[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+ #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 --- fs/btrfs/extent_io.c | 54 ++++++++++++++++++++++++++++++++++++++------ 1 file changed, 47 insertions(+), 7 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index e629d2ee152a..1c2246d36672 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -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) @@ -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) - @@ -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: @@ -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 @@ -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; @@ -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); }

@@ -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);