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From: Christoph Hellwig <hch@infradead.org>
To: Jeff Layton <jlayton@poochiereds.net>
Cc: Christoph Hellwig <hch@infradead.org>,
	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 00:00:44 -0700	[thread overview]
Message-ID: <20160510070044.GA30896@infradead.org> (raw)
In-Reply-To: <1462795378.4481.31.camel@poochiereds.net>

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.

WARNING: multiple messages have this Message-ID
From: Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
To: Jeff Layton <jlayton-vpEMnDpepFuMZCB2o+C8xQ@public.gmane.org>
Cc: Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
	David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-afs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	samba-technical-w/Ol4Ecudpl8XjKLYN78aQ@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH 1/6] statx: Add a system call to make enhanced file info available
Date: Tue, 10 May 2016 00:00:44 -0700	[thread overview]
Message-ID: <20160510070044.GA30896@infradead.org> (raw)
In-Reply-To: <1462795378.4481.31.camel-vpEMnDpepFuMZCB2o+C8xQ@public.gmane.org>

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.
--
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  reply	other threads:[~2016-05-10  7:00 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 [this message]
2016-05-10  7:00         ` Christoph Hellwig
2016-05-10 13:21         ` Jeff Layton
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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