• David Chinner's avatar
    [XFS] Use a cursor for AIL traversal. · 27d8d5fe
    David Chinner authored
    To replace the current generation number ensuring sanity of the AIL
    traversal, replace it with an external cursor that is linked to the AIL.
    
    Basically, we store the next item in the cursor whenever we want to drop
    the AIL lock to do something to the current item. When we regain the lock.
    the current item may already be free, so we can't reference it, but the
    next item in the traversal is already held in the cursor.
    
    When we move or delete an object, we search all the active cursors and if
    there is an item match we clear the cursor(s) that point to the object.
    This forces the traversal to restart transparently.
    
    We don't invalidate the cursor on insert because the cursor still points
    to a valid item. If the intem is inserted between the current item and the
    cursor it does not matter; the traversal is considered to be past the
    insertion point so it will be picked up in the next traversal.
    
    Hence traversal restarts pretty much disappear altogether with this method
    of traversal, which should substantially reduce the overhead of pushing on
    a busy AIL.
    
    Version 2 o add restart logic o comment cursor interface o minor cleanups
    
    SGI-PV: 988143
    
    SGI-Modid: xfs-linux-melb:xfs-kern:32347a
    Signed-off-by: default avatarDavid Chinner <david@fromorbit.com>
    Signed-off-by: default avatarLachlan McIlroy <lachlan@sgi.com>
    Signed-off-by: default avatarChristoph Hellwig <hch@infradead.org>
    27d8d5fe
xfs_log_recover.c 110 KB