Merge branch 'for-linus' of git://oss.sgi.com/xfs/xfs

* 'for-linus' of git://oss.sgi.com/xfs/xfs:
  xfs: use proper interfaces for on-stack plugging
  xfs: fix xfs_debug warnings
  xfs: fix variable set but not used warnings
  xfs: convert log tail checking to a warning
  xfs: catch bad block numbers freeing extents.
  xfs: push the AIL from memory reclaim and periodic sync
  xfs: clean up code layout in xfs_trans_ail.c
  xfs: convert the xfsaild threads to a workqueue
  xfs: introduce background inode reclaim work
  xfs: convert ENOSPC inode flushing to use new syncd workqueue
  xfs: introduce a xfssyncd workqueue
  xfs: fix extent format buffer allocation size
  xfs: fix unreferenced var error in xfs_buf.c

Also, applied patch from Tony Luck that fixes ia64:
  xfs_destroy_workqueues() should not be tagged with__exit
in the branch before merging.

6 files changed, 194 insertions, 240 deletions

diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c
index 5ea4020..9ef9ed2 100644
--- a/fs/xfs/linux-2.6/xfs_buf.c
+++ b/fs/xfs/linux-2.6/xfs_buf.c
@@ -293,7 +293,6 @@ xfs_buf_allocate_memory(
 	size_t			nbytes, offset;
 	gfp_t			gfp_mask = xb_to_gfp(flags);
 	unsigned short		page_count, i;
-	pgoff_t			first;
 	xfs_off_t		end;
 	int			error;
 
@@ -333,7 +332,6 @@ use_alloc_page:
 		return error;
 
 	offset = bp->b_offset;
-	first = bp->b_file_offset >> PAGE_SHIFT;
 	bp->b_flags |= _XBF_PAGES;
 
 	for (i = 0; i < bp->b_page_count; i++) {
@@ -657,8 +655,6 @@ xfs_buf_readahead(
 	xfs_off_t		ioff,
 	size_t			isize)
 {
-	struct backing_dev_info *bdi;
-
 	if (bdi_read_congested(target->bt_bdi))
 		return;
 
@@ -919,8 +915,6 @@ xfs_buf_lock(
 
 	if (atomic_read(&bp->b_pin_count) && (bp->b_flags & XBF_STALE))
 		xfs_log_force(bp->b_target->bt_mount, 0);
-	if (atomic_read(&bp->b_io_remaining))
-		blk_flush_plug(current);
 	down(&bp->b_sema);
 	XB_SET_OWNER(bp);
 
@@ -1309,8 +1303,6 @@ xfs_buf_iowait(
 {
 	trace_xfs_buf_iowait(bp, _RET_IP_);
 
-	if (atomic_read(&bp->b_io_remaining))
-		blk_flush_plug(current);
 	wait_for_completion(&bp->b_iowait);
 
 	trace_xfs_buf_iowait_done(bp, _RET_IP_);
@@ -1747,8 +1739,8 @@ xfsbufd(
 	do {
 		long	age = xfs_buf_age_centisecs * msecs_to_jiffies(10);
 		long	tout = xfs_buf_timer_centisecs * msecs_to_jiffies(10);
-		int	count = 0;
 		struct list_head tmp;
+		struct blk_plug plug;
 
 		if (unlikely(freezing(current))) {
 			set_bit(XBT_FORCE_SLEEP, &target->bt_flags);
@@ -1764,16 +1756,15 @@ xfsbufd(
 
 		xfs_buf_delwri_split(target, &tmp, age);
 		list_sort(NULL, &tmp, xfs_buf_cmp);
+
+		blk_start_plug(&plug);
 		while (!list_empty(&tmp)) {
 			struct xfs_buf *bp;
 			bp = list_first_entry(&tmp, struct xfs_buf, b_list);
 			list_del_init(&bp->b_list);
 			xfs_bdstrat_cb(bp);
-			count++;
 		}
-		if (count)
-			blk_flush_plug(current);
-
+		blk_finish_plug(&plug);
 	} while (!kthread_should_stop());
 
 	return 0;
@@ -1793,6 +1784,7 @@ xfs_flush_buftarg(
 	int		pincount = 0;
 	LIST_HEAD(tmp_list);
 	LIST_HEAD(wait_list);
+	struct blk_plug plug;
 
