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=-2.2 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 8D272C67839 for ; Tue, 11 Dec 2018 18:53:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5597020870 for ; Tue, 11 Dec 2018 18:53:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Bt1Ufs1r" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5597020870 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org 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 S1726852AbeLKSxP (ORCPT ); Tue, 11 Dec 2018 13:53:15 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:38588 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726313AbeLKSxN (ORCPT ); Tue, 11 Dec 2018 13:53:13 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=nw6gn98kOeoOvbqz55rm/FYxZbQcsNmtwlPp0QYTMl8=; b=Bt1Ufs1rGUuKuPX9FPPhRGAjk ATyCVLwMga5rmHuaH3ToIWqHw2EpfccHAi6YE1i6GKsGHi67nP1i7Z6xc5C7Jrow1gJc6lJz7AmnG +b3OFSsw6pqOGo80O+pa0NAlfn60UDsLHzkUatuNRh/Aggv7S5uSTzQUEk+Ya5ia2B/I1H0iH6C2Y LaQWwDgUdK1ToURhs21I8ahduzDwZlirQzJ69JCkrfeuJrtrfNhPgZtTjzENsDMiTU6a4YREvijcl gygc4YnAN6s1/BfdP2KcED2q2EeLelAoxqzdYvQg5gcx5mwnHZtkMg7Zp7hx2oyT/x58NU2u3Lw/t NjNJOUZhg==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1gWn9b-0000ti-MW; Tue, 11 Dec 2018 18:53:11 +0000 Date: Tue, 11 Dec 2018 10:53:11 -0800 From: Matthew Wilcox To: Jens Axboe Cc: Al Viro , Benjamin LaHaise , Andrew Morton , Kees Cook , fsdevel , linux-aio@kvack.org, linux-mm , linux-kernel , Dan Carpenter Subject: Re: [PATCH] aio: Convert ioctx_table to XArray Message-ID: <20181211185311.GJ6830@bombadil.infradead.org> References: <20181128183531.5139-1-willy@infradead.org> <09e3d156-66fc-ca17-efac-63f080a27a1d@kernel.dk> <20181211184553.GH6830@bombadil.infradead.org> <75267003-9407-101f-33ee-685e345a2c8a@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <75267003-9407-101f-33ee-685e345a2c8a@kernel.dk> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 11, 2018 at 11:46:53AM -0700, Jens Axboe wrote: > On 12/11/18 11:45 AM, Matthew Wilcox wrote: > > 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? I've been considering adding it to the API, yes. I was under the impression that nested rcu_read_lock() calls were not expensive, even with CONFIG_PREEMPT.