From: Jeff Layton <jlayton@kernel.org>
To: NeilBrown <neilb@suse.de>
Cc: "J. Bruce Fields" <bfields@fieldses.org>,
Theodore Ts'o <tytso@mit.edu>, Jan Kara <jack@suse.cz>,
adilger.kernel@dilger.ca, djwong@kernel.org, david@fromorbit.com,
trondmy@hammerspace.com, viro@zeniv.linux.org.uk,
zohar@linux.ibm.com, xiubli@redhat.com, chuck.lever@oracle.com,
lczerner@redhat.com, brauner@kernel.org, fweimer@redhat.com,
linux-man@vger.kernel.org, linux-api@vger.kernel.org,
linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, ceph-devel@vger.kernel.org,
linux-ext4@vger.kernel.org, linux-nfs@vger.kernel.org,
linux-xfs@vger.kernel.org
Subject: Re: [man-pages RFC PATCH v4] statx, inode: document the new STATX_INO_VERSION field
Date: Thu, 08 Sep 2022 19:23:36 -0400 [thread overview]
Message-ID: <53298467f5fce443c70ef6821e055d10caf9331e.camel@kernel.org> (raw)
In-Reply-To: <166267807678.30452.18035749642786839300@noble.neil.brown.name>
On Fri, 2022-09-09 at 09:01 +1000, NeilBrown wrote:
> On Fri, 09 Sep 2022, Jeff Layton wrote:
> > On Thu, 2022-09-08 at 14:22 -0400, J. Bruce Fields wrote:
> > > On Thu, Sep 08, 2022 at 01:40:11PM -0400, Jeff Layton wrote:
> > > > Yeah, ok. That does make some sense. So we would mix this into the
> > > > i_version instead of the ctime when it was available. Preferably, we'd
> > > > mix that in when we store the i_version rather than adding it afterward.
> > > >
> > > > Ted, how would we access this? Maybe we could just add a new (generic)
> > > > super_block field for this that ext4 (and other filesystems) could
> > > > populate at mount time?
> > >
> > > Couldn't the filesystem just return an ino_version that already includes
> > > it?
> > >
> >
> > Yes. That's simple if we want to just fold it in during getattr. If we
> > want to fold that into the values stored on disk, then I'm a little less
> > clear on how that will work.
> >
> > Maybe I need a concrete example of how that will work:
> >
> > Suppose we have an i_version value X with the previous crash counter
> > already factored in that makes it to disk. We hand out a newer version
> > X+1 to a client, but that value never makes it to disk.
>
> As I understand it, the crash counter would NEVER appear in the on-disk
> i_version.
> The crash counter is stable while a filesystem is mounted so is the same
> when loading an inode from disk and when writing it back.
>
> When loading, add crash counter to on-disk i_version to provide
> in-memory i_version.
> when storing, subtract crash counter from in-memory i_version to provide
> on-disk i_version.
>
> "add" and "subtract" could be any reversible hash, and its inverse. I
> would probably shift the crash counter up 16 and add/subtract.
>
>
If you store the value with the crash counter already factored-in, then
not every inode would end up being invalidated after a crash. If we try
to mix it in later, the client will end up invalidating the cache even
for inodes that had no changes.
> >
> > The machine crashes and comes back up, and we get a query for i_version
> > and it comes back as X. Fine, it's an old version. Now there is a write.
> > What do we do to ensure that the new value doesn't collide with X+1?
> > --
> > Jeff Layton <jlayton@kernel.org>
> >
--
Jeff Layton <jlayton@kernel.org>
next prev parent reply other threads:[~2022-09-08 23:23 UTC|newest]
Thread overview: 126+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-07 11:16 [man-pages RFC PATCH v4] statx, inode: document the new STATX_INO_VERSION field Jeff Layton
2022-09-07 11:37 ` NeilBrown
2022-09-07 12:20 ` J. Bruce Fields
2022-09-07 12:58 ` Jeff Layton
2022-09-07 12:47 ` Jeff Layton
2022-09-07 12:52 ` J. Bruce Fields
2022-09-07 13:12 ` Jeff Layton
2022-09-07 13:51 ` Jan Kara
2022-09-07 14:43 ` Jeff Layton
