blk-mq: initialize request on allocation

If we want to share tag and request allocation between queues we cannot
initialize the request at init/free time, but need to initialize it
at allocation time as it might get used for different queues over its
lifetime.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

block/blk-mq.c

@@ -82,6 +82,7 @@ static struct request *__blk_mq_alloc_request(struct blk_mq_hw_ctx *hctx,
  tag = blk_mq_get_tag(hctx->tags, gfp, reserved);
  if (tag != BLK_MQ_TAG_FAIL) {
  rq = hctx->rqs[tag];
+ blk_rq_init(hctx->queue, rq);
  rq->tag = tag;
 
  return rq;
@@ -257,9 +258,7 @@ static void __blk_mq_free_request(struct blk_mq_hw_ctx *hctx,
  const int tag = rq->tag;
  struct request_queue *q = rq->q;
 
- blk_rq_init(hctx->queue, rq);
  blk_mq_put_tag(hctx->tags, tag);
-
  blk_mq_queue_exit(q);
 }
 
@@ -1122,7 +1121,6 @@ static int blk_mq_init_rq_map(struct blk_mq_hw_ctx *hctx,
  left -= to_do * rq_size;
  for (j = 0; j < to_do; j++) {
  hctx->rqs[i] = p;
- blk_rq_init(hctx->queue, hctx->rqs[i]);
  if (reg->ops->init_request) {
  error = reg->ops->init_request(driver_data,
  hctx, hctx->rqs[i], i);