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_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 5D0A8C4CEC7 for ; Mon, 16 Sep 2019 01:49:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 394542067B for ; Mon, 16 Sep 2019 01:49:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726676AbfIPBt3 (ORCPT ); Sun, 15 Sep 2019 21:49:29 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55374 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726298AbfIPBt3 (ORCPT ); Sun, 15 Sep 2019 21:49:29 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id C879E3DE0B; Mon, 16 Sep 2019 01:49:28 +0000 (UTC) Received: from ming.t460p (ovpn-8-18.pek2.redhat.com [10.72.8.18]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8D6B260BF3; Mon, 16 Sep 2019 01:49:21 +0000 (UTC) Date: Mon, 16 Sep 2019 09:49:16 +0800 From: Ming Lei To: xiubli@redhat.com Cc: josef@toxicpanda.com, axboe@kernel.dk, mchristi@redhat.com, linux-block@vger.kernel.org, Gabriel Krisman Bertazi Subject: Re: [RFC PATCH] blk-mq: Avoid memory reclaim when allocating request map Message-ID: <20190916014915.GB5162@ming.t460p> References: <20190915122656.11376-1-xiubli@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190915122656.11376-1-xiubli@redhat.com> User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Mon, 16 Sep 2019 01:49:29 +0000 (UTC) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Sun, Sep 15, 2019 at 05:56:56PM +0530, xiubli@redhat.com wrote: > From: Xiubo Li > > For some storage drivers, such as the nbd, when there has new socket > connections added, it will update the hardware queue number by calling > blk_mq_update_nr_hw_queues(), in which it will freeze all the queues > first. And then tries to do the hardware queue updating stuff. > > But int blk_mq_alloc_rq_map()-->blk_mq_init_tags(), when allocating > memory for tags, it may cause the mm do the memories direct reclaiming, > since the queues has been freezed, so if needs to flush the page cache > to disk, it will stuck in generic_make_request()-->blk_queue_enter() by > waiting the queues to be unfreezed and then cause deadlock here. > > Since the memory size requested here is a small one, which will make > it not that easy to happen with a large size, but in theory this could > happen when the OS is running in pressure and out of memory. > > Gabriel Krisman Bertazi has hit the similar issue by fixing it in > commit 36e1f3d10786 ("blk-mq: Avoid memory reclaim when remapping > queues"), but might forget this part. > > Signed-off-by: Xiubo Li > CC: Gabriel Krisman Bertazi > --- > block/blk-mq-tag.c | 5 +++-- > block/blk-mq-tag.h | 5 ++++- > block/blk-mq.c | 3 ++- > 3 files changed, 9 insertions(+), 4 deletions(-) > > diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c > index 008388e82b5c..04ee0e4c3fa1 100644 > --- a/block/blk-mq-tag.c > +++ b/block/blk-mq-tag.c > @@ -462,7 +462,8 @@ static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags, > > struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags, > unsigned int reserved_tags, > - int node, int alloc_policy) > + int node, int alloc_policy, > + gfp_t flags) > { > struct blk_mq_tags *tags; > > @@ -471,7 +472,7 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags, > return NULL; > } > > - tags = kzalloc_node(sizeof(*tags), GFP_KERNEL, node); > + tags = kzalloc_node(sizeof(*tags), flags, node); > if (!tags) > return NULL; > > diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h > index 61deab0b5a5a..296e0bc97126 100644 > --- a/block/blk-mq-tag.h > +++ b/block/blk-mq-tag.h > @@ -22,7 +22,10 @@ struct blk_mq_tags { > }; > > > -extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags, unsigned int reserved_tags, int node, int alloc_policy); > +extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags, > + unsigned int reserved_tags, > + int node, int alloc_policy, > + gfp_t flags); > extern void blk_mq_free_tags(struct blk_mq_tags *tags); > > extern unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data); > diff --git a/block/blk-mq.c b/block/blk-mq.c > index 240416057f28..9c52e4dfe132 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -2090,7 +2090,8 @@ struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set, > node = set->numa_node; > > tags = blk_mq_init_tags(nr_tags, reserved_tags, node, > - BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags)); > + BLK_MQ_FLAG_TO_ALLOC_POLICY(set->flags), > + GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY); Now, there are three uses on 'GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY', and code gets cleaner if you make it as one const variable in blk_mq_alloc_rq_map. Otherwise, looks fine: Reviewed-by: Ming Lei thanks, Ming