW fork hasn't changed from the last time we looked
339          * at it.
340          *
341          * It's safe to check the COW fork if_seq here without the ILOCK because
342          * we've indirectly protected against concurrent updates: writeback has
343          * the page locked, which prevents concurrent invalidations by reflink
344          * and directio and prevents concurrent buffered writes to the same
345          * page.  Changes to if_seq always happen under i_lock, which protects
346          * against concurrent updates and provides a memory barrier on the way
347          * out that ensures that we always see the current value.
348          */
349         imap_valid = offset_fsb >= wpc->imap.br_startoff &&
350                      offset_fsb < wpc->imap.br_startoff + wpc->imap.br_blockcount;
351         if (imap_valid &&
352             (!xfs_inode_has_cow_data(ip) ||
353              wpc->io_type == XFS_IO_COW ||
354              wpc->cow_seq == READ_ONCE(ip->i_cowfp->if_seq)))
355                 return 0;
356 
357         if (XFS_FORCED_SHUTDOWN(mp))
358                 return -EIO;
359 
360         /*
361          * If we don't have a valid map, now it's time to get a new one for this
362          * offset.  This will convert delayed allocations (including COW ones)
363          * into real extents.  If we return without a valid map, it means we
364          * landed in a hole and we skip the block.
365          */
366         xfs_ilock(ip, XFS_ILOCK_SHARED);
367         ASSERT(ip->i_d.di_format != XFS_DINODE_FMT_BTREE ||
368                (ip->i_df.if_flags & XFS_IFEXTENTS));
369         ASSERT(offset <= mp->m_super->s_maxbytes);
370 
371         if (offset > mp->m_super->s_maxbytes - count)
372                 count = mp->m_super->s_maxbytes - offset;
373         end_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + count);
374 
375         /*
376          * Check if this is offset is covered by a COW extents, and if yes use
377          * it directly instead of looking up anything in the data fork.
378          */
379         if (xfs_inode_has_cow_data(ip) &&
380             xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &imap))
381                 cow_fsb = imap.br_startoff;
382         if (cow_fsb != NULLFILEOFF && cow_fsb <= offset_fsb) {
383                 wpc->cow_seq = READ_ONCE(ip->i_cowfp->if_seq);
384                 xfs_iunlock(ip, XFS_ILOCK_SHARED);
385                 /*
386                  * Truncate can race with writeback since writeback doesn't
387                  * take the iolock and truncate decreases the file size before
388                  * it starts truncating the pages between new_size and old_size.
389                  * Therefore, we can end up in the situation where writeback
390                  * gets a CoW fork mapping but the truncate makes the mapping
391                  * invalid and we end up in here trying to get a new mapping.
392                  * bail out here so that we simply never get a valid mapping
393                  * and so we drop the write altogether.  The page truncation
394                  * will kill the contents anyway.
395                  */
396                 if (offset > i_size_read(inode)) {
397                         wpc->io_type = XFS_IO_HOLE;
398                         return 0;
399                 }
400                 whichfork = XFS_COW_FORK;
401                 wpc->io_type = XFS_IO_COW;
402                 goto allocate_blocks;
403         }
404 
405         /*
406          * Map valid and no COW extent in the way?  We're done.
407          */
408         if (imap_valid) {
409                 xfs_iunlock(ip, XFS_ILOCK_SHARED);
410                 return 0;
411         }
412 
413         /*
414          * If we don't have a valid map, now it's time to get a new one for this
415          * offset.  This will convert delayed allocations (including COW ones)
416          * into real extents.
417          */
418         if (!xfs_iext_lookup_extent(ip, &ip->i_df, offset_fsb, &icur, &imap))
419                 imap.br_startoff = end_fsb;     /* fake a hole past EOF */
420         xfs_iunlock(ip, XFS_ILOCK_SHARED);
421 
422         if (imap.br_startoff > offset_fsb) {
423                 /* landed in a hole or beyond EOF */
424                 imap.br_blockcount = imap.br_startoff - offset_fsb;
425                 imap.br_startoff = offset_fsb;
426                 imap.br_startblock = HOLESTARTBLOCK;
427                 wpc->io_type = XFS_IO_HOLE;
428         } else {
429                 /*
430                  * Truncate to the next COW extent if there is one.  This is the
431                  * only opportunity to do this because we can skip COW fork
432                  * lookups for the subsequent blocks in the mapping; however,
433                  * the requirement to treat the COW range separately remains.
