From: Kent Overstreet <kent.overstreet@gmail.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>, Coly Li <colyli@suse.de>,
linux-bcache@vger.kernel.org, linux-block@vger.kernel.org
Subject: Re: [PATCH 1/6] block: add a bio_reuse helper
Date: Wed, 13 Jun 2018 04:54:41 -0400 [thread overview]
Message-ID: <20180613085441.GA15100@kmo-pixel> (raw)
In-Reply-To: <20180613073204.GA22435@lst.de>
On Wed, Jun 13, 2018 at 09:32:04AM +0200, Christoph Hellwig wrote:
> On Tue, Jun 12, 2018 at 02:16:30AM -0400, Kent Overstreet wrote:
> > On Mon, Jun 11, 2018 at 09:48:01PM +0200, Christoph Hellwig wrote:
> > > This abstracts out a way to reuse a bio without destroying the
> > > data pointers.
> >
> > What is the point of this? What "data pointers" does it not destroy?
>
> It keeps bi_vcnt and bi_size intact in addition to bi_max_vecs/bi_io_vec
> already kept by the existing bio_reset.
>
> The befit is that you don't need to rebuild bi_vcnt, bio_io_vec and
> bi_size when reusing the bio.
bi_size is not immutable though, it will usually be modified by drivers when you
submit a bio.
I see what you're trying to do, but your approach is busted given the way the
block layer works today. You'd have to save bio->bi_iter before submitting the
bio and restore it afterwards for it to work.
next prev parent reply other threads:[~2018-06-13 8:54 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-11 19:48 [RFC] cleanup bcache bio handling Christoph Hellwig
2018-06-11 19:48 ` [PATCH 1/6] block: add a bio_reuse helper Christoph Hellwig
2018-06-12 6:16 ` Kent Overstreet
2018-06-13 7:32 ` Christoph Hellwig
2018-06-13 8:54 ` Kent Overstreet [this message]
2018-06-13 13:59 ` Christoph Hellwig
2018-06-13 14:49 ` Kent Overstreet
2018-06-11 19:48 ` [PATCH 2/6] bcache: use bio_reuse instead of bio_reinit where applicable Christoph Hellwig
2018-06-11 19:48 ` [PATCH 3/6] bcache: clean up bio reuse for struct moving_io Christoph Hellwig
2018-06-11 19:48 ` [PATCH 4/6] bcache: clean up bio reuse for struct dirty_io Christoph Hellwig
2018-06-11 19:48 ` [PATCH 5/6] bcache: don't clone bio in bch_data_verify Christoph Hellwig
2018-06-11 19:48 ` [PATCH 6/6] bcache: use bio_add_page instead of open coded bio manipulation Christoph Hellwig
2018-06-12 4:40 ` [RFC] cleanup bcache bio handling Coly Li
2018-06-13 9:58 ` Kent Overstreet
2018-06-13 11:06 ` Ming Lei
2018-06-13 13:56 ` Christoph Hellwig
2018-06-13 14:54 ` Kent Overstreet
2018-06-14 1:55 ` Ming Lei
2018-06-14 7:20 ` Christoph Hellwig
-- strict thread matches above, loose matches on Subject: below --
2018-06-13 13:51 [RFC] cleanup bcache bio handling v2 Christoph Hellwig
2018-06-13 13:51 ` [PATCH 1/6] block: add a bio_reuse helper Christoph Hellwig
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