From: Jens Axboe <axboe@suse.de>
Date: Thu, 1 Jun 2006 16:53:43 +0000 (+0200)
Subject: [PATCH] cfq-iosched: busy_rr fairness fix
X-Git-Tag: v2.6.17-rc6~52
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b52a834892f17b6c54c34ab65f1fad1a9229e764;p=linux-2.6

[PATCH] cfq-iosched: busy_rr fairness fix

Now that we select busy_rr for possible service, insert entries at the
back of that list instead of at the front.

Signed-off-by: Jens Axboe <axboe@suse.de>
---

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 85d188a30f..8e9d84825e 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -501,10 +501,13 @@ static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
 
 	/*
 	 * if queue was preempted, just add to front to be fair. busy_rr
-	 * isn't sorted.
+	 * isn't sorted, but insert at the back for fairness.
 	 */
 	if (preempted || list == &cfqd->busy_rr) {
-		list_add(&cfqq->cfq_list, list);
+		if (preempted)
+			list = list->prev;
+
+		list_add_tail(&cfqq->cfq_list, list);
 		return;
 	}