From: Kiryl Shutsemau <kas@kernel.org>
To: Sasha Levin <sashal@kernel.org>
Cc: akpm@linux-foundation.org, david@kernel.org,
muchun.song@linux.dev, osalvador@suse.de, peterz@infradead.org,
fvdl@google.com, willy@infradead.org, ljs@kernel.org,
liam@infradead.org, vbabka@kernel.org, rppt@kernel.org,
surenb@google.com, mhocko@suse.com, corbet@lwn.net,
skhan@linuxfoundation.org, rdunlap@infradead.org,
stable@vger.kernel.org
Subject: Re: FAILED: patch "[PATCH] mm/hugetlb_vmemmap: map the shared tail page writable" failed to apply to 6.18-stable tree
Date: Tue, 10 Nov 2026 12:11:44 +0000 [thread overview]
Message-ID: <avMJ1sVDviavKjQu@thinkstation> (raw)
In-Reply-To: <20261109200434-failed-6.18-0120a603afad@kernel.org>
On Mon, Nov 09, 2026 at 08:04:34PM -0500, Sasha Levin wrote:
> The patch below does not apply to the 6.18-stable tree.
It is not needed for 6.18. The bug came with 32c440d67e6c ("mm: drop
fake head checks"), which 6.18 does not have.
But 6.18.y has its sibling, 01b1d0ffb6f7 ("hugetlb: remove
VMEMMAP_SYNCHRONIZE_RCU"), picked up in 6.18.51 as a Stable-dep-of
6e25c6a9c7ef ("mm/hugetlb_vmemmap: fix
__hugetlb_vmemmap_optimize_folios()"). It is only correct once fake
heads are gone. 6.18 still has them, and page_ref_add_unless() still
relies on the synchronize_rcu() it removed, see bd225530a4c7
("mm/hugetlb_vmemmap: fix race with speculative PFN walkers").
So the race bd225530a4c7 fixed is back in 6.18.y: compaction takes a
speculative reference on a PFN, passes page_count_writable() before HVO
remaps the tail vmemmap read-only, does its cmpxchg after the remap and
oopses.
Please revert dba93b8cceb0 from 6.18.y. It reverts cleanly, and
6e25c6a9c7ef applies to 6.18 without it.
--
Kiryl Shutsemau / Kirill A. Shutemov
next prev parent reply other threads:[~2026-11-10 12:11 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-10 1:04 FAILED: patch "[PATCH] mm/hugetlb_vmemmap: map the shared tail page writable" failed to apply to 6.18-stable tree Sasha Levin
2026-11-10 12:11 ` Kiryl Shutsemau [this message]
2026-11-10 20:58 ` Sasha Levin
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=avMJ1sVDviavKjQu@thinkstation \
--to=kas@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=corbet@lwn.net \
--cc=david@kernel.org \
--cc=fvdl@google.com \
--cc=liam@infradead.org \
--cc=ljs@kernel.org \
--cc=mhocko@suse.com \
--cc=muchun.song@linux.dev \
--cc=osalvador@suse.de \
--cc=peterz@infradead.org \
--cc=rdunlap@infradead.org \
--cc=rppt@kernel.org \
--cc=sashal@kernel.org \
--cc=skhan@linuxfoundation.org \
--cc=stable@vger.kernel.org \
--cc=surenb@google.com \
--cc=vbabka@kernel.org \
--cc=willy@infradead.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.