xfs: exit AIL push work correctly when AIL is empty

The recent conversion of the xfsaild functionality to a work queue
introduced a hard-to-hit log space grant hang. The main cause is a
regression where a work exit path fails to clear the PUSHING state
and recheck the target correctly.

Make both exit paths do the same PUSHING bit clearing and target
checking when the "no more work to be done" condition is hit.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>
(cherry picked from commit ea35a20021f8497390d05b93271b4d675516c654)

diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c
index acdb92f..226c58b 100644 (file)
--- a/fs/xfs/xfs_trans_ail.c
+++ b/fs/xfs/xfs_trans_ail.c
@@ -346,18 +346,20 @@ xfs_ail_delete(
  */
 STATIC void
 xfs_ail_worker(
-       struct work_struct *work)
+       struct work_struct      *work)
 {
-       struct xfs_ail  *ailp = container_of(to_delayed_work(work),
+       struct xfs_ail          *ailp = container_of(to_delayed_work(work),
                                        struct xfs_ail, xa_work);
-       long            tout;
-       xfs_lsn_t       target =  ailp->xa_target;
-       xfs_lsn_t       lsn;
-       xfs_log_item_t  *lip;
-       int             flush_log, count, stuck;
-       xfs_mount_t     *mp = ailp->xa_mount;
+       xfs_mount_t             *mp = ailp->xa_mount;
        struct xfs_ail_cursor   *cur = &ailp->xa_cursors;
-       int             push_xfsbufd = 0;
+       xfs_log_item_t          *lip;
+       xfs_lsn_t               lsn;
+       xfs_lsn_t               target = ailp->xa_target;
+       long                    tout = 10;
+       int                     flush_log = 0;
+       int                     stuck = 0;
+       int                     count = 0;
+       int                     push_xfsbufd = 0;
 
        spin_lock(&ailp->xa_lock);
        xfs_trans_ail_cursor_init(ailp, cur);
@@ -368,8 +370,7 @@ xfs_ail_worker(
                 */
                xfs_trans_ail_cursor_done(ailp, cur);
                spin_unlock(&ailp->xa_lock);
-               ailp->xa_last_pushed_lsn = 0;
-               return;
+               goto out_done;
        }
 
        XFS_STATS_INC(xs_push_ail);
@@ -386,7 +387,6 @@ xfs_ail_worker(
         * lots of contention on the AIL lists.
         */
        lsn = lip->li_lsn;
-       flush_log = stuck = count = 0;
        while ((XFS_LSN_CMP(lip->li_lsn, target) < 0)) {
                int     lock_result;
                /*
@@ -480,7 +480,7 @@ xfs_ail_worker(
        }
 
        /* assume we have more work to do in a short while */
-       tout = 10;
+out_done:
        if (!count) {
                /* We're past our target or empty, so idle */
                ailp->xa_last_pushed_lsn = 0;