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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 A227CC4361B for ; Fri, 11 Dec 2020 19:16:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 62BB82405A for ; Fri, 11 Dec 2020 19:16:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2395286AbgLKReD (ORCPT ); Fri, 11 Dec 2020 12:34:03 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44854 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2395072AbgLKRdw (ORCPT ); Fri, 11 Dec 2020 12:33:52 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 33570C0613CF for ; Fri, 11 Dec 2020 09:33:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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; bh=PBIrwD1P7M5TNEvEysxG6boHsOMcDdQN593BPQ8Y0dQ=; b=aEoh0RYSgtERt+pIvEOSwE/ZiY B6eU4rWxBovW2vkY8to/gYLLRpRaBsdayWU5donmhfytziLGEtjceuIgWw9eZBG6yy3Aub7wV7eQ0 nKPuSBuI6+Bo84cONLPUjih2Jh6BeKLvnYRjEX0aT5LwXYaO6p+fGhzCZgoVOv8vkYdCgE/sguFH7 PRAjJ5fShZelvCxq0RmLJ3PTlX9KnO3qQnJHfUnT7iQggIiNQcp8iHHRSrk5mqxL29hgjaGXMRSQe FHk4NLtDqVNxmC7saimJewYfmNuWMIPHL3gppAbtEnk6VJShlPf2rKmyUUwiV4UzTZnbtQavutqu2 +VoDD1+w==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1knmHy-00072b-2f; Fri, 11 Dec 2020 17:33:06 +0000 Date: Fri, 11 Dec 2020 17:33:05 +0000 From: Matthew Wilcox To: Jens Axboe Cc: Al Viro , Linus Torvalds , linux-fsdevel Subject: Re: [PATCH 1/2] fs: add support for LOOKUP_NONBLOCK Message-ID: <20201211173305.GB2443@casper.infradead.org> References: <20201210200114.525026-1-axboe@kernel.dk> <20201210200114.525026-2-axboe@kernel.dk> <139ecda1-bb08-b1f2-655f-eeb9976e8cff@kernel.dk> <20201211024553.GW3579531@ZenIV.linux.org.uk> <89f96b42-9d58-cd46-e157-758e91269d89@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <89f96b42-9d58-cd46-e157-758e91269d89@kernel.dk> Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Fri, Dec 11, 2020 at 09:05:26AM -0700, Jens Axboe wrote: > On 12/10/20 7:45 PM, Al Viro wrote: > > So how hard are your "we don't want to block here" requirements? Because > > the stuff you do after complete_walk() can easily be much longer than > > everything else. > > Ideally it'd extend a bit beyond the RCU lookup, as things like proc > resolution will still fail with the proposed patch. But that's not a > huge deal to me, I consider the dentry lookup to be Good Enough. FWIW, /proc/$pid always falls back to REF walks. Here's a patch from one of my colleagues that aims to fix that. https://lore.kernel.org/linux-fsdevel/20201204000212.773032-1-stephen.s.brennan@oracle.com/ Maybe you had one of the other parts of /proc in mind?