3 files changed, 151 insertions, 16 deletions

diff --git a/fs/xfs/xfs_inode_item.c b/fs/xfs/xfs_inode_item.c
index 7c8d30c..fd4f398 100644
--- a/fs/xfs/xfs_inode_item.c
+++ b/fs/xfs/xfs_inode_item.c
@@ -842,15 +842,64 @@ xfs_inode_item_destroy(
  * flushed to disk.  It is responsible for removing the inode item
  * from the AIL if it has not been re-logged, and unlocking the inode's
  * flush lock.
+ *
+ * To reduce AIL lock traffic as much as possible, we scan the buffer log item
+ * list for other inodes that will run this function. We remove them from the
+ * buffer list so we can process all the inode IO completions in one AIL lock
+ * traversal.
  */
 void
 xfs_iflush_done(
 	struct xfs_buf		*bp,
 	struct xfs_log_item	*lip)
 {
-	struct xfs_inode_log_item *iip = INODE_ITEM(lip);
-	xfs_inode_t		*ip = iip->ili_inode;
+	struct xfs_inode_log_item *iip;
+	struct xfs_log_item	*blip;
+	struct xfs_log_item	*next;
+	struct xfs_log_item	*prev;
 	struct xfs_ail		*ailp = lip->li_ailp;
+	int			need_ail = 0;
+
+	/*
+	 * Scan the buffer IO completions for other inodes being completed and
+	 * attach them to the current inode log item.
+	 */
+	blip = XFS_BUF_FSPRIVATE(bp, xfs_log_item_t *);
+	prev = NULL;
+	while (blip != NULL) {
+		if (lip->li_cb != xfs_iflush_done) {
+			prev = blip;
+			blip = blip->li_bio_list;
+			continue;
+		}
+
+		/* remove from list */
+		next = blip->li_bio_list;
+		if (!prev) {
+			XFS_BUF_SET_FSPRIVATE(bp, next);
+		} else {
+			prev->li_bio_list = next;
+		}
+
+		/* add to current list */
+		blip->li_bio_list = lip->li_bio_list;
+		lip->li_bio_list = blip;
+
+		/*
+		 * while we have the item, do the unlocked check for needing
+		 * the AIL lock.
+		 */
+		iip = INODE_ITEM(blip);
+		if (iip->ili_logged && blip->li_lsn == iip->ili_flush_lsn)
+			need_ail++;
+
+		blip = next;
+	}
+
+	/* make sure we capture the state of the initial inode. */
+	iip = INODE_ITEM(lip);
+	if (iip->ili_logged && lip->li_lsn == iip->ili_flush_lsn)
+		need_ail++;
 
 	/*
 	 * We only want to pull the item from the AIL if it is
@@ -861,28 +910,37 @@ xfs_iflush_done(
 	 * the lock since it's cheaper, and then we recheck while
 	 * holding the lock before removing the inode from the AIL.
 	 */
-	if (iip->ili_logged && lip->li_lsn == iip->ili_flush_lsn) {
+	if (need_ail) {
+		struct xfs_log_item *log_items[need_ail];
+		int i = 0;
 		spin_lock(&ailp->xa_lock);
-		if (lip->li_lsn == iip->ili_flush_lsn) {
-			/* xfs_trans_ail_delete() drops the AIL lock. */
-			xfs_trans_ail_delete(ailp, lip);
-		} else {
-			spin_unlock(&ailp->xa_lock);
+		for (blip = lip; blip; blip = blip->li_bio_list) {
+			iip = INODE_ITEM(blip);
+			if (iip->ili_logged &&
+			    blip->li_lsn == iip->ili_flush_lsn) {
+				log_items[i++] = blip;
+			}
+			ASSERT(i <= need_ail);
 		}
+		/* xfs_trans_ail_delete_bulk() drops the AIL lock. */
+		xfs_trans_ail_delete_bulk(ailp, log_items, i);
 	}
 
-	iip->ili_logged = 0;
 
 	/*
-	 * Clear the ili_last_fields bits now that we know that the
-	 * data corresponding to them is safely on disk.
+	 * clean up and unlock the flush lock now we are done. We can clear the
+	 * ili_last_fields bits now that we know that the data corresponding to
+	 * them is safely on disk.
 	 */
-	iip->ili_last_fields = 0;
+	for (blip = lip; blip; blip = next) {
+		next = blip->li_bio_list;
+		blip->li_bio_list = NULL;
 
