From: Christoph Hellwig <hch@infradead.org>
To: Hannes Reinecke <hare@suse.de>
Cc: Mike Christie <michaelc@cs.wisc.edu>,
Mike Snitzer <snitzer@redhat.com>,
Christoph Hellwig <hch@infradead.org>,
dm-devel@redhat.com, Jun'ichi Nomura <j-nomura@ce.jp.nec.com>,
Alasdair Kergon <agk@redhat.com>
Subject: Re: [RFC PATCH 0/7] dm-mpath: Do not clone requests
Date: Thu, 5 Jun 2014 07:44:32 -0700 [thread overview]
Message-ID: <20140605144432.GD4590@infradead.org> (raw)
In-Reply-To: <539076D1.9000704@suse.de>
On Thu, Jun 05, 2014 at 03:55:29PM +0200, Hannes Reinecke wrote:
> The primary reason for cloning the bios would from my POV would be
> so that we can handle partial completion properly. When eliminating
> it we would be always return an error here.
I don't see how partial completions matter - we never finish a partial
request in the low level driver and let DM retry. All partial
completion handling stays in the low level driver.
If we'd didn't clone bios the workflow would look something like this:
- allocate new clone request in dm-mpath
- point clone->bio and clone->biotail to the original bio, zero
them out in the original request
- the low level driver does one or more calls to blk_update_request
until clone->bio is NULL, and then calls blk_finish_request (or
__blk_mq_end_io) once the request has been completed,
- This hands control back to dm-mpath, which can now call
__blk_mq_end_io without blk_update_request as the low level driver
took care of the bio completions.
next prev parent reply other threads:[~2014-06-05 14:44 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-05 13:11 [RFC PATCH 0/7] dm-mpath: Do not clone requests Hannes Reinecke
2014-06-05 13:11 ` [PATCH 1/7] dm: use dm_rq_target_io as argument for dm_done() Hannes Reinecke
2014-06-05 13:11 ` [PATCH 2/7] dm: remove handling of DM_ENDIO_INCOMPLETE Hannes Reinecke
2014-06-05 13:11 ` [PATCH 3/7] dm: move rq_completed() out of enclosing functions Hannes Reinecke
2014-06-05 13:11 ` [PATCH 4/7] dm: open-code dm_kill_unmapped_request() Hannes Reinecke
2014-06-05 13:11 ` [PATCH 5/7] dm: move free_rq_clone() out of dm_unprep_request() Hannes Reinecke
2014-06-05 13:11 ` [PATCH 6/7] dm: open-code free_rq_clone() Hannes Reinecke
2014-06-05 13:11 ` [PATCH 7/7] dm: do not clone requests Hannes Reinecke
2014-06-05 13:36 ` [RFC PATCH 0/7] dm-mpath: Do " Christoph Hellwig
2014-06-05 13:55 ` Hannes Reinecke
2014-06-05 14:44 ` Christoph Hellwig [this message]
2014-06-06 5:25 ` Junichi Nomura
2014-06-05 14:01 ` Mike Snitzer
2014-06-05 14:40 ` Christoph Hellwig
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20140605144432.GD4590@infradead.org \
--to=hch@infradead.org \
--cc=agk@redhat.com \
--cc=dm-devel@redhat.com \
--cc=hare@suse.de \
--cc=j-nomura@ce.jp.nec.com \
--cc=michaelc@cs.wisc.edu \
--cc=snitzer@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.