From 95e5d6f62693f27d9011ec307eb32c6126314ea3 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Tue, 18 Aug 2015 14:54:58 -0700
Subject: [PATCH] cfq-iosched: fix async oom queue handling
Async cfqq's (cfq_queue's) are shared across cfq_data. When
cfq_get_queue() obtains a new queue from cfq_find_alloc_queue(), it
stashes the pointer in cfq_data and reuses it from then on; however,
the function doesn't consider that cfq_find_alloc_queue() may return
the oom_cfqq under memory pressure and installs the returned queue
unconditionally.
If the oom_cfqq is installed as an async cfqq, cfq_set_request() will
continue calling cfq_get_queue() hoping to replace it with a proper
queue; however, cfq_get_queue() will keep returning the cached queue
for the slot - the oom_cfqq.
Fix it by skipping caching if the queue is the oom one.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
---
block/cfq-iosched.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index e91093d0c0eb3..baf0b706169da 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -3751,7 +3751,7 @@ cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct cfq_io_cq *cic,
/*
* pin the queue now that it's allocated, scheduler exit will prune it
*/
- if (!is_sync) {
+ if (!is_sync && cfqq != &cfqd->oom_cfqq) {
cfqq->ref++;
*async_cfqq = cfqq;
}
--
2.30.2