xfs: introduce a xfssyncd workqueue

All of the work xfssyncd does is background functionality. There is
no need for a thread per filesystem to do this work - it can al be
managed by a global workqueue now they manage concurrency
effectively.

Introduce a new gglobal xfssyncd workqueue, and convert the periodic
work to use this new functionality. To do this, use a delayed work
construct to schedule the next running of the periodic sync work
for the filesystem. When the sync work is complete, queue a new
delayed work for the next running of the sync work.

For laptop mode, we wait on completion for the sync works, so ensure
that the sync work queuing interface can flush and wait for work to
complete to enable the work queue infrastructure to replace the
current sequence number and wakeup that is used.

Because the sync work does non-trivial amounts of work, mark the
new work queue as CPU intensive.

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

1 files changed, 43 insertions, 45 deletions

diff --git a/fs/xfs/linux-2.6/xfs_sync.c b/fs/xfs/linux-2.6/xfs_sync.c
index 594cd822d84..4a582d8100e 100644
--- a/fs/xfs/linux-2.6/xfs_sync.c
+++ b/fs/xfs/linux-2.6/xfs_sync.c
@@ -39,6 +39,8 @@
 #include <linux/kthread.h>
 #include <linux/freezer.h>
 
+struct workqueue_struct	*xfs_syncd_wq;	/* sync workqueue */
+
 /*
  * The inode lookup is done in batches to keep the amount of lock traffic and
  * radix tree lookups to a minimum. The batch size is a trade off between
@@ -489,32 +491,6 @@ xfs_flush_inodes(
 	xfs_log_force(ip->i_mount, XFS_LOG_SYNC);
 }
 
-/*
- * Every sync period we need to unpin all items, reclaim inodes and sync
- * disk quotas.  We might need to cover the log to indicate that the
- * filesystem is idle and not frozen.
- */
-STATIC void
-xfs_sync_worker(
-	struct xfs_mount *mp,
-	void		*unused)
-{
-	int		error;
-
-	if (!(mp->m_flags & XFS_MOUNT_RDONLY)) {
-		/* dgc: errors ignored here */
-		if (mp->m_super->s_frozen == SB_UNFROZEN &&
-		    xfs_log_need_covered(mp))
-			error = xfs_fs_log_dummy(mp);
-		else
-			xfs_log_force(mp, 0);
-		xfs_reclaim_inodes(mp, 0);
-		error = xfs_qm_sync(mp, SYNC_TRYLOCK);
-	}
-	mp->m_sync_seq++;
-	wake_up(&mp->m_wait_single_sync_task);
-}
-
 STATIC int
 xfssyncd(
 	void			*arg)
@@ -528,34 +504,19 @@ xfssyncd(
 	timeleft = xfs_syncd_centisecs * msecs_to_jiffies(10);
 	for (;;) {
 		if (list_empty(&mp->m_sync_list))
-			timeleft = schedule_timeout_interruptible(timeleft);
+			schedule_timeout_interruptible(timeleft);
 		/* swsusp */
 		try_to_freeze();
 		if (kthread_should_stop() && list_empty(&mp->m_sync_list))
 			break;
 
 		spin_lock(&mp->m_sync_lock);
-		/*
-		 * We can get woken by laptop mode, to do a sync -
-		 * that's the (only!) case where the list would be
-		 * empty with time remaining.
-		 */
-		if (!timeleft || list_empty(&mp->m_sync_list)) {
-			if (!timeleft)
-				timeleft = xfs_syncd_centisecs *
-							msecs_to_jiffies(10);
-			INIT_LIST_HEAD(&mp->m_sync_work.w_list);
-			list_add_tail(&mp->m_sync_work.w_list,
-					&mp->m_sync_list);
-		}
 		list_splice_init(&mp->m_sync_list, &tmp);
 		spin_unlock(&mp->m_sync_lock);
 
 		list_for_each_entry_safe(work, n, &tmp, w_list) {
 			(*work->w_syncer)(mp, work->w_data);
 			list_del(&work->w_list);
-			if (work == &mp->m_sync_work)
-				continue;
 			if (work->w_completion)
 				complete(work->w_completion);
 			kmem_free(work);
@@ -565,13 +526,49 @@ xfssyncd(
 	return 0;
 }
 
+static void
+xfs_syncd_queue_sync(
+	struct xfs_mount        *mp)
+{
+	queue_delayed_work(xfs_syncd_wq, &mp->m_sync_work,
+				msecs_to_jiffies(xfs_syncd_centisecs * 10));
+}
+
+/*
+ * Every sync period we need to unpin all items, reclaim inodes and sync
+ * disk quotas.  We might need to cover the log to indicate that the
+ * filesystem is idle and not frozen.
+ */
+STATIC void
+xfs_sync_worker(
+	struct work_struct *work)
+{
+	struct xfs_mount *mp = container_of(to_delayed_work(work),
+					struct xfs_mount, m_sync_work);
+	int		error;
+
+	if (!(mp->m_flags & XFS_MOUNT_RDONLY)) {
+		/* dgc: errors ignored here */
+		if (mp->m_super->s_frozen == SB_UNFROZEN &&
+		    xfs_log_need_covered(mp))
+			error = xfs_fs_log_dummy(mp);
+		else
+			xfs_log_force(mp, 0);
+		xfs_reclaim_inodes(mp, 0);
+		error = xfs_qm_sync(mp, SYNC_TRYLOCK);
+	}
+
+	/* queue us up again */
+	xfs_syncd_queue_sync(mp);
+}
+
 int
 xfs_syncd_init(
 	struct xfs_mount	*mp)
 {
-	mp->m_sync_work.w_syncer = xfs_sync_worker;
-	mp->m_sync_work.w_mount = mp;
-	mp->m_sync_work.w_completion = NULL;
+	INIT_DELAYED_WORK(&mp->m_sync_work, xfs_sync_worker);
+	xfs_syncd_queue_sync(mp);
+
 	mp->m_sync_task = kthread_run(xfssyncd, mp, "xfssyncd/%s", mp->m_fsname);
 	if (IS_ERR(mp->m_sync_task))
 		return -PTR_ERR(mp->m_sync_task);
@@ -582,6 +579,7 @@ void
 xfs_syncd_stop(
 	struct xfs_mount	*mp)
 {
+	cancel_delayed_work_sync(&mp->m_sync_work);
 	kthread_stop(mp->m_sync_task);
 }