From: Christoph Hellwig <hch@infradead.org>
To: dsterba@suse.cz, Christophe Leroy <christophe.leroy@c-s.fr>,
erhard_f@mailbox.org, Chris Mason <clm@fb.com>,
Josef Bacik <josef@toxicpanda.com>,
David Sterba <dsterba@suse.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-btrfs@vger.kernel.org, linux-mm@kvack.org,
stable@vger.kernel.org
Subject: Re: [PATCH] btrfs: fix allocation of bitmap pages.
Date: Mon, 19 Aug 2019 19:30:31 -0700 [thread overview]
Message-ID: <20190820023031.GC9594@infradead.org> (raw)
In-Reply-To: <20190819174600.GN24086@twin.jikos.cz>
On Mon, Aug 19, 2019 at 07:46:00PM +0200, David Sterba wrote:
> Another thing that is lost is the slub debugging support for all
> architectures, because get_zeroed_pages lacking the red zones and sanity
> checks.
>
> I find working with raw pages in this code a bit inconsistent with the
> rest of btrfs code, but that's rather minor compared to the above.
>
> Summing it up, I think that the proper fix should go to copy_page
> implementation on architectures that require it or make it clear what
> are the copy_page constraints.
The whole point of copy_page is to copy exactly one page and it makes
sense to assume that is aligned. A sane memcpy would use the same
underlying primitives as well after checking they fit. So I think the
prime issue here is btrfs' use of copy_page instead of memcpy. The
secondary issue is slub fucking up alignments for no good reason. We
just got bitten by that crap again in XFS as well :(
next prev parent reply other threads:[~2019-08-20 2:30 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-17 7:44 [PATCH] btrfs: fix allocation of bitmap pages Christophe Leroy
2019-08-17 7:44 ` Christophe Leroy
2019-08-17 18:11 ` Sasha Levin
2019-08-19 17:46 ` David Sterba
2019-08-19 17:46 ` David Sterba
2019-08-19 20:32 ` Christophe Leroy
2019-08-20 2:30 ` Christoph Hellwig [this message]
2019-08-20 11:06 ` Vlastimil Babka
2019-08-21 1:48 ` Christoph Hellwig
2019-08-21 1:48 ` 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=20190820023031.GC9594@infradead.org \
--to=hch@infradead.org \
--cc=akpm@linux-foundation.org \
--cc=christophe.leroy@c-s.fr \
--cc=clm@fb.com \
--cc=dsterba@suse.com \
--cc=dsterba@suse.cz \
--cc=erhard_f@mailbox.org \
--cc=josef@toxicpanda.com \
--cc=linux-btrfs@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=stable@vger.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.