 	xfs_buf_runall_queues(xfsconvertd_workqueue);
 	xfs_buf_runall_queues(xfsdatad_workqueue);
@@ -1807,6 +1799,8 @@ xfs_flush_buftarg(
 	 * we do that after issuing all the IO.
 	 */
 	list_sort(NULL, &tmp_list, xfs_buf_cmp);
+
+	blk_start_plug(&plug);
 	while (!list_empty(&tmp_list)) {
 		bp = list_first_entry(&tmp_list, struct xfs_buf, b_list);
 		ASSERT(target == bp->b_target);
@@ -1817,10 +1811,10 @@ xfs_flush_buftarg(
 		}
 		xfs_bdstrat_cb(bp);
 	}
+	blk_finish_plug(&plug);
 
 	if (wait) {
-		/* Expedite and wait for IO to complete. */
-		blk_flush_plug(current);
+		/* Wait for IO to complete. */
 		while (!list_empty(&wait_list)) {
 			bp = list_first_entry(&wait_list, struct xfs_buf, b_list);
 
diff --git a/fs/xfs/linux-2.6/xfs_message.c b/fs/xfs/linux-2.6/xfs_message.c
index 508e06f..3ca7956 100644
--- a/fs/xfs/linux-2.6/xfs_message.c
+++ b/fs/xfs/linux-2.6/xfs_message.c
@@ -28,53 +28,47 @@
 /*
  * XFS logging functions
  */
-static int
+static void
 __xfs_printk(
 	const char		*level,
 	const struct xfs_mount	*mp,
 	struct va_format	*vaf)
 {
 	if (mp && mp->m_fsname)
-		return printk("%sXFS (%s): %pV\n", level, mp->m_fsname, vaf);
-	return printk("%sXFS: %pV\n", level, vaf);
+		printk("%sXFS (%s): %pV\n", level, mp->m_fsname, vaf);
+	printk("%sXFS: %pV\n", level, vaf);
 }
 
-int xfs_printk(
+void xfs_printk(
 	const char		*level,
 	const struct xfs_mount	*mp,
 	const char		*fmt, ...)
 {
 	struct va_format	vaf;
 	va_list			args;
-	int			 r;
 
 	va_start(args, fmt);
 
 	vaf.fmt = fmt;
 	vaf.va = &args;
 
-	r = __xfs_printk(level, mp, &vaf);
+	__xfs_printk(level, mp, &vaf);
 	va_end(args);
-
-	return r;
 }
 
 #define define_xfs_printk_level(func, kern_level)		\
-int func(const struct xfs_mount *mp, const char *fmt, ...)	\
+void func(const struct xfs_mount *mp, const char *fmt, ...)	\
 {								\
 	struct va_format	vaf;				\
 	va_list			args;				\
-	int			r;				\
 								\
 	va_start(args, fmt);					\
 								\
 	vaf.fmt = fmt;						\
 	vaf.va = &args;						\
 								\
-	r = __xfs_printk(kern_level, mp, &vaf);			\
+	__xfs_printk(kern_level, mp, &vaf);			\
 	va_end(args);						\
-								\
-	return r;						\
 }								\
 
 define_xfs_printk_level(xfs_emerg, KERN_EMERG);
@@ -88,7 +82,7 @@ define_xfs_printk_level(xfs_info, KERN_INFO);
 define_xfs_printk_level(xfs_debug, KERN_DEBUG);
 #endif
 
-int
+void
 xfs_alert_tag(
 	const struct xfs_mount	*mp,
 	int			panic_tag,
@@ -97,7 +91,6 @@ xfs_alert_tag(
 	struct va_format	vaf;
 	va_list			args;
 	int			do_panic = 0;
-	int			r;
 
 	if (xfs_panic_mask && (xfs_panic_mask & panic_tag)) {
 		xfs_printk(KERN_ALERT, mp,
@@ -110,12 +103,10 @@ xfs_alert_tag(
 	vaf.fmt = fmt;
 	vaf.va = &args;
 
-	r = __xfs_printk(KERN_ALERT, mp, &vaf);
+	__xfs_printk(KERN_ALERT, mp, &vaf);
 	va_end(args);
 
