[PATCH] CFQ: request <-> request merging rr_list fixup

In very rare circumstances would we be pruning a merged request and at the same time delete the implicated cfqq from the rr_list, and not readd it when the merged request got added. This could cause io stalls until that process issued io again. Fix it up by putting the rr_list add handling into cfq_add_rq_rb(), identical to how pruning is handled in cfq_del_rq_rb(). This fixes a hang reproducible with fsx-linux. Signed-off-by: Jens Axboe <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
josf · Oct 31, 2006 · 5fccbf6 · 5fccbf6
1 parent eafa6cb
commit 5fccbf6
Showing 1 changed file with 3 additions and 3 deletions.
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
@@ -456,6 +456,9 @@ static void cfq_add_rq_rb(struct request *rq)
 	 */
 	while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
 		cfq_dispatch_insert(cfqd->queue, __alias);
+
+	if (!cfq_cfqq_on_rr(cfqq))
+		cfq_add_cfqq_rr(cfqd, cfqq);
 }
 
 static inline void
@@ -1652,9 +1655,6 @@ static void cfq_insert_request(request_queue_t *q, struct request *rq)
 
 	cfq_add_rq_rb(rq);
 
-	if (!cfq_cfqq_on_rr(cfqq))
-		cfq_add_cfqq_rr(cfqd, cfqq);
-
 	list_add_tail(&rq->queuelist, &cfqq->fifo);
 
 	cfq_rq_enqueued(cfqd, cfqq, rq);