• Ryusuke Konishi's avatar
    nilfs2: fix timing issue between rmcp and chcp ioctls · fe0627e7
    Ryusuke Konishi authored
    The checkpoint deletion ioctl (rmcp ioctl) has potential for breaking
    snapshot because it is not fully exclusive with checkpoint mode change
    ioctl (chcp ioctl).
    The rmcp ioctl first tests if the specified checkpoint is a snapshot or
    not within nilfs_cpfile_delete_checkpoint function, and then calls
    nilfs_cpfile_delete_checkpoints function to actually invalidate the
    checkpoint only if it's not a snapshot.  However, the checkpoint can be
    changed into a snapshot by the chcp ioctl between these two operations.
    In that case, calling nilfs_cpfile_delete_checkpoints() wrongly
    invalidates the snapshot, which leads to snapshot list corruption and
    snapshot count mismatch.
    This fixes the issue by changing nilfs_cpfile_delete_checkpoints() so
    that it reconfirms the target checkpoints are snapshot or not.
    This second check is exclusive with the chcp operation since it is
    protected by an existing semaphore.
    Signed-off-by: default avatarRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
    Cc: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
cpfile.c 24.5 KB