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From: NeilBrown <neilb@suse.de>
To: Ming Lin <mlin@kernel.org>
Cc: linux-kernel@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
	Jens Axboe <axboe@kernel.dk>,
	Kent Overstreet <kent.overstreet@gmail.com>,
	Dongsu Park <dongsu.park@profitbricks.com>,
	Lars Ellenberg <drbd-dev@lists.linbit.com>,
	drbd-user@lists.linbit.com, Jiri Kosina <jkosina@suse.cz>,
	Yehuda Sadeh <yehuda@inktank.com>, Sage Weil <sage@inktank.com>,
	Alex Elder <elder@kernel.org>,
	ceph-devel@vger.kernel.org, Alasdair Kergon <agk@redhat.com>,
	Mike Snitzer <snitzer@redhat.com>,
	dm-devel@redhat.com, linux-raid@vger.kernel.org,
	Christoph Hellwig <hch@infradead.org>,
	"Martin K. Petersen" <martin.petersen@oracle.com>
Subject: Re: [PATCH 07/10] block: kill merge_bvec_fn() completely
Date: Wed, 29 Apr 2015 08:09:19 +1000	[thread overview]
Message-ID: <20150429080919.342fddfd@notabene.brown> (raw)
In-Reply-To: <1430203717-13307-8-git-send-email-mlin@kernel.org>

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On Mon, 27 Apr 2015 23:48:34 -0700 Ming Lin <mlin@kernel.org> wrote:

> From: Kent Overstreet <kent.overstreet@gmail.com>
> 
> As generic_make_request() is now able to handle arbitrarily sized bios,
> it's no longer necessary for each individual block driver to define its
> own ->merge_bvec_fn() callback. Remove every invocation completely.

This patch it just a little premature I think.

md/raid5 still assumes read requests will mostly fit within a single chunk
(which merge_bvec_fn encourages) so they can be serviced without using the
stripe-cache.
You've just broken that assumption.

I think 'chunk_aligned_read' needs to get a loop using bio_split, a bit like
raid0, first.

Thanks,
NeilBrown

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  parent reply	other threads:[~2015-04-28 22:09 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-28  6:48 [RFC PATCH v2 00/10] simplify block layer based on immutable biovecs Ming Lin
2015-04-28  6:48 ` [PATCH 01/10] block: make generic_make_request handle arbitrarily sized bios Ming Lin
2015-04-28 11:43   ` Christoph Hellwig
2015-04-28 16:01     ` Keith Busch
2015-05-06  6:08     ` Ming Lin
2015-05-06  6:48       ` Christoph Hellwig
2015-05-06  7:13         ` Ming Lin
2015-04-28  6:48 ` [PATCH 02/10] block: simplify bio_add_page() Ming Lin
2015-04-28 12:12   ` Christoph Hellwig
2015-04-29  5:42     ` Ming Lin
2015-04-28  6:48 ` [PATCH 03/10] block: allow __blk_queue_bounce() to handle bios larger than BIO_MAX_PAGES Ming Lin
2015-04-28  6:48 ` [PATCH 04/10] bcache: clean up hacks around bio_split_pool Ming Lin
2015-04-28 12:14   ` Christoph Hellwig
2015-04-28 12:14     ` Christoph Hellwig
2015-04-29  5:43     ` Ming Lin
2015-04-28  6:48 ` [PATCH 05/10] btrfs: remove bio splitting and merge_bvec_fn() calls Ming Lin
2015-04-28  6:48 ` [PATCH 06/10] md/raid5: get rid of bio_fits_rdev() Ming Lin
2015-04-28  6:48 ` [PATCH 07/10] block: kill merge_bvec_fn() completely Ming Lin
2015-04-28 17:31   ` Alasdair G Kergon
2015-04-29  6:32     ` Ming Lin
2015-04-28 22:09   ` NeilBrown [this message]
2015-05-04  7:47     ` Ming Lin
2015-05-06  7:10       ` Ming Lin
2015-05-06  7:26       ` Christoph Hellwig
2015-05-06 17:05         ` Ming Lin
2015-04-28  6:48 ` [PATCH 08/10] fs: use helper bio_add_page() instead of open coding on bi_io_vec Ming Lin
2015-04-28  6:48 ` [PATCH 09/10] md/raid10: make sync_request_write() call bio_copy_data() Ming Lin
2015-04-28  6:48 ` [PATCH 10/10] Documentation: update notes in biovecs about arbitrarily sized bios Ming Lin

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