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From: "Serge E. Hallyn" <serue@us.ibm.com>
To: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>,
	Ingo Molnar <mingo@elte.hu>,
	containers <containers@lists.linux-foundation.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Oren Laadan <orenl@cs.columbia.edu>,
	Alexey Dobriyan <adobriyan@gmail.com>
Subject: Re: [RFC][PATCH 5/8] add f_op for checkpointability
Date: Sun, 1 Mar 2009 09:19:28 -0600	[thread overview]
Message-ID: <20090301151928.GB18867@us.ibm.com> (raw)
In-Reply-To: <1235857026.26788.421.camel@nimitz>

Quoting Dave Hansen (dave@linux.vnet.ibm.com):
> > Also the double-use of the op seem not very nice to me.  Is there any
> > real life use case were you would have the operation on a file but
> > sometimes not allow checkpoiting?
> 
> No, I don't have any good concrete ones.  The first thing that comes to
> mind is something like a pipe.  We can checkpoint when there's no data,
> but must refuse when there's data in the pipe.  In practice, pipes are
> fixable, but it is the kind of situation where I expected it to get
> used.

Hmm, but that's the kind of thing Ingo is resolutely against,
right?  If you've opened some resource that may in certain
cases not be checkpointable, then checkpointing it in certain
states is just wrong, as the app can never know for sure (without
knowing the fragile and temporary implementation details)
whether it is checkpointable.

So we either support pipes or we don't.

(Now maybe you have another use in mind for it...)

-serge

  reply	other threads:[~2009-03-01 15:19 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-02-27 20:34 [RFC][PATCH 1/8] kill '_data' in cr_hdr_fd_data name Dave Hansen
2009-02-27 20:34 ` [RFC][PATCH 2/8] breakout fdinfo sprintf() into its own function Dave Hansen
2009-02-27 20:56   ` Vegard Nossum
2009-02-27 21:23     ` Dave Hansen
2009-02-27 20:34 ` [RFC][PATCH 3/8] create fs flags to mark c/r supported fs's Dave Hansen
2009-02-27 21:16   ` Alexey Dobriyan
2009-02-27 21:20     ` Dave Hansen
2009-02-27 20:34 ` [RFC][PATCH 4/8] file c/r: expose functions to query fs support Dave Hansen
2009-02-27 21:14   ` Sukadev Bhattiprolu
2009-02-27 21:24     ` Dave Hansen
2009-02-27 21:32       ` Dave Hansen
2009-02-28  1:33   ` Sukadev Bhattiprolu
2009-02-27 20:34 ` [RFC][PATCH 5/8] add f_op for checkpointability Dave Hansen
2009-02-28  2:14   ` Sukadev Bhattiprolu
2009-02-28  2:51     ` Dave Hansen
2009-02-28 20:53   ` Christoph Hellwig
2009-02-28 21:37     ` Dave Hansen
2009-03-01 15:19       ` Serge E. Hallyn [this message]
2009-03-02 17:05     ` Dave Hansen
2009-03-03 13:15       ` Christoph Hellwig
2009-03-20 21:13         ` Dave Hansen
2009-03-20 21:30           ` Oren Laadan
2009-02-27 20:34 ` [RFC][PATCH 6/8] mark /dev/null and zero as checkpointable Dave Hansen
2009-02-27 20:34 ` [RFC][PATCH 7/8] add c/r info to fdinfo Dave Hansen
2009-02-27 20:34 ` [RFC][PATCH 8/8] check files for checkpointability Dave Hansen
2009-02-28  2:57   ` Sukadev Bhattiprolu
2009-03-01 17:00     ` Serge E. Hallyn
2009-03-04 23:41     ` Dave Hansen
2009-03-01 19:43   ` Serge E. Hallyn
2009-03-02 13:37   ` Serge E. Hallyn
2009-03-02 15:56     ` Dave Hansen
2009-03-02 15:59     ` Nathan Lynch
2009-03-02 16:27       ` Dave Hansen
2009-03-02 17:22         ` Nathan Lynch
2009-03-02 17:30           ` Dave Hansen
2009-03-02 17:44             ` Serge E. Hallyn
2009-03-02 17:58               ` Dave Hansen
2009-03-02 18:13               ` Dave Hansen
2009-03-02 18:35                 ` Serge E. Hallyn
2009-03-05  8:20                 ` Cedric Le Goater
2009-03-02 16:28       ` Serge E. Hallyn

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