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From: Jeff Layton <jlayton@poochiereds.net>
To: Christoph Hellwig <hch@infradead.org>
Cc: David Howells <dhowells@redhat.com>,
	linux-fsdevel@vger.kernel.org, linux-afs@vger.kernel.org,
	linux-nfs@vger.kernel.org, samba-technical@lists.samba.org,
	linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org
Subject: Re: [PATCH 1/6] statx: Add a system call to make enhanced file info available
Date: Tue, 10 May 2016 09:21:05 -0400	[thread overview]
Message-ID: <1462886465.20038.6.camel@poochiereds.net> (raw)
In-Reply-To: <20160510070044.GA30896@infradead.org>

On Tue, 2016-05-10 at 00:00 -0700, Christoph Hellwig wrote:
> On Mon, May 09, 2016 at 08:02:58AM -0400, Jeff Layton wrote:
> > > > AT_FORCE_ATTR_SYNC can be set in flags.????This will require a
> > > > network
> > > > filesystem to synchronise its attributes with the server.
> > > > 
> > > > AT_NO_ATTR_SYNC can be set in flags.????This will suppress
> > > > synchronisation
> > > > with the server in a network filesystem.????The resulting
> > > > values should be
> > > > considered approximate.
> > > 
> > > And what happens if neither is set?
> > > 
> > 
> > I'd suggest we have the documentation state that the lack of either
> > flag leaves it up to the filesystem. In the case of NFS, you'd get
> > "normal" attribute cache behavior, for instance which is governed
> > by
> > the ac* attributes.
> > 
> > We should also note that in the case of something like
> > AT_NO_ATTR_SYNC
> > on NFS, you might _still_ end up talking to the server if the
> > client
> > has nothing in-core for that inode.
> 
> File systems specific "legacy" defaults are a bad idea.  If we can't
> describe the semantics we should not allow them, never mind making
> the the default.  I'd strongly suggest picking one of the above flags
> as the default behavior and only allowing the other as optional flag.
> I suspect NO_SYNC is the better one for the flag, as otherwise people
> will be surprised once they test their default case on a network
> filesystem.

Ok, that's a good point. So basically you suggest that xstat should
always have FORCE_SYNC semantics unless the NO_SYNC flag is set? Given
that we don't need to worry about legacy users with this interface,
that seems like a reasonable approach to me.
 
-- 
Jeff Layton <jlayton@poochiereds.net>

WARNING: multiple messages have this Message-ID
From: Jeff Layton <jlayton@poochiereds.net>
To: Christoph Hellwig <hch@infradead.org>
Cc: David Howells <dhowells@redhat.com>,
	linux-fsdevel@vger.kernel.org, linux-afs@vger.kernel.org,
	linux-nfs@vger.kernel.org, samba-technical@lists.samba.org,
	linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org
Subject: Re: [PATCH 1/6] statx: Add a system call to make enhanced file info available
Date: Tue, 10 May 2016 09:21:05 -0400	[thread overview]
Message-ID: <1462886465.20038.6.camel@poochiereds.net> (raw)
In-Reply-To: <20160510070044.GA30896@infradead.org>

On Tue, 2016-05-10 at 00:00 -0700, Christoph Hellwig wrote:
> On Mon, May 09, 2016 at 08:02:58AM -0400, Jeff Layton wrote:
> > > > AT_FORCE_ATTR_SYNC can be set in flags.????This will require a
> > > > network
> > > > filesystem to synchronise its attributes with the server.
> > > > 
> > > > AT_NO_ATTR_SYNC can be set in flags.????This will suppress
> > > > synchronisation
> > > > with the server in a network filesystem.????The resulting
> > > > values should be
> > > > considered approximate.
> > > 
> > > And what happens if neither is set?
> > > 
> > 
> > I'd suggest we have the documentation state that the lack of either
> > flag leaves it up to the filesystem. In the case of NFS, you'd get
> > "normal" attribute cache behavior, for instance which is governed
> > by
> > the ac* attributes.
> > 
> > We should also note that in the case of something like
> > AT_NO_ATTR_SYNC
> > on NFS, you might _still_ end up talking to the server if the
> > client
> > has nothing in-core for that inode.
> 
> File systems specific "legacy" defaults are a bad idea.  If we can't
> describe the semantics we should not allow them, never mind making
> the the default.  I'd strongly suggest picking one of the above flags
> as the default behavior and only allowing the other as optional flag.
> I suspect NO_SYNC is the better one for the flag, as otherwise people
> will be surprised once they test their default case on a network
> filesystem.

Ok, that's a good point. So basically you suggest that xstat should
always have FORCE_SYNC semantics unless the NO_SYNC flag is set? Given
that we don't need to worry about legacy users with this interface,
that seems like a reasonable approach to me.
 
