+ mm-shmem-ignore-sysfs-configs-for-shmem-forced-collapse.patch added to mm-hotfixes-unstable branch

+ mm-shmem-ignore-sysfs-configs-for-shmem-forced-collapse.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm: shmem: ignore sysfs configs for shmem forced collapse
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-shmem-ignore-sysfs-configs-for-shmem-forced-collapse.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-shmem-ignore-sysfs-configs-for-shmem-forced-collapse.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Baolin Wang <baolin.wang@linux.alibaba.com>
Subject: mm: shmem: ignore sysfs configs for shmem forced collapse
Date: Mon, 14 Sep 2026 10:12:41 +0800

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.

Link: https://lore.kernel.org/063f655b4d6c4234f3aa27ed6ecab10283ecb880.1789351825.git.baolin.wang@linux.alibaba.com
Fixes: 26c7d8413aaf ("mm: thp: support "THPeligible" semantics for mTHP with anonymous shmem")
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reported-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Closes: https://lore.kernel.org/all/20260908125105.1510704-7-kirill@shutemov.name/
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Acked-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Reviewed-by: Barry Song <baohua@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
---

 mm/shmem.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/mm/shmem.c~mm-shmem-ignore-sysfs-configs-for-shmem-forced-collapse
+++ a/mm/shmem.c
@@ -1847,8 +1847,11 @@ unsigned long shmem_allowable_huge_order
 
 	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;
 
 	/*
_

Patches currently in -mm which might be from baolin.wang@linux.alibaba.com are

maintainers-add-baoquan-and-me-as-mglru-reviewers.patch
mm-shmem-ignore-sysfs-configs-for-shmem-forced-collapse.patch
mm-mglru-clear-the-reference-counter-for-rejected-folios.patch