434                  */
435                 if (cow_fsb != NULLFILEOFF &&
436                     cow_fsb < imap.br_startoff + imap.br_blockcount)
437                         imap.br_blockcount = cow_fsb - imap.br_startoff;
438 
439                 if (isnullstartblock(imap.br_startblock)) {
440                         /* got a delalloc extent */
441                         wpc->io_type = XFS_IO_DELALLOC;
442                         goto allocate_blocks;
443                 }
444 
445                 if (imap.br_state == XFS_EXT_UNWRITTEN)
446                         wpc->io_type = XFS_IO_UNWRITTEN;
447                 else
448                         wpc->io_type = XFS_IO_OVERWRITE;
449         }
450 
451         wpc->imap = imap;
452         xfs_trim_extent_eof(&wpc->imap, ip);
453         trace_xfs_map_blocks_found(ip, offset, count, wpc->io_type, &imap);
454         return 0;
455 allocate_blocks:
456         error = xfs_iomap_write_allocate(ip, whichfork, offset, &imap,
457                         &wpc->cow_seq);
458         if (error)
459                 return error;
460         ASSERT(whichfork == XFS_COW_FORK || cow_fsb == NULLFILEOFF ||
461                imap.br_startoff + imap.br_blockcount <= cow_fsb);
462         wpc->imap = imap;
463         xfs_trim_extent_eof(&wpc->imap, ip);
464         trace_xfs_map_blocks_alloc(ip, offset, count, wpc->io_type, &imap);
465         return 0;
466 }
467 
468 /*
469  * Submit the bio for an ioend. We are passed an ioend with a bio attached to
470  * it, and we submit that bio. The ioend may be used for multiple bio
471  * submissions, so we only want to allocate an append transaction for the ioend
472  * once. In the case of multiple bio submission, each bio will take an IO
473  * reference to the ioend to ensure that the ioend completion is only done once
474  * all bios have been submitted and the ioend is really done.
475  *
476  * If @fail is non-zero, it means that we have a situation where some part of
477  * the submission process has failed after we have marked paged for writeback
478  * and unlocked them. In this situation, we need to fail the bio and ioend
479  * rather than submit it to IO. This typically only happens on a filesystem
480  * shutdown.
481  */
482 STATIC int
483 xfs_submit_ioend(
484         struct writeback_control *wbc,
485         struct xfs_ioend        *ioend,
486         int                     status)
487 {
488         /* Convert CoW extents to regular */
489         if (!status && ioend->io_type == XFS_IO_COW) {
490                 /*
491                  * Yuk. This can do memory allocation, but is not a
492                  * transactional operation so everything is done in GFP_KERNEL
493                  * context. That can deadlock, because we hold pages in
494                  * writeback state and GFP_KERNEL allocations can block on them.
495                  * Hence we must operate in nofs conditions here.
496                  */
497                 unsigned nofs_flag;
498 
499                 nofs_flag = memalloc_nofs_save();
500                 status = xfs_reflink_convert_cow(XFS_I(ioend->io_inode),
501                                 ioend->io_offset, ioend->io_size);
502                 memalloc_nofs_restore(nofs_flag);
503         }
504 
505         /* Reserve log space if we might write beyond the on-disk inode size. */
506         if (!status &&
507             ioend->io_type != XFS_IO_UNWRITTEN &&
508             xfs_ioend_is_append(ioend) &&
509             !ioend->io_append_trans)
510                 status = xfs_setfilesize_trans_alloc(ioend);
511 
512         ioend->io_bio->bi_private = ioend;
513         ioend->io_bio->bi_end_io = xfs_end_bio;
514         ioend->io_bio->bi_opf = REQ_OP_WRITE | wbc_to_write_flags(wbc);
515 
516         /*
517          * If we are failing the IO now, just mark the ioend with an
518          * error and finish it. This will run IO completion immediately
519          * as there is only one reference to the ioend at this point in
520          * time.
