From: Jeff Layton Subject: Re: [PATCH v4 19/19] fs: handle inode->i_version more efficiently Date: Mon, 08 Jan 2018 08:46:24 -0500 Message-ID: <1515419184.3486.21.camel@kernel.org> References: <20171222120556.7435-1-jlayton@kernel.org> <20171222120556.7435-20-jlayton@kernel.org> <20180108133025.GA31867@bombadil.infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: linux-fsdevel@vger.kernel.org, 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 To: Matthew Wilcox Return-path: In-Reply-To: <20180108133025.GA31867@bombadil.infradead.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Mon, 2018-01-08 at 05:30 -0800, Matthew Wilcox wrote: > On Fri, Dec 22, 2017 at 07:05:56AM -0500, Jeff Layton wrote: > > + cur = inode_peek_iversion_raw(inode); > > + for (;;) { > > + /* If flag is clear then we needn't do anything */ > > + if (!force && !(cur & I_VERSION_QUERIED)) > > + return false; > > + /* Since lowest bit is flag, add 2 to avoid it */ > > + new = (cur & ~I_VERSION_QUERIED) + I_VERSION_INCREMENT; > > Isn't this an extraordinarily complicated way of spelling: > > new = cur + 1; > > We know 'cur' has I_VERSION_QUERIED set, so clearing that bit and adding > two is going to be the same as adding 1 ... right? > It would be, but if "force" is true, then I_VERSION_QUERIED may not be set. -- Jeff Layton