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=-0.9 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED 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 C0675C5CFFE for ; Tue, 11 Dec 2018 18:46:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 871422087F for ; Tue, 11 Dec 2018 18:46:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="am/aK0qw" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 871422087F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.dk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726578AbeLKSq5 (ORCPT ); Tue, 11 Dec 2018 13:46:57 -0500 Received: from mail-io1-f65.google.com ([209.85.166.65]:40277 "EHLO mail-io1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726350AbeLKSq5 (ORCPT ); Tue, 11 Dec 2018 13:46:57 -0500 Received: by mail-io1-f65.google.com with SMTP id n9so12654992ioh.7 for ; Tue, 11 Dec 2018 10:46:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=1UuBn7QfyEgJbYlSxhHcHzu7EKmlGeFsx2YSV3KduyU=; b=am/aK0qwK9lkkiGz2gZPI/63RPPFjOnbTILx/zcBPnD04kevu5HzAQtZhXR67t/hlL fQVo3ino7+V6QfWST5fKV6mAyuN7OtH7+WFpc5RRwz6f4EwX9Zbkp8acR8dH1XJDVeVp 9byf8Fiba//RB4fJrcdyvAPMbhyUgS5j2rfAy0GtX1zibAqK7GM4zktkSW2jWl2UGXWu 2gywk/jCzLi3y1/waYjbP8NkyMeE7siEO/MjIYURjFj4s54VIpSNsuI2ac7BOAaLFbty GollSctKboxXsbsK7K0Rc65mTaTMOnmScXkovm2woE909ioq8/bFYnwnc6TG2KZTnVvX sR2Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=1UuBn7QfyEgJbYlSxhHcHzu7EKmlGeFsx2YSV3KduyU=; b=K2fauf5I16lu3iQJ4M5AoVObEsNx8H6fMWnFzuoHloMNPZPMhpIOELS96XpuM1Xbtr vLqTG+Wag44pwipyEeJ8Dnoye7R75GqXK7hbs/qkVcvhPr/JSBAkDS8jkLQhCauWl0OH wxfSnQw0xnmdsXGX6mnNcsnJqlLkx+/V+7N+Vke327avVufWslAYwiXELPIpA0v0T82N qk9HGM0g4lBClq+ber9osehHN9GTIZUuvQOX5/006k5qVNlesAkqEnp5ETB7Ugbknruk ZFCjgISedz5zWddQ2CDIFPaCO+MS/x+0rc9B50lvrqwOoRX+TGHYoFCjyynPNjPapv49 ht+Q== X-Gm-Message-State: AA+aEWZRBLH2BHuwIeaZsXbghvfj58cz15xsji6Q5vA02B6ZZ1xxniWx tqQCFFb3nc89u/HOyLXhj//FdA== X-Google-Smtp-Source: AFSGD/UYgXFWZLhyD6Ck/WfUsXGKxf/PbYGsZQKvEQDf6ScWH30CNHv9N5txbNyz8ZJNtUdzP7j7lg== X-Received: by 2002:a5e:8618:: with SMTP id z24mr5593023ioj.35.1544554015966; Tue, 11 Dec 2018 10:46:55 -0800 (PST) Received: from [192.168.1.56] ([216.160.245.98]) by smtp.gmail.com with ESMTPSA id r85sm5943022iod.13.2018.12.11.10.46.54 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 11 Dec 2018 10:46:55 -0800 (PST) Subject: Re: [PATCH] aio: Convert ioctx_table to XArray To: Matthew Wilcox Cc: Al Viro , Benjamin LaHaise , Andrew Morton , Kees Cook , fsdevel , linux-aio@kvack.org, linux-mm , linux-kernel , Dan Carpenter References: <20181128183531.5139-1-willy@infradead.org> <09e3d156-66fc-ca17-efac-63f080a27a1d@kernel.dk> <20181211184553.GH6830@bombadil.infradead.org> From: Jens Axboe Message-ID: <75267003-9407-101f-33ee-685e345a2c8a@kernel.dk> Date: Tue, 11 Dec 2018 11:46:53 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20181211184553.GH6830@bombadil.infradead.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/11/18 11:45 AM, Matthew Wilcox wrote: > On Tue, Dec 11, 2018 at 11:41:55AM -0700, Jens Axboe wrote: >> On Wed, Nov 28, 2018 at 11:35 AM Matthew Wilcox wrote: >>> >>> rcu_read_lock(); >>> - table = rcu_dereference(mm->ioctx_table); >>> - >>> - if (!table || id >= table->nr) >>> - goto out; >>> - >>> - ctx = rcu_dereference(table->table[id]); >>> + ctx = xa_load(&mm->ioctx, id); >>> if (ctx && ctx->user_id == ctx_id) { >>> if (percpu_ref_tryget_live(&ctx->users)) >>> ret = ctx; >>> } >> >> Question on this part - do we need that RCU read lock around this now? I >> don't think we do. > > I think we need the rcu read lock here to prevent ctx from being freed > under us by free_ioctx(). Then that begs the question, how about __xa_load() that is already called under RCU read lock? -- Jens Axboe