521          */
522         if (status) {
523                 ioend->io_bio->bi_status = errno_to_blk_status(status);
524                 bio_endio(ioend->io_bio);
525                 return status;
526         }
527 
528         ioend->io_bio->bi_write_hint = ioend->io_inode->i_write_hint;
529         submit_bio(ioend->io_bio);
530         return 0;
531 }
532 
533 static struct xfs_ioend *
534 xfs_alloc_ioend(
535         struct inode            *inode,
536         unsigned int            type,
537         xfs_off_t               offset,
538         struct block_device     *bdev,
539         sector_t                sector)
540 {
541         struct xfs_ioend        *ioend;
542         struct bio              *bio;
543 
544         bio = bio_alloc_bioset(GFP_NOFS, BIO_MAX_PAGES, &xfs_ioend_bioset);
545         bio_set_dev(bio, bdev);
546         bio->bi_iter.bi_sector = sector;
547 
548         ioend = container_of(bio, struct xfs_ioend, io_inline_bio);
549         INIT_LIST_HEAD(&ioend->io_list);
550         ioend->io_type = type;
551         ioend->io_inode = inode;
552         ioend->io_size = 0;
553         ioend->io_offset = offset;
554         INIT_WORK(&ioend->io_work, xfs_end_io);
555         ioend->io_append_trans = NULL;
556         ioend->io_bio = bio;
557         return ioend;
558 }
559 
560 /*
561  * Allocate a new bio, and chain the old bio to the new one.
562  *
563  * Note that we have to do perform the chaining in this unintuitive order
564  * so that the bi_private linkage is set up in the right direction for the
565  * traversal in xfs_destroy_ioend().
566  */
567 static void
568 xfs_chain_bio(
569         struct xfs_ioend        *ioend,
570         struct writeback_control *wbc,
571         struct block_device     *bdev,
572         sector_t                sector)
573 {
574         struct bio *new;
575 
576         new = bio_alloc(GFP_NOFS, BIO_MAX_PAGES);
577         bio_set_dev(new, bdev);
578         new->bi_iter.bi_sector = sector;
579         bio_chain(ioend->io_bio, new);
580         bio_get(ioend->io_bio);         /* for xfs_destroy_ioend */
581         ioend->io_bio->bi_opf = REQ_OP_WRITE | wbc_to_write_flags(wbc);
582         ioend->io_bio->bi_write_hint = ioend->io_inode->i_write_hint;
583         submit_bio(ioend->io_bio);
584         ioend->io_bio = new;
585 }
586 
587 /*
588  * Test to see if we have an existing ioend structure that we could append to
589  * first, otherwise finish off the current ioend and start another.
590  */
591 STATIC void
592 xfs_add_to_ioend(
593         struct inode            *inode,
594         xfs_off_t               offset,
595         struct page             *page,
596         struct iomap_page       *iop,
597         struct xfs_writepage_ctx *wpc,
598         struct writeback_control *wbc,
599         struct list_head        *iolist)
600 {
601         struct xfs_inode        *ip = XFS_I(inode);
602         struct xfs_mount        *mp = ip->i_mount;
603         struct block_device     *bdev = xfs_find_bdev_for_inode(inode);
604         unsigned                len = i_blocksize(inode);
605         unsigned                poff = offset & (PAGE_SIZE - 1);
606         sector_t                sector;
607 
608         sector = xfs_fsb_to_db(ip, wpc->imap.br_startblock) +
609                 ((offset - XFS_FSB_TO_B(mp, wpc->imap.br_startoff)) >> 9);
610 
611         if (!wpc->ioend || wpc->io_type != wpc->ioend->io_type ||
612             sector != bio_end_sector(wpc->ioend->io_bio) ||
613             offset != wpc->ioend->io_offset + wpc->ioend->io_size) {
614                 if (wpc->ioend)
615                         list_add(&wpc->ioend->io_list, iolist);
616                 wpc->ioend = xfs_alloc_ioend(inode, wpc->io_type, offset,
617                                 bdev, sector);
618         }
619 
620         if (!__bio_try_merge_page(wpc->ioend->io_bio, page, len, poff)) {
621                 if (iop)
622                         atomic_inc(&iop->write_count);
623                 if (bio_full(wpc->ioend->io_bio))
624                         xfs_chain_bio(wpc->ioend, wbc, bdev, sector);
625                 __bio_add_page(wpc->ioend->io_bio, page, len, poff);
626         }
627 
628         wpc->ioend->io_size += len;
629 }
630 
631 STATIC void
632 xfs_vm_invalidatepage(
633         struct page             *page,
634         unsigned int            offset,
635         unsigned int            length)
636 {
637         trace_xfs_invalidatepage(page->mapping->host, page, offset, length);
638         iomap_invalidatepage(page, offset, length);
639 }
640 
641 /*
642  * If the page has delalloc blocks on it, we need to punch them out before we
643  * invalidate the page.  If we don't, we leave a stale delalloc mapping on the
644  * inode that can trip up a later direct I/O read operation on the same region.
