From: Jens Axboe <axboe@suse.de>
Date: Tue, 2 Aug 2005 18:08:02 +0000 (+0200)
Subject: [PATCH] cfq-iosched: fix problem with barriers and max_depth == 1
X-Git-Tag: v2.6.13-rc6~81
X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=d7ed538a02c219119adb20f1dccbf0f8015e53f3;p=linux-2.6-omap-h63xx.git

[PATCH] cfq-iosched: fix problem with barriers and max_depth == 1

CFQ will currently stall when using write barriers and the default
max_depth setting of 1, since we artificially need a depth of 2 when
pre-pending the first flush. So never deny the barrier request going to
the device.

This is a regression since 2.6.12, it was found in SUSE testing.

Signed-off-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

diff --git a/drivers/block/cfq-iosched.c b/drivers/block/cfq-iosched.c
index de5746e38af..2435a7c99b2 100644
--- a/drivers/block/cfq-iosched.c
+++ b/drivers/block/cfq-iosched.c
@@ -1281,6 +1281,7 @@ dispatch:
 			 */
 			if (!cfq_crq_in_driver(crq) &&
 			    !cfq_cfqq_idle_window(cfqq) &&
+			    !blk_barrier_rq(rq) &&
 			    cfqd->rq_in_driver >= cfqd->cfq_max_depth)
 				return NULL;