 	BUG_ON(do_panic);
-
-	return r;
 }
 
 void
diff --git a/fs/xfs/linux-2.6/xfs_message.h b/fs/xfs/linux-2.6/xfs_message.h
index e77ffa1..f1b3fc1 100644
--- a/fs/xfs/linux-2.6/xfs_message.h
+++ b/fs/xfs/linux-2.6/xfs_message.h
@@ -3,32 +3,34 @@
 
 struct xfs_mount;
 
-extern int xfs_printk(const char *level, const struct xfs_mount *mp,
+extern void xfs_printk(const char *level, const struct xfs_mount *mp,
                       const char *fmt, ...)
         __attribute__ ((format (printf, 3, 4)));
-extern int xfs_emerg(const struct xfs_mount *mp, const char *fmt, ...)
+extern void xfs_emerg(const struct xfs_mount *mp, const char *fmt, ...)
         __attribute__ ((format (printf, 2, 3)));
-extern int xfs_alert(const struct xfs_mount *mp, const char *fmt, ...)
+extern void xfs_alert(const struct xfs_mount *mp, const char *fmt, ...)
         __attribute__ ((format (printf, 2, 3)));
-extern int xfs_alert_tag(const struct xfs_mount *mp, int tag,
+extern void xfs_alert_tag(const struct xfs_mount *mp, int tag,
 			 const char *fmt, ...)
         __attribute__ ((format (printf, 3, 4)));
-extern int xfs_crit(const struct xfs_mount *mp, const char *fmt, ...)
+extern void xfs_crit(const struct xfs_mount *mp, const char *fmt, ...)
         __attribute__ ((format (printf, 2, 3)));
-extern int xfs_err(const struct xfs_mount *mp, const char *fmt, ...)
+extern void xfs_err(const struct xfs_mount *mp, const char *fmt, ...)
         __attribute__ ((format (printf, 2, 3)));
-extern int xfs_warn(const struct xfs_mount *mp, const char *fmt, ...)
+extern void xfs_warn(const struct xfs_mount *mp, const char *fmt, ...)
         __attribute__ ((format (printf, 2, 3)));
-extern int xfs_notice(const struct xfs_mount *mp, const char *fmt, ...)
+extern void xfs_notice(const struct xfs_mount *mp, const char *fmt, ...)
         __attribute__ ((format (printf, 2, 3)));
-extern int xfs_info(const struct xfs_mount *mp, const char *fmt, ...)
+extern void xfs_info(const struct xfs_mount *mp, const char *fmt, ...)
         __attribute__ ((format (printf, 2, 3)));
 
 #ifdef DEBUG
-extern int xfs_debug(const struct xfs_mount *mp, const char *fmt, ...)
+extern void xfs_debug(const struct xfs_mount *mp, const char *fmt, ...)
         __attribute__ ((format (printf, 2, 3)));
 #else
-#define xfs_debug(mp, fmt, ...)	(0)
+static inline void xfs_debug(const struct xfs_mount *mp, const char *fmt, ...)
+{
+}
 #endif
 
 extern void assfail(char *expr, char *f, int l);
diff --git a/fs/xfs/linux-2.6/xfs_super.c b/fs/xfs/linux-2.6/xfs_super.c
index 1ba5c45..b38e58d 100644
--- a/fs/xfs/linux-2.6/xfs_super.c
+++ b/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(
@@ -1191,22 +1122,12 @@ xfs_fs_sync_fs(
 		return -error;
 
 	if (laptop_mode) {
-		int	prev_sync_seq = mp->m_sync_seq;
-
 		/*
 		 * The disk must be active because we're syncing.
 		 * We schedule xfssyncd now (now that the disk is
 		 * active) instead of later (when it might not be).
 		 */
-		wake_up_process(mp->m_sync_task);
-		/*
-		 * We have to wait for the sync iteration to complete.
-		 * If we don't, the disk activity caused by the sync
-		 * will come after the sync is completed, and that
-		 * triggers another sync from laptop mode.
-		 */
-		wait_event(mp->m_wait_single_sync_task,
-				mp->m_sync_seq != prev_sync_seq);
+		flush_delayed_work_sync(&mp->m_sync_work);
 	}
 
