+ mm-drop-oom-code-from-exit_mmap-fix-fix.patch added to mm-unstable branch

+ mm-drop-oom-code-from-exit_mmap-fix-fix.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm-drop-oom-code-from-exit_mmap-fix-fix
has been added to the -mm mm-unstable branch.  Its filename is
     mm-drop-oom-code-from-exit_mmap-fix-fix.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-drop-oom-code-from-exit_mmap-fix-fix.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: Andrew Morton <akpm@linux-foundation.org>
Subject: mm-drop-oom-code-from-exit_mmap-fix-fix
Date: Wed Jun  1 03:17:52 PM PDT 2022

restore Suren's mmap_read_lock() optimization

Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/mmap.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/mm/mmap.c~mm-drop-oom-code-from-exit_mmap-fix-fix
+++ a/mm/mmap.c
@@ -3171,13 +3171,13 @@ void exit_mmap(struct mm_struct *mm)
 	/* mm's last user has gone, and its about to be pulled down */
 	mmu_notifier_release(mm);
 
-	mmap_write_lock(mm);
+	mmap_read_lock(mm);
 	arch_exit_mmap(mm);
 
 	vma = mas_find(&mas, ULONG_MAX);
 	if (!vma) {
 		/* Can happen if dup_mmap() received an OOM */
-		mmap_write_unlock(mm);
+		mmap_read_unlock(mm);
 		return;
 	}
 
@@ -3187,6 +3187,7 @@ void exit_mmap(struct mm_struct *mm)
 	/* update_hiwater_rss(mm) here? but nobody should be looking */
 	/* Use ULONG_MAX here to ensure all VMAs in the mm are unmapped */
 	unmap_vmas(&tlb, &mm->mm_mt, vma, 0, ULONG_MAX);
+	mmap_read_unlock(mm);
 
 	/*
 	 * Set MMF_OOM_SKIP to hide this task from the oom killer/reaper
@@ -3194,6 +3195,7 @@ void exit_mmap(struct mm_struct *mm)
 	 * mm_is_oom_victim because setting a bit unconditionally is cheaper.
 	 */
 	set_bit(MMF_OOM_SKIP, &mm->flags);
+	mmap_write_unlock(mm);
 	free_pgtables(&tlb, &mm->mm_mt, vma, FIRST_USER_ADDRESS,
 		      USER_PGTABLES_CEILING);
 	tlb_finish_mmu(&tlb);
_

Patches currently in -mm which might be from akpm@linux-foundation.org are

mm-oom_killc-fix-vm_oom_kill_table-ifdeffery.patch
mm-page_alloc-remotely-drain-per-cpu-lists-checkpatch-fixes.patch
mm-start-tracking-vmas-with-maple-tree-fix.patch
damon-convert-__damon_va_three_regions-to-use-the-vma-iterator-fix.patch
mm-mmap-use-advanced-maple-tree-api-for-mmap_region-fix-checkpatch-fixes.patch
mm-remove-the-vma-linked-list-fix-fix.patch
mm-handling-non-lru-pages-returned-by-vm_normal_pages-fix.patch
mm-introduce-clear_highpage_tagged-fix.patch
kasan-fix-zeroing-vmalloc-memory-with-hw_tags-fix.patch
mm-drop-oom-code-from-exit_mmap-fix.patch
mm-drop-oom-code-from-exit_mmap-fix-fix.patch
squashfs-implement-readahead-checkpatch-fixes.patch