Hi Bart On 4/4/19 4:11 AM, Bart Van Assche wrote: > If blk_mq_try_issue_directly() returns BLK_STS*_RESOURCE that means that > the request has not been queued and that the caller should retry to submit > the request. Both blk_mq_request_bypass_insert() and > blk_mq_sched_insert_request() guarantee that a request will be processed. > Hence return BLK_STS_OK if one of these functions is called. This patch > avoids that blk_mq_dispatch_rq_list() crashes when using dm-mpath.
Sorry, I seem to miss the original mail list that reported this issue. As your comment, it looks like that the request is handled again when the blk_mq_try_issue_directly return BLK_STS*_RESOURCE, right ? The usage of this helper interface is, if care about the return value and want to handle the request yourself when return BLK_STS*_RESOURCE, pass 'byass' as true. otherwise, just pass 'bypass' as false, then blk_mq_try_issue_directly would take over all of the work including requeue or complete the request. if dm-mpath case, the driver should only invoke dm_dispatch_clone_request, the 'bypass' parameter should only be true. as the blk_mq_try_issue_directly, it would return BLK_STS_OK when have to insert the request, otherwise, it would do nothing but return BLK_STS*_RESOURCE. Would you please show the cause that the dm-mpath driver invoke blk_mq_try_issue_direclty with 'bypass == false' ? Thanks Jianchao > > Cc: Christoph Hellwig <[email protected]> > Cc: Hannes Reinecke <[email protected]> > Cc: James Smart <[email protected]> > Cc: Ming Lei <[email protected]> > Cc: Jianchao Wang <[email protected]> > Cc: Keith Busch <[email protected]> > Cc: Dongli Zhang <[email protected]> > Cc: Laurence Oberman <[email protected]> > Tested-by: Laurence Oberman <[email protected]> > Reviewed-by: Laurence Oberman <[email protected]> > Reported-by: Laurence Oberman <[email protected]> > Fixes: 7f556a44e61d ("blk-mq: refactor the code of issue request directly") # > v5.0. > Cc: <[email protected]> > Signed-off-by: Bart Van Assche <[email protected]> > --- > block/blk-mq.c | 9 ++------- > 1 file changed, 2 insertions(+), 7 deletions(-) > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index 652d0c6d5945..b2c20dce8a30 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -1859,16 +1859,11 @@ blk_status_t blk_mq_try_issue_directly(struct > blk_mq_hw_ctx *hctx, > case BLK_STS_RESOURCE: > if (force) { > blk_mq_request_bypass_insert(rq, run_queue); > - /* > - * We have to return BLK_STS_OK for the DM > - * to avoid livelock. Otherwise, we return > - * the real result to indicate whether the > - * request is direct-issued successfully. > - */ > - ret = bypass ? BLK_STS_OK : ret; > + ret = BLK_STS_OK; > } else if (!bypass) { > blk_mq_sched_insert_request(rq, false, > run_queue, false); > + ret = BLK_STS_OK; > } > break; > default: >
