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=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 5EF56C10F14 for ; Mon, 22 Apr 2019 03:31:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2D1E52075A for ; Mon, 22 Apr 2019 03:31:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726234AbfDVDbS (ORCPT ); Sun, 21 Apr 2019 23:31:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47298 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726210AbfDVDbS (ORCPT ); Sun, 21 Apr 2019 23:31:18 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D027B99D2E; Mon, 22 Apr 2019 03:31:15 +0000 (UTC) Received: from ming.t460p (ovpn-8-23.pek2.redhat.com [10.72.8.23]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E0C6C5D710; Mon, 22 Apr 2019 03:31:04 +0000 (UTC) Date: Mon, 22 Apr 2019 11:30:59 +0800 From: Ming Lei To: Hannes Reinecke Cc: Jens Axboe , linux-block@vger.kernel.org, Hannes Reinecke , Keith Busch , linux-nvme@lists.infradead.org, Sagi Grimberg , Dongli Zhang , James Smart , Bart Van Assche , linux-scsi@vger.kernel.org, "Martin K . Petersen" , Christoph Hellwig , "James E . J . Bottomley" , jianchao wang Subject: Re: [PATCH V6 6/9] blk-mq: always free hctx after request queue is freed Message-ID: <20190422033057.GC21375@ming.t460p> References: <20190417034410.31957-1-ming.lei@redhat.com> <20190417034410.31957-7-ming.lei@redhat.com> <63c09210-c20e-6b4a-56fa-b9eac2807cc1@suse.de> <20190417125943.GB5007@ming.t460p> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190417125943.GB5007@ming.t460p> User-Agent: Mutt/1.9.1 (2017-09-22) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Mon, 22 Apr 2019 03:31:17 +0000 (UTC) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Wed, Apr 17, 2019 at 08:59:43PM +0800, Ming Lei wrote: > On Wed, Apr 17, 2019 at 02:08:59PM +0200, Hannes Reinecke wrote: > > On 4/17/19 5:44 AM, Ming Lei wrote: > > > In normal queue cleanup path, hctx is released after request queue > > > is freed, see blk_mq_release(). > > > > > > However, in __blk_mq_update_nr_hw_queues(), hctx may be freed because > > > of hw queues shrinking. This way is easy to cause use-after-free, > > > because: one implicit rule is that it is safe to call almost all block > > > layer APIs if the request queue is alive; and one hctx may be retrieved > > > by one API, then the hctx can be freed by blk_mq_update_nr_hw_queues(); > > > finally use-after-free is triggered. > > > > > > Fixes this issue by always freeing hctx after releasing request queue. > > > If some hctxs are removed in blk_mq_update_nr_hw_queues(), introduce > > > a per-queue list to hold them, then try to resuse these hctxs if numa > > > node is matched. > > > > > > 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 | 40 +++++++++++++++++++++++++++------------- > > > include/linux/blk-mq.h | 2 ++ > > > include/linux/blkdev.h | 7 +++++++ > > > 3 files changed, 36 insertions(+), 13 deletions(-) > > > > > > diff --git a/block/blk-mq.c b/block/blk-mq.c > > > index eeebba6ec0f7..2ca4395f794d 100644 > > > --- a/block/blk-mq.c > > > +++ b/block/blk-mq.c > > > @@ -2274,6 +2274,10 @@ static void blk_mq_exit_hctx(struct request_queue *q, > > > set->ops->exit_hctx(hctx, hctx_idx); > > > blk_mq_remove_cpuhp(hctx); > > > + > > > + spin_lock(&q->dead_hctx_lock); > > > + list_add(&hctx->hctx_list, &q->dead_hctx_list); > > > + spin_unlock(&q->dead_hctx_lock); > > > } > > > static void blk_mq_exit_hw_queues(struct request_queue *q, > > > @@ -2675,15 +2679,13 @@ static int blk_mq_alloc_ctxs(struct request_queue *q) > > > */ > > > void blk_mq_release(struct request_queue *q) > > > { > > > - struct blk_mq_hw_ctx *hctx; > > > - unsigned int i; > > > + struct blk_mq_hw_ctx *hctx, *next; > > > cancel_delayed_work_sync(&q->requeue_work); > > > - /* hctx kobj stays in hctx */ > > > - queue_for_each_hw_ctx(q, hctx, i) { > > > - if (!hctx) > > > - continue; > > > + /* all hctx are in .dead_hctx_list now */ > > > + list_for_each_entry_safe(hctx, next, &q->dead_hctx_list, hctx_list) { > > > + list_del_init(&hctx->hctx_list); > > > kobject_put(&hctx->kobj); > > > } > > > @@ -2750,9 +2752,22 @@ static struct blk_mq_hw_ctx *blk_mq_alloc_and_init_hctx( > > > struct blk_mq_tag_set *set, struct request_queue *q, > > > int hctx_idx, int node) > > > { > > > - struct blk_mq_hw_ctx *hctx; > > > + struct blk_mq_hw_ctx *hctx = NULL, *tmp; > > > + > > > + /* reuse dead hctx first */ > > > + spin_lock(&q->dead_hctx_lock); > > > + list_for_each_entry(tmp, &q->dead_hctx_list, hctx_list) { > > > + if (tmp->numa_node == node) { > > > + hctx = tmp; > > > + break; > > > + } > > > + } > > > + if (hctx) > > > + list_del_init(&hctx->hctx_list); > > > + spin_unlock(&q->dead_hctx_lock); > > > - hctx = blk_mq_alloc_hctx(q, set, hctx_idx, node); > > > + if (!hctx) > > > + hctx = blk_mq_alloc_hctx(q, set, hctx_idx, node); > > > if (!hctx) > > > goto fail; > > > @@ -2790,10 +2805,8 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set, > > > hctx = blk_mq_alloc_and_init_hctx(set, q, i, node); > > > if (hctx) { > > > - if (hctxs[i]) { > > > + if (hctxs[i]) > > > blk_mq_exit_hctx(q, set, hctxs[i], i); > > > - kobject_put(&hctxs[i]->kobj); > > > - } > > > hctxs[i] = hctx; > > > } else { > > > if (hctxs[i]) > > > @@ -2824,9 +2837,7 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set, > > > if (hctx->tags) > > > blk_mq_free_map_and_requests(set, j); > > > blk_mq_exit_hctx(q, set, hctx, j); > > > - kobject_put(&hctx->kobj); > > > hctxs[j] = NULL; > > > - > > > } > > > } > > > mutex_unlock(&q->sysfs_lock); > > > @@ -2869,6 +2880,9 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set, > > > if (!q->queue_hw_ctx) > > > goto err_sys_init; > > > + INIT_LIST_HEAD(&q->dead_hctx_list); > > > + spin_lock_init(&q->dead_hctx_lock); > > > + > > > blk_mq_realloc_hw_ctxs(set, q); > > > if (!q->nr_hw_queues) > > > goto err_hctxs; > > > diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h > > > index db29928de467..15d1aa53d96c 100644 > > > --- a/include/linux/blk-mq.h > > > +++ b/include/linux/blk-mq.h > > > @@ -70,6 +70,8 @@ struct blk_mq_hw_ctx { > > > struct dentry *sched_debugfs_dir; > > > #endif > > > + struct list_head hctx_list; > > > + > > > /* Must be the last member - see also blk_mq_hw_ctx_size(). */ > > > struct srcu_struct srcu[0]; > > > }; > > > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h > > > index 4b85dc066264..1325f941f0be 100644 > > > --- a/include/linux/blkdev.h > > > +++ b/include/linux/blkdev.h > > > @@ -535,6 +535,13 @@ struct request_queue { > > > struct mutex sysfs_lock; > > > + /* > > > + * for reusing dead hctx instance in case of updating > > > + * nr_hw_queues > > > + */ > > > + struct list_head dead_hctx_list; > > > + spinlock_t dead_hctx_lock; > > > + > > > atomic_t mq_freeze_depth; > > > #if defined(CONFIG_BLK_DEV_BSG) > > > > > Hmm. > > I don't particularly like this approach. > > The much saner approach would be to avoid having I/O in-flight in the first > > place by setting the queue to something else than live, no? > > There isn't any in-flight IO since blk_mq_freeze_queue() is returned > from __blk_mq_update_nr_hw_queues(). > > However, there can be reference to hctx in other code paths via > arbitrary block layer APIs. > > Quiesce can't avoid the use-after-free too given RCU read lock may > not be held in lots of reference to hctx, such as queue_for_each_hw_ctx(). > > So this patch might be the simplest approach to fix this issue, IMO. > > However, I am open to any solution for this issue. Hi Hannes, Could you please let us know if you have better idea for this issue? Otherwise, I think we need to move on since it is real issue, and users want to fix that. Thanks, Ming