645  *
646  * We prevent this by truncating away the delalloc regions on the page.  Because
647  * they are delalloc, we can do this without needing a transaction. Indeed - if
648  * we get ENOSPC errors, we have to be able to do this truncation without a
649  * transaction as there is no space left for block reservation (typically why we
650  * see a ENOSPC in writeback).
651  */
652 STATIC void
653 xfs_aops_discard_page(
654         struct page             *page)
655 {
656         struct inode            *inode = page->mapping->host;
657         struct xfs_inode        *ip = XFS_I(inode);
658         struct xfs_mount        *mp = ip->i_mount;
659         loff_t                  offset = page_offset(page);
660         xfs_fileoff_t           start_fsb = XFS_B_TO_FSBT(mp, offset);
661         int                     error;
662 
663         if (XFS_FORCED_SHUTDOWN(mp))
664                 goto out_invalidate;
665 
666         xfs_alert(mp,
667                 "page discard on page "PTR_FMT", inode 0x%llx, offset %llu.",
668                         page, ip->i_ino, offset);
669 
670         error = xfs_bmap_punch_delalloc_range(ip, start_fsb,
671                         PAGE_SIZE / i_blocksize(inode));
672         if (error && !XFS_FORCED_SHUTDOWN(mp))
673                 xfs_alert(mp, "page discard unable to remove delalloc mapping.");
674 out_invalidate:
675         xfs_vm_invalidatepage(page, 0, PAGE_SIZE);
676 }
677 
678 /*
679  * We implement an immediate ioend submission policy here to avoid needing to
680  * chain multiple ioends and hence nest mempool allocations which can violate
681  * forward progress guarantees we need to provide. The current ioend we are
682  * adding blocks to is cached on the writepage context, and if the new block
683  * does not append to the cached ioend it will create a new ioend and cache that
684  * instead.
685  *
686  * If a new ioend is created and cached, the old ioend is returned and queued
687  * locally for submission once the entire page is processed or an error has been
688  * detected.  While ioends are submitted immediately after they are completed,
689  * batching optimisations are provided by higher level block plugging.
690  *
691  * At the end of a writeback pass, there will be a cached ioend remaining on the
692  * writepage context that the caller will need to submit.
693  */
694 static int
695 xfs_writepage_map(
696         struct xfs_writepage_ctx *wpc,
697         struct writeback_control *wbc,
698         struct inode            *inode,
699         struct page             *page,
700         uint64_t                end_offset)
701 {
702         LIST_HEAD(submit_list);
703         struct iomap_page       *iop = to_iomap_page(page);
704         unsigned                len = i_blocksize(inode);
705         struct xfs_ioend        *ioend, *next;
706         uint64_t                file_offset;    /* file offset of page */
707         int                     error = 0, count = 0, i;
708 
709         ASSERT(iop || i_blocksize(inode) == PAGE_SIZE);
710         ASSERT(!iop || atomic_read(&iop->write_count) == 0);
711 
712         /*
713          * Walk through the page to find areas to write back. If we run off the
714          * end of the current map or find the current map invalid, grab a new
715          * one.
