+ mm-shmem-disallow-hugepages-if-the-system-wide-shmem-thp-sysfs-settings-are-disabled.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

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The patch titled
     Subject: mm: shmem: disallow hugepages if the system-wide shmem THP sysfs settings are disabled
has been added to the -mm mm-new branch.  Its filename is
     mm-shmem-disallow-hugepages-if-the-system-wide-shmem-thp-sysfs-settings-are-disabled.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-shmem-disallow-hugepages-if-the-system-wide-shmem-thp-sysfs-settings-are-disabled.patch

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

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

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------------------------------------------------------
From: Baolin Wang <baolin.wang@linux.alibaba.com>
Subject: mm: shmem: disallow hugepages if the system-wide shmem THP sysfs settings are disabled
Date: Thu, 5 Jun 2025 16:00:59 +0800

MADV_COLLAPSE will ignore the system-wide shmem THP sysfs settings, which
means that even though we have disabled the shmem THP configuration,
MADV_COLLAPSE will still attempt to collapse into a shmem THP.  This
violates the rule we have agreed upon: never means never.

Another rule for madvise, referring to David's suggestion: “allowing for
collapsing in a VM without VM_HUGEPAGE in the "madvise" mode would be
fine".

Then the current strategy is:

For shmem, if none of always, madvise, within_size, and inherit have
enabled PMD-sized THP, then MADV_COLLAPSE will be prohibited from
collapsing PMD-sized THP.

For tmpfs, if the mount option is set with the 'huge=never' parameter,
then MADV_COLLAPSE will be prohibited from collapsing PMD-sized THP.

Link: https://lkml.kernel.org/r/39d7617a6142c6091f233357171c5793e0992d36.1749109709.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/huge_memory.c |    2 +-
 mm/shmem.c       |    6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

--- a/mm/huge_memory.c~mm-shmem-disallow-hugepages-if-the-system-wide-shmem-thp-sysfs-settings-are-disabled
+++ a/mm/huge_memory.c
@@ -166,7 +166,7 @@ unsigned long __thp_vma_allowable_orders
 	 * own flags.
 	 */
 	if (!in_pf && shmem_file(vma->vm_file))
-		return shmem_allowable_huge_orders(file_inode(vma->vm_file),
+		return orders & shmem_allowable_huge_orders(file_inode(vma->vm_file),
 						   vma, vma->vm_pgoff, 0,
 						   !enforce_sysfs);
 
--- a/mm/shmem.c~mm-shmem-disallow-hugepages-if-the-system-wide-shmem-thp-sysfs-settings-are-disabled
+++ a/mm/shmem.c
@@ -625,7 +625,7 @@ static unsigned int shmem_huge_global_en
 		return 0;
 	if (shmem_huge == SHMEM_HUGE_DENY)
 		return 0;
-	if (shmem_huge_force || shmem_huge == SHMEM_HUGE_FORCE)
+	if (shmem_huge == SHMEM_HUGE_FORCE)
 		return maybe_pmd_order;
 
 	/*
@@ -660,7 +660,7 @@ static unsigned int shmem_huge_global_en
 
 		fallthrough;
 	case SHMEM_HUGE_ADVISE:
-		if (vm_flags & VM_HUGEPAGE)
+		if (shmem_huge_force || (vm_flags & VM_HUGEPAGE))
 			return maybe_pmd_order;
 		fallthrough;
 	default:
@@ -1783,7 +1783,7 @@ unsigned long shmem_allowable_huge_order
 	/* Allow mTHP that will be fully within i_size. */
 	mask |= shmem_get_orders_within_size(inode, within_size_orders, index, 0);
 
-	if (vm_flags & VM_HUGEPAGE)
+	if (shmem_huge_force || (vm_flags & VM_HUGEPAGE))
 		mask |= READ_ONCE(huge_shmem_orders_madvise);
 
 	if (global_orders > 0)
_

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

mm-fix-the-inaccurate-memory-statistics-issue-for-users.patch
mm-huge_memory-disallow-hugepages-if-the-system-wide-thp-sysfs-settings-are-disabled.patch
mm-shmem-disallow-hugepages-if-the-system-wide-shmem-thp-sysfs-settings-are-disabled.patch