From 7ae801cc6ae603bfd84be2a49d7d2286c3204887 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@woody.osdl.org>
Date: Fri, 22 Dec 2006 14:14:17 -0800
Subject: [PATCH] --- yaml --- r: 44930 b: refs/heads/master c:
 f2a67a576959025549a3b6a884bdd21f4dc107da h: refs/heads/master v: v3

---
 [refs]                    |  2 +-
 trunk/block/cfq-iosched.c | 21 ++++++++-------------
 2 files changed, 9 insertions(+), 14 deletions(-)

diff --git a/[refs] b/[refs]
index fd831ada6a88..feb5fd5cb331 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 5c668704b7fa5a4ebf21a490ddfbd6dc2e01fc97
+refs/heads/master: f2a67a576959025549a3b6a884bdd21f4dc107da
diff --git a/trunk/block/cfq-iosched.c b/trunk/block/cfq-iosched.c
index 9fc5eafa6c0e..4b4217d9be78 100644
--- a/trunk/block/cfq-iosched.c
+++ b/trunk/block/cfq-iosched.c
@@ -577,25 +577,20 @@ static int cfq_allow_merge(request_queue_t *q, struct request *rq,
 	pid_t key;
 
 	/*
-	 * If bio is async or a write, always allow merge
+	 * Disallow merge, if bio and rq aren't both sync or async
 	 */
-	if (!bio_sync(bio) || rw == WRITE)
-		return 1;
-
-	/*
-	 * bio is sync. if request is not, disallow.
-	 */
-	if (!rq_is_sync(rq))
+	if (!!bio_sync(bio) != !!rq_is_sync(rq))
 		return 0;
 
 	/*
-	 * Ok, both bio and request are sync. Allow merge if they are
-	 * from the same queue.
+	 * Lookup the cfqq that this bio will be queued with. Allow
+	 * merge only if rq is queued there.
 	 */
-	key = cfq_queue_pid(current, rw, 1);
+	key = cfq_queue_pid(current, rw, bio_sync(bio));
 	cfqq = cfq_find_cfq_hash(cfqd, key, current->ioprio);
-	if (cfqq != RQ_CFQQ(rq))
-		return 0;
+
+	if (cfqq == RQ_CFQQ(rq))
+		return 1;
 
 	return 1;
 }