• NeilBrown's avatar
    lockd: send correct lock when granting a delayed lock. · 2ec197db
    NeilBrown authored
    
    
    If an NFS client attempts to get a lock (using NLM) and the lock is
    not available, the server will remember the request and when the lock
    becomes available it will send a GRANT request to the client to
    provide the lock.
    
    If the client already held an adjacent lock, the GRANT callback will
    report the union of the existing and new locks, which can confuse the
    client.
    
    This happens because __posix_lock_file (called by vfs_lock_file)
    updates the passed-in file_lock structure when adjacent or
    over-lapping locks are found.
    
    To avoid this problem we take a copy of the two fields that can
    be changed (fl_start and fl_end) before the call and restore them
    afterwards.
    An alternate would be to allocate a 'struct file_lock', initialise it,
    use locks_copy_lock() to take a copy, then locks_release_private()
    after the vfs_lock_file() call.  But that is a lot more work.
    Reported-by: default avatarOlaf Kirch <okir@suse.com>
    Signed-off-by: default avatarNeilBrown <neilb@suse.de>
    Cc: stable@vger.kernel.org
    Signed-off-by: default avatarJ. Bruce Fields <bfields@redhat.com>
    
    --
    v1 had a couple of issues (large on-stack struct and didn't really work properly).
    This version is much better tested.
    Signed-off-by: default avatarJ. Bruce Fields <bfields@redhat.com>
    2ec197db
svclock.c 26.2 KB