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btrfs: fix double accounting of ordered extents during errors
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[BUG]
Btrfs will fail generic/750 randomly if its sector size is smaller than
page size.

One of the warning looks like this:

 ------------[ cut here ]------------
 WARNING: CPU: 1 PID: 90263 at fs/btrfs/ordered-data.c:360 can_finish_ordered_extent+0x33c/0x390 [btrfs]
 CPU: 1 UID: 0 PID: 90263 Comm: kworker/u18:1 Tainted: G           OE      6.12.0-rc3-custom+ torvalds#79
 Workqueue: events_unbound btrfs_async_reclaim_metadata_space [btrfs]
 pc : can_finish_ordered_extent+0x33c/0x390 [btrfs]
 lr : can_finish_ordered_extent+0xdc/0x390 [btrfs]
 Call trace:
  can_finish_ordered_extent+0x33c/0x390 [btrfs]
  btrfs_mark_ordered_io_finished+0x130/0x2b8 [btrfs]
  extent_writepage+0xfc/0x338 [btrfs]
  extent_write_cache_pages+0x1d4/0x4b8 [btrfs]
  btrfs_writepages+0x94/0x158 [btrfs]
  do_writepages+0x74/0x190
  filemap_fdatawrite_wbc+0x88/0xc8
  start_delalloc_inodes+0x180/0x3b0 [btrfs]
  btrfs_start_delalloc_roots+0x17c/0x288 [btrfs]
  shrink_delalloc+0x11c/0x280 [btrfs]
  flush_space+0x27c/0x310 [btrfs]
  btrfs_async_reclaim_metadata_space+0xcc/0x208 [btrfs]
  process_one_work+0x228/0x670
  worker_thread+0x1bc/0x360
  kthread+0x100/0x118
  ret_from_fork+0x10/0x20
 irq event stamp: 9784200
 hardirqs last  enabled at (9784199): [<ffffd21ec54dc01c>] _raw_spin_unlock_irqrestore+0x74/0x80
 hardirqs last disabled at (9784200): [<ffffd21ec54db374>] _raw_spin_lock_irqsave+0x8c/0xa0
 softirqs last  enabled at (9784148): [<ffffd21ec472ff44>] handle_softirqs+0x45c/0x4b0
 softirqs last disabled at (9784141): [<ffffd21ec46d01e4>] __do_softirq+0x1c/0x28
 ---[ end trace 0000000000000000 ]---
 BTRFS critical (device dm-2): bad ordered extent accounting, root=5 ino=1492 OE offset=1654784 OE len=57344 to_dec=49152 left=0

[CAUSE]
There are several error paths not properly handling during folio
writeback:

1) Partially submitted folio
   During extent_writepage_io() if some error happened (the only
   possible case is submit_one_sector() failed to grab an extent map),
   then we can have partially submitted folio.

   Since extent_writepage_io() failed, we need to call
   btrfs_mark_ordered_io_finished() to cleanup the submitted range.

   But we will call btrfs_mark_ordered_io_finished() for submitted range
   too, causing double accounting.

2) Partially created ordered extents
   We cal also fail at writepage_delalloc(), which will stop creating
   new ordered extents if it hit any error from
   btrfs_run_delalloc_range().

   In that case, we will call btrfs_mark_ordered_io_finished() for
   ranges where there is no ordered extent at all.

Both bugs are only affecting sector size < page size cases.

[FIX]
- Introduce a new member btrfs_bio_ctrl::last_submitted
  This will trace the last sector submitted through
  extent_writepage_io().

  So for the above extent_writepage() case, we will know exactly which
  sectors are submitted and should not do the ordered extent accounting.

- Clear the submit_bitmap for ranges where no ordered extent is created
  So if btrfs_run_delalloc_range() failed for a range, it will be not
  cleaned up.

- Introduce a helper cleanup_ordered_extents()
  This will do a sector-by-sector cleanup with
  btrfs_bio_ctrl::last_submitted and btrfs_bio_ctrl::submit_bitmap into
  consideartion.

