• Ian Kent's avatar
    autofs4: remove hashed check in validate_wait() · 463aea1a
    Ian Kent authored
    The recent ->lookup() deadlock correction required the directory inode
    mutex to be dropped while waiting for expire completion.  We were
    concerned about side effects from this change and one has been identified.
    I saw several error messages.
    They cause autofs to become quite confused and don't really point to the
    actual problem.
    Things like:
    handle_packet_missing_direct:1376: can't find map entry for (43,1827932)
    which is usually totally fatal (although in this case it wouldn't be
    except that I treat is as such because it normally is).
    do_mount_direct: direct trigger not valid or already mounted
    which is recoverable, however if this problem is at play it can cause
    autofs to become quite confused as to the dependencies in the mount tree
    because mount triggers end up mounted multiple times.  It's hard to
    accurately check for this over mounting case and automount shouldn't need
    to if the kernel module is doing its job.
    There was one other message, similar in consequence of this last one but I
    can't locate a log example just now.
    When checking if a mount has already completed prior to adding a new mount
    request to the wait queue we check if the dentry is hashed and, if so, if
    it is a mount point.  But, if a mount successfully completed while we
    slept on the wait queue mutex the dentry must exist for the mount to have
    completed so the test is not really needed.
    Mounts can also be done on top of a global root dentry, so for the above
    case, where a mount request completes and the wait queue entry has already
    been removed, the hashed test returning false can cause an incorrect
    callback to the daemon.  Also, d_mountpoint() is not sufficient to check
    if a mount has completed for the multi-mount case when we don't have a
    real mount at the base of the tree.
    Signed-off-by: default avatarIan Kent <raven@themaw.net>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
waitq.c 13.1 KB