 	return 0;
@@ -1490,9 +1411,6 @@ xfs_fs_fill_super(
 	spin_lock_init(&mp->m_sb_lock);
 	mutex_init(&mp->m_growlock);
 	atomic_set(&mp->m_active_trans, 0);
-	INIT_LIST_HEAD(&mp->m_sync_list);
-	spin_lock_init(&mp->m_sync_lock);
-	init_waitqueue_head(&mp->m_wait_single_sync_task);
 
 	mp->m_super = sb;
 	sb->s_fs_info = mp;
@@ -1799,6 +1717,38 @@ 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
+xfs_destroy_workqueues(void)
+{
+	destroy_workqueue(xfs_ail_wq);
+	destroy_workqueue(xfs_syncd_wq);
+}
+
+STATIC int __init
 init_xfs_fs(void)
 {
 	int			error;
@@ -1813,10 +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;
@@ -1833,6 +1787,10 @@ init_xfs_fs(void)
 	if (error)
 		goto out_cleanup_procfs;
 
+	error = xfs_init_workqueues();
+	if (error)
+		goto out_sysctl_unregister;
+
 	vfs_initquota();
 
 	error = register_filesystem(&xfs_fs_type);
@@ -1850,6 +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:
@@ -1866,6 +1826,7 @@ exit_xfs_fs(void)
 	xfs_buf_terminate();
 	xfs_filestream_uninit();
 	xfs_mru_cache_uninit();
+	xfs_destroy_workqueues();
 	xfs_destroy_zones();
 }
 
diff --git a/fs/xfs/linux-2.6/xfs_sync.c b/fs/xfs/linux-2.6/xfs_sync.c
index 9cf35a6..e4f9c1b 100644
--- a/fs/xfs/linux-2.6/xfs_sync.c
+++ b/fs/xfs/linux-2.6/xfs_sync.c
@@ -22,6 +22,7 @@
 #include "xfs_log.h"
 #include "xfs_inum.h"
 #include "xfs_trans.h"
+#include "xfs_trans_priv.h"
 #include "xfs_sb.h"
 #include "xfs_ag.h"
 #include "xfs_mount.h"
@@ -39,6 +40,8 @@
 #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
@@ -431,62 +434,12 @@ xfs_quiesce_attr(
 	xfs_unmountfs_writesb(mp);
 }
 
-/*
- * Enqueue a work item to be picked up by the vfs xfssyncd thread.
- * Doing this has two advantages:
- * - It saves on stack space, which is tight in certain situations
- * - It can be used (with care) as a mechanism to avoid deadlocks.
- * Flushing while allocating in a full filesystem requires both.
- */
-STATIC void
-xfs_syncd_queue_work(
-	struct xfs_mount *mp,
-	void		*data,
-	void		(*syncer)(struct xfs_mount *, void *),
-	struct completion *completion)
-{
-	struct xfs_sync_work *work;
-
-	work = kmem_alloc(sizeof(struct xfs_sync_work), KM_SLEEP);
-	INIT_LIST_HEAD(&work->w_list);
-	work->w_syncer = syncer;
-	work->w_data = data;
-	work->w_mount = mp;
-	work->w_completion = completion;
-	spin_lock(&mp->m_sync_lock);
-	list_add_tail(&work->w_list, &mp->m_sync_list);
-	spin_unlock(&mp->m_sync_lock);
-	wake_up_process(mp->m_sync_task);
-}
-
-/*
- * Flush delayed allocate data, attempting to free up reserved space
- * from existing allocations.  At this point a new allocation attempt
- * has failed with ENOSPC and we are in the process of scratching our
- * heads, looking about for more room...
- */
-STATIC void
-xfs_flush_inodes_work(
-	struct xfs_mount *mp,
-	void		*arg)
-{
-	struct inode	*inode = arg;
-	xfs_sync_data(mp, SYNC_TRYLOCK);
-	xfs_sync_data(mp, SYNC_TRYLOCK | SYNC_WAIT);
-	iput(inode);
-}
-
-void
-xfs_flush_inodes(
-	xfs_inode_t	*ip)
+static void
+xfs_syncd_queue_sync(
+	struct xfs_mount        *mp)
 {
-	struct inode	*inode = VFS_I(ip);
-	DECLARE_COMPLETION_ONSTACK(completion);
-
-	igrab(inode);
-	xfs_syncd_queue_work(ip->i_mount, inode, xfs_flush_inodes_work, &completion);
-	wait_for_completion(&completion);
-	xfs_log_force(ip->i_mount, XFS_LOG_SYNC);
+	queue_delayed_work(xfs_syncd_wq, &mp->m_sync_work,
+				msecs_to_jiffies(xfs_syncd_centisecs * 10));
 }
 
