From patchwork Fri Jan 12 16:03:52 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mike Snitzer X-Patchwork-Id: 10161297 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 611E2602B3 for ; Fri, 12 Jan 2018 16:04:11 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 51344289CD for ; Fri, 12 Jan 2018 16:04:11 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 45F50289D0; Fri, 12 Jan 2018 16:04:11 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id DC7D3289CD for ; Fri, 12 Jan 2018 16:04:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934011AbeALQEJ (ORCPT ); Fri, 12 Jan 2018 11:04:09 -0500 Received: from mx1.redhat.com ([209.132.183.28]:53704 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934004AbeALQEJ (ORCPT ); Fri, 12 Jan 2018 11:04:09 -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 5330F4FCCA; Fri, 12 Jan 2018 16:04:04 +0000 (UTC) Received: from localhost (ovpn-112-12.rdu2.redhat.com [10.10.112.12]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 68F984CE; Fri, 12 Jan 2018 16:03:54 +0000 (UTC) Date: Fri, 12 Jan 2018 11:03:52 -0500 From: Mike Snitzer To: axboe@kernel.dk Cc: David Jeffery , Ming Lei , linux-block@vger.kernel.org, dm-devel@redhat.com, Bart.VanAssche@wdc.com Subject: [for-4.16 PATCH v6 2/4] block: properly protect the 'queue' kobj in blk_unregister_queue Message-ID: <20180112160352.GA6270@redhat.com> References: <20180112150606.6037-1-snitzer@redhat.com> <20180112150606.6037-3-snitzer@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20180112150606.6037-3-snitzer@redhat.com> User-Agent: Mutt/1.5.23 (2014-03-12) 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 [10.5.110.30]); Fri, 12 Jan 2018 16:04:09 +0000 (UTC) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP The original commit e9a823fb34a8b (block: fix warning when I/O elevator is changed as request_queue is being removed) is pretty conflated. "conflated" because the resource being protected by q->sysfs_lock isn't the queue_flags (it is the 'queue' kobj). q->sysfs_lock serializes __elevator_change() (via elv_iosched_store) from racing with blk_unregister_queue(): 1) By holding q->sysfs_lock first, __elevator_change() can complete before a racing blk_unregister_queue(). 2) Conversely, __elevator_change() is testing for QUEUE_FLAG_REGISTERED in case elv_iosched_store() loses the race with blk_unregister_queue(), it needs a way to know the 'queue' kobj isn't there. Expand the scope of blk_unregister_queue()'s q->sysfs_lock use so it is held until after the 'queue' kobj is removed. To do so blk_mq_unregister_dev() must not also take q->sysfs_lock. So rename __blk_mq_unregister_dev() to blk_mq_unregister_dev(). Also, blk_unregister_queue() should use q->queue_lock to protect against any concurrent writes to q->queue_flags -- even though chances are the queue is being cleaned up so no concurrent writes are likely. Fixes: e9a823fb34a8b ("block: fix warning when I/O elevator is changed as request_queue is being removed") Signed-off-by: Mike Snitzer Reviewed-by: Ming Lei --- block/blk-mq-sysfs.c | 9 +-------- block/blk-sysfs.c | 13 ++++++++++--- 2 files changed, 11 insertions(+), 11 deletions(-) v6: blk_mq_unregister_dev now requires q->sysfs_lock be held, Ming: I am not seeing any lockdep complaints with this. I've tested bio-based, blk-mq and old .request_fn request-based. diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c index 79969c3c234f..a54b4b070f1c 100644 --- a/block/blk-mq-sysfs.c +++ b/block/blk-mq-sysfs.c @@ -248,7 +248,7 @@ static int blk_mq_register_hctx(struct blk_mq_hw_ctx *hctx) return ret; } -static void __blk_mq_unregister_dev(struct device *dev, struct request_queue *q) +void blk_mq_unregister_dev(struct device *dev, struct request_queue *q) { struct blk_mq_hw_ctx *hctx; int i; @@ -265,13 +265,6 @@ static void __blk_mq_unregister_dev(struct device *dev, struct request_queue *q) q->mq_sysfs_init_done = false; } -void blk_mq_unregister_dev(struct device *dev, struct request_queue *q) -{ - mutex_lock(&q->sysfs_lock); - __blk_mq_unregister_dev(dev, q); - mutex_unlock(&q->sysfs_lock); -} - void blk_mq_hctx_kobj_init(struct blk_mq_hw_ctx *hctx) { kobject_init(&hctx->kobj, &blk_mq_hw_ktype); diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index 870484eaed1f..9272452ff456 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -929,12 +929,17 @@ void blk_unregister_queue(struct gendisk *disk) if (WARN_ON(!q)) return; + /* + * Protect against the 'queue' kobj being accessed + * while/after it is removed. + */ mutex_lock(&q->sysfs_lock); - queue_flag_clear_unlocked(QUEUE_FLAG_REGISTERED, q); - mutex_unlock(&q->sysfs_lock); - wbt_exit(q); + spin_lock_irq(q->queue_lock); + queue_flag_clear(QUEUE_FLAG_REGISTERED, q); + spin_unlock_irq(q->queue_lock); + wbt_exit(q); if (q->mq_ops) blk_mq_unregister_dev(disk_to_dev(disk), q); @@ -946,4 +951,6 @@ void blk_unregister_queue(struct gendisk *disk) kobject_del(&q->kobj); blk_trace_remove_sysfs(disk_to_dev(disk)); kobject_put(&disk_to_dev(disk)->kobj); + + mutex_unlock(&q->sysfs_lock); }