blk_mq_get_tag() can modify data->ctx. This means that in the
error path of blk_mq_get_request() data->ctx should be passed to
blk_mq_put_ctx() instead of local_ctx. Note: since blk_mq_put_ctx()
ignores its argument, this patch does not change any functionality.
References: commit 1ad43c0078b7 ("blk-mq: don't leak preempt counter/q_usage_counter when allocating rq failed")
Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxx>
Cc: Ming Lei <ming.lei@xxxxxxxxxx>
---
Changes compared to v1:
- Removed "Cc: <stable>"
- Removed "bug fix" from the description.
block/blk-mq.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 097ca3ece716..d9b3b5dc66ab 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -336,12 +336,14 @@ static struct request *blk_mq_get_request(struct request_queue *q,
struct elevator_queue *e = q->elevator;
struct request *rq;
unsigned int tag;
- struct blk_mq_ctx *local_ctx = NULL;
+ bool put_ctx_on_error = false;
blk_queue_enter_live(q);
data->q = q;
- if (likely(!data->ctx))
- data->ctx = local_ctx = blk_mq_get_ctx(q);
+ if (likely(!data->ctx)) {
+ data->ctx = blk_mq_get_ctx(q);
+ put_ctx_on_error = true;
+ }
if (likely(!data->hctx))
data->hctx = blk_mq_map_queue(q, data->ctx->cpu);
if (op & REQ_NOWAIT)
@@ -360,8 +362,8 @@ static struct request *blk_mq_get_request(struct request_queue *q,
tag = blk_mq_get_tag(data);
if (tag == BLK_MQ_TAG_FAIL) {
- if (local_ctx) {
- blk_mq_put_ctx(local_ctx);
+ if (put_ctx_on_error) {
+ blk_mq_put_ctx(data->ctx);
data->ctx = NULL;
}
blk_queue_exit(q);
--
2.14.2
