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>

1 files changed, 6 insertions, 3 deletions

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;
         }