On Thu, Sep 19, 2019 at 11:45:46AM +0200, Hannes Reinecke wrote:
> From: Hannes Reinecke <hare@xxxxxxxx>
>
> When blk_mq_request_issue_directly() returns BLK_STS_RESOURCE we
> need to requeue the I/O, but adding it to the global request list
> will mess up with the passed-in request list. So re-add the request
We always add request to hctx->dispatch_list after .queue_rq() returns
BLK_STS_RESOURCE or BLK_STS_DEV_RESOURCE, so what is the messing up?
> to the original list and leave it to the caller to handle situations
> where the list wasn't completely emptied.
>
> Signed-off-by: Hannes Reinecke <hare@xxxxxxxx>
> ---
> block/blk-mq.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index b038ec680e84..44ff3c1442a4 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1899,8 +1899,7 @@ void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
> if (ret != BLK_STS_OK) {
> if (ret == BLK_STS_RESOURCE ||
> ret == BLK_STS_DEV_RESOURCE) {
> - blk_mq_request_bypass_insert(rq,
> - list_empty(list));
> + list_add(list, &rq->queuelist);
This way may let this request(DONTPREP set) to be merged with other rq
or bio, and potential data corruption may be caused, please see commit:
c616cbee97ae blk-mq: punt failed direct issue to dispatch list
Thanks,
Ming
