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 27F6CC433E0 for ; Mon, 29 Jun 2020 21:15:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 035DC20724 for ; Mon, 29 Jun 2020 21:15:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593465356; bh=Jo8In8pOuQGqnMtj6T+n6gTtyibSKsc+LNmmeZu4R8w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=aBcsWmO8yiiVwa+mJFbKd4whh1UMLfoziFfaH0s8XjFHo3n8z30nc/0adstitHFwz 5TN3kjNsYO/Y/zUxcxqvaDT+erUsCXhuTDfBoIibIXp9SGe0PoSB/TbTqwyEe7sNrJ U99Ak5ZQwIt00GIwZdBKrNLzg97lHmKXfQdObKWM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390675AbgF2VPy (ORCPT ); Mon, 29 Jun 2020 17:15:54 -0400 Received: from mail.kernel.org ([198.145.29.99]:42454 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729955AbgF2SzQ (ORCPT ); Mon, 29 Jun 2020 14:55:16 -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 56A8525569; Mon, 29 Jun 2020 15:55:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593446128; bh=Jo8In8pOuQGqnMtj6T+n6gTtyibSKsc+LNmmeZu4R8w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=yMDGvTXD5gOJ0EloMKNQ64W8Jsh7qpZzyzFoSDCjJ4fRRD5k943hFmUoJKjjaYQMX jcXmiEuSXHOBG8KFXm+85RaMZh76PjJV7uH4g0HgCvgMiQOtxrmP3JuLJFxNpBI8zJ t+Rih80sOG2GrgqhqT9/cwnL4ImOUlLaMcGAZCJU= 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 Subject: [PATCH 4.4 119/135] blktrace: break out of blktrace setup on concurrent calls Date: Mon, 29 Jun 2020 11:52:53 -0400 Message-Id: <20200629155309.2495516-120-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200629155309.2495516-1-sashal@kernel.org> References: <20200629155309.2495516-1-sashal@kernel.org> MIME-Version: 1.0 X-KernelTest-Patch: http://kernel.org/pub/linux/kernel/v4.x/stable-review/patch-4.4.229-rc1.gz X-KernelTest-Tree: git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git X-KernelTest-Branch: linux-4.4.y X-KernelTest-Patches: git://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git X-KernelTest-Version: 4.4.229-rc1 X-KernelTest-Deadline: 2020-07-01T15:53+00:00 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 6737564680193..8ac3663e0012d 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