From: Andrew Morton <akpm@linux-foundation.org>
To: David Hildenbrand <david@redhat.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Michal Hocko <mhocko@kernel.org>
Subject: Re: [PATCH v2 2/2] mm/memory-failure.c: Don't access uninitialized memmaps in memory_failure()
Date: Fri, 18 Oct 2019 19:05:31 -0700 [thread overview]
Message-ID: <20191018190531.975b70fabdce5f7e5d6b27df@linux-foundation.org> (raw)
In-Reply-To: <134d4f03-a40a-fe62-fb93-53d209a91d2e@redhat.com>
On Thu, 10 Oct 2019 09:17:42 +0200 David Hildenbrand <david@redhat.com> wrote:
> >> - pgmap = get_dev_pagemap(pfn, NULL);
> >> - if (pgmap)
> >> - return memory_failure_dev_pagemap(pfn, flags, pgmap);
> >> -
> >> - p = pfn_to_page(pfn);
> >
> > This change seems to assume that memory_failure_dev_pagemap() is never
> > called for online pages. Is it an intended behavior?
> > Or the concept "online pages" is not applicable to zone device pages?
>
> Yes, that's the real culprit. ZONE_DEVICE/devmem pages are never online
> (SECTION_IS_ONLINE). The terminology "online" only applies to pages that
> were given to the buddy. And as we support sup-section hotadd for
> devmem, we cannot easily make use of the section flag it. I already
> proposed somewhere to convert SECTION_IS_ONLINE to a subsection bitmap
> and call it something like pfn_active().
>
> pfn_online() would then be "pfn_active() && zone != ZONE_DEVICE". And we
> could use pfn_active() everywhere to test for initialized memmaps (well,
> besides some special cases like device reserved memory that does not
> span full sub-sections). Until now, nobody volunteered and I have other
> things to do.
Is it worth a code comment or two to make this clearer?
next prev parent reply other threads:[~2019-10-19 2:05 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-09 14:24 [PATCH v2 0/2] mm: Don't access uninitialized memmaps in PFN walkers David Hildenbrand
2019-10-09 14:24 ` [PATCH v2 1/2] mm: Don't access uninitialized memmaps in fs/proc/page.c David Hildenbrand
2019-10-09 14:41 ` Michal Hocko
2019-10-14 8:44 ` David Hildenbrand
2019-10-09 14:24 ` [PATCH v2 2/2] mm/memory-failure.c: Don't access uninitialized memmaps in memory_failure() David Hildenbrand
2019-10-09 14:43 ` Michal Hocko
2019-10-10 7:27 ` David Hildenbrand
2019-10-10 7:35 ` Michal Hocko
2019-10-10 7:52 ` David Hildenbrand
2019-10-10 7:58 ` David Hildenbrand
2019-10-11 6:02 ` Naoya Horiguchi
2019-10-11 10:13 ` David Hildenbrand
2019-10-14 13:36 ` Michal Hocko
2019-10-15 14:23 ` Oscar Salvador
2019-10-10 0:26 ` Naoya Horiguchi
2019-10-10 7:17 ` David Hildenbrand
2019-10-11 6:50 ` Naoya Horiguchi
2019-10-19 2:05 ` Andrew Morton [this message]
2019-10-21 9:44 ` David Hildenbrand
2019-10-14 8:41 ` David Hildenbrand
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=20191018190531.975b70fabdce5f7e5d6b27df@linux-foundation.org \
--to=akpm@linux-foundation.org \
--cc=david@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@kernel.org \
--cc=n-horiguchi@ah.jp.nec.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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox