From: Joel Becker <jlbec@evilplan.org>
To: Ted Ts'o <tytso@mit.edu>, Ric Wheeler <ricwheeler@gmail.com>,
Dave Chinner <david@fromorbit.com>,
lsf@lists.linux-foundation.org,
"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.>
Subject: Re: [Lsf] Preliminary Agenda and Activities for LSF
Date: Fri, 1 Apr 2011 14:43:03 -0700 [thread overview]
Message-ID: <20110401214302.GB25355@noexit> (raw)
In-Reply-To: <20110401151907.GG21075@thunk.org>
On Fri, Apr 01, 2011 at 11:19:07AM -0400, Ted Ts'o wrote:
> The closest place that we have to any official documentation about
> O_DIRECT semantics is the open(2) man page in the Linux manpages, and
> it doesn't say anything about this. It does give a recommendation
> against not mixing buffered and O_DIRECT accesses to the same file,
> but it does promise that things will work in that case. (Even if it
> does, do we really want to make the promise that it will always work?)
No, we do not. Some OSes will silently turn buffered I/O into
direct I/O if another file already has it opened O_DIRECT. Some OSes
will fail the write, or the open, or both, if it doesn't match the mode
of an existing fd. Some just leave O_DIRECT and buffered access
inconsistent.
I think that Linux should strive to make the mixed
buffered/direct case work; it's the nicest thing we can do. But we
should not promise it.
Joel
--
Life's Little Instruction Book #24
"Drink champagne for no reason at all."
http://www.jlbec.org/
jlbec@evilplan.org
next prev parent reply other threads:[~2011-04-01 21:43 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1301373398.2590.20.camel@mulgrave.site>
2011-03-29 11:16 ` [Lsf] Preliminary Agenda and Activities for LSF Ric Wheeler
2011-03-29 11:22 ` Matthew Wilcox
2011-03-29 12:17 ` Jens Axboe
2011-03-29 13:09 ` Martin K. Petersen
2011-03-29 13:12 ` Ric Wheeler
2011-03-29 13:38 ` James Bottomley
2011-03-29 17:20 ` Shyam_Iyer
2011-03-29 17:33 ` Vivek Goyal
2011-03-29 18:10 ` Shyam_Iyer
2011-03-29 18:45 ` Vivek Goyal
2011-03-29 19:13 ` Shyam_Iyer
2011-03-29 19:57 ` Vivek Goyal
2011-03-29 19:59 ` Mike Snitzer
2011-03-29 20:12 ` Shyam_Iyer
2011-03-29 20:23 ` Mike Snitzer
2011-03-29 23:09 ` Shyam_Iyer
2011-03-30 5:58 ` [Lsf] " Hannes Reinecke
2011-03-30 14:02 ` James Bottomley
2011-03-30 14:10 ` Hannes Reinecke
2011-03-30 14:26 ` James Bottomley
2011-03-30 14:55 ` Hannes Reinecke
2011-03-30 15:33 ` James Bottomley
2011-03-30 15:46 ` Shyam_Iyer
2011-03-30 20:32 ` Giridhar Malavali
2011-03-30 20:45 ` James Bottomley
2011-03-29 19:47 ` Nicholas A. Bellinger
2011-03-29 20:29 ` Jan Kara
2011-03-29 20:31 ` Ric Wheeler
2011-03-30 0:33 ` Mingming Cao
2011-03-30 2:17 ` Dave Chinner
2011-03-30 11:13 ` Theodore Tso
2011-03-30 11:28 ` Ric Wheeler
2011-03-30 14:07 ` Chris Mason
2011-04-01 15:19 ` Ted Ts'o
2011-04-01 16:30 ` Amir Goldstein
2011-04-01 21:46 ` Joel Becker
2011-04-02 3:26 ` Amir Goldstein
2011-04-01 21:43 ` Joel Becker [this message]
2011-03-30 21:49 ` Mingming Cao
2011-03-31 0:05 ` Matthew Wilcox
2011-03-31 1:00 ` Joel Becker
2011-04-01 21:34 ` Mingming Cao
2011-04-01 21:49 ` Joel Becker
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