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,URIBL_BLOCKED, 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 21CBCC5CFFE for ; Tue, 11 Dec 2018 18:45:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DA6EA20811 for ; Tue, 11 Dec 2018 18:45:57 +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="ZcblGBm/" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DA6EA20811 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 S1726637AbeLKSp4 (ORCPT ); Tue, 11 Dec 2018 13:45:56 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:34808 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726252AbeLKSp4 (ORCPT ); Tue, 11 Dec 2018 13:45:56 -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=OFsjesJxwe0Vvh/qsKmn4MXZMHYRnB7GtkkpOsO61XI=; b=ZcblGBm/Tk8pwHw5+ww7dWvIO 7rcL1m1gTmUPj9rERTMhZl++9JL4OqEX9uclu5Y5OoyXLfVlNPcBZ2xGQ9cy+xIuKvMAjKwBssqnc F0Cc28AwPe0liA4rjsDnQv04lEu3DbbcrKvNorM/+SksGl93+bQMuD8XWNNOCqUljBW+8xd3lsU43 9TzaQvY6YSjDP1D5GOQzCWtXKcrA92p3V5em2j1ZXchfyE9VRB2shRhNk4iJ581x3JhToiuhT9Asu bq/R7ZYRSq4H/SbpAJVNNYn3rEth3OPdiKNhTri6fczikfxRQUbuwH6arXvglHV7dDNNN4iVfrflJ masn1Uh+A==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1gWn2X-00073W-SE; Tue, 11 Dec 2018 18:45:53 +0000 Date: Tue, 11 Dec 2018 10:45:53 -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: <20181211184553.GH6830@bombadil.infradead.org> References: <20181128183531.5139-1-willy@infradead.org> <09e3d156-66fc-ca17-efac-63f080a27a1d@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <09e3d156-66fc-ca17-efac-63f080a27a1d@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 11:41:55AM -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().