From: Qu Wenruo wqu@suse.com
[ Upstream commit e3c62324e470c0a89df966603156b34fccd01708 ]
[BUG] When relocating partial preallocated data extents (part of the preallocated extent is written) for subpage, it can cause the following false alert and make the relocation to fail:
BTRFS info (device dm-3): balance: start -d BTRFS info (device dm-3): relocating block group 13631488 flags data BTRFS warning (device dm-3): csum failed root -9 ino 257 off 4096 csum 0x98757625 expected csum 0x00000000 mirror 1 BTRFS error (device dm-3): bdev /dev/mapper/arm_nvme-test errs: wr 0, rd 0, flush 0, corrupt 1, gen 0 BTRFS warning (device dm-3): csum failed root -9 ino 257 off 4096 csum 0x98757625 expected csum 0x00000000 mirror 1 BTRFS error (device dm-3): bdev /dev/mapper/arm_nvme-test errs: wr 0, rd 0, flush 0, corrupt 2, gen 0 BTRFS info (device dm-3): balance: ended with status: -5
The minimal script to reproduce looks like this:
mkfs.btrfs -f -s 4k $dev mount $dev -o nospace_cache $mnt xfs_io -f -c "falloc 0 8k" $mnt/file xfs_io -f -c "pwrite 0 4k" $mnt/file btrfs balance start -d $mnt
[CAUSE] Function btrfs_verify_data_csum() checks if the full range has EXTENT_NODATASUM bit for data reloc inode, if *all* bytes of the range have EXTENT_NODATASUM bit, then it skip the range.
This works pretty well for regular sectorsize, as in that case btrfs_verify_data_csum() is called for each sector, thus no problem at all.
But for subpage case, btrfs_verify_data_csum() is called on each bvec, which can contain several sectors, and since it checks *all* bytes for EXTENT_NODATASUM bit, if we have some range with csum, then we will continue checking all the sectors.
For the preallocated sectors, it doesn't have any csum, thus obviously the csum won't match and cause the false alert.
[FIX] Move the EXTENT_NODATASUM check into the main loop, so that we can check each sector for EXTENT_NODATASUM bit for subpage case.
Signed-off-by: Qu Wenruo wqu@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/btrfs/inode.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index f1fd88137003..1477cd4f3eac 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -3276,19 +3276,24 @@ int btrfs_verify_data_csum(struct btrfs_io_bio *io_bio, u32 bio_offset, if (!root->fs_info->csum_root) return 0;
- if (root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID && - test_range_bit(io_tree, start, end, EXTENT_NODATASUM, 1, NULL)) { - clear_extent_bits(io_tree, start, end, EXTENT_NODATASUM); - return 0; - } - ASSERT(page_offset(page) <= start && end <= page_offset(page) + PAGE_SIZE - 1); for (pg_off = offset_in_page(start); pg_off < offset_in_page(end); pg_off += sectorsize, bio_offset += sectorsize) { + u64 file_offset = pg_off + page_offset(page); int ret;
+ if (root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID && + test_range_bit(io_tree, file_offset, + file_offset + sectorsize - 1, + EXTENT_NODATASUM, 1, NULL)) { + /* Skip the range without csum for data reloc inode */ + clear_extent_bits(io_tree, file_offset, + file_offset + sectorsize - 1, + EXTENT_NODATASUM); + continue; + } ret = check_data_csum(inode, io_bio, bio_offset, page, pg_off, page_offset(page) + pg_off); if (ret < 0)