+ mm-shmem-restore-shmem_huge_deny-precedence-over-madv_collapse.patch added to mm-hotfixes-unstable branch

+ mm-shmem-restore-shmem_huge_deny-precedence-over-madv_collapse.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/shmem: restore SHMEM_HUGE_DENY precedence over MADV_COLLAPSE
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-shmem-restore-shmem_huge_deny-precedence-over-madv_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-restore-shmem_huge_deny-precedence-over-madv_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: "Zach O'Keefe" <zokeefe@google.com>
Subject: mm/shmem: restore SHMEM_HUGE_DENY precedence over MADV_COLLAPSE
Date: Sat, 24 Dec 2022 00:20:35 -0800

SHMEM_HUGE_DENY is for emergency use by the admin, to disable allocation
of shmem huge pages if, for example, a dangerous bug is found in their
usage: see "deny" in Documentation/mm/transhuge.rst.  An app using
madvise(,,MADV_COLLAPSE) should not be allowed to override it: restore its
precedence over shmem_huge_force.

Restore SHMEM_HUGE_DENY precedence over MADV_COLLAPSE.

Link: https://lkml.kernel.org/r/20221224082035.3197140-2-zokeefe@google.com
Fixes: 7c6c6cc4d3a2 ("mm/shmem: add flag to enforce shmem THP in hugepage_vma_check()")
Signed-off-by: Zach O'Keefe <zokeefe@google.com>
Suggested-by: Hugh Dickins <hughd@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---


--- a/mm/shmem.c~mm-shmem-restore-shmem_huge_deny-precedence-over-madv_collapse
+++ a/mm/shmem.c
@@ -478,12 +478,10 @@ bool shmem_is_huge(struct vm_area_struct
 	if (vma && ((vma->vm_flags & VM_NOHUGEPAGE) ||
 	    test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)))
 		return false;
-	if (shmem_huge_force)
-		return true;
-	if (shmem_huge == SHMEM_HUGE_FORCE)
-		return true;
 	if (shmem_huge == SHMEM_HUGE_DENY)
 		return false;
+	if (shmem_huge_force || shmem_huge == SHMEM_HUGE_FORCE)
+		return true;
 
 	switch (SHMEM_SB(inode->i_sb)->huge) {
 	case SHMEM_HUGE_ALWAYS:
_

Patches currently in -mm which might be from zokeefe@google.com are

mm-madv_collapse-dont-expand-collapse-when-vm_end-is-past-requested-end.patch
mm-shmem-restore-shmem_huge_deny-precedence-over-madv_collapse.patch