• Qu Wenruo's avatar
    btrfs: qgroup: Fix qgroup corruption caused by inode_cache mount option · 82bafb38
    Qu Wenruo authored
    [BUG]
    The easist way to reproduce the bug is:
    ------
     # mkfs.btrfs -f $dev -n 16K
     # mount $dev $mnt -o inode_cache
     # btrfs quota enable $mnt
     # btrfs quota rescan -w $mnt
     # btrfs qgroup show $mnt
    qgroupid         rfer         excl
    --------         ----         ----
    0/5          32.00KiB     32.00KiB
                 ^^ Twice the correct value
    ------
    
    And fstests/btrfs qgroup test group can easily detect them with
    inode_cache mount option.
    Although some of them are false alerts since old test cases are using
    fixed golden output.
    While new test cases will use "btrfs check" to detect qgroup mismatch.
    
    [CAUSE]
    Inode_cache mount option will make commit_fs_roots() to call
    btrfs_save_ino_cache() to update fs/subvol trees, and generate new
    delayed refs.
    
    However we call btrfs_qgroup_prepare_account_extents() too early, before
    commit_fs_roots().
    This makes the "old_roots" for newly generated extents are always NULL.
    For freeing extent case, this makes both new_roots and old_roots to be
    empty, while correct old_roots should not be empty.
    This causing qgroup numbers not decreased correctly.
    
    [FIX]
    Modify the timing of calling btrfs_qgroup_prepare_account_extents() to
    just before btrfs_qgroup_account_extents(), and add needed delayed_refs
    handler.
    So qgroup can handle inode_map mount options correctly.
    Signed-off-by: default avatarQu Wenruo <quwenruo@cn.fujitsu.com>
    Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
    Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
    82bafb38
transaction.c 66 KB