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blk-mq: streamline handling of q->mq_ops->queue_rq result

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Current handling of q->mq_ops->queue_rq result is a bit ugly:

- two branches which needs to 'continue' have to check if the
dispatch local list is empty, otherwise one bad request may
be retrieved via 'rq = list_first_entry(list, struct request, queuelist);'

- the branch of 'if (unlikely(ret != BLK_STS_OK))' isn't easy
to follow, since it is actually one error branch.

Streamline this handling, so the code becomes more readable, meantime
potential kernel oops can be avoided in case that the last request in
local dispatch list is failed.

Fixes: fc17b6534e ("blk-mq: switch ->queue_rq return value to blk_status_t")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2020-07-01 21:58:57 +08:00 committed by Jens Axboe
parent 0e6e255e7a
commit 7bf137298c
1 changed files with 11 additions and 13 deletions
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24
block/blk-mq.c
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@ -1387,30 +1387,28 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
if (nr_budgets) if (nr_budgets)
nr_budgets--; nr_budgets--;
ret = q->mq_ops->queue_rq(hctx, &bd); ret = q->mq_ops->queue_rq(hctx, &bd);
if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE) { switch (ret) {
blk_mq_handle_dev_resource(rq, list); case BLK_STS_OK:
queued++;
break; break;
} else if (ret == BLK_STS_ZONE_RESOURCE) { case BLK_STS_RESOURCE:
case BLK_STS_DEV_RESOURCE:
blk_mq_handle_dev_resource(rq, list);
goto out;
case BLK_STS_ZONE_RESOURCE:
/* /*
* Move the request to zone_list and keep going through * Move the request to zone_list and keep going through
* the dispatch list to find more requests the drive can * the dispatch list to find more requests the drive can
* accept. * accept.
*/ */
blk_mq_handle_zone_resource(rq, &zone_list); blk_mq_handle_zone_resource(rq, &zone_list);
if (list_empty(list)) break;
break; default:
continue;
}
if (unlikely(ret != BLK_STS_OK)) {
errors++; errors++;
blk_mq_end_request(rq, BLK_STS_IOERR); blk_mq_end_request(rq, BLK_STS_IOERR);
continue;
} }
queued++;
} while (!list_empty(list)); } while (!list_empty(list));
out:
if (!list_empty(&zone_list)) if (!list_empty(&zone_list))
list_splice_tail_init(&zone_list, list); list_splice_tail_init(&zone_list, list);