2022-09-08 0:44 ` NeilBrown
2022-09-08 8:33 ` Jan Kara
2022-09-08 15:21 ` Theodore Ts'o
2022-09-08 15:44 ` J. Bruce Fields
2022-09-08 15:44 ` Jeff Layton
2022-09-08 15:56 ` J. Bruce Fields
2022-09-08 16:15 ` Chuck Lever III
2022-09-08 17:40 ` Jeff Layton
2022-09-08 18:22 ` J. Bruce Fields
2022-09-08 19:07 ` Jeff Layton
2022-09-08 23:01 ` NeilBrown
2022-09-08 23:23 ` Jeff Layton [this message]
2022-09-08 23:45 ` NeilBrown
2022-09-09 15:45 ` J. Bruce Fields
2022-09-09 16:36 ` Jeff Layton
2022-09-10 14:56 ` J. Bruce Fields
2022-09-12 11:42 ` Jeff Layton
2022-09-12 12:13 ` Florian Weimer
2022-09-12 12:55 ` Jeff Layton
2022-09-12 13:20 ` Florian Weimer
2022-09-12 13:49 ` Jeff Layton
2022-09-12 13:51 ` J. Bruce Fields
2022-09-12 14:02 ` Jeff Layton
2022-09-12 14:47 ` J. Bruce Fields
2022-09-12 14:15 ` Trond Myklebust
2022-09-12 14:50 ` J. Bruce Fields
2022-09-12 14:56 ` Trond Myklebust
2022-09-12 15:32 ` Trond Myklebust
2022-09-12 15:49 ` Jeff Layton
2022-09-12 12:54 ` J. Bruce Fields
2022-09-12 12:59 ` Jeff Layton
2022-09-13 0:29 ` John Stoffel
2022-09-13 0:41 ` Dave Chinner
2022-09-13 1:49 ` NeilBrown
2022-09-13 2:41 ` Dave Chinner
2022-09-13 3:30 ` NeilBrown
2022-09-13 9:38 ` Theodore Ts'o
2022-09-13 19:02 ` J. Bruce Fields
2022-09-13 23:19 ` NeilBrown
2022-09-14 0:08 ` J. Bruce Fields
2022-09-09 20:34 ` John Stoffel
2022-09-10 22:13 ` NeilBrown
2022-09-12 10:43 ` Jeff Layton
2022-09-12 13:42 ` J. Bruce Fields
2022-09-12 23:14 ` NeilBrown
2022-09-15 14:06 ` J. Bruce Fields
2022-09-15 15:08 ` Trond Myklebust
2022-09-15 16:45 ` Jeff Layton
2022-09-15 17:49 ` Trond Myklebust
2022-09-15 18:11 ` Jeff Layton
2022-09-15 19:03 ` Trond Myklebust
2022-09-15 19:25 ` Jeff Layton
2022-09-15 22:23 ` NeilBrown
2022-09-16 6:54 ` Theodore Ts'o
2022-09-16 11:36 ` Jeff Layton
2022-09-16 15:11 ` Jeff Layton
2022-09-18 23:53 ` Dave Chinner
2022-09-19 13:13 ` Jeff Layton
2022-09-20 0:16 ` Dave Chinner
2022-09-20 10:26 ` Jeff Layton
2022-09-21 0:00 ` Dave Chinner
2022-09-21 10:33 ` Jeff Layton
2022-09-21 21:41 ` Dave Chinner
2022-09-22 10:18 ` Jeff Layton
2022-09-22 20:18 ` Jeff Layton
2022-09-23 9:56 ` Jan Kara
2022-09-23 10:19 ` Jeff Layton
2022-09-23 13:44 ` Trond Myklebust
2022-09-23 13:50 ` Jeff Layton
2022-09-23 14:58 ` Frank Filz
2022-09-26 22:43 ` NeilBrown
2022-09-27 11:14 ` Jeff Layton
2022-09-27 13:18 ` Jeff Layton
2022-09-15 15:41 ` Jeff Layton
2022-09-15 22:42 ` NeilBrown
2022-09-16 11:32 ` Jeff Layton
2022-09-09 12:11 ` Theodore Ts'o
2022-09-09 12:47 ` Jeff Layton
2022-09-09 13:48 ` Theodore Ts'o
2022-09-09 14:43 ` Jeff Layton
2022-09-09 14:58 ` Theodore Ts'o
2022-09-08 22:55 ` NeilBrown
2022-09-08 23:59 ` Trond Myklebust
2022-09-09 0:51 ` NeilBrown
2022-09-09 1:05 ` Trond Myklebust
2022-09-09 1:07 ` NeilBrown
2022-09-09 1:10 ` Trond Myklebust
2022-09-09 2:14 ` Trond Myklebust
2022-09-09 6:41 ` NeilBrown
2022-09-10 12:39 ` Jeff Layton
2022-09-10 22:53 ` NeilBrown
2022-09-12 10:25 ` Jeff Layton
2022-09-12 23:29 ` NeilBrown
2022-09-13 1:15 ` Dave Chinner
2022-09-13 1:41 ` NeilBrown
2022-09-13 19:01 ` Jeff Layton
2022-09-13 23:24 ` NeilBrown
2022-09-14 11:51 ` Jeff Layton
2022-09-14 22:45 ` NeilBrown
2022-09-14 23:02 ` NeilBrown
2022-09-08 22:40 ` NeilBrown
2022-09-07 13:55 ` Trond Myklebust
2022-09-07 14:05 ` Jeff Layton
2022-09-07 15:04 ` Trond Myklebust
2022-09-07 15:11 ` Jeff Layton
2022-09-08 0:40 ` NeilBrown
2022-09-08 11:34 ` Jeff Layton
2022-09-08 22:29 ` NeilBrown
2022-09-09 11:53 ` Jeff Layton
2022-09-10 22:58 ` NeilBrown
2022-09-10 19:46 ` Al Viro
2022-09-10 23:00 ` NeilBrown
2022-09-08 0:31 ` NeilBrown
2022-09-08 0:41 ` Trond Myklebust
2022-09-08 0:53 ` NeilBrown
2022-09-08 11:37 ` Jeff Layton
2022-09-08 12:40 ` Trond Myklebust
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