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Btrfs-progs: add fsck test for filesystem with shared prealloc extents 

Verify that a filesystem check operation (fsck) does not report the
following scenario as an error:

An extent is shared between two inodes, as a result of clone/reflink
operation, and for one of the inodes, lets call it inode A, the extent is
referenced through a file extent item as a prealloc extent, while for the
other inode, call it inode B, the extent is referenced through a regular
file extent item, that is, it was written to. The goal of this test is to
make sure a filesystem check operation will not report "odd csum items"
errors for the prealloc extent at inode A, because this scenario is valid
since the extent was written through inode B and therefore it is expected
to have checksum items in the filesystem's checksum btree for that shared
extent.

Such scenario can be created with the following steps for example:

 mkfs.btrfs -f /dev/sdb
 mount /dev/sdb /mnt

 touch /mnt/foo
 xfs_io -c "falloc 0 256K" /mnt/foo
 sync

 xfs_io -c "pwrite -S 0xab 0 256K" /mnt/foo
 touch /mnt/bar
 xfs_io -c "reflink /mnt/foo 0 0 256K" /mnt/bar
 xfs_io -c "fsync" /mnt/bar

 <power fail>
 mount /dev/sdb /mnt
 umount /mnt

This scenario is fixed by the following patch for the filesystem checker:

 "Btrfs-progs: check, fix false error reports for shared prealloc extents"

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Filipe Manana 2018-03-14 20:11:18 +00:00 committed by David Sterba
parent 457a288cb5
commit 7a8d5d5014
2 changed files with 42 additions and 0 deletions
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tests/fsck-tests/030-reflinked-prealloc-extents/reflinked-prealloc-extents.img.xz Normal file
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tests/fsck-tests/030-reflinked-prealloc-extents/test.sh Executable file
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#!/bin/bash
#
# Verify that a filesystem check operation (fsck) does not report the following
# scenario as an error:
#
# An extent is shared between two inodes, as a result of clone/reflink operation,
# and for one of the inodes, lets call it inode A, the extent is referenced
# through a file extent item as a prealloc extent, while for the other inode,
# call it inode B, the extent is referenced through a regular file extent item,
# that is, it was written to. The goal of this test is to make sure a filesystem
# check operation will not report "odd csum items" errors for the prealloc
# extent at inode A, because this scenario is valid since the extent was written
# through inode B and therefore it is expected to have checksum items in the
# filesystem's checksum btree for that shared extent.
#
# Such scenario can be created with the following steps for example:
#
# mkfs.btrfs -f /dev/sdb
# mount /dev/sdb /mnt
#
# touch /mnt/foo
# xfs_io -c "falloc 0 256K" /mnt/foo
# sync
#
# xfs_io -c "pwrite -S 0xab 0 256K" /mnt/foo
# touch /mnt/bar
# xfs_io -c "reflink /mnt/foo 0 0 256K" /mnt/bar
# xfs_io -c "fsync" /mnt/bar
#
# <power fail>
# mount /dev/sdb /mnt
# umount /mnt
source "$TEST_TOP/common"
check_prereq btrfs
check_image() {
run_check "$TOP/btrfs" check "$1"
}
check_all_images