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=-0.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=unavailable 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 AC5E9C282CE for ; Wed, 10 Apr 2019 23:15:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 72CEC217D9 for ; Wed, 10 Apr 2019 23:15:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554938152; bh=1gxdAOnNojCmWwSJ0r0v7Nz8pxGPPrn4uqvTyWoyzj0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=rix01YvRH9d7vofkeUAArm99Xchbdh8D/C86Z5DczfzNP5Y9wi6jlzTBU9t5gy5Fm ZcQI4xignAbIDmudg9pqMLFtRKO4nbvt6ssr1XRkDjaEdFsLh2FB+C6Mdhi/BshZz+ ShIBelhmuskscnsFhTrKnvRnravS5wPi65Q56+ds= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726870AbfDJXPv (ORCPT ); Wed, 10 Apr 2019 19:15:51 -0400 Received: from mail.kernel.org ([198.145.29.99]:53580 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726713AbfDJXPu (ORCPT ); Wed, 10 Apr 2019 19:15:50 -0400 Received: from gmail.com (unknown [104.132.1.77]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 7E03D20820; Wed, 10 Apr 2019 23:15:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554938149; bh=1gxdAOnNojCmWwSJ0r0v7Nz8pxGPPrn4uqvTyWoyzj0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=OxyQkFX684C7eZmJwptSahUQ6Wbb6ZK4wZtvbcsutr0tFJjQ/W8lk55uWFGIghziA C8nWLHF5D1l4fg/KzPfKa/PAFmoGv/Mmp3WmNrsh7YmxX7JuXi0IK40U5AUltPI0oR 8+A435xGUwMS1PsigLo/PgxVTeG454qdYDNzEVhk= Date: Wed, 10 Apr 2019 16:15:48 -0700 From: Eric Biggers To: Al Viro Cc: linux-fscrypt@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org Subject: Re: [PATCH v2 1/2] vfs: use READ_ONCE() to access ->i_link Message-ID: <20190410231547.GC120258@gmail.com> References: <20190410202115.64501-1-ebiggers@kernel.org> <20190410202115.64501-2-ebiggers@kernel.org> <20190410210657.GA2217@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190410210657.GA2217@ZenIV.linux.org.uk> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, Apr 10, 2019 at 10:06:57PM +0100, Al Viro wrote: > On Wed, Apr 10, 2019 at 01:21:14PM -0700, Eric Biggers wrote: > > From: Eric Biggers > > > > Use 'READ_ONCE(inode->i_link)' to explicitly support filesystems caching > > the symlink target in ->i_link later if it was unavailable at iget() > > time, or wasn't easily available. I'll be doing this in fscrypt, to > > improve the performance of encrypted symlinks on ext4, f2fs, and ubifs. > > > > ->i_link will start NULL and may later be set to a non-NULL value by a > > smp_store_release() or cmpxchg_release(). READ_ONCE() is needed on the > > read side. smp_load_acquire() is unnecessary because only a data > > dependency barrier is required. (Thanks to Al for pointing this out.) > > You've missed vfs_readlink()... How so? The patch already updates vfs_readlink(). - Eric