From patchwork Thu May 30 03:02:08 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 10968081 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 4526F92A for ; Thu, 30 May 2019 03:13:26 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 31DC528A26 for ; Thu, 30 May 2019 03:13:26 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 2403C28A46; Thu, 30 May 2019 03:13:26 +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=-7.9 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,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 9EB6F28A26 for ; Thu, 30 May 2019 03:13:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729441AbfE3DNZ (ORCPT ); Wed, 29 May 2019 23:13:25 -0400 Received: from mail.kernel.org ([198.145.29.99]:58448 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729426AbfE3DNY (ORCPT ); Wed, 29 May 2019 23:13:24 -0400 Received: from localhost (ip67-88-213-2.z213-88-67.customer.algx.net [67.88.213.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 306E623D14; Thu, 30 May 2019 03:13:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559186003; bh=/27MC/24vy0pzlQ1bxrg2WEVvYdYFBSyYBq0wfcmfUc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dy2mbto3EfvGjw8SNcvX6OkaAf3S63Q4DKdbzKEJVIBq88Ykz1uGJpuFmNLhNXQIE VL/OBed8ujaSBxiFIOMF7oERee+GAT9ckERP0T6AeD3k+NQBwzkMsLPnXBGLMY5p7n YUtEFD5w8xSflD47fpAlvtK4lDSrEIPOOkz0VjFg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dongli Zhang , James Smart , Bart Van Assche , Ming Lei , Jens Axboe , Sasha Levin , linux-scsi@vger.kernel.org, "Martin K . Petersen" , Christoph Hellwig , "James E . J . Bottomley" Subject: [PATCH 5.0 055/346] blk-mq: grab .q_usage_counter when queuing request from plug code path Date: Wed, 29 May 2019 20:02:08 -0700 Message-Id: <20190530030543.736817542@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190530030540.363386121@linuxfoundation.org> References: <20190530030540.363386121@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP [ Upstream commit e87eb301bee183d82bb3d04bd71b6660889a2588 ] 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. blk_freeze_queue() works with blk_sync_queue() together for avoiding race between cleanup queue and IO submission, given async run queue activities are canceled because hctx->run_work is scheduled with the refcount held, so it is fine to not hold the refcount when running the run queue work function for dispatch IO. 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 because the queue's kobject refcount isn't guaranteed to be grabbed in flushing plug list context, then kernel oops is triggered, see the following race: blk_mq_flush_plug_list(): blk_mq_sched_insert_requests() insert requests to sw queue or scheduler queue blk_mq_run_hw_queue Because of concurrent run queue, all requests inserted above may be completed before calling the above blk_mq_run_hw_queue. Then queue can be freed during the above blk_mq_run_hw_queue(). 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: linux-scsi@vger.kernel.org, Cc: Martin K . Petersen , Cc: Christoph Hellwig , Cc: James E . J . Bottomley , Reviewed-by: Bart Van Assche Tested-by: James Smart Signed-off-by: Ming Lei Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- block/blk-mq-sched.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c index 0c98b6c1ca49c..1213556a20dad 100644 --- a/block/blk-mq-sched.c +++ b/block/blk-mq-sched.c @@ -413,6 +413,14 @@ void blk_mq_sched_insert_requests(struct blk_mq_hw_ctx *hctx, struct list_head *list, bool run_queue_async) { struct elevator_queue *e; + struct request_queue *q = hctx->queue; + + /* + * blk_mq_sched_insert_requests() is called from flush plug + * context only, and hold one usage counter to prevent queue + * from being released. + */ + percpu_ref_get(&q->q_usage_counter); e = hctx->queue->elevator; if (e && e->type->ops.insert_requests) @@ -426,12 +434,14 @@ void blk_mq_sched_insert_requests(struct blk_mq_hw_ctx *hctx, if (!hctx->dispatch_busy && !e && !run_queue_async) { blk_mq_try_issue_list_directly(hctx, list); if (list_empty(list)) - return; + goto out; } blk_mq_insert_requests(hctx, ctx, list); } blk_mq_run_hw_queue(hctx, run_queue_async); + out: + percpu_ref_put(&q->q_usage_counter); } static void blk_mq_sched_free_tags(struct blk_mq_tag_set *set,