716          */
717         for (i = 0, file_offset = page_offset(page);
718              i < (PAGE_SIZE >> inode->i_blkbits) && file_offset < end_offset;
719              i++, file_offset += len) {
720                 if (iop && !test_bit(i, iop->uptodate))
721                         continue;
722 
723                 error = xfs_map_blocks(wpc, inode, file_offset);
724                 if (error)
725                         break;
726                 if (wpc->io_type == XFS_IO_HOLE)
727                         continue;
728                 xfs_add_to_ioend(inode, file_offset, page, iop, wpc, wbc,
729                                  &submit_list);
730                 count++;
731         }
732 
733         ASSERT(wpc->ioend || list_empty(&submit_list));
734         ASSERT(PageLocked(page));
735         ASSERT(!PageWriteback(page));
736 
737         /*
738          * On error, we have to fail the ioend here because we may have set
739          * pages under writeback, we have to make sure we run IO completion to
740          * mark the error state of the IO appropriately, so we can't cancel the
741          * ioend directly here.  That means we have to mark this page as under
742          * writeback if we included any blocks from it in the ioend chain so
743          * that completion treats it correctly.
744          *
745          * If we didn't include the page in the ioend, the on error we can
746          * simply discard and unlock it as there are no other users of the page
747          * now.  The caller will still need to trigger submission of outstanding
748          * ioends on the writepage context so they are treated correctly on
749          * error.
750          */
751         if (unlikely(error)) {
752                 if (!count) {
753                         xfs_aops_discard_page(page);
754                         ClearPageUptodate(page);
755                         unlock_page(page);
756                         goto done;
757                 }
758 
759                 /*
760                  * If the page was not fully cleaned, we need to ensure that the
761                  * higher layers come back to it correctly.  That means we need
762                  * to keep the page dirty, and for WB_SYNC_ALL writeback we need
763                  * to ensure the PAGECACHE_TAG_TOWRITE index mark is not removed
764                  * so another attempt to write this page in this writeback sweep
765                  * will be made.
766                  */
767                 set_page_writeback_keepwrite(page);
768         } else {
769                 clear_page_dirty_for_io(page);
770                 set_page_writeback(page);
771         }
772 
773         unlock_page(page);
774 
775         /*
776          * Preserve the original error if there was one, otherwise catch
777          * submission errors here and propagate into subsequent ioend
778          * submissions.
779          */
780         list_for_each_entry_safe(ioend, next, &submit_list, io_list) {
781                 int error2;
782 
783                 list_del_init(&ioend->io_list);
784                 error2 = xfs_submit_ioend(wbc, ioend, error);
785                 if (error2 && !error)
786                         error = error2;
787         }
788 
789         /*
790          * We can end up here with no error and nothing to write only if we race
791          * with a partial page truncate on a sub-page block sized filesystem.
792          */
793         if (!count)
794                 end_page_writeback(page);
795 done:
796         mapping_set_error(page->mapping, error);
797         return error;
798 }
799 
800 /*
801  * Write out a dirty page.
802  *
803  * For delalloc space on the page we need to allocate space and flush it.
804  * For unwritten space on the page we need to start the conversion to
805  * regular allocated space.
806  */
807 STATIC int
808 xfs_do_writepage(
809         struct page             *page,
810         struct writeback_control *wbc,
811         void                    *data)
812 {
813         struct xfs_writepage_ctx *wpc = data;
814         struct inode            *inode = page->mapping->host;
815         loff_t                  offset;
816         uint64_t              end_offset;
817         pgoff_t                 end_index;
818 
819         trace_xfs_writepage(inode, page, 0, 0);
820 
821         /*
822          * Refuse to write the page out if we are called from reclaim context.
823          *
824          * This avoids stack overflows when called from deeply used stacks in
825          * random callers for direct reclaim or memcg reclaim.  We explicitly
826          * allow reclaim from kswapd as the stack usage there is relatively low.
827          *
828          * This should never happen except in the case of a VM regression so
829          * warn about it.
830          */
831         if (WARN_ON_ONCE((current->flags & (PF_MEMALLOC|PF_KSWAPD)) ==
832                         PF_MEMALLOC))
833                 goto redirty;
834 
835         /*
836          * Given that we do not allow direct reclaim to call us, we should
837          * never be called while in a filesystem transaction.