  Using @last_submitted is to avoid double accounting on the submitted
  ranges.
  Meanwhile using @submit_bitmap is to avoid touching ranges going
  through compression.

cc: stable@vger.kernel.org # 5.15+
Signed-off-by: Qu Wenruo <wqu@suse.com>
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@adam900710 @intel-lab-lkp
adam900710 authored and intel-lab-lkp committed Nov 25, 2024
1 parent 5f1be03 commit e2d58e4
Showing 1 changed file with 47 additions and 7 deletions.
54 changes: 47 additions & 7 deletions fs/btrfs/extent_io.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -108,6 +108,14 @@ struct btrfs_bio_ctrl {
* This is to avoid touching ranges covered by compression/inline.
*/
unsigned long submit_bitmap;

/*
* The end (exclusive) of the last submitted range in the folio.
*
* This is for sector size < page size case where we may hit error
* half way.
*/
u64 last_submitted;
};

static void submit_one_bio(struct btrfs_bio_ctrl *bio_ctrl)
Expand Down Expand Up @@ -1254,11 +1262,18 @@ static noinline_for_stack int writepage_delalloc(struct btrfs_inode *inode,

/*
* We have some ranges that's going to be submitted asynchronously
* (compression or inline). These range have their own control
* (compression or inline, ret > 0). These range have their own control
* on when to unlock the pages. We should not touch them
* anymore, so clear the range from the submission bitmap.
* anymore.
*
* We can also have some ranges where we didn't even call
* btrfs_run_delalloc_range() (as previous run failed, ret < 0).
* These error ranges should not be submitted nor cleaned up as
* there is no ordered extent allocated for them.
*
* For either cases, we should clear the submit_bitmap.
*/
if (ret > 0) {
if (ret) {
unsigned int start_bit = (found_start - page_start) >>
fs_info->sectorsize_bits;
unsigned int end_bit = (min(page_end + 1, found_start + found_len) -
Expand Down Expand Up @@ -1435,6 +1450,7 @@ static noinline_for_stack int extent_writepage_io(struct btrfs_inode *inode,
ret = submit_one_sector(inode, folio, cur, bio_ctrl, i_size);
if (ret < 0)
goto out;
bio_ctrl->last_submitted = cur + fs_info->sectorsize;
submitted_io = true;
}
out:
Expand All @@ -1453,6 +1469,24 @@ static noinline_for_stack int extent_writepage_io(struct btrfs_inode *inode,
return ret;
}

static void cleanup_ordered_extents(struct btrfs_inode *inode,
struct folio *folio, u64 file_pos,
u64 num_bytes, unsigned long *bitmap)
{
struct btrfs_fs_info *fs_info = inode->root->fs_info;
unsigned int cur_bit = (file_pos - folio_pos(folio)) >> fs_info->sectorsize_bits;

for_each_set_bit_from(cur_bit, bitmap, fs_info->sectors_per_page) {
u64 cur_pos = folio_pos(folio) + (cur_bit << fs_info->sectorsize_bits);

if (cur_pos >= file_pos + num_bytes)
break;

btrfs_mark_ordered_io_finished(inode, folio, cur_pos,
fs_info->sectorsize, false);
}
}

/*
* the writepage semantics are similar to regular writepage. extent
* records are inserted to lock ranges in the tree, and as dirty areas
Expand Down Expand Up @@ -1492,6 +1526,7 @@ static int extent_writepage(struct folio *folio, struct btrfs_bio_ctrl *bio_ctrl
* The proper bitmap can only be initialized until writepage_delalloc().
*/
bio_ctrl->submit_bitmap = (unsigned long)-1;
bio_ctrl->last_submitted = page_start;
ret = set_folio_extent_mapped(folio);
if (ret < 0)
goto done;
Expand All @@ -1511,8 +1546,10 @@ static int extent_writepage(struct folio *folio, struct btrfs_bio_ctrl *bio_ctrl

done:
if (ret) {
btrfs_mark_ordered_io_finished(BTRFS_I(inode), folio,
page_start, PAGE_SIZE, !ret);
cleanup_ordered_extents(BTRFS_I(inode), folio,
bio_ctrl->last_submitted,
page_start + PAGE_SIZE - bio_ctrl->last_submitted,
&bio_ctrl->submit_bitmap);
mapping_set_error(folio->mapping, ret);
}

Expand Down Expand Up @@ -2288,14 +2325,17 @@ void extent_write_locked_range(struct inode *inode, const struct folio *locked_f
* extent_writepage_io() will do the truncation correctly.
*/
bio_ctrl.submit_bitmap = (unsigned long)-1;
bio_ctrl.last_submitted = cur;
ret = extent_writepage_io(BTRFS_I(inode), folio, cur, cur_len,
&bio_ctrl, i_size);
if (ret == 1)
goto next_page;

if (ret) {
btrfs_mark_ordered_io_finished(BTRFS_I(inode), folio,
cur, cur_len, !ret);
cleanup_ordered_extents(BTRFS_I(inode), folio,
bio_ctrl.last_submitted,
cur_end + 1 - bio_ctrl.last_submitted,
&bio_ctrl.submit_bitmap);
mapping_set_error(mapping, ret);
}
btrfs_folio_end_lock(fs_info, folio, cur, cur_len);
Expand Down

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