From: Keith Busch <keith.busch@intel.com>
Date: Thu, 12 Mar 2015 03:56:39 +0000 (-0400)
Subject: blk-mq: don't wait in blk_mq_queue_enter() if __GFP_WAIT isn't set
X-Git-Tag: v4.1-rc1~106^2~6
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=bfd343aa1718457d34b99ce6573085ac340da288;p=linux.git

blk-mq: don't wait in blk_mq_queue_enter() if __GFP_WAIT isn't set

Return -EBUSY if we're unable to enter a queue immediately when
allocating a blk-mq request without __GFP_WAIT.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
---

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 06614ce0f475..59fa23935a0f 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -77,7 +77,7 @@ static void blk_mq_hctx_clear_pending(struct blk_mq_hw_ctx *hctx,
 	clear_bit(CTX_TO_BIT(hctx, ctx), &bm->word);
 }
 
-static int blk_mq_queue_enter(struct request_queue *q)
+static int blk_mq_queue_enter(struct request_queue *q, gfp_t gfp)
 {
 	while (true) {
 		int ret;
@@ -85,6 +85,9 @@ static int blk_mq_queue_enter(struct request_queue *q)
 		if (percpu_ref_tryget_live(&q->mq_usage_counter))
 			return 0;
 
+		if (!(gfp & __GFP_WAIT))
+			return -EBUSY;
+
 		ret = wait_event_interruptible(q->mq_freeze_wq,
 				!q->mq_freeze_depth || blk_queue_dying(q));
 		if (blk_queue_dying(q))
@@ -256,7 +259,7 @@ struct request *blk_mq_alloc_request(struct request_queue *q, int rw, gfp_t gfp,
 	struct blk_mq_alloc_data alloc_data;
 	int ret;
 
-	ret = blk_mq_queue_enter(q);
+	ret = blk_mq_queue_enter(q, gfp);
 	if (ret)
 		return ERR_PTR(ret);
 
@@ -1186,7 +1189,7 @@ static struct request *blk_mq_map_request(struct request_queue *q,
 	int rw = bio_data_dir(bio);
 	struct blk_mq_alloc_data alloc_data;
 
-	if (unlikely(blk_mq_queue_enter(q))) {
+	if (unlikely(blk_mq_queue_enter(q, GFP_KERNEL))) {
 		bio_endio(bio, -EIO);
 		return NULL;
 	}