 /*
@@ -496,9 +449,10 @@ xfs_flush_inodes(
  */
 STATIC void
 xfs_sync_worker(
-	struct xfs_mount *mp,
-	void		*unused)
+	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)) {
@@ -508,73 +462,106 @@ xfs_sync_worker(
 			error = xfs_fs_log_dummy(mp);
 		else
 			xfs_log_force(mp, 0);
-		xfs_reclaim_inodes(mp, 0);
 		error = xfs_qm_sync(mp, SYNC_TRYLOCK);
+
+		/* start pushing all the metadata that is currently dirty */
+		xfs_ail_push_all(mp->m_ail);
 	}
-	mp->m_sync_seq++;
-	wake_up(&mp->m_wait_single_sync_task);
+
+	/* queue us up again */
+	xfs_syncd_queue_sync(mp);
 }
 
-STATIC int
-xfssyncd(
-	void			*arg)
+/*
+ * Queue a new inode reclaim pass if there are reclaimable inodes and there
+ * isn't a reclaim pass already in progress. By default it runs every 5s based
+ * on the xfs syncd work default of 30s. Perhaps this should have it's own
+ * tunable, but that can be done if this method proves to be ineffective or too
+ * aggressive.
+ */
+static void
+xfs_syncd_queue_reclaim(
+	struct xfs_mount        *mp)
 {
-	struct xfs_mount	*mp = arg;
-	long			timeleft;
-	xfs_sync_work_t		*work, *n;
-	LIST_HEAD		(tmp);
-
-	set_freezable();
-	timeleft = xfs_syncd_centisecs * msecs_to_jiffies(10);
-	for (;;) {
-		if (list_empty(&mp->m_sync_list))
-			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);
+	/*
+	 * We can have inodes enter reclaim after we've shut down the syncd
+	 * workqueue during unmount, so don't allow reclaim work to be queued
+	 * during unmount.
+	 */
+	if (!(mp->m_super->s_flags & MS_ACTIVE))
+		return;
 
-		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);
-		}
+	rcu_read_lock();
+	if (radix_tree_tagged(&mp->m_perag_tree, XFS_ICI_RECLAIM_TAG)) {
+		queue_delayed_work(xfs_syncd_wq, &mp->m_reclaim_work,
+			msecs_to_jiffies(xfs_syncd_centisecs / 6 * 10));
 	}
+	rcu_read_unlock();
+}
 
-	return 0;
+/*
+ * This is a fast pass over the inode cache to try to get reclaim moving on as
+ * many inodes as possible in a short period of time. It kicks itself every few
+ * seconds, as well as being kicked by the inode cache shrinker when memory
+ * goes low. It scans as quickly as possible avoiding locked inodes or those
+ * already being flushed, and once done schedules a future pass.
+ */
+STATIC void
+xfs_reclaim_worker(
+	struct work_struct *work)
+{
+	struct xfs_mount *mp = container_of(to_delayed_work(work),
+					struct xfs_mount, m_reclaim_work);
+
+	xfs_reclaim_inodes(mp, SYNC_TRYLOCK);
+	xfs_syncd_queue_reclaim(mp);
+}
+
+/*
+ * Flush delayed allocate data, attempting to free up reserved space
+ * from existing allocations.  At this point a new allocation attempt
+ * has failed with ENOSPC and we are in the process of scratching our
+ * heads, looking about for more room.
+ *
+ * Queue a new data flush if there isn't one already in progress and
+ * wait for completion of the flush. This means that we only ever have one
+ * inode flush in progress no matter how many ENOSPC events are occurring and
+ * so will prevent the system from bogging down due to every concurrent
+ * ENOSPC event scanning all the active inodes in the system for writeback.
+ */
+void
+xfs_flush_inodes(
+	struct xfs_inode	*ip)
+{
+	struct xfs_mount	*mp = ip->i_mount;
+
+	queue_work(xfs_syncd_wq, &mp->m_flush_work);
+	flush_work_sync(&mp->m_flush_work);
+}
+
+STATIC void
+xfs_flush_worker(
+	struct work_struct *work)
+{
+	struct xfs_mount *mp = container_of(work,
+					struct xfs_mount, m_flush_work);
+
+	xfs_sync_data(mp, SYNC_TRYLOCK);
+	xfs_sync_data(mp, SYNC_TRYLOCK | SYNC_WAIT);
 }
 
