3 files changed, 151 insertions, 16 deletions

diff --git a/fs/xfs/xfs_inode_item.c b/fs/xfs/xfs_inode_item.c
index 7c8d30c453c3..fd4f398bd6f1 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 fe991a76bf14..218f96861c80 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 e039729186e9..246ca4dcb5c4 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 *);