blk-mq: Document locking assumptions

Document the locking assumptions in functions that modify
blk_mq_ctx.rq_list to make it easier for humans to verify
this code.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Omar Sandoval <osandov@fb.com>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

2 files changed, 6 insertions, 0 deletions

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 9f025289da63..191bf82d185e 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -150,6 +150,8 @@ static bool blk_mq_attempt_merge(struct request_queue *q,
         struct request *rq;
         int checked = 8;
 
+        lockdep_assert_held(&ctx->lock);
+
         list_for_each_entry_reverse(rq, &ctx->rq_list, queuelist) {
                 bool merged = false;
 
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 6268380c680f..1d8050e49a94 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1317,6 +1317,8 @@ static inline void __blk_mq_insert_req_list(struct blk_mq_hw_ctx *hctx,
 {
         struct blk_mq_ctx *ctx = rq->mq_ctx;
 
+        lockdep_assert_held(&ctx->lock);
+
         trace_block_rq_insert(hctx->queue, rq);
 
         if (at_head)
@@ -1330,6 +1332,8 @@ void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
 {
         struct blk_mq_ctx *ctx = rq->mq_ctx;
 
+        lockdep_assert_held(&ctx->lock);
+
         __blk_mq_insert_req_list(hctx, rq, at_head);
         blk_mq_hctx_mark_pending(hctx, ctx);
 }