From patchwork Tue Jan 9 14:10:42 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeff Layton X-Patchwork-Id: 10152363 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 C1925603ED for ; Tue, 9 Jan 2018 14:21:22 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B5DCB2854A for ; Tue, 9 Jan 2018 14:21:22 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B40E228A4A; Tue, 9 Jan 2018 14:21:22 +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 566DD28A03 for ; Tue, 9 Jan 2018 14:21:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754192AbeAIOUk (ORCPT ); Tue, 9 Jan 2018 09:20:40 -0500 Received: from mail.kernel.org ([198.145.29.99]:41964 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756347AbeAIOLJ (ORCPT ); Tue, 9 Jan 2018 09:11:09 -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 C27932173D; Tue, 9 Jan 2018 14:11:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C27932173D 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, krzk@kernel.org Subject: [PATCH v5 02/19] fs: don't take the i_lock in inode_inc_iversion Date: Tue, 9 Jan 2018 09:10:42 -0500 Message-Id: <20180109141059.25929-3-jlayton@kernel.org> X-Mailer: git-send-email 2.14.3 In-Reply-To: <20180109141059.25929-1-jlayton@kernel.org> References: <20180109141059.25929-1-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 Reviewed-by: Jan Kara --- 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 d09cc3a08740..5ad9eaa3a9b0 100644 --- a/include/linux/iversion.h +++ b/include/linux/iversion.h @@ -104,12 +104,13 @@ inode_set_iversion_queried(struct inode *inode, 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