Messages in this thread | | | Subject | Re: [PATCH] blk-mq: Put driver tag in blk_mq_dispatch_rq_list() when no budget | From | Bart Van Assche <> | Date | Mon, 20 Apr 2020 05:48:32 -0700 |
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On 4/20/20 1:22 AM, John Garry wrote: > On 18/04/2020 03:43, Bart Van Assche wrote: >> On 2020-04-16 04:18, John Garry wrote: >>> If in blk_mq_dispatch_rq_list() we find no budget, then we break of the >>> dispatch loop, but the request may keep the driver tag, evaulated >>> in 'nxt' in the previous loop iteration. >>> >>> Fix by putting the driver tag for that request. >>> >>> Signed-off-by: John Garry <john.garry@huawei.com> >>> >>> diff --git a/block/blk-mq.c b/block/blk-mq.c >>> index 8e56884fd2e9..a7785df2c944 100644 >>> --- a/block/blk-mq.c >>> +++ b/block/blk-mq.c >>> @@ -1222,8 +1222,10 @@ bool blk_mq_dispatch_rq_list(struct >>> request_queue *q, struct list_head *list, >>> rq = list_first_entry(list, struct request, queuelist); >>> hctx = rq->mq_hctx; >>> - if (!got_budget && !blk_mq_get_dispatch_budget(hctx)) >>> + if (!got_budget && !blk_mq_get_dispatch_budget(hctx)) { >>> + blk_mq_put_driver_tag(rq); >>> break; >>> + } >>> if (!blk_mq_get_driver_tag(rq)) { >>> /* >> >> Is this something that can only happen if q->mq_ops->queue_rq(hctx, &bd) >> returns another value than BLK_STS_OK, BLK_STS_RESOURCE and >> BLK_STS_DEV_RESOURCE? > > Right, as that case is handled in blk_mq_handle_dev_resource() > > If so, please add a comment in the source code >> that explains this. > > So important that we should now do this in an extra patch?
Probably not, unless someone else feels strongly about this.
Thanks,
Bart.
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