dm snapshot: optimize track_chunk

Mikulas Patocka · kergon · commit 9aa0c0e60ffc · 2012-12-21T20:23:33.000Z
track_chunk is always called with interrupts enabled. Consequently, we
do not need to save and restore interrupt state in "flags" variable.
This patch changes spin_lock_irqsave to spin_lock_irq and
spin_unlock_irqrestore to spin_unlock_irq.

Signed-off-by: Mikulas Patocka &lt;mpatocka@redhat.com&gt;
Signed-off-by: Alasdair G Kergon &lt;agk@redhat.com&gt;
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
@@ -198,14 +198,13 @@ static struct dm_snap_tracked_chunk *track_chunk(struct dm_snapshot *s,
 {
 	struct dm_snap_tracked_chunk *c = mempool_alloc(s->tracked_chunk_pool,
 							GFP_NOIO);
-	unsigned long flags;
 
 	c->chunk = chunk;
 
-	spin_lock_irqsave(&s->tracked_chunk_lock, flags);
+	spin_lock_irq(&s->tracked_chunk_lock);
 	hlist_add_head(&c->node,
 		       &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]);
-	spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
+	spin_unlock_irq(&s->tracked_chunk_lock);
 
 	return c;
 }

Original file line number	Diff line number	Diff line change
`@@ -198,14 +198,13 @@ static struct dm_snap_tracked_chunk track_chunk(struct dm_snapshot s,`
`198`	`198`	`{`
`199`	`199`	`struct dm_snap_tracked_chunk *c = mempool_alloc(s->tracked_chunk_pool,`
`200`	`200`	`GFP_NOIO);`
`201`		`- unsigned long flags;`
`202`	`201`
`203`	`202`	`c->chunk = chunk;`
`204`	`203`
`205`		`- spin_lock_irqsave(&s->tracked_chunk_lock, flags);`
	`204`	`+ spin_lock_irq(&s->tracked_chunk_lock);`
`206`	`205`	`hlist_add_head(&c->node,`
`207`	`206`	`&s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]);`
`208`		`- spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);`
	`207`	`+ spin_unlock_irq(&s->tracked_chunk_lock);`
`209`	`208`
`210`	`209`	`return c;`
`211`	`210`	`}`