From: Gregory Price <gourry@gourry.net>
To: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
kernel-team@meta.com, akpm@linux-foundation.org,
liam@infradead.org, david@kernel.org, vbabka@kernel.org,
jannh@google.com, sashiko-bot <sashiko-bot@kernel.org>
Subject: Re: [PATCH] mm/madvise: use folio_trylock() in the cold/pageout PMD split
Date: Fri, 21 Aug 2026 14:42:01 -0400 [thread overview]
Message-ID: <aoiap-yBdPaM_YQG@gourry-fedora-PF4VCD3F> (raw)
In-Reply-To: <aoiWZjgcitp0nSk0@gremlin>
On Fri, Aug 21, 2026 at 07:23:34PM +0100, Lorenzo Stoakes (ARM) wrote:
> On Fri, Aug 21, 2026 at 11:09:12AM -0400, Gregory Price wrote:
>
> I am _so_ glad to see an actual reproducer used in a sashiko bug fix. THANKS. :)
>
fwiw i try to produce reproducers on all my sashiko submitted fixes,
i've just been dumb about including them in the changelog. Trying to
fix that from now on.
> > + if (!folio_trylock(folio))
> > + goto huge_unlock;
>
> Doesn't this violate lock ordering?
>
> From rmap.c:
>
> folio_lock
> ...
> mm->page_table_lock or pte_lock
>
> So now you hold the ptl lock _before_ you obtain the folio lock?
>
> I'm not sure if it being a trylock gets us out of that particular situation? And
> I'd be reticent for us to violate it... unless I'm missing something :)
>
This was the thing i was least sure about, but the deadlock condition
should only happen if we tried to spin on the folio lock right?
It does look weird, so it would be wrong of me to say i'm 100%
confident this is the best change.
~Gregory
next prev parent reply other threads:[~2026-08-21 18:42 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-21 15:09 [PATCH] mm/madvise: use folio_trylock() in the cold/pageout PMD split Gregory Price
2026-08-21 18:23 ` Lorenzo Stoakes (ARM)
2026-08-21 18:42 ` Gregory Price [this message]
2026-08-21 19:18 ` Lorenzo Stoakes (ARM)
2026-08-21 19:48 ` Matthew Wilcox
2026-08-21 20:38 ` Gregory Price
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=aoiap-yBdPaM_YQG@gourry-fedora-PF4VCD3F \
--to=gourry@gourry.net \
--cc=akpm@linux-foundation.org \
--cc=david@kernel.org \
--cc=jannh@google.com \
--cc=kernel-team@meta.com \
--cc=liam@infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=ljs@kernel.org \
--cc=sashiko-bot@kernel.org \
--cc=vbabka@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