From: Ming Lin <mlin@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Ming Lin <mlin@kernel.org>, lkml <linux-kernel@vger.kernel.org>,
Jens Axboe <axboe@kernel.dk>,
Kent Overstreet <kent.overstreet@gmail.com>,
Dongsu Park <dpark@posteo.net>,
Christoph Hellwig <hch@infradead.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Ming Lei <ming.lei@canonical.com>, Neil Brown <neilb@suse.de>,
Alasdair Kergon <agk@redhat.com>,
Mike Snitzer <snitzer@redhat.com>,
dm-devel@redhat.com, Lars Ellenberg <drbd-dev@lists.linbit.com>,
drbd-user@lists.linbit.com, Jiri Kosina <jkosina@suse.cz>,
Geoff Levand <geoff@infradead.org>, Jim Paris <jim@jtan.com>,
Joshua Morris <josh.h.morris@us.ibm.com>,
Philip Kelleher <pjk1939@linux.vnet.ibm.com>,
Minchan Kim <minchan@kernel.org>, Nitin Gupta <ngupta@vflare.org>,
Oleg Drokin <oleg.drokin@intel.com>,
Andreas Dilger <andreas.dilger@intel.com>
Subject: Re: [PATCH v3 01/11] block: make generic_make_request handle arbitrarily sized bios
Date: Wed, 20 May 2015 11:16:20 -0700 [thread overview]
Message-ID: <CAF1ivSbu4e2MzUB2CPJi92PpkOvLrLA=TO55-=7m07GpYz98Xw@mail.gmail.com> (raw)
In-Reply-To: <20150520124418.GA15594@lst.de>
On Wed, May 20, 2015 at 5:44 AM, Christoph Hellwig <hch@lst.de> wrote:
> This needs the patch below for the blk-mq case with multiple queues.
Will add it.
>
> Also I wonder why we really want to push this below ->make_request.
> Moving it just outside ->make_request would make the callchain more
> obvious and avoid the recursion into the driver.
Are you saying move the split to generic_make_request()?
Below is an off-list discussion.
Ming Lei asked:
> > I am wondering why the bio isn't splitted just before q->make_request_fn
> > is called in generic_make_request()? By this way, drivers won't need
> > to call blk_queue_split() at all. Is it because performance reason? or
> > others?
Kent replied:
> > The reasoning was because blk_queue_split() was only an interim solution -
> > there's actually no inherent need to split the bios at all, but not splitting
> > them takes (a small amount of) driver modification. You just have the driver
> > consume the bios incrementally, advancing the iterator and using bi_remaining
> > when they have multiple tags pointing to the same bio.
>
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index e9bbc04..e7fae76 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1256,6 +1256,8 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
> return;
> }
>
> + blk_queue_split(q, &bio, q->bio_split);
> +
> rq = blk_mq_map_request(q, bio, &data);
> if (unlikely(!rq))
> return;
next prev parent reply other threads:[~2015-05-20 18:16 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-07 6:34 [PATCH v3 00/11] simplify block layer based on immutable biovecs Ming Lin
2015-05-07 6:34 ` [PATCH v3 01/11] block: make generic_make_request handle arbitrarily sized bios Ming Lin
2015-05-18 16:52 ` Jeff Moyer
2015-05-18 17:22 ` Christoph Hellwig
2015-05-22 7:51 ` Ming Lin
2015-05-20 18:30 ` Ming Lin
2015-05-20 18:58 ` Jeff Moyer
2015-05-20 20:18 ` Ming Lin
2015-05-22 17:49 ` Ming Lin
2015-05-20 12:44 ` Christoph Hellwig
2015-05-20 18:16 ` Ming Lin [this message]
2015-05-07 6:34 ` [PATCH v3 02/11] block: simplify bio_add_page() Ming Lin
2015-05-07 6:34 ` [PATCH v3 03/11] block: allow __blk_queue_bounce() to handle bios larger than BIO_MAX_PAGES Ming Lin
2015-05-19 8:44 ` Christoph Hellwig
2015-05-20 18:17 ` Ming Lin
2015-05-07 6:34 ` [PATCH v3 04/11] bcache: remove driver private bio splitting code Ming Lin
2015-05-07 6:34 ` [PATCH v3 05/11] btrfs: remove bio splitting and merge_bvec_fn() calls Ming Lin
2015-05-07 6:34 ` [PATCH v3 06/11] md/raid5: get rid of bio_fits_rdev() Ming Lin
2015-05-07 6:34 ` [PATCH v3 07/11] md/raid5: split bio for chunk_aligned_read Ming Lin
2015-05-08 4:14 ` NeilBrown
2015-05-08 5:57 ` Ming Lin
2015-05-07 6:34 ` [PATCH v3 08/11] block: kill merge_bvec_fn() completely Ming Lin
2015-05-07 6:34 ` [PATCH v3 09/11] fs: use helper bio_add_page() instead of open coding on bi_io_vec Ming Lin
2015-05-07 6:34 ` [PATCH v3 10/11] md/raid10: make sync_request_write() call bio_copy_data() Ming Lin
2015-05-19 8:45 ` Christoph Hellwig
2015-05-20 3:09 ` NeilBrown
2015-05-07 6:34 ` [PATCH v3 11/11] Documentation: update notes in biovecs about arbitrarily sized bios Ming Lin
2015-05-18 16:13 ` [PATCH v3 00/11] simplify block layer based on immutable biovecs Christoph Hellwig
2015-05-20 12:48 ` Christoph Hellwig
2015-05-20 18:10 ` Ming Lin
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