+ mm-introduce-vm_flags_reset_once-to-replace-write_once-vm_flags-updates.patch added to mm-unstable branch

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

The patch titled
     Subject: mm: introduce vm_flags_reset_once to replace WRITE_ONCE vm_flags updates
has been added to the -mm mm-unstable branch.  Its filename is
     mm-introduce-vm_flags_reset_once-to-replace-write_once-vm_flags-updates.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-introduce-vm_flags_reset_once-to-replace-write_once-vm_flags-updates.patch

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

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------------------------------------------------------
From: Suren Baghdasaryan <surenb@google.com>
Subject: mm: introduce vm_flags_reset_once to replace WRITE_ONCE vm_flags updates
Date: Tue, 31 Jan 2023 16:01:16 -0800

Provide vm_flags_reset_once() and replace the vm_flags updates which used
WRITE_ONCE() to prevent compiler optimizations.

Link: https://lkml.kernel.org/r/20230201000116.1333160-1-surenb@google.com
Fixes: 0cce31a0aa0e ("mm: replace vma->vm_flags direct modifications with modifier calls")
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---


--- a/include/linux/mm.h~mm-introduce-vm_flags_reset_once-to-replace-write_once-vm_flags-updates
+++ a/include/linux/mm.h
@@ -648,6 +648,13 @@ static inline void vm_flags_reset(struct
 	vm_flags_init(vma, flags);
 }
 
+static inline void vm_flags_reset_once(struct vm_area_struct *vma,
+				       vm_flags_t flags)
+{
+	mmap_assert_write_locked(vma->vm_mm);
+	WRITE_ONCE(ACCESS_PRIVATE(vma, __vm_flags), flags);
+}
+
 static inline void vm_flags_set(struct vm_area_struct *vma,
 				vm_flags_t flags)
 {
--- a/mm/mlock.c~mm-introduce-vm_flags_reset_once-to-replace-write_once-vm_flags-updates
+++ a/mm/mlock.c
@@ -380,7 +380,7 @@ static void mlock_vma_pages_range(struct
 	 */
 	if (newflags & VM_LOCKED)
 		newflags |= VM_IO;
-	vm_flags_reset(vma, newflags);
+	vm_flags_reset_once(vma, newflags);
 
 	lru_add_drain();
 	walk_page_range(vma->vm_mm, start, end, &mlock_walk_ops, NULL);
@@ -388,7 +388,7 @@ static void mlock_vma_pages_range(struct
 
 	if (newflags & VM_IO) {
 		newflags &= ~VM_IO;
-		vm_flags_reset(vma, newflags);
+		vm_flags_reset_once(vma, newflags);
 	}
 }
 
_

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

kernel-fork-convert-vma-assignment-to-a-memcpy.patch
mm-introduce-vma-vm_flags-wrapper-functions.patch
mm-replace-vm_locked_clear_mask-with-vm_locked_mask.patch
mm-replace-vma-vm_flags-direct-modifications-with-modifier-calls.patch
mm-replace-vma-vm_flags-indirect-modification-in-ksm_madvise.patch
mm-introduce-__vm_flags_mod-and-use-it-in-untrack_pfn.patch
mm-export-dump_mm.patch
mm-introduce-vm_flags_reset_once-to-replace-write_once-vm_flags-updates.patch