From: Ming Lei <minlei@xxxxxxxxxx>
When blk_mq_get_request() failed, preempt counter isn't
released, and blk_mq_make_request() doesn't release the counter
too.
This patch fixes the issue, and makes sure that preempt counter
is only held if rq is allocated successfully. The same policy is
applied on .q_usage_counter too.
Signed-off-by: Ming Lei <minlei@xxxxxxxxxx>
---
V2: use local_ctx, and clear data->ctx if allocation fails, as
suggested by Jens.
block/blk-mq.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 041f7b7fa0d6..211ef367345f 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -301,11 +301,12 @@ 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;
blk_queue_enter_live(q);
data->q = q;
if (likely(!data->ctx))
- data->ctx = blk_mq_get_ctx(q);
+ data->ctx = local_ctx = blk_mq_get_ctx(q);
if (likely(!data->hctx))
data->hctx = blk_mq_map_queue(q, data->ctx->cpu);
if (op & REQ_NOWAIT)
@@ -324,6 +325,10 @@ 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);
+ data->ctx = NULL;
+ }
blk_queue_exit(q);
return NULL;
}
@@ -356,12 +361,12 @@ struct request *blk_mq_alloc_request(struct request_queue *q, unsigned int op,
rq = blk_mq_get_request(q, NULL, op, &alloc_data);
- blk_mq_put_ctx(alloc_data.ctx);
- blk_queue_exit(q);
-
if (!rq)
return ERR_PTR(-EWOULDBLOCK);
+ blk_mq_put_ctx(alloc_data.ctx);
+ blk_queue_exit(q);
+
rq->__data_len = 0;
rq->__sector = (sector_t) -1;
rq->bio = rq->biotail = NULL;
@@ -407,11 +412,11 @@ struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
rq = blk_mq_get_request(q, NULL, op, &alloc_data);
- blk_queue_exit(q);
-
if (!rq)
return ERR_PTR(-EWOULDBLOCK);
+ blk_queue_exit(q);
+
return rq;
}
EXPORT_SYMBOL_GPL(blk_mq_alloc_request_hctx);
--
2.9.4
