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Commit 21e768b4 authored by Bart Van Assche's avatar Bart Van Assche Committed by Jens Axboe
Browse files

blk-mq: Make blk_mq_get_request() error path less confusing 



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 1ad43c00 ("blk-mq: don't leak preempt counter/q_usage_counter when allocating rq failed")
Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Reviewed-by: default avatarHannes Reinecke <hare@suse.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarJohannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: default avatarBart Van Assche <bart.vanassche@wdc.com>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent c2e82a23

block/blk-mq.c

+7 −5
Original line number Diff line number Diff line
@@ -337,12 +337,14 @@ 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)
@@ -361,8 +363,8 @@ 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);