From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3C320C4360F for ; Wed, 3 Apr 2019 10:26:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 14A6E2147C for ; Wed, 3 Apr 2019 10:26:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726316AbfDCK0V (ORCPT ); Wed, 3 Apr 2019 06:26:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52964 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726199AbfDCK0V (ORCPT ); Wed, 3 Apr 2019 06:26:21 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 098C93091747; Wed, 3 Apr 2019 10:26:21 +0000 (UTC) Received: from localhost (ovpn-8-25.pek2.redhat.com [10.72.8.25]) by smtp.corp.redhat.com (Postfix) with ESMTP id 11C21608AA; Wed, 3 Apr 2019 10:26:19 +0000 (UTC) From: Ming Lei To: Jens Axboe Cc: linux-block@vger.kernel.org, Ming Lei , Dongli Zhang , James Smart , Bart Van Assche , linux-scsi@vger.kernel.org, "Martin K . Petersen" , Christoph Hellwig , "James E . J . Bottomley" , jianchao wang Subject: [PATCH V3 1/6] blk-mq: grab .q_usage_counter when queuing request from plug code path Date: Wed, 3 Apr 2019 18:26:04 +0800 Message-Id: <20190403102609.18707-2-ming.lei@redhat.com> In-Reply-To: <20190403102609.18707-1-ming.lei@redhat.com> References: <20190403102609.18707-1-ming.lei@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.41]); Wed, 03 Apr 2019 10:26:21 +0000 (UTC) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Just like aio/io_uring, we need to grab 2 refcount for queuing one request, one is for submission, another is for completion. If the request isn't queued from plug code path, the refcount grabbed in generic_make_request() serves for submission. In theroy, this refcount should have been released after the sumission(async run queue) is done. But blk_freeze_queue() is working with blk_sync_queue() together for canceling async run queue work activities if hctx->run_work is scheduled with holding the refcount. However, if request is staggered into plug list, and finally queued from plug code path, the refcount in submission side is actually missed. And we may start to run queue after queue is removed, then kernel oops is triggered. Fixes the issue by grab .q_usage_counter before calling blk_mq_sched_insert_requests() in blk_mq_flush_plug_list(). This way is safe because the queue is absolutely alive before inserting request. Cc: Dongli Zhang Cc: James Smart Cc: Bart Van Assche Cc: linux-scsi@vger.kernel.org, Cc: Martin K . Petersen , Cc: Christoph Hellwig , Cc: James E . J . Bottomley , Cc: jianchao wang Signed-off-by: Ming Lei --- block/blk-mq.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/block/blk-mq.c b/block/blk-mq.c index 3ff3d7b49969..5b586affee09 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1728,9 +1728,12 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule) if (rq->mq_hctx != this_hctx || rq->mq_ctx != this_ctx) { if (this_hctx) { trace_block_unplug(this_q, depth, !from_schedule); + + percpu_ref_get(&this_q->q_usage_counter); blk_mq_sched_insert_requests(this_hctx, this_ctx, &rq_list, from_schedule); + percpu_ref_put(&this_q->q_usage_counter); } this_q = rq->q; @@ -1749,8 +1752,11 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule) */ if (this_hctx) { trace_block_unplug(this_q, depth, !from_schedule); + + percpu_ref_get(&this_q->q_usage_counter); blk_mq_sched_insert_requests(this_hctx, this_ctx, &rq_list, from_schedule); + percpu_ref_put(&this_q->q_usage_counter); } } -- 2.9.5