From patchwork Mon Dec 18 15:11:39 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeff Layton X-Patchwork-Id: 10120141 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 09A5960390 for ; Mon, 18 Dec 2017 15:26:00 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id EFFF028502 for ; Mon, 18 Dec 2017 15:25:59 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id E439D2842A; Mon, 18 Dec 2017 15:25:59 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7A1D02842A for ; Mon, 18 Dec 2017 15:25:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932541AbdLRPZl (ORCPT ); Mon, 18 Dec 2017 10:25:41 -0500 Received: from mail.kernel.org ([198.145.29.99]:54832 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758053AbdLRPMG (ORCPT ); Mon, 18 Dec 2017 10:12:06 -0500 Received: from tleilax.poochiereds.net (cpe-71-70-156-158.nc.res.rr.com [71.70.156.158]) (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 46D70218B0; Mon, 18 Dec 2017 15:12:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 46D70218B0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=jlayton@kernel.org From: Jeff Layton To: linux-fsdevel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk, linux-nfs@vger.kernel.org, bfields@fieldses.org, neilb@suse.de, jack@suse.de, linux-ext4@vger.kernel.org, tytso@mit.edu, adilger.kernel@dilger.ca, linux-xfs@vger.kernel.org, darrick.wong@oracle.com, david@fromorbit.com, linux-btrfs@vger.kernel.org, clm@fb.com, jbacik@fb.com, dsterba@suse.com, linux-integrity@vger.kernel.org, zohar@linux.vnet.ibm.com, dmitry.kasatkin@gmail.com, linux-afs@lists.infradead.org, dhowells@redhat.com, jaltman@auristor.com Subject: [PATCH v3 02/19] fs: don't take the i_lock in inode_inc_iversion Date: Mon, 18 Dec 2017 10:11:39 -0500 Message-Id: <20171218151156.14565-3-jlayton@kernel.org> X-Mailer: git-send-email 2.14.3 In-Reply-To: <20171218151156.14565-1-jlayton@kernel.org> References: <20171218151156.14565-1-jlayton@kernel.org> Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Jeff Layton The rationale for taking the i_lock when incrementing this value is lost in antiquity. The readers of the field don't take it (at least not universally), so my assumption is that it was only done here to serialize incrementors. If that is indeed the case, then we can drop the i_lock from this codepath and treat it as a atomic64_t for the purposes of incrementing it. This allows us to use inode_inc_iversion without any danger of lock inversion. Note that the read side is not fetched atomically with this change. The assumption here is that that is not a critical issue since the i_version is not fully synchronized with anything else anyway. Signed-off-by: Jeff Layton --- include/linux/iversion.h | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/include/linux/iversion.h b/include/linux/iversion.h index bb50d27c71f9..e08c634779df 100644 --- a/include/linux/iversion.h +++ b/include/linux/iversion.h @@ -104,12 +104,13 @@ inode_set_iversion_queried(struct inode *inode, const u64 new) static inline bool inode_maybe_inc_iversion(struct inode *inode, bool force) { - spin_lock(&inode->i_lock); - inode->i_version++; - spin_unlock(&inode->i_lock); + atomic64_t *ivp = (atomic64_t *)&inode->i_version; + + atomic64_inc(ivp); return true; } + /** * inode_inc_iversion - forcibly increment i_version * @inode: inode that needs to be updated