From patchwork Sat May 9 03:10:57 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Luis Chamberlain X-Patchwork-Id: 11537929 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 081BE1668 for ; Sat, 9 May 2020 03:11:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E4B4B24953 for ; Sat, 9 May 2020 03:11:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588993869; bh=mumtTjnBXpPOJDvplILVq74Ll9gZyOnf4d7uCmTHZL8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=PCa9+4lIOk4x7+FdLsb5fqr2GbweGzQZZfXbDGXvrmCkdOFoUKLilpQSCVMxg2Mcy 9S5kFyXFuK6xSf0niMzYFRS1A1q/pka48AvEgemqpve68AVim+OkEGeZnlwX96axkO F7TJuUG+Era+/smAEG/qStSHpzSOMzwEQ3fQfDXI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728739AbgEIDLG (ORCPT ); Fri, 8 May 2020 23:11:06 -0400 Received: from mail-pf1-f194.google.com ([209.85.210.194]:42350 "EHLO mail-pf1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728714AbgEIDLD (ORCPT ); Fri, 8 May 2020 23:11:03 -0400 Received: by mail-pf1-f194.google.com with SMTP id f7so1983634pfa.9; Fri, 08 May 2020 20:11:03 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=cEK33y5M3evHk3zepZBRBq1zuAEKJAta0bGSZcp5I7U=; b=P2MMSNtH09kHBsfo9hEs/+6n8k/UR8fx/+4he9p+vl1kfCZOEQAghgyjGgkzYXH+5E HElIJqtCpOuwB61c+GewMyswsUFwBAUCtvv5Aeq+Oz6BZinoYc1IQcmud5RQsOfZ+VT7 EN7uQBp2EhLxzB2Cpb3LZmVVRwHrSA7QfSPvmuxJoghJr8+SD/0WIzofgJTVPglH7KTa 5oeeDsNQThlLijuu0ezNJ3diYzlH4cukZRKISP69yFbAdk3uNSaNFwe1uP0jprTujjNr D1BQkJDrMBQVrwc+qF3Tj8ZkbYhW80W8Icowji4ftAnPnruuXyyo588NGDc3lBbZBpXE x9Lw== X-Gm-Message-State: AGi0PuY/uTbcihKn7NwY6cssG08fbE/DLCrrJjV2rnf/PtM62hR3JWOF xQnQ/CvJjICz3Qh5J89PWQc= X-Google-Smtp-Source: APiQypLJMN/211bTPotanM4jUsK4k4pu+kicwA68ZAITFqqfkEyvZgoqNiyBViyjSN8+owsWBeCmNA== X-Received: by 2002:a62:6545:: with SMTP id z66mr5765485pfb.87.1588993863018; Fri, 08 May 2020 20:11:03 -0700 (PDT) Received: from 42.do-not-panic.com (42.do-not-panic.com. [157.230.128.187]) by smtp.gmail.com with ESMTPSA id k186sm2518635pga.94.2020.05.08.20.11.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 08 May 2020 20:11:00 -0700 (PDT) Received: by 42.do-not-panic.com (Postfix, from userid 1000) id 0657241D67; Sat, 9 May 2020 03:11:00 +0000 (UTC) From: Luis Chamberlain To: axboe@kernel.dk, viro@zeniv.linux.org.uk, bvanassche@acm.org, gregkh@linuxfoundation.org, rostedt@goodmis.org, mingo@redhat.com, jack@suse.cz, ming.lei@redhat.com, nstange@suse.de, akpm@linux-foundation.org Cc: mhocko@suse.com, yukuai3@huawei.com, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Luis Chamberlain Subject: [PATCH v4 4/5] blktrace: break out of blktrace setup on concurrent calls Date: Sat, 9 May 2020 03:10:57 +0000 Message-Id: <20200509031058.8239-5-mcgrof@kernel.org> X-Mailer: git-send-email 2.23.0.rc1 In-Reply-To: <20200509031058.8239-1-mcgrof@kernel.org> References: <20200509031058.8239-1-mcgrof@kernel.org> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org 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 --- kernel/trace/blktrace.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c index 6c10a1427de2..bd5ec2184d46 100644 --- a/kernel/trace/blktrace.c +++ b/kernel/trace/blktrace.c @@ -3,6 +3,9 @@ * Copyright (C) 2006 Jens Axboe * */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + #include #include #include @@ -493,6 +496,12 @@ static int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev, */ strreplace(buts->name, '/', '_'); + 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;