[PATCH 17/19] blk-mq: Document locking assumptions

[Bart Van Assche]

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.vanass...@sandisk.com>
Cc: Christoph Hellwig <h...@lst.de>
Cc: Hannes Reinecke <h...@suse.com>
Cc: Omar Sandoval <osan...@fb.com>
Cc: Ming Lei <ming....@redhat.com>
---
 block/blk-mq.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index b230038eba1d..4b1b2c7b4344 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -785,6 +785,8 @@ 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;
 
@@ -1338,6 +1340,8 @@ 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)
@@ -1351,6 +1355,8 @@ 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);
 }
-- 
2.12.2