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From: NeilBrown <neilb@suse.de>
To: Christoph Hellwig <hch@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>,
	xfs@oss.sgi.com,
	Bernd Schubert <bernd.schubert@itwm.fraunhofer.de>,
	Kent Overstreet <kmo@daterainc.com>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	linux-ext4@vger.kernel.org
Subject: Re: bio_add_page rw mode check by merge_bvec_fn
Date: Sat, 23 Nov 2013 16:12:34 +1100	[thread overview]
Message-ID: <20131123161234.20ae4f9d@notabene.brown> (raw)
In-Reply-To: <20131122153618.GB15143@infradead.org>


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On Fri, 22 Nov 2013 07:36:18 -0800 Christoph Hellwig <hch@infradead.org>
wrote:

> While this is trivial to fix it's also fairly unexpected and easy
> to get wrong for new callers.  Neil, can you explain why you
> desperately need it?

Desperately?  Not at all?
Need?  Not really.  This is just in RAID5 and merge_bvec_fn is purely an
optimisation for RAID5.
Limiting read BIOs to one chunk allows us to bypass the stripe-cache, so can
be good.
Limiting write BIOs is completely unnecessary so we currently don't bother.

So I have no objection to bvm->bi_rw being removed.

Thanks,
NeilBrown

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      reply	other threads:[~2013-11-23  5:12 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-11-21 18:00 bio_add_page rw mode check by merge_bvec_fn Bernd Schubert
2013-11-21 18:08 ` Bernd Schubert
2013-11-22 15:36   ` Christoph Hellwig
2013-11-23  5:12     ` NeilBrown [this message]

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