838          */
839         if (WARN_ON_ONCE(current->flags & PF_MEMALLOC_NOFS))
840                 goto redirty;
841 
842         /*
843          * Is this page beyond the end of the file?
844          *
845          * The page index is less than the end_index, adjust the end_offset
846          * to the highest offset that this page should represent.
847          * -----------------------------------------------------
848          * |                    file mapping           | <EOF> |
849          * -----------------------------------------------------
850          * | Page ... | Page N-2 | Page N-1 |  Page N  |       |
851          * ^--------------------------------^----------|--------
852          * |     desired writeback range    |      see else    |
853          * ---------------------------------^------------------|
854          */
855         offset = i_size_read(inode);
856         end_index = offset >> PAGE_SHIFT;
857         if (page->index < end_index)
858                 end_offset = (xfs_off_t)(page->index + 1) << PAGE_SHIFT;
859         else {
860                 /*
861                  * Check whether the page to write out is beyond or straddles
862                  * i_size or not.
863                  * -------------------------------------------------------
864                  * |            file mapping                    | <EOF>  |
865                  * -------------------------------------------------------
866                  * | Page ... | Page N-2 | Page N-1 |  Page N   | Beyond |
867                  * ^--------------------------------^-----------|---------
868                  * |                                |      Straddles     |
869                  * ---------------------------------^-----------|--------|
870                  */
871                 unsigned offset_into_page = offset & (PAGE_SIZE - 1);
872 
873                 /*
874                  * Skip the page if it is fully outside i_size, e.g. due to a
875                  * truncate operation that is in progress. We must redirty the
876                  * page so that reclaim stops reclaiming it. Otherwise
877                  * xfs_vm_releasepage() is called on it and gets confused.
878                  *
879                  * Note that the end_index is unsigned long, it would overflow
880                  * if the given offset is greater than 16TB on 32-bit system
881                  * and if we do check the page is fully outside i_size or not
882                  * via "if (page->index >= end_index + 1)" as "end_index + 1"
883                  * will be evaluated to 0.  Hence this page will be redirtied
884                  * and be written out repeatedly which would result in an
885                  * infinite loop, the user program that perform this operation
886                  * will hang.  Instead, we can verify this situation by checking
887                  * if the page to write is totally beyond the i_size or if it's
888                  * offset is just equal to the EOF.
889                  */
890                 if (page->index > end_index ||
891                     (page->index == end_index && offset_into_page == 0))
892                         goto redirty;
893 
894                 /*
895                  * The page straddles i_size.  It must be zeroed out on each
896                  * and every writepage invocation because it may be mmapped.
897                  * "A file is mapped in multiples of the page size.  For a file
898                  * that is not a multiple of the page size, the remaining
899                  * memory is zeroed when mapped, and writes to that region are
900                  * not written out to the file."
901                  */
902                 zero_user_segment(page, offset_into_page, PAGE_SIZE);
903 
904                 /* Adjust the end_offset to the end of file */
905                 end_offset = offset;
906         }
907 
908         return xfs_writepage_map(wpc, wbc, inode, page, end_offset);
909 
910 redirty:
911         redirty_page_for_writepage(wbc, page);
912         unlock_page(page);
913         return 0;
914 }
915 
916 STATIC int
917 xfs_vm_writepage(
918         struct page             *page,
919         struct writeback_control *wbc)
920 {
921         struct xfs_writepage_ctx wpc = {
922                 .io_type = XFS_IO_HOLE,
923         };
924         int                     ret;
925 
926         ret = xfs_do_writepage(page, wbc, &wpc);
