From: Kent Overstreet <kmo@daterainc.com>
To: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Hugh Dickins <hughd@google.com>, Jens Axboe <axboe@kernel.dk>,
Shaohua Li <shli@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org
Subject: Re: next bio iters break discard?
Date: Mon, 13 Jan 2014 20:48:41 -0800 [thread overview]
Message-ID: <20140114044841.GO9037@kmo> (raw)
In-Reply-To: <yq161pnmcl2.fsf@sermon.lab.mkp.net>
On Mon, Jan 13, 2014 at 11:06:33PM -0500, Martin K. Petersen wrote:
> >>>>> "Kent" == Kent Overstreet <kmo@daterainc.com> writes:
>
> Kent,
>
> Kent> I think for discards we can deal with this easily enough -
> Kent> __blk_recalc_rq_segments() will have to special case them - but
> Kent> there's a similar (but worse) issue with WRITE_SAME, and looking
> Kent> at the code it does attempt to merge WRITE_SAME requests too.
>
> DISCARD bios have no payload going down the stack. They get a payload
> attached in the sd driver and will therefore have a single bvec at
> completion time.
>
> WRITE_SAME bios have a single bvec payload throughout their lifetime.
>
> For both these types of requests we never attempt to merge the actual
> payloads. But the block range worked on may shrink or grow as the bio is
> split or merged going down the stack.
>
> IOW, DISCARD, WRITE SAME and the impending COPY requests do not have a
> 1:1 mapping between the block range worked on and the size of any bvecs
> attached. Your recent changes must have changed the way we handled that
> in the past.
Yeah - but with WRITE_SAME bios, wouldn't we at least have to check that they're
writing the same data to merge them?
next prev parent reply other threads:[~2014-01-14 4:48 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-13 3:52 next bio iters break discard? Hugh Dickins
2014-01-14 2:33 ` Kent Overstreet
2014-01-14 4:06 ` Martin K. Petersen
2014-01-14 4:48 ` Kent Overstreet [this message]
2014-01-14 20:17 ` Martin K. Petersen
2014-01-14 22:24 ` Kent Overstreet
2014-01-16 1:39 ` Martin K. Petersen
2014-01-16 20:21 ` Hugh Dickins
2014-01-17 1:06 ` Kent Overstreet
2014-01-17 1:21 ` Kent Overstreet
2014-01-31 17:17 ` Hugh Dickins
2014-01-31 21:58 ` Jens Axboe
2014-02-04 10:17 ` [PATCH] block: Explicitly handle discard/write same segments Kent Overstreet
2014-02-04 12:25 ` Hugh Dickins
2014-02-04 12:35 ` Kent Overstreet
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=20140114044841.GO9037@kmo \
--to=kmo@daterainc.com \
--cc=akpm@linux-foundation.org \
--cc=axboe@kernel.dk \
--cc=hughd@google.com \
--cc=linux-kernel@vger.kernel.org \
--cc=martin.petersen@oracle.com \
--cc=shli@kernel.org \
/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.