 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;
-	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);
+	INIT_WORK(&mp->m_flush_work, xfs_flush_worker);
+	INIT_DELAYED_WORK(&mp->m_sync_work, xfs_sync_worker);
+	INIT_DELAYED_WORK(&mp->m_reclaim_work, xfs_reclaim_worker);
+
+	xfs_syncd_queue_sync(mp);
+	xfs_syncd_queue_reclaim(mp);
+
 	return 0;
 }
 
@@ -582,7 +569,9 @@ void
 xfs_syncd_stop(
 	struct xfs_mount	*mp)
 {
-	kthread_stop(mp->m_sync_task);
+	cancel_delayed_work_sync(&mp->m_sync_work);
+	cancel_delayed_work_sync(&mp->m_reclaim_work);
+	cancel_work_sync(&mp->m_flush_work);
 }
 
 void
@@ -601,6 +590,10 @@ __xfs_inode_set_reclaim_tag(
 				XFS_INO_TO_AGNO(ip->i_mount, ip->i_ino),
 				XFS_ICI_RECLAIM_TAG);
 		spin_unlock(&ip->i_mount->m_perag_lock);
+
+		/* schedule periodic background inode reclaim */
+		xfs_syncd_queue_reclaim(ip->i_mount);
+
 		trace_xfs_perag_set_reclaim(ip->i_mount, pag->pag_agno,
 							-1, _RET_IP_);
 	}
@@ -1017,7 +1010,13 @@ xfs_reclaim_inodes(
 }
 
 /*
- * Shrinker infrastructure.
+ * Inode cache shrinker.
+ *
+ * When called we make sure that there is a background (fast) inode reclaim in
+ * progress, while we will throttle the speed of reclaim via doiing synchronous
+ * reclaim of inodes. That means if we come across dirty inodes, we wait for
+ * them to be cleaned, which we hope will not be very long due to the
+ * background walker having already kicked the IO off on those dirty inodes.
  */
 static int
 xfs_reclaim_inode_shrink(
@@ -1032,10 +1031,15 @@ xfs_reclaim_inode_shrink(
 
 	mp = container_of(shrink, struct xfs_mount, m_inode_shrink);
 	if (nr_to_scan) {
+		/* kick background reclaimer and push the AIL */
+		xfs_syncd_queue_reclaim(mp);
+		xfs_ail_push_all(mp->m_ail);
+
 		if (!(gfp_mask & __GFP_FS))
 			return -1;
 
-		xfs_reclaim_inodes_ag(mp, SYNC_TRYLOCK, &nr_to_scan);
+		xfs_reclaim_inodes_ag(mp, SYNC_TRYLOCK | SYNC_WAIT,
+					&nr_to_scan);
 		/* terminate if we don't exhaust the scan */
 		if (nr_to_scan > 0)
 			return -1;
diff --git a/fs/xfs/linux-2.6/xfs_sync.h b/fs/xfs/linux-2.6/xfs_sync.h
index 32ba662..e3a6ad2 100644
--- a/fs/xfs/linux-2.6/xfs_sync.h
+++ b/fs/xfs/linux-2.6/xfs_sync.h
@@ -32,6 +32,8 @@ typedef struct xfs_sync_work {
 #define SYNC_WAIT		0x0001	/* wait for i/o to complete */
 #define SYNC_TRYLOCK		0x0002  /* only try to lock inodes */
 
+extern struct workqueue_struct	*xfs_syncd_wq;	/* sync workqueue */
+
 int xfs_syncd_init(struct xfs_mount *mp);
 void xfs_syncd_stop(struct xfs_mount *mp);