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blk-mq: re-check for available tags after running the hardware queue

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If we run out of tags and have to sleep, we run the hardware queue
to kick pending IO into gear. During that run, we may have completed
requests, so re-check if we have free tags before going to sleep.

Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Jens Axboe 2014-12-08 08:49:06 -07:00
parent b32232073e
commit 080ff35114
1 changed files with 8 additions and 0 deletions
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8
block/blk-mq-tag.c
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@ -261,6 +261,14 @@ static int bt_get(struct blk_mq_alloc_data *data,
*/
blk_mq_run_hw_queue(hctx, false);
/*
* Retry tag allocation after running the hardware queue,
* as running the queue may also have found completions.
*/
tag = __bt_get(hctx, bt, last_tag);
if (tag != -1)
break;
blk_mq_put_ctx(data->ctx);
io_schedule();