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From: Jeff Layton <jlayton@redhat.com>
To: Jan Kara <jack@suse.cz>
Cc: "J. Bruce Fields" <bfields@fieldses.org>,
	Christoph Hellwig <hch@infradead.org>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-nfs@vger.kernel.org, linux-ext4@vger.kernel.org,
	linux-btrfs@vger.kernel.org, linux-xfs@vger.kernel.org
Subject: Re: [RFC PATCH v1 00/30] fs: inode->i_version rework and optimization
Date: Wed, 29 Mar 2017 13:54:31 -0400	[thread overview]
Message-ID: <1490810071.2678.6.camel@redhat.com> (raw)
In-Reply-To: <20170329111507.GA18467@quack2.suse.cz>

On Wed, 2017-03-29 at 13:15 +0200, Jan Kara wrote:
> On Tue 21-03-17 14:46:53, Jeff Layton wrote:
> > On Tue, 2017-03-21 at 14:30 -0400, J. Bruce Fields wrote:
> > > On Tue, Mar 21, 2017 at 01:23:24PM -0400, Jeff Layton wrote:
> > > > On Tue, 2017-03-21 at 12:30 -0400, J. Bruce Fields wrote:
> > > > > - It's durable; the above comparison still works if there were reboots
> > > > >   between the two i_version checks.
> > > > > 	- I don't know how realistic this is--we may need to figure out
> > > > > 	  if there's a weaker guarantee that's still useful.  Do
> > > > > 	  filesystems actually make ctime/mtime/i_version changes
> > > > > 	  atomically with the changes that caused them?  What if a
> > > > > 	  change attribute is exposed to an NFS client but doesn't make
> > > > > 	  it to disk, and then that value is reused after reboot?
> > > > > 
> > > > 
> > > > Yeah, there could be atomicity there. If we bump i_version, we'll mark
> > > > the inode dirty and I think that will end up with the new i_version at
> > > > least being journalled before __mark_inode_dirty returns.
> > > 
> > > So you think the filesystem can provide the atomicity?  In more detail:
> > > 
> > 
> > Sorry, I hit send too quickly. That should have read:
> > 
> > "Yeah, there could be atomicity issues there."
> > 
> > I think providing that level of atomicity may be difficult, though
> > maybe there's some way to make the querying of i_version block until
> > the inode update has been journalled?
> 
> Just to complement what Dave said from ext4 side - similarly as with XFS
> ext4 doesn't guarantee atomicity unless fsync() has completed on the file.
> Until that you can see arbitrary combination of data & i_version after the
> crash. We do take care to keep data and metadata in sync only when there
> are security implications to that (like exposing uninitialized disk blocks)
> and if not, we are as lazy as we can to improve performance...
> 
> 

Yeah, I think what we'll have to do here is ensure that those
filesystems do an fsync prior to reporting the i_version getattr
codepath. It's not pretty, but I don't see a real alternative.

-- 
Jeff Layton <jlayton@redhat.com>

  reply	other threads:[~2017-03-29 17:54 UTC|newest]

