X-Git-Url: http://drtracing.org/?a=blobdiff_plain;f=block%2Fblk-mq.c;h=e931a0e8e73dfb23761a0fa2f2819e43207dc07c;hb=b9a4a0d02c5b8d9a1397c11d741d2a1a56381178;hp=576e7112f8071179b0c8f44bef799dfa5bc75c33;hpb=574c7e233344b58c6b14b305c93de361d3e7d35d;p=deliverable%2Flinux.git

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 576e7112f807..e931a0e8e73d 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -672,7 +672,20 @@ static void blk_mq_timeout_work(struct work_struct *work)
 	};
 	int i;
 
-	if (blk_queue_enter(q, true))
+	/* A deadlock might occur if a request is stuck requiring a
+	 * timeout at the same time a queue freeze is waiting
+	 * completion, since the timeout code would not be able to
+	 * acquire the queue reference here.
+	 *
+	 * That's why we don't use blk_queue_enter here; instead, we use
+	 * percpu_ref_tryget directly, because we need to be able to
+	 * obtain a reference even in the short window between the queue
+	 * starting to freeze, by dropping the first reference in
+	 * blk_mq_freeze_queue_start, and the moment the last request is
+	 * consumed, marked by the instant q_usage_counter reaches
+	 * zero.
+	 */
+	if (!percpu_ref_tryget(&q->q_usage_counter))
 		return;
 
 	blk_mq_queue_tag_busy_iter(q, blk_mq_check_expired, &data);
@@ -1221,7 +1234,7 @@ static struct request *blk_mq_map_request(struct request_queue *q,
 	ctx = blk_mq_get_ctx(q);
 	hctx = q->mq_ops->map_queue(q, ctx->cpu);
 
-	if (rw_is_sync(bio_op(bio), bio->bi_rw))
+	if (rw_is_sync(bio_op(bio), bio->bi_opf))
 		op_flags |= REQ_SYNC;
 
 	trace_block_getrq(q, bio, op);
@@ -1289,8 +1302,8 @@ static int blk_mq_direct_issue_request(struct request *rq, blk_qc_t *cookie)
  */
 static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
 {
-	const int is_sync = rw_is_sync(bio_op(bio), bio->bi_rw);
-	const int is_flush_fua = bio->bi_rw & (REQ_PREFLUSH | REQ_FUA);
+	const int is_sync = rw_is_sync(bio_op(bio), bio->bi_opf);
+	const int is_flush_fua = bio->bi_opf & (REQ_PREFLUSH | REQ_FUA);
 	struct blk_map_ctx data;
 	struct request *rq;
 	unsigned int request_count = 0;
@@ -1383,8 +1396,8 @@ done:
  */
 static blk_qc_t blk_sq_make_request(struct request_queue *q, struct bio *bio)
 {
-	const int is_sync = rw_is_sync(bio_op(bio), bio->bi_rw);
-	const int is_flush_fua = bio->bi_rw & (REQ_PREFLUSH | REQ_FUA);
+	const int is_sync = rw_is_sync(bio_op(bio), bio->bi_opf);
+	const int is_flush_fua = bio->bi_opf & (REQ_PREFLUSH | REQ_FUA);
 	struct blk_plug *plug;
 	unsigned int request_count = 0;
 	struct blk_map_ctx data;