On 12/08/2016 09:13 PM, Jens Axboe wrote:
+static inline void blk_mq_sched_put_request(struct request *rq)
+{
+ struct request_queue *q = rq->q;
+ struct elevator_queue *e = q->elevator;
+
+ if (e && e->type->mq_ops.put_request)
+ e->type->mq_ops.put_request(rq);
+ else
+ blk_mq_free_request(rq);
+}
blk_mq_free_request() always triggers a call of blk_queue_exit().
dd_put_request() only triggers a call of blk_queue_exit() if it is not a
shadow request. Is that on purpose?
+static inline struct request *
+blk_mq_sched_get_request(struct request_queue *q, unsigned int op,
+ struct blk_mq_alloc_data *data)
+{
+ struct elevator_queue *e = q->elevator;
+ struct blk_mq_hw_ctx *hctx;
+ struct blk_mq_ctx *ctx;
+ struct request *rq;
+
+ blk_queue_enter_live(q);
+ ctx = blk_mq_get_ctx(q);
+ hctx = blk_mq_map_queue(q, ctx->cpu);
+
+ blk_mq_set_alloc_data(data, q, 0, ctx, hctx);
+
+ if (e && e->type->mq_ops.get_request)
+ rq = e->type->mq_ops.get_request(q, op, data);
+ else
+ rq = __blk_mq_alloc_request(data, op);
+
+ if (rq)
+ data->hctx->queued++;
+
+ return rq;
+
+}
Some but not all callers of blk_mq_sched_get_request() call
blk_queue_exit() if this function returns NULL. Please consider to move
the blk_queue_exit() call from the blk_mq_alloc_request() error path
into this function. I think that will make it a lot easier to verify
whether or not the blk_queue_enter() / blk_queue_exit() calls are
balanced properly.
Additionally, since blk_queue_enter() / blk_queue_exit() calls by
blk_mq_sched_get_request() and blk_mq_sched_put_request() must be
balanced and since the latter function only calls blk_queue_exit() for
non-shadow requests, shouldn't blk_mq_sched_get_request() call
blk_queue_enter_live() only if __blk_mq_alloc_request() is called?
Thanks,
Bart.
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