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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT autolearn=unavailable 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 DD397C4360F for ; Fri, 15 Feb 2019 02:28:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B75072073D for ; Fri, 15 Feb 2019 02:28:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727123AbfBOC2V (ORCPT ); Thu, 14 Feb 2019 21:28:21 -0500 Received: from mx1.redhat.com ([209.132.183.28]:53460 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727894AbfBOC2U (ORCPT ); Thu, 14 Feb 2019 21:28:20 -0500 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E8616C0AC921; Fri, 15 Feb 2019 02:28:19 +0000 (UTC) Received: from ming.t460p (ovpn-8-28.pek2.redhat.com [10.72.8.28]) by smtp.corp.redhat.com (Postfix) with ESMTPS id CD73A5C54B; Fri, 15 Feb 2019 02:28:12 +0000 (UTC) Date: Fri, 15 Feb 2019 10:28:08 +0800 From: Ming Lei To: Sasha Levin Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Tetsuo Handa , NeilBrown , Jens Axboe , linux-block@vger.kernel.org Subject: Re: [PATCH AUTOSEL 4.20 49/77] block: cover another queue enter recursion via BIO_QUEUE_ENTERED Message-ID: <20190215022807.GC21045@ming.t460p> References: <20190215020855.176727-1-sashal@kernel.org> <20190215020855.176727-49-sashal@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190215020855.176727-49-sashal@kernel.org> User-Agent: Mutt/1.9.1 (2017-09-22) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Fri, 15 Feb 2019 02:28:20 +0000 (UTC) Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Thu, Feb 14, 2019 at 09:08:27PM -0500, Sasha Levin wrote: > From: Ming Lei > > [ Upstream commit 698cef173983b086977e633e46476e0f925ca01e ] > > Except for blk_queue_split(), bio_split() is used for splitting bio too, > then the remained bio is often resubmit to queue via generic_make_request(). > So the same queue enter recursion exits in this case too. Unfortunatley > commit cd4a4ae4683dc2 doesn't help this case. > > This patch covers the above case by setting BIO_QUEUE_ENTERED before calling > q->make_request_fn. > > In theory the per-bio flag is used to simulate one stack variable, it is > just fine to clear it after q->make_request_fn is returned. Especially > the same bio can't be submitted from another context. > > Fixes: cd4a4ae4683dc2 ("block: don't use blocking queue entered for recursive bio submits") > Cc: Tetsuo Handa > Cc: NeilBrown > Reviewed-by: Mike Snitzer > Signed-off-by: Ming Lei > Signed-off-by: Jens Axboe > Signed-off-by: Sasha Levin > --- > block/blk-core.c | 11 +++++++++++ > block/blk-merge.c | 10 ---------- > 2 files changed, 11 insertions(+), 10 deletions(-) > > diff --git a/block/blk-core.c b/block/blk-core.c > index deb56932f8c4..22260339f66f 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -2449,7 +2449,18 @@ blk_qc_t generic_make_request(struct bio *bio) > /* Create a fresh bio_list for all subordinate requests */ > bio_list_on_stack[1] = bio_list_on_stack[0]; > bio_list_init(&bio_list_on_stack[0]); > + > + /* > + * Since we're recursing into make_request here, ensure > + * that we mark this bio as already having entered the queue. > + * If not, and the queue is going away, we can get stuck > + * forever on waiting for the queue reference to drop. But > + * that will never happen, as we're already holding a > + * reference to it. > + */ > + bio_set_flag(bio, BIO_QUEUE_ENTERED); > ret = q->make_request_fn(q, bio); > + bio_clear_flag(bio, BIO_QUEUE_ENTERED); > > /* sort new bios into those for a lower level > * and those for the same level > diff --git a/block/blk-merge.c b/block/blk-merge.c > index 7695034f4b87..adfe835ab258 100644 > --- a/block/blk-merge.c > +++ b/block/blk-merge.c > @@ -272,16 +272,6 @@ void blk_queue_split(struct request_queue *q, struct bio **bio) > /* there isn't chance to merge the splitted bio */ > split->bi_opf |= REQ_NOMERGE; > > - /* > - * Since we're recursing into make_request here, ensure > - * that we mark this bio as already having entered the queue. > - * If not, and the queue is going away, we can get stuck > - * forever on waiting for the queue reference to drop. But > - * that will never happen, as we're already holding a > - * reference to it. > - */ > - bio_set_flag(*bio, BIO_QUEUE_ENTERED); > - > bio_chain(split, *bio); > trace_block_split(q, split, (*bio)->bi_iter.bi_sector); > generic_make_request(*bio); > -- > 2.19.1 > This one should be dropped, given it has been reverted. -- Ming