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Date: Thu, 15 Sep 2022 08:45:21 +1000 From: "NeilBrown" <neilb@...e.de> To: "Jeff Layton" <jlayton@...nel.org> Cc: "Dave Chinner" <david@...morbit.com>, "Trond Myklebust" <trondmy@...merspace.com>, "zohar@...ux.ibm.com" <zohar@...ux.ibm.com>, "djwong@...nel.org" <djwong@...nel.org>, "xiubli@...hat.com" <xiubli@...hat.com>, "brauner@...nel.org" <brauner@...nel.org>, "linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>, "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>, "bfields@...ldses.org" <bfields@...ldses.org>, "fweimer@...hat.com" <fweimer@...hat.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "chuck.lever@...cle.com" <chuck.lever@...cle.com>, "linux-man@...r.kernel.org" <linux-man@...r.kernel.org>, "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>, "tytso@....edu" <tytso@....edu>, "viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>, "jack@...e.cz" <jack@...e.cz>, "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>, "linux-btrfs@...r.kernel.org" <linux-btrfs@...r.kernel.org>, "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>, "adilger.kernel@...ger.ca" <adilger.kernel@...ger.ca>, "lczerner@...hat.com" <lczerner@...hat.com>, "ceph-devel@...r.kernel.org" <ceph-devel@...r.kernel.org> Subject: Re: [man-pages RFC PATCH v4] statx, inode: document the new STATX_INO_VERSION field On Wed, 14 Sep 2022, Jeff Layton wrote: > On Wed, 2022-09-14 at 09:24 +1000, NeilBrown wrote: > > On Wed, 14 Sep 2022, Jeff Layton wrote: > > > > > > At that point, bumping i_version both before and after makes a bit more > > > sense, since it better ensures that a change will be noticed, whether > > > the related read op comes before or after the statx. > > > > How does bumping it before make any sense at all? Maybe it wouldn't > > hurt much, but how does it help anyone at all? > > > > My assumption (maybe wrong) was that timestamp updates were done before > the actual write by design. Does doing it before the write make increase > the chances that the inode metadata writeout will get done in the same > physical I/O as the data write? IDK, just speculating here. When the code was written, the inode semaphore (before mutexes) was held over the whole thing, and timestamp resolution was 1 second. So ordering didn't really matter. Since then locking has bee reduced and precision increased but no-one saw any need to fix the ordering. I think that is fine for timestamps. But i_version is about absolute precision, so we need to think carefully about what meets our needs. > > If there's no benefit to doing it before then we should just move it > afterward. Great! Thanks, NeilBrown
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