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Mon, 14 Sep 2026 03:09:15 +0000 X-Mizu-Trace-ID: ab92a83b59a5437d X-Migadu-Flow: FLOW_OUT Message-ID: Date: Mon, 14 Sep 2026 11:09:08 +0800 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, david@kernel.org 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: Qi Zheng In-Reply-To: <063f655b4d6c4234f3aa27ed6ecab10283ecb880.1789351825.git.baolin.wang@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: E150A80003 X-Stat-Signature: dx9ec8e6t9zhi7emi6uybny5rfiwwhk7 X-HE-Tag: 1789355356-179781 X-HE-Meta: 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 qV8f7ab0 sUXB6yPpS/2WqSkY6YF/lJvm8KnIYk95AvBody4nu5qBPBH/hWlbFsg8OTJCNuuwYqK+y1/uHIBDImCTk5HKuMasNNtDyz2EI9mCikumI0Ofm/f+ssG1ofm3c7SpxsEqWThK3lJmT4xEnSlVGaCaXnUdEqrxvAkmUWPDOMUQqpVhwa8mvBQN65cVNpzbZlFALBqyESuX3dQKWorWlqe1BULLIfdkkVz3PWkKdrut5pOmmKrsDvhzn2CkP1hQ7eM5141TVsPSGKZwVWu2fm8AW+b4COiqrbeh8vQ/O8KGgQMjFSMQ/4aUios0Uw2EWKHqU6njUp7UU/+74p0uXdGCLa8QOsLEx3MSK2deh Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/14/26 10:12 AM, 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 > --- > Changes from v1: > - Use the correct fixes tag (per Kiryl). > - Collect reviewed tags from Kiryl, Zi and Lance. Thanks. > --- > mm/shmem.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) Acked-by: Qi Zheng Thanks, Qi > > diff --git a/mm/shmem.c b/mm/shmem.c > index c92ed17dbc4a..b572c60f2af8 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -2049,8 +2049,11 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode, > > global_orders = shmem_huge_global_enabled(inode, index, write_end, > shmem_huge_force, vma, vm_flags); > - /* Tmpfs huge pages allocation */ > - if (!vma || !vma_is_anon_shmem(vma)) > + /* > + * Tmpfs huge pages allocation or forced collapse ignores > + * sysfs configs. > + */ > + if (!vma || !vma_is_anon_shmem(vma) || shmem_huge_force) > return global_orders; > > /*