dm cache background tracker: limit amount of background work that may…

… be issued at once On large systems the cache policy can be over enthusiastic and queue far too much dirty data to be written back. This consumes memory. Signed-off-by: Joe Thornber <[email protected]> Signed-off-by: Mike Snitzer <[email protected]>
ambv · Nov 10, 2017 · 64748b1 · 64748b1
1 parent deb7191
commit 64748b1
Showing 1 changed file with 12 additions and 6 deletions.
diff --git a/drivers/md/dm-cache-background-tracker.c b/drivers/md/dm-cache-background-tracker.c
@@ -161,8 +161,17 @@ EXPORT_SYMBOL_GPL(btracker_nr_demotions_queued);
 
 static bool max_work_reached(struct background_tracker *b)
 {
-	// FIXME: finish
-	return false;
+	return atomic_read(&b->pending_promotes) +
+		atomic_read(&b->pending_writebacks) +
+		atomic_read(&b->pending_demotes) >= b->max_work;
+}
+
+struct bt_work *alloc_work(struct background_tracker *b)
+{
+	if (max_work_reached(b))
+		return NULL;
+
+	return kmem_cache_alloc(b->work_cache, GFP_NOWAIT);
 }
 
 int btracker_queue(struct background_tracker *b,
@@ -174,10 +183,7 @@ int btracker_queue(struct background_tracker *b,
 	if (pwork)
 		*pwork = NULL;
 
-	if (max_work_reached(b))
-		return -ENOMEM;
-
-	w = kmem_cache_alloc(b->work_cache, GFP_NOWAIT);
+	w = alloc_work(b);
 	if (!w)
 		return -ENOMEM;