xfs: convert the xfsaild threads to a workqueue

Similar to the xfssyncd, the per-filesystem xfsaild threads can be
converted to a global workqueue and run periodically by delayed
works. This makes sense for the AIL pushing because it uses
variable timeouts depending on the work that needs to be done.

By removing the xfsaild, we simplify the AIL pushing code and
remove the need to spread the code to implement the threading
and pushing across multiple files.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>

fs/xfs/linux-2.6/xfs_super.c

@@ -816,75 +816,6 @@ xfs_setup_devices(
 	return 0;
 }
 
-/*
- * XFS AIL push thread support
- */
-void
-xfsaild_wakeup(
-	struct xfs_ail		*ailp,
-	xfs_lsn_t		threshold_lsn)
-{
-	/* only ever move the target forwards */
-	if (XFS_LSN_CMP(threshold_lsn, ailp->xa_target) > 0) {
-		ailp->xa_target = threshold_lsn;
-		wake_up_process(ailp->xa_task);
-	}
-}
-
-STATIC int
-xfsaild(
-	void	*data)
-{
-	struct xfs_ail	*ailp = data;
-	xfs_lsn_t	last_pushed_lsn = 0;
-	long		tout = 0; /* milliseconds */
-
-	while (!kthread_should_stop()) {
-		/*
-		 * for short sleeps indicating congestion, don't allow us to
-		 * get woken early. Otherwise all we do is bang on the AIL lock
-		 * without making progress.
-		 */
-		if (tout && tout <= 20)
-			__set_current_state(TASK_KILLABLE);
-		else
-			__set_current_state(TASK_INTERRUPTIBLE);
-		schedule_timeout(tout ?
-				 msecs_to_jiffies(tout) : MAX_SCHEDULE_TIMEOUT);
-
-		/* swsusp */
-		try_to_freeze();
-
-		ASSERT(ailp->xa_mount->m_log);
-		if (XFS_FORCED_SHUTDOWN(ailp->xa_mount))
-			continue;
-
-		tout = xfsaild_push(ailp, &last_pushed_lsn);
-	}
-
-	return 0;
-}	/* xfsaild */
-
-int
-xfsaild_start(
-	struct xfs_ail	*ailp)
-{
-	ailp->xa_target = 0;
-	ailp->xa_task = kthread_run(xfsaild, ailp, "xfsaild/%s",
-				    ailp->xa_mount->m_fsname);
-	if (IS_ERR(ailp->xa_task))
-		return -PTR_ERR(ailp->xa_task);
-	return 0;
-}
-
-void
-xfsaild_stop(
-	struct xfs_ail	*ailp)
-{
-	kthread_stop(ailp->xa_task);
-}
-
-
 /* Catch misguided souls that try to use this interface on XFS */
 STATIC struct inode *
 xfs_fs_alloc_inode(
@@ -1785,6 +1716,38 @@ xfs_destroy_zones(void)
 
 }
 
+STATIC int __init
+xfs_init_workqueues(void)
+{
+	/*
+	 * max_active is set to 8 to give enough concurency to allow
+	 * multiple work operations on each CPU to run. This allows multiple
+	 * filesystems to be running sync work concurrently, and scales with
+	 * the number of CPUs in the system.
+	 */
+	xfs_syncd_wq = alloc_workqueue("xfssyncd", WQ_CPU_INTENSIVE, 8);
+	if (!xfs_syncd_wq)
+		goto out;
+
+	xfs_ail_wq = alloc_workqueue("xfsail", WQ_CPU_INTENSIVE, 8);
+	if (!xfs_ail_wq)
+		goto out_destroy_syncd;
+
+	return 0;
+
+out_destroy_syncd:
+	destroy_workqueue(xfs_syncd_wq);
+out:
+	return -ENOMEM;
+}
+
+STATIC void __exit
+xfs_destroy_workqueues(void)
+{
+	destroy_workqueue(xfs_ail_wq);
+	destroy_workqueue(xfs_syncd_wq);
+}
+
 STATIC int __init
 init_xfs_fs(void)
 {
@@ -1800,10 +1763,14 @@ init_xfs_fs(void)
 	if (error)
 		goto out;
 
-	error = xfs_mru_cache_init();
+	error = xfs_init_workqueues();
 	if (error)
 		goto out_destroy_zones;
 
+	error = xfs_mru_cache_init();
+	if (error)
+		goto out_destroy_wq;
+
 	error = xfs_filestream_init();
 	if (error)
 		goto out_mru_cache_uninit;
@@ -1820,27 +1787,17 @@ init_xfs_fs(void)
 	if (error)
 		goto out_cleanup_procfs;
 
-	/*
-	 * max_active is set to 8 to give enough concurency to allow
-	 * multiple work operations on each CPU to run. This allows multiple
-	 * filesystems to be running sync work concurrently, and scales with
-	 * the number of CPUs in the system.
-	 */
-	xfs_syncd_wq = alloc_workqueue("xfssyncd", WQ_CPU_INTENSIVE, 8);
-	if (!xfs_syncd_wq) {
-		error = -ENOMEM;
+	error = xfs_init_workqueues();
+	if (error)
 		goto out_sysctl_unregister;
-	}
 
 	vfs_initquota();
 
 	error = register_filesystem(&xfs_fs_type);
 	if (error)
-		goto out_destroy_xfs_syncd;
+		goto out_sysctl_unregister;
 	return 0;
 
- out_destroy_xfs_syncd:
-	destroy_workqueue(xfs_syncd_wq);
  out_sysctl_unregister:
 	xfs_sysctl_unregister();
  out_cleanup_procfs:
@@ -1851,6 +1808,8 @@ init_xfs_fs(void)
 	xfs_filestream_uninit();
  out_mru_cache_uninit:
 	xfs_mru_cache_uninit();
+ out_destroy_wq:
+	xfs_destroy_workqueues();
  out_destroy_zones:
 	xfs_destroy_zones();
  out:
@@ -1862,12 +1821,12 @@ exit_xfs_fs(void)
 {
 	vfs_exitquota();
 	unregister_filesystem(&xfs_fs_type);
-	destroy_workqueue(xfs_syncd_wq);
 	xfs_sysctl_unregister();
 	xfs_cleanup_procfs();
 	xfs_buf_terminate();
 	xfs_filestream_uninit();
 	xfs_mru_cache_uninit();
+	xfs_destroy_workqueues();
 	xfs_destroy_zones();
 }