-	/*
-	 * Release the inode's flush lock since we're done with it.
-	 */
-	xfs_ifunlock(ip);
+		iip = INODE_ITEM(blip);
+		iip->ili_logged = 0;
+		iip->ili_last_fields = 0;
+		xfs_ifunlock(iip->ili_inode);
+	}
 }
 
 /*
diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c
index fe991a7..218f968 100644
--- a/fs/xfs/xfs_trans_ail.c
+++ b/fs/xfs/xfs_trans_ail.c
@@ -639,6 +639,79 @@ xfs_trans_ail_delete(
 	}
 }
 
+/*
+ * xfs_trans_ail_delete_bulk - remove multiple log items from the AIL
+ *
+ * @xfs_trans_ail_delete_bulk takes an array of log items that all need to
+ * removed from the AIL. The caller is already holding the AIL lock, and done
+ * all the checks necessary to ensure the items passed in via @log_items are
+ * ready for deletion. This includes checking that the items are in the AIL.
+ *
+ * For each log item to be removed, unlink it  from the AIL, clear the IN_AIL
+ * flag from the item and reset the item's lsn to 0. If we remove the first
+ * item in the AIL, update the log tail to match the new minimum LSN in the
+ * AIL.
+ *
+ * This function will not drop the AIL lock until all items are removed from
+ * the AIL to minimise the amount of lock traffic on the AIL. This does not
+ * greatly increase the AIL hold time, but does significantly reduce the amount
+ * of traffic on the lock, especially during IO completion.
+ *
+ * This function must be called with the AIL lock held.  The lock is dropped
+ * before returning.
+ */
+void
+xfs_trans_ail_delete_bulk(
+	struct xfs_ail		*ailp,
+	struct xfs_log_item	**log_items,
+	int			nr_items) __releases(ailp->xa_lock)
+{
+	xfs_log_item_t		*mlip;
+	xfs_lsn_t		tail_lsn;
+	int			mlip_changed = 0;
+	int			i;
+
+	mlip = xfs_ail_min(ailp);
+
+	for (i = 0; i < nr_items; i++) {
+		struct xfs_log_item *lip = log_items[i];
+		if (!(lip->li_flags & XFS_LI_IN_AIL)) {
+			struct xfs_mount	*mp = ailp->xa_mount;
+
+			spin_unlock(&ailp->xa_lock);
+			if (!XFS_FORCED_SHUTDOWN(mp)) {
+				xfs_cmn_err(XFS_PTAG_AILDELETE, CE_ALERT, mp,
+		"%s: attempting to delete a log item that is not in the AIL",
+						__func__);
+				xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
+			}
+			return;
+		}
+
+		xfs_ail_delete(ailp, lip);
+		lip->li_flags &= ~XFS_LI_IN_AIL;
+		lip->li_lsn = 0;
+		if (mlip == lip)
+			mlip_changed = 1;
+	}
+
+	if (!mlip_changed) {
+		spin_unlock(&ailp->xa_lock);
+		return;
+	}
+
+	/*
+	 * It is not safe to access mlip after the AIL lock is dropped, so we
+	 * must get a copy of li_lsn before we do so.  This is especially
+	 * important on 32-bit platforms where accessing and updating 64-bit
+	 * values like li_lsn is not atomic. It is possible we've emptied the
+	 * AIL here, so if that is the case, pass an LSN of 0 to the tail move.
+	 */
+	mlip = xfs_ail_min(ailp);
+	tail_lsn = mlip ? mlip->li_lsn : 0;
+	spin_unlock(&ailp->xa_lock);
+	xfs_log_move_tail(ailp->xa_mount, tail_lsn);
+}
 
 
 /*
diff --git a/fs/xfs/xfs_trans_priv.h b/fs/xfs/xfs_trans_priv.h
index e039729..246ca4d 100644
--- a/fs/xfs/xfs_trans_priv.h
+++ b/fs/xfs/xfs_trans_priv.h
@@ -85,6 +85,10 @@ void			 xfs_trans_ail_update_bulk(struct xfs_ail *ailp,
 void			xfs_trans_ail_delete(struct xfs_ail *ailp,
 					struct xfs_log_item *lip)
 					__releases(ailp->xa_lock);
+void			xfs_trans_ail_delete_bulk(struct xfs_ail *ailp,
+					struct xfs_log_item **log_items,
+					int nr_items)
+					__releases(ailp->xa_lock);
 void			xfs_trans_ail_push(struct xfs_ail *, xfs_lsn_t);
 void			xfs_trans_unlocked_item(struct xfs_ail *,
 					xfs_log_item_t *);