From 95e5d6f62693f27d9011ec307eb32c6126314ea3 Mon Sep 17 00:00:00 2001 From: Tejun Heo 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 Acked-by: Jeff Moyer Cc: Vivek Goyal Cc: Arianna Avanzini Signed-off-by: Jens Axboe --- 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 e91093d..baf0b70 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; } -- 2.7.4