From: Ming Lei <ming.lei@redhat.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Guoqing Jiang <guoqing.jiang@linux.dev>,
song@kernel.org, linux-raid@vger.kernel.org,
jens@chianterastutte.eu, linux-block@vger.kernel.org
Subject: Re: [PATCH] raid1: ensure bio doesn't have more than BIO_MAX_VECS sectors
Date: Tue, 17 Aug 2021 20:32:42 +0800 [thread overview]
Message-ID: <YRusakafZq0NMqLe@T590> (raw)
In-Reply-To: <YRtDxEw7Zp2H7mxp@infradead.org>
On Tue, Aug 17, 2021 at 06:06:12AM +0100, Christoph Hellwig wrote:
> On Mon, Aug 16, 2021 at 07:40:48PM +0800, Ming Lei wrote:
> > > >
> > > > 0 ~ 254: each bvec's length is 512
> > > > 255: bvec's length is 8192
> > > >
> > > > the total length is just 512*255 + 8192 = 138752 bytes = 271 sectors, but it
> > > > still may need 257 bvecs, which can't be allocated via bio_alloc_bioset().
> > >
> > > Yes, we still need the rounding magic that alloc_behind_master_bio uses
> > > here.
> >
> > But it is wrong to use max sectors to limit number of bvecs(segments), isn't it?
>
> The raid1 write behind code cares about the size ofa bio it can reach by
> adding order 0 pages to it. The bvecs are part of that and I think the
> calculation in the patch documents that a well.
Thinking of further, your and Guoqing's patch are correct & enough since
bio_copy_data() just copies bytes(sectors) stream from fs bio to the
write behind bio.
Thanks,
Ming
next prev parent reply other threads:[~2021-08-17 12:33 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-13 6:05 [PATCH] raid1: ensure bio doesn't have more than BIO_MAX_VECS sectors Guoqing Jiang
2021-08-13 7:49 ` Christoph Hellwig
2021-08-13 8:38 ` Guoqing Jiang
2021-08-14 7:55 ` Christoph Hellwig
2021-08-14 8:57 ` Ming Lei
2021-08-16 6:27 ` Guoqing Jiang
2021-08-16 7:13 ` Ming Lei
2021-08-16 9:37 ` Christoph Hellwig
2021-08-16 11:40 ` Ming Lei
2021-08-17 5:06 ` Christoph Hellwig
2021-08-17 12:32 ` Ming Lei [this message]
2021-09-24 15:34 ` Jens Stutte (Archiv)
2021-09-25 23:02 ` Guoqing Jiang
2021-08-13 9:27 ` kernel test robot
2021-08-13 10:12 ` kernel test robot
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=YRusakafZq0NMqLe@T590 \
--to=ming.lei@redhat.com \
--cc=guoqing.jiang@linux.dev \
--cc=hch@infradead.org \
--cc=jens@chianterastutte.eu \
--cc=linux-block@vger.kernel.org \
--cc=linux-raid@vger.kernel.org \
--cc=song@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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox