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=-1.0 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 DC0DEC43387 for ; Thu, 20 Dec 2018 21:40:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AA3C4218FD for ; Thu, 20 Dec 2018 21:40:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731515AbeLTVkr (ORCPT ); Thu, 20 Dec 2018 16:40:47 -0500 Received: from mail-pg1-f171.google.com ([209.85.215.171]:46856 "EHLO mail-pg1-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728803AbeLTVkr (ORCPT ); Thu, 20 Dec 2018 16:40:47 -0500 Received: by mail-pg1-f171.google.com with SMTP id w7so1459485pgp.13 for ; Thu, 20 Dec 2018 13:40:45 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:message-id:subject:from:to:date:in-reply-to :references:mime-version:content-transfer-encoding; bh=yeQh7i8dbepu2C0Yz/QhSIjyws5hJYI37dpegN0P63g=; b=S4nhY29Hnx/hNFfSBwlRDqDcpd73CyZdYJu6BnbHml2Wvvm+qVcSnYEUY2pbKmQL0b Rp8/tNJfENnoJAqEbKc6E9snHxcD+bUQ9Im/fJwH2LZ5YgEujILopW9SB/BfxgkkLkCt rNuj4aeB2/j5GwoCl1YOJXIxrJP2ijXoKdFiRVzF7ReaChWAIRs814QEFEehZYyHdufN wi2McIWmeMuEgkU+pxWkZCUvGTtuuGiXJfRDZq0XfdjXJX71GhrtzlKnvJAzxnX8a+sv xlHQpFbFDZfYPXHKCO5fuForl/e0jyJdiTbrMi7Ozow1vYjBmQH4NtfVHkQX+gmaV4tC gdyA== X-Gm-Message-State: AA+aEWaDYmAdvThSnedHVqw8YKx61oeLeoeE4q4WBHJrQi/v3S72bRAm /wpH83wcwAEgDBjaenYvZSyqlA8VA0M= X-Google-Smtp-Source: AFSGD/X5GHN1I3orbXRi1IARhx0jN3/LVg6k37HpWjni10uVhoXvZltXyo8BjskOBuuEBG3UQpCa1Q== X-Received: by 2002:a62:de06:: with SMTP id h6mr26656842pfg.158.1545342045351; Thu, 20 Dec 2018 13:40:45 -0800 (PST) Received: from ?IPv6:2620:15c:2cd:203:5cdc:422c:7b28:ebb5? ([2620:15c:2cd:203:5cdc:422c:7b28:ebb5]) by smtp.gmail.com with ESMTPSA id c72sm21015611pfb.107.2018.12.20.13.40.44 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 20 Dec 2018 13:40:44 -0800 (PST) Message-ID: <1545342043.185366.523.camel@acm.org> Subject: Re: v4.20-rc6: Sporadic use-after-free in bt_iter() From: Bart Van Assche To: Jens Axboe , "jianchao.wang" , "linux-block@vger.kernel.org" Date: Thu, 20 Dec 2018 13:40:43 -0800 In-Reply-To: <61515137-0565-e3b7-e6de-554af7d49753@kernel.dk> References: <1545261885.185366.488.camel@acm.org> <74c0280c-e557-ad03-cd75-98dd6d868da3@kernel.dk> <1545265001.185366.496.camel@acm.org> <1ca5cd37-87ce-8cff-6cb4-1fdb29bd4da2@kernel.dk> <0560802f-efc0-e9ec-99f7-4bdbdbc234f8@oracle.com> <372d2960-ff0c-1135-28f9-23eea8670463@oracle.com> <6ae35005-7ba9-91e1-f315-d128f410c12c@kernel.dk> <1545328865.185366.508.camel@acm.org> <1545339362.185366.511.camel@acm.org> <1545340987.185366.515.camel@acm.org> <120bb59a-af93-7d8c-9afc-7087973632bf@kernel.dk> <1545341470.185366.519.camel@acm.org> <61515137-0565-e3b7-e6de-554af7d49753@kernel.dk> Content-Type: text/plain; charset="UTF-7" X-Mailer: Evolution 3.26.2-1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Thu, 2018-12-20 at 14:34 -0700, Jens Axboe wrote: +AD4 Yeah, I don't think it's bullet proof either, it just closes the gap. +AD4 I'm fine with fiddling with the tag iteration. On top of what I sent, we +AD4 could have tag iteration hold the RCU read lock, and then we just need +AD4 to ensure that the tags are freed with RCU. Do you mean using call+AF8-rcu() to free tags? Would that require to add a struct rcu+AF8-head to every request? Would it be acceptable to increase the size of struct request with an rcu+AF8-head? Additionally, could that reduce the queue depth if the time between grace periods is larger than the time between I/O submissions? Thanks, Bart.