Thread overview: 87+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-21 17:03 Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 01/30] lustre: don't set f_version in ll_readdir Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 02/30] ecryptfs: remove unnecessary i_version bump Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 03/30] ceph: remove the bump of i_version Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 04/30] f2fs: don't bother setting i_version Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 05/30] hpfs: don't bother with the i_version counter Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 06/30] jfs: remove initialization of " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 07/30] nilfs2: remove inode->i_version initialization Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 08/30] orangefs: remove initialization of i_version Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 09/30] reiserfs: remove unneeded i_version bump Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 10/30] ntfs: remove i_version handling Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 11/30] fs: new API for handling i_version Jeff Layton
2017-03-03 22:36   ` J. Bruce Fields
2017-03-04  0:09     ` Jeff Layton
2017-03-03 23:55   ` NeilBrown
2017-03-04  1:58     ` Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 12/30] fat: convert to new i_version API Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 13/30] affs: " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 14/30] afs: " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 15/30] btrfs: " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 16/30] exofs: switch " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 17/30] ext2: convert " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 18/30] ext4: " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 19/30] nfs: " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 20/30] nfsd: " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 21/30] ocfs2: " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 22/30] ufs: use " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 23/30] xfs: convert to " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 24/30] IMA: switch IMA over " Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 25/30] fs: add a "force" parameter to inode_inc_iversion Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 26/30] fs: only set S_VERSION when updating times if it has been queried Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 27/30] xfs: avoid setting XFS_ILOG_CORE if i_version doesn't need incrementing Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 28/30] btrfs: only dirty the inode in btrfs_update_time if something was changed Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 29/30] fs: track whether the i_version has been queried with an i_state flag Jeff Layton
2017-03-04  0:03   ` NeilBrown
2017-03-04  0:43     ` Jeff Layton
2016-12-21 17:03 ` [RFC PATCH v1 30/30] fs: convert i_version counter over to an atomic64_t Jeff Layton
2016-12-22  8:38   ` Amir Goldstein
2016-12-22 13:27     ` Jeff Layton
2017-03-04  0:00   ` NeilBrown
2016-12-22  8:45 ` [RFC PATCH v1 00/30] fs: inode->i_version rework and optimization Christoph Hellwig
2016-12-22 14:42   ` Jeff Layton
2017-03-20 21:43     ` J. Bruce Fields
2017-03-21 13:45       ` Christoph Hellwig
2017-03-21 16:30         ` J. Bruce Fields
2017-03-21 17:23           ` Jeff Layton
2017-03-21 17:37             ` J. Bruce Fields
2017-03-21 17:51               ` J. Bruce Fields
2017-03-21 18:30             ` J. Bruce Fields
2017-03-21 18:46               ` Jeff Layton
2017-03-21 19:13                 ` J. Bruce Fields
2017-03-21 21:54                   ` Jeff Layton
2017-03-29 11:15                 ` Jan Kara
2017-03-29 17:54                   ` Jeff Layton [this message]
2017-03-29 23:41                     ` Dave Chinner
2017-03-30 11:24                       ` Jeff Layton
2017-04-04 18:38                       ` J. Bruce Fields
2017-03-30  6:47                     ` Jan Kara
2017-03-30 11:11                       ` Jeff Layton
2017-03-30 16:12                         ` J. Bruce Fields
2017-03-30 18:35                           ` Jeff Layton
2017-03-30 21:11                             ` Boaz Harrosh
2017-04-04 18:31                             ` J. Bruce Fields
2017-04-05  1:43                               ` NeilBrown
2017-04-05  8:05                                 ` Jan Kara
2017-04-05 18:14                                   ` J. Bruce Fields
2017-05-11 18:59                                     ` J. Bruce Fields
2017-05-11 22:22                                       ` NeilBrown
2017-05-12 16:21                                         ` J. Bruce Fields
2017-10-30 13:21                                           ` Jeff Layton
2017-05-12  8:27                                       ` Jan Kara
2017-05-12 15:56                                         ` J. Bruce Fields
2017-05-12 11:01                                       ` Jeff Layton
2017-05-12 15:57                                         ` J. Bruce Fields
2017-04-06  1:12                                   ` NeilBrown
2017-04-06  7:22                                     ` Jan Kara
2017-04-05 17:26                                 ` J. Bruce Fields
2017-04-01 23:05                           ` Dave Chinner
2017-04-03 14:00                             ` Jan Kara
2017-04-04 12:34                               ` Dave Chinner
2017-04-04 17:53                                 ` J. Bruce Fields
2017-04-05  1:26                                 ` NeilBrown
2017-03-21 21:45             ` Dave Chinner
2017-03-22 19:53               ` Jeff Layton
2017-03-03 23:00 ` J. Bruce Fields
2017-03-04  0:53   ` Jeff Layton
2017-03-08 17:29     ` J. Bruce Fields

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