2 files changed, 33 insertions, 3 deletions

diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c
index 9c514483e599..6011ee661339 100644
--- a/fs/xfs/xfs_trans_ail.c
+++ b/fs/xfs/xfs_trans_ail.c
@@ -383,6 +383,12 @@ xfsaild_push(
         }
 
         spin_lock(&ailp->xa_lock);
+
+        /* barrier matches the xa_target update in xfs_ail_push() */
+        smp_rmb();
+        target = ailp->xa_target;
+        ailp->xa_target_prev = target;
+
         lip = xfs_trans_ail_cursor_first(ailp, &cur, ailp->xa_last_pushed_lsn);
         if (!lip) {
                 /*
@@ -397,7 +403,6 @@ xfsaild_push(
         XFS_STATS_INC(xs_push_ail);
 
         lsn = lip->li_lsn;
-        target = ailp->xa_target;
         while ((XFS_LSN_CMP(lip->li_lsn, target) <= 0)) {
                 int     lock_result;
 
@@ -527,8 +532,32 @@ xfsaild(
                         __set_current_state(TASK_KILLABLE);
                 else
                         __set_current_state(TASK_INTERRUPTIBLE);
-                schedule_timeout(tout ?
-                                 msecs_to_jiffies(tout) : MAX_SCHEDULE_TIMEOUT);
+
+                spin_lock(&ailp->xa_lock);
+
+                /*
+                 * Idle if the AIL is empty and we are not racing with a target
+                 * update. We check the AIL after we set the task to a sleep
+                 * state to guarantee that we either catch an xa_target update
+                 * or that a wake_up resets the state to TASK_RUNNING.
+                 * Otherwise, we run the risk of sleeping indefinitely.
+                 *
+                 * The barrier matches the xa_target update in xfs_ail_push().
+                 */
+                smp_rmb();
+                if (!xfs_ail_min(ailp) &&
+                    ailp->xa_target == ailp->xa_target_prev) {
+                        spin_unlock(&ailp->xa_lock);
+                        schedule();
+                        tout = 0;
+                        continue;
+                }
+                spin_unlock(&ailp->xa_lock);
+
+                if (tout)
+                        schedule_timeout(msecs_to_jiffies(tout));
+
+                __set_current_state(TASK_RUNNING);
 
                 try_to_freeze();
 
diff --git a/fs/xfs/xfs_trans_priv.h b/fs/xfs/xfs_trans_priv.h
index fb62377d1cbc..53b7c9b0f8f7 100644
--- a/fs/xfs/xfs_trans_priv.h
+++ b/fs/xfs/xfs_trans_priv.h
@@ -67,6 +67,7 @@ struct xfs_ail {
         struct task_struct      *xa_task;
         struct list_head        xa_ail;
         xfs_lsn_t               xa_target;
+        xfs_lsn_t               xa_target_prev;
         struct list_head        xa_cursors;
         spinlock_t              xa_lock;
         xfs_lsn_t               xa_last_pushed_lsn;