927         if (wpc.ioend)
928                 ret = xfs_submit_ioend(wbc, wpc.ioend, ret);
929         return ret;
930 }
931 
932 STATIC int
933 xfs_vm_writepages(
934         struct address_space    *mapping,
935         struct writeback_control *wbc)
936 {
937         struct xfs_writepage_ctx wpc = {
938                 .io_type = XFS_IO_HOLE,
939         };
940         int                     ret;
941 
942         xfs_iflags_clear(XFS_I(mapping->host), XFS_ITRUNCATED);
943         ret = write_cache_pages(mapping, wbc, xfs_do_writepage, &wpc);
944         if (wpc.ioend)
945                 ret = xfs_submit_ioend(wbc, wpc.ioend, ret);
946         return ret;
947 }
948 
949 STATIC int
950 xfs_dax_writepages(
951         struct address_space    *mapping,
952         struct writeback_control *wbc)
953 {
954         xfs_iflags_clear(XFS_I(mapping->host), XFS_ITRUNCATED);
955         return dax_writeback_mapping_range(mapping,
956                         xfs_find_bdev_for_inode(mapping->host), wbc);
957 }
958 
959 STATIC int
960 xfs_vm_releasepage(
961         struct page             *page,
962         gfp_t                   gfp_mask)
963 {
964         trace_xfs_releasepage(page->mapping->host, page, 0, 0);
965         return iomap_releasepage(page, gfp_mask);
966 }
967 
968 STATIC sector_t
969 xfs_vm_bmap(
970         struct address_space    *mapping,
971         sector_t                block)
972 {
973         struct xfs_inode        *ip = XFS_I(mapping->host);
974 
975         trace_xfs_vm_bmap(ip);
976 
977         /*
978          * The swap code (ab-)uses ->bmap to get a block mapping and then
979          * bypasses the file system for actual I/O.  We really can't allow
980          * that on reflinks inodes, so we have to skip out here.  And yes,
981          * 0 is the magic code for a bmap error.
982          *
983          * Since we don't pass back blockdev info, we can't return bmap
984          * information for rt files either.
985          */
986         if (xfs_is_reflink_inode(ip) || XFS_IS_REALTIME_INODE(ip))
987                 return 0;
988         return iomap_bmap(mapping, block, &xfs_iomap_ops);
989 }
990 
991 STATIC int
992 xfs_vm_readpage(
993         struct file             *unused,
994         struct page             *page)
995 {
996         trace_xfs_vm_readpage(page->mapping->host, 1);
997         return iomap_readpage(page, &xfs_iomap_ops);
998 }
999 
1000 STATIC int
1001 xfs_vm_readpages(
1002         struct file             *unused,
1003         struct address_space    *mapping,
1004         struct list_head        *pages,
1005         unsigned                nr_pages)
1006 {
1007         trace_xfs_vm_readpages(mapping->host, nr_pages);
1008         return iomap_readpages(mapping, pages, nr_pages, &xfs_iomap_ops);
1009 }
1010 
1011 static int
1012 xfs_iomap_swapfile_activate(
1013         struct swap_info_struct         *sis,
1014         struct file                     *swap_file,
1015         sector_t                        *span)
1016 {
1017         sis->bdev = xfs_find_bdev_for_inode(file_inode(swap_file));
1018         return iomap_swapfile_activate(sis, swap_file, span, &xfs_iomap_ops);
1019 }
1020 
1021 const struct address_space_operations xfs_address_space_operations = {
1022         .readpage               = xfs_vm_readpage,
1023         .readpages              = xfs_vm_readpages,
1024         .writepage              = xfs_vm_writepage,
1025         .writepages             = xfs_vm_writepages,
1026         .set_page_dirty         = iomap_set_page_dirty,
1027         .releasepage            = xfs_vm_releasepage,
1028         .invalidatepage         = xfs_vm_invalidatepage,
1029         .bmap                   = xfs_vm_bmap,
1030         .direct_IO              = noop_direct_IO,
1031         .migratepage            = iomap_migrate_page,
1032         .is_partially_uptodate  = iomap_is_partially_uptodate,
1033         .error_remove_page      = generic_error_remove_page,
1034         .swap_activate          = xfs_iomap_swapfile_activate,
1035 };
1036 
1037 const struct address_space_operations xfs_dax_aops = {
1038         .writepages             = xfs_dax_writepages,
1039         .direct_IO              = noop_direct_IO,
1040         .set_page_dirty         = noop_set_page_dirty,
1041         .invalidatepage         = noop_invalidatepage,
1042         .swap_activate          = xfs_iomap_swapfile_activate,
1043 };
1044 

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