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b=EdTV3YmltqmF7He/aozNeHtXl+aENragv8NRXN70r1qHSHp/eP3SWcC14FNNWWGJb M++wWTN0EcIT6IgJ8nBfUwJyBNySJuXFxepYnqGuMHEu616jhzt6Szp+jZdn1ARx4I m0SLpWyh/bmDdH+6ovd7cNxC7PgisL07t1EWIpo4TqG9mv3Udf6D7K5esrHlNoAnDj +sbRzCt0A4e/+y11s1n/hF0L2/FtNccOqGxq+2uZyvp9tNkPd2dai+8ikN3Wnl5vZp sIeZgbAgxuNkznWkdAamJxgzygvLMiYBYJuL+e0A55B0eJI0oH7WFZMkDqCNAa4Px3 EVZt/DVA+s1cw== Message-ID: <66f5a0c2-6adb-4e03-9225-cf566b7f76f8@kernel.org> Date: Fri, 25 Sep 2026 13:29:11 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm: shmem: ignore sysfs configs for shmem forced collapse To: Baolin Wang , akpm@linux-foundation.org, hughd@google.com Cc: 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, kas@kernel.org, ljs@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <063f655b4d6c4234f3aa27ed6ecab10283ecb880.1789351825.git.baolin.wang@linux.alibaba.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: y5smyt9sgm7931dbwgzmrrp6jmde5usp X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: E85652000B X-HE-Tag: 1790344976-188415 X-HE-Meta: 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 9Aph7icg Be5f60eAnDv6G7OQHWZqvJ0JmbczHoT4+uKtkmGLUPJJ2BQ+VWC/DJVuiCHDGzsTLdmTcOogMRgwmp+U7/uSiWGE3Huj4EQ9ubAsaWvTyc9z3QuP+mt5TLJZZ+wh+CSf9PTdsnu8GpCoCY+duWdTKmvxhzELwNK35lFmy8f4A/JHVdkGyCOVsLEZVCTuhqsDeZPOE9rVMMEAe6M4ng5/isg3g1hQACAytxC9q+8vug/XwGmEaBrghqx1+50+xumcjd/Ttse136AeyRh+Uw87l4NpjrW08nSIPwkGIpEWK424Xm32NuoGLXhFJqR6Iw0V6wgfZ/hw0uZYad98= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/14/26 04:12, Baolin Wang wrote: > According to Documentation/mm/transhuge.rst, MADV_COLLAPSE is expected to > ignore any THP or mTHP interface settings. > > However, after commit 26c7d8413aaf ("mm: thp: support "THPeligible" semantics > for mTHP with anonymous shmem"), 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: 26c7d8413aaf ("mm: thp: support "THPeligible" semantics for mTHP with anonymous shmem") > Reported-by: Kiryl Shutsemau (Meta) > Closes: https://lore.kernel.org/all/20260908125105.1510704-7-kirill@shutemov.name/ > Reviewed-by: Kiryl Shutsemau (Meta) > Acked-by: Zi Yan > Reviewed-by: Lance Yang > Signed-off-by: Baolin Wang > --- Acked-by: David Hildenbrand (Arm) -- Cheers, David