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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 1ad43c0078 ("blk-mq: don't leak preempt counter/q_usage_counter when allocating rq failed")
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Bart Van Assche 2017-10-16 16:32:26 -07:00 committed by Jens Axboe
parent c2e82a2348
commit 21e768b442
1 changed files with 7 additions and 5 deletions
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12
block/blk-mq.c
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@ -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);