• Anand Jain's avatar
    btrfs: send: remove WARN_ON for readonly mount · fbd54297
    Anand Jain authored
    We log warning if root::orphan_cleanup_state is not set to
    ORPHAN_CLEANUP_DONE in btrfs_ioctl_send(). However if the filesystem is
    mounted as readonly we skip the orphan item cleanup during the lookup
    and root::orphan_cleanup_state remains at the init state 0 instead of
    ORPHAN_CLEANUP_DONE (2). So during send in btrfs_ioctl_send() we hit the
    warning as below.
      WARN_ON(send_root->orphan_cleanup_state != ORPHAN_CLEANUP_DONE);
    WARNING: CPU: 0 PID: 2616 at /Volumes/ws/btrfs-devel/fs/btrfs/send.c:7090 btrfs_ioctl_send+0xb2f/0x18c0 [btrfs]
    RIP: 0010:btrfs_ioctl_send+0xb2f/0x18c0 [btrfs]
    Call Trace:
    _btrfs_ioctl_send+0x7b/0x110 [btrfs]
    btrfs_ioctl+0x150a/0x2b00 [btrfs]
    ? __fget+0xac/0xe0
      mkfs.btrfs -fq /dev/sdb
      mount /dev/sdb /btrfs
      btrfs subvolume create /btrfs/sv1
      btrfs subvolume snapshot -r /btrfs/sv1 /btrfs/ss1
      umount /btrfs
      mount -o ro /dev/sdb /btrfs
      btrfs send /btrfs/ss1 -f /tmp/f
    The warning exists because having orphan inodes could confuse send and
    cause it to fail or produce incorrect streams.  The two cases that would
    cause such send failures, which are already fixed are:
    1) Inodes that were unlinked - these are orphanized and remain with a
       link count of 0. These caused send operations to fail because it
       expected to always find at least one path for an inode. However this
       is no longer a problem since send is now able to deal with such
       inodes since commit 46b2f459 ("Btrfs: fix send failure when root
       has deleted files still open") and treats them as having been
       completely removed (the state after an orphan cleanup is performed).
    2) Inodes that were in the process of being truncated. These resulted in
       send not knowing about the truncation and potentially issue write
       operations full of zeroes for the range from the new file size to the
       old file size. This is no longer a problem because we no longer
       create orphan items for truncation since commit f7e9e8fc
       stop creating orphan items for truncate").
    As such before these commits, the WARN_ON here provided a clue in case
    something went wrong. Instead of being a warning against the
    root::orphan_cleanup_state value, it could have been more accurate by
    checking if there were actually any orphan items, and then issue a
    warning only if any exists, but that would be more expensive to check.
    Since orphanized inodes no longer cause problems for send, just remove
    the warning.
    Reported-by: default avatarChristoph Anton Mitterer <calestyo@scientia.net>
    Link: https://lore.kernel.org/linux-btrfs/21cb5e8d059f6e1496a903fa7bfc0a297e2f5370.camel@scientia.net/
    CC: stable@vger.kernel.org # 4.19+
    Suggested-by: default avatarFilipe Manana <fdmanana@suse.com>
    Reviewed-by: default avatarFilipe Manana <fdmanana@suse.com>
    Signed-off-by: default avatarAnand Jain <anand.jain@oracle.com>
    Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>