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=-15.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 D57B6C433DF for ; Tue, 23 Jun 2020 17:37:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AD37920781 for ; Tue, 23 Jun 2020 17:37:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592933840; bh=pF3pWv/GOcDxOoaEshP3nh+jd3va/7b8gr2M0p5wcCY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=DKvkQEBM3GS//ImNbyJpQVeSv2ZjxyBgND6QY+vIDJhPnzQ/DKxXMVIlJ4EH0tk0u IvofqjBtiQJ/fJWdOBmzO41JnmQ63mZX1iAN4Yl8nqtXXyQPeZTzyqWfmBkBKtw91C 9jsudzOUrKtZcA8q4mAGLd/sepPaE9XFvZn72nQ8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387788AbgFWRhT (ORCPT ); Tue, 23 Jun 2020 13:37:19 -0400 Received: from mail.kernel.org ([198.145.29.99]:34872 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387740AbgFWRhH (ORCPT ); Tue, 23 Jun 2020 13:37:07 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2F77E20706; Tue, 23 Jun 2020 17:37:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592933826; bh=pF3pWv/GOcDxOoaEshP3nh+jd3va/7b8gr2M0p5wcCY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=yU+ZncpjrKRCNfILpNzw+Fe6/Yp0Elzd74GXV1aGshpF05xSuALgzghPk8b9mj/ko wQnaGO3X+BgJpDbN6+q1hkYcnLC4uIfCqbTCFwWVuq9/pCLDQwbPVBQhuVwFTZA0EB crZMliUgX3J10p2x8Qn5gtA/8FD67AUAO5kaE618= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Luis Chamberlain , Jan Kara , Bart Van Assche , Christoph Hellwig , Jens Axboe , Sasha Levin , linux-block@vger.kernel.org Subject: [PATCH AUTOSEL 4.9 6/6] blktrace: break out of blktrace setup on concurrent calls Date: Tue, 23 Jun 2020 13:36:58 -0400 Message-Id: <20200623173658.1356241-6-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200623173658.1356241-1-sashal@kernel.org> References: <20200623173658.1356241-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Luis Chamberlain [ Upstream commit 1b0b283648163dae2a214ca28ed5a99f62a77319 ] We use one blktrace per request_queue, that means one per the entire disk. So we cannot run one blktrace on say /dev/vda and then /dev/vda1, or just two calls on /dev/vda. We check for concurrent setup only at the very end of the blktrace setup though. If we try to run two concurrent blktraces on the same block device the second one will fail, and the first one seems to go on. However when one tries to kill the first one one will see things like this: The kernel will show these: ``` debugfs: File 'dropped' in directory 'nvme1n1' already present! debugfs: File 'msg' in directory 'nvme1n1' already present! debugfs: File 'trace0' in directory 'nvme1n1' already present! `` And userspace just sees this error message for the second call: ``` blktrace /dev/nvme1n1 BLKTRACESETUP(2) /dev/nvme1n1 failed: 5/Input/output error ``` The first userspace process #1 will also claim that the files were taken underneath their nose as well. The files are taken away form the first process given that when the second blktrace fails, it will follow up with a BLKTRACESTOP and BLKTRACETEARDOWN. This means that even if go-happy process #1 is waiting for blktrace data, we *have* been asked to take teardown the blktrace. This can easily be reproduced with break-blktrace [0] run_0005.sh test. Just break out early if we know we're already going to fail, this will prevent trying to create the files all over again, which we know still exist. [0] https://github.com/mcgrof/break-blktrace Signed-off-by: Luis Chamberlain Signed-off-by: Jan Kara Reviewed-by: Bart Van Assche Reviewed-by: Christoph Hellwig Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- kernel/trace/blktrace.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c index 6d3b432a748a6..88eb9261c7b5c 100644 --- a/kernel/trace/blktrace.c +++ b/kernel/trace/blktrace.c @@ -15,6 +15,9 @@ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA * */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + #include #include #include @@ -481,6 +484,16 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev, */ strreplace(buts->name, '/', '_'); + /* + * bdev can be NULL, as with scsi-generic, this is a helpful as + * we can be. + */ + if (q->blk_trace) { + pr_warn("Concurrent blktraces are not allowed on %s\n", + buts->name); + return -EBUSY; + } + bt = kzalloc(sizeof(*bt), GFP_KERNEL); if (!bt) return -ENOMEM; -- 2.25.1