xfs: push the AIL from memory reclaim and periodic sync

When we are short on memory, we want to expedite the cleaning of
dirty objects.  Hence when we run short on memory, we need to kick
the AIL flushing into action to clean as many dirty objects as
quickly as possible.  To implement this, sample the lsn of the log
item at the head of the AIL and use that as the push target for the
AIL flush.

Further, we keep items in the AIL that are dirty that are not
tracked any other way, so we can get objects sitting in the AIL that
don't get written back until the AIL is pushed. Hence to get the
filesystem to the idle state, we might need to push the AIL to flush
out any remaining dirty objects sitting in the AIL. This requires
the same push mechanism as the reclaim push.

This patch also renames xfs_trans_ail_tail() to xfs_ail_min_lsn() to
match the new xfs_ail_max_lsn() function introduced in this patch.
Similarly for xfs_trans_ail_push -> xfs_ail_push.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Alex Elder <aelder@sgi.com>

1 files changed, 48 insertions, 2 deletions

diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c
index 8012bfb..acdb92f 100644
--- a/fs/xfs/xfs_trans_ail.c
+++ b/fs/xfs/xfs_trans_ail.c
@@ -90,6 +90,20 @@ xfs_ail_min(
 	return list_first_entry(&ailp->xa_ail, xfs_log_item_t, li_ail);
 }
 
+ /*
+ * Return a pointer to the last item in the AIL.  If the AIL is empty, then
+ * return NULL.
+ */
+static xfs_log_item_t *
+xfs_ail_max(
+	struct xfs_ail  *ailp)
+{
+	if (list_empty(&ailp->xa_ail))
+		return NULL;
+
+	return list_entry(ailp->xa_ail.prev, xfs_log_item_t, li_ail);
+}
+
 /*
  * Return a pointer to the item which follows the given item in the AIL.  If
  * the given item is the last item in the list, then return NULL.
@@ -114,7 +128,7 @@ xfs_ail_next(
  * item in the AIL.
  */
 xfs_lsn_t
-xfs_trans_ail_tail(
+xfs_ail_min_lsn(
 	struct xfs_ail	*ailp)
 {
 	xfs_lsn_t	lsn = 0;
@@ -130,6 +144,25 @@ xfs_trans_ail_tail(
 }
 
 /*
+ * Return the maximum lsn held in the AIL, or zero if the AIL is empty.
+ */
+static xfs_lsn_t
+xfs_ail_max_lsn(
+	struct xfs_ail  *ailp)
+{
+	xfs_lsn_t       lsn = 0;
+	xfs_log_item_t  *lip;
+
+	spin_lock(&ailp->xa_lock);
+	lip = xfs_ail_max(ailp);
+	if (lip)
+		lsn = lip->li_lsn;
+	spin_unlock(&ailp->xa_lock);
+
+	return lsn;
+}
+
+/*
  * AIL traversal cursor initialisation.
  *
  * The cursor keeps track of where our current traversal is up
@@ -504,7 +537,7 @@ xfs_ail_worker(
  * any of the objects, so the lock is not needed.
  */
 void
-xfs_trans_ail_push(
+xfs_ail_push(
 	struct xfs_ail	*ailp,
 	xfs_lsn_t	threshold_lsn)
 {
@@ -526,6 +559,19 @@ xfs_trans_ail_push(
 }
 
 /*
+ * Push out all items in the AIL immediately
+ */
+void
+xfs_ail_push_all(
+	struct xfs_ail  *ailp)
+{
+	xfs_lsn_t       threshold_lsn = xfs_ail_max_lsn(ailp);
+
+	if (threshold_lsn)
+		xfs_ail_push(ailp, threshold_lsn);
+}
+
+/*
  * This is to be called when an item is unlocked that may have
  * been in the AIL.  It will wake up the first member of the AIL
  * wait list if this item's unlocking might allow it to progress.