-- 
Jeff Layton <jlayton@poochiereds.net>
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  reply	other threads:[~2016-05-10 13:21 UTC|newest]

Thread overview: 76+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-04-29 12:57 [RFC][PATCH 0/6] Enhanced file stat system call David Howells
2016-04-29 12:57 ` [PATCH 1/6] statx: Add a system call to make enhanced file info available David Howells
2016-05-02 22:46   ` Andreas Dilger
2016-05-02 22:46     ` Andreas Dilger
2016-05-03 15:53   ` David Howells
2016-05-04 22:56   ` Dave Chinner
2016-05-05  0:09     ` NeilBrown
2016-05-05  0:09       ` NeilBrown
2016-05-05 19:48       ` Jeff Layton
2016-05-06 18:07         ` J. Bruce Fields
2016-05-06 18:07           ` J. Bruce Fields
2016-05-05 20:04       ` David Howells
2016-05-05 20:04         ` David Howells
2016-05-06  1:39         ` Dave Chinner
2016-05-06  1:39           ` Dave Chinner
2016-05-06  1:39           ` Dave Chinner
2016-05-06 18:29     ` J. Bruce Fields
2016-05-09  1:45       ` Dave Chinner
2016-05-09  2:46         ` J. Bruce Fields
2016-05-04 23:56   ` NeilBrown
2016-05-08  8:35   ` Christoph Hellwig
2016-05-08  8:35     ` Christoph Hellwig
2016-05-09 12:02     ` Jeff Layton
2016-05-09 12:02       ` Jeff Layton
2016-05-10  7:00       ` Christoph Hellwig
2016-05-10  7:00         ` Christoph Hellwig
2016-05-10 13:21         ` Jeff Layton [this message]
2016-05-10 13:21           ` Jeff Layton
2016-05-09 12:57   ` David Howells
2016-05-09 12:57     ` David Howells
2016-05-09 13:23     ` Trond Myklebust
2016-05-09 13:23       ` Trond Myklebust
2016-05-09 13:23       ` Trond Myklebust
2016-05-10  7:04     ` Christoph Hellwig
2016-05-10  8:25     ` David Howells
2016-05-12  9:11       ` Christoph Hellwig
2016-05-13 15:28         ` Arnd Bergmann
2016-05-13 15:28           ` Arnd Bergmann
2016-05-23  8:22           ` Christoph Hellwig
2016-05-23  9:33           ` David Howells
2016-05-18 10:55         ` David Howells
2016-05-09 13:00   ` David Howells
2016-05-09 13:00     ` David Howells
2016-05-09 13:38   ` David Howells
2016-05-10  7:08     ` Christoph Hellwig
2016-05-10  8:43     ` David Howells
2016-05-12  9:12       ` Christoph Hellwig
2016-05-09 13:40   ` David Howells
2016-04-29 12:57 ` [PATCH 2/6] statx: AFS: Return enhanced file attributes David Howells
2016-04-29 12:57 ` [PATCH 3/6] statx: Ext4: " David Howells
2016-05-02 22:48   ` Andreas Dilger
2016-05-03 20:24   ` David Howells
2016-05-03 20:24     ` David Howells
2016-05-08  8:38   ` Christoph Hellwig
2016-05-08  8:38     ` Christoph Hellwig
2016-04-29 12:58 ` [PATCH 4/6] statx: NFS: " David Howells
2016-05-02 22:48   ` Andreas Dilger
2016-04-29 12:58 ` [PATCH 5/6] statx: Make windows attributes available for CIFS, NTFS and FAT to use David Howells
2016-05-02 22:52   ` Andreas Dilger
2016-10-03 21:03     ` Steve French
2016-10-03 21:03       ` Steve French
2016-05-03 20:23   ` David Howells
2016-05-08  8:39   ` Christoph Hellwig
2016-05-08  8:39     ` Christoph Hellwig
2016-04-29 12:58 ` [PATCH 6/6] statx: CIFS: Return enhanced attributes David Howells
2016-04-30 21:05 ` [RFC][PATCH 0/6] Enhanced file stat system call Jeff Layton
2016-04-30 21:05   ` Jeff Layton
2016-05-04 13:46 ` Arnd Bergmann
2016-05-04 13:46   ` Arnd Bergmann
2016-05-05 22:54   ` Steve French
2016-05-06  2:00     ` Steve French
2016-05-09 13:09       ` Arnd Bergmann
2016-05-09 13:09         ` Arnd Bergmann
2016-05-13 14:28         ` Richard Sharpe
2016-05-13 14:28           ` Richard Sharpe
2016-05-13 15:08           ` Arnd Bergmann

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