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b=GXewc01/R8D6CuSugKRzRVSbYHz161gyghKdjbBLXgPoxnBYiwvlYMDy19RpgyO7z RoAzuRyYQ1wUfenQJmIctyatSXZcfRy5yPXkHfRwbN+jNZkFNP/CXJyPMBv0PPf7wA vB4GnsqGDG7W6YJJqHefdXeSqauBqsOF18fAxiPxFr4KmGyX6xqGN7XED4SE+qWjGm 09Cm5j0x/RqY/Gb9iU2wNz3k8E3P0NuRI2X8cyJSIGHBi6WON277di/UhPFcHYlrH7 ORuvIf6RIOXvnNbe1wqxNAHRMUBuWZJgB+cw5tuDSNk4IgY47Z91uDoVBFO+TD2xKU zCpLfnfzWlt7Q== Date: Fri, 25 Sep 2026 15:19:31 +0100 From: "Lorenzo Stoakes (ARM)" To: Baolin Wang 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, kas@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm: shmem: ignore sysfs configs for shmem forced collapse Message-ID: References: <063f655b4d6c4234f3aa27ed6ecab10283ecb880.1789351825.git.baolin.wang@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <063f655b4d6c4234f3aa27ed6ecab10283ecb880.1789351825.git.baolin.wang@linux.alibaba.com> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: E2C92140004 X-Stat-Signature: kyfqfw8f9sdzsaj8s1mrc93jm7w1zge7 X-Rspam-User: X-HE-Tag: 1790345978-589887 X-HE-Meta: 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 BQx0LgJB I67ZORkC19jHlonHiajIQU20Odji01fcGggpqtTMVTx2HNLuT/FcIHt92lhdA5DIzkoEo22R8iHF/fM0KYYFGS78Z6r89jvstwNtVx26bnqyRivDW+WbBITcGrKwGTmdKrqKjkHBtZIlsI/3C+pAgg888nKFGVihO7O9Jb524GNUhHQTF9vP7SbWX5Occm0yOZBdbO08tIKNasZziXO2MgGRDU/irVDOJUBtQhijAFASXWipO6PrYPrnaKWTNsZI+Kae12xAEu00XlCVMO7klUAFF6UDhZbuGabwjXCn4Oapa0HzsKQnvPFn4TnfmmlXSk964TAxhRxUhPc0= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Sep 14, 2026 at 10:12:41AM +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 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 Seemes reasonable! Reviewed-by: Lorenzo Stoakes (ARM) > --- > 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(-) > > 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; > > /* > -- > 2.47.3 > -- Cheers, Lorenzo