• David Sterba's avatar
    btrfs: Check read-only status of roots during send · 2c686537
    David Sterba authored
    All the subvolues that are involved in send must be read-only during the
    whole operation. The ioctl SUBVOL_SETFLAGS could be used to change the
    status to read-write and the result of send stream is undefined if the
    data change unexpectedly.
    
    Fix that by adding a refcount for all involved roots and verify that
    there's no send in progress during SUBVOL_SETFLAGS ioctl call that does
    read-only -> read-write transition.
    
    We need refcounts because there are no restrictions on number of send
    parallel operations currently run on a single subvolume, be it source,
    parent or one of the multiple clone sources.
    
    Kernel is silent when the RO checks fail and returns EPERM. The same set
    of checks is done already in userspace before send starts.
    Signed-off-by: default avatarDavid Sterba <dsterba@suse.cz>
    Signed-off-by: default avatarJosef Bacik <jbacik@fb.com>
    Signed-off-by: default avatarChris Mason <clm@fb.com>
    2c686537
ctree.h 130 KB