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Message-ID: <Pine.LNX.4.64.0903261430410.32095@blonde.anvils>
Date: Thu, 26 Mar 2009 14:47:34 +0000 (GMT)
From: Hugh Dickins <hugh@...itas.com>
To: Jens Axboe <jens.axboe@...cle.com>
cc: Ric Wheeler <rwheeler@...hat.com>, Jeff Garzik <jeff@...zik.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Theodore Tso <tytso@....edu>, Ingo Molnar <mingo@...e.hu>,
Alan Cox <alan@...rguk.ukuu.org.uk>,
Arjan van de Ven <arjan@...radead.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Nick Piggin <npiggin@...e.de>, David Rees <drees76@...il.com>,
Jesper Krogh <jesper@...gh.cc>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Linux 2.6.29
On Thu, 26 Mar 2009, Jens Axboe wrote:
> On Wed, Mar 25 2009, Hugh Dickins wrote:
> >
> > Tangential question, but am I right in thinking that BIO_RW_BARRIER
> > similarly bars across all partitions, whereas its WRITE_BARRIER and
> > DISCARD_BARRIER users would actually prefer it to apply to just one?
>
> All the barriers refer to just that range which the barrier itself
> references.
Ah, thank you: then I had a fundamental misunderstanding of them,
and need to go away and work that out some more.
Though I didn't read it before asking, doesn't the I/O Barriers section
of Documentation/block/biodoc.txt give a very different impression?
> The problem with the full device flushes is implementation
> on the hardware side, since we can't do small range flushes. So it's not
> as-designed, but rather the best we can do...
Right, that part of it I did get.
Hugh
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