commit 238f8363b6661fd9dd9aae854917ab9c661f3652
author Joe Thornber <ejt@redhat.com> Wed Oct 30 17:29:30 2013 +0000
committer Mike Snitzer <snitzer@redhat.com> Sat Nov 09 18:19:59 2013 -0500
tree c1ea27daf3c5b2b0ff37f2ee2037bd74458f1d23
parent 66cb1910df17b38334153462ec8166e48058035f

dm cache: improve efficiency of quiescing flag management

Make the quiescing flag an atomic_t and stop protecting it with a spin
lock.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-cache-target.c

diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index 25d3253..50afdf7 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -149,6 +149,7 @@
 	atomic_t nr_migrations;
 
 	wait_queue_head_t quiescing_wait;
+	atomic_t quiescing;
 	atomic_t quiescing_ack;
 
 	/*
@@ -189,7 +190,6 @@
 
 	bool need_tick_bio:1;
 	bool sized:1;
-	bool quiescing:1;
 	bool commit_requested:1;
 	bool loaded_mappings:1;
 	bool loaded_discards:1;
@@ -1353,14 +1353,7 @@
  *--------------------------------------------------------------*/
 static bool is_quiescing(struct cache *cache)
 {
-	int r;
-	unsigned long flags;
-
-	spin_lock_irqsave(&cache->lock, flags);
-	r = cache->quiescing;
-	spin_unlock_irqrestore(&cache->lock, flags);
-
-	return r;
+	return atomic_read(&cache->quiescing);
 }
 
 static void ack_quiescing(struct cache *cache)
@@ -1378,23 +1371,13 @@
 
 static void start_quiescing(struct cache *cache)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&cache->lock, flags);
-	cache->quiescing = true;
-	spin_unlock_irqrestore(&cache->lock, flags);
-
+	atomic_inc(&cache->quiescing);
 	wait_for_quiescing_ack(cache);
 }
 
 static void stop_quiescing(struct cache *cache)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&cache->lock, flags);
-	cache->quiescing = false;
-	spin_unlock_irqrestore(&cache->lock, flags);
-
+	atomic_set(&cache->quiescing, 0);
 	atomic_set(&cache->quiescing_ack, 0);
 }
 
@@ -2030,6 +2013,7 @@
 	init_waitqueue_head(&cache->migration_wait);
 
 	init_waitqueue_head(&cache->quiescing_wait);
+	atomic_set(&cache->quiescing, 0);
 	atomic_set(&cache->quiescing_ack, 0);
 
 	r = -ENOMEM;
@@ -2091,7 +2075,6 @@
 
 	cache->need_tick_bio = true;
 	cache->sized = false;
-	cache->quiescing = false;
 	cache->commit_requested = false;
 	cache->loaded_mappings = false;
 	cache->loaded_discards = false;