From: Kiryl Shutsemau <kas@kernel.org>
To: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: akpm@linux-foundation.org, hughd@google.com, david@kernel.org,
ziy@nvidia.com, liam@infradead.org, nico.pache@linux.dev,
ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org,
lance.yang@linux.dev, usama.arif@linux.dev, ljs@kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: shmem: ignore sysfs configs for shmem forced collapse
Date: Fri, 11 Sep 2026 12:37:30 +0100 [thread overview]
Message-ID: <aqPmxRkJokRyVzdU@thinkstation> (raw)
In-Reply-To: <b1829ac0d3f38217f031854ff0f40abef614ac0d.1789098446.git.baolin.wang@linux.alibaba.com>
On Fri, Sep 11, 2026 at 12:04:33PM +0800, Baolin Wang wrote:
> According to Documentation/mm/transhuge.rst, MADV_COLLAPSE is expected to
> ignore any THP or mTHP interface settings.
>
> However, after commit 6beeab870e70 ("mm: shmem: move shmem_huge_global_enabled()
> into shmem_allowable_huge_orders()"), performing MADV_COLLAPSE on shmem
> will depend on /sys/.../hugepages-2048kB/shmem_enabled being set to "inherit"
> (although that is the default), which can cause MADV_COLLAPSE to fail
> unexpectedly.
>
> Fix this by returning the result of shmem_huge_global_enabled() directly
> when MADV_COLLAPSE is requested, allowing PMD-order collapse while ignoring
> shmem THP/mTHP settings.
>
> Fixes: 6beeab870e70 ("mm: shmem: move shmem_huge_global_enabled() into shmem_allowable_huge_orders()")
Hm. I don't think it is the right Fixes tag. "No functional changes" in
its commit message seems to be true.
This might be a better fit:
Fixes: 26c7d8413aaf ("mm: thp: support "THPeligible" semantics for mTHP with anonymous shmem")
> Reported-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
> Closes: https://lore.kernel.org/all/20260908125105.1510704-7-kirill@shutemov.name/
> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Thanks!
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
--
Kiryl Shutsemau / Kirill A. Shutemov
next prev parent reply other threads:[~2026-09-11 11:37 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-11 4:04 [PATCH] mm: shmem: ignore sysfs configs for shmem forced collapse Baolin Wang
2026-09-11 11:37 ` Kiryl Shutsemau [this message]
2026-09-11 14:34 ` Zi Yan
2026-09-11 15:47 ` Lance Yang
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