+ mm-mmap-change-detached-vma-locking-scheme.patch added to mm-unstable branch

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

The patch titled
     Subject: mm/mmap: change detached vma locking scheme
has been added to the -mm mm-unstable branch.  Its filename is
     mm-mmap-change-detached-vma-locking-scheme.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mmap-change-detached-vma-locking-scheme.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: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Subject: mm/mmap: change detached vma locking scheme
Date: Fri, 14 Jul 2023 15:55:50 -0400

Don't set the lock to the mm lock so that the detached VMA tree does not
complain about being unlocked when the mmap_lock is dropped prior to
freeing the tree.

Move the destroying of the detached tree outside the mmap lock all
together.

Link: https://lkml.kernel.org/r/20230714195551.894800-4-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oliver Sang <oliver.sang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

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

--- a/mm/mmap.c~mm-mmap-change-detached-vma-locking-scheme
+++ a/mm/mmap.c
@@ -2427,7 +2427,7 @@ do_vmi_align_munmap(struct vma_iterator
 	unsigned long locked_vm = 0;
 	MA_STATE(mas_detach, &mt_detach, 0, 0);
 	mt_init_flags(&mt_detach, vmi->mas.tree->ma_flags & MT_FLAGS_LOCK_MASK);
-	mt_set_external_lock(&mt_detach, &mm->mmap_lock);
+	mt_detach.ma_external_lock = NULL;
 
 	/*
 	 * If we need to split any vma, do it now to save pain later.
@@ -2545,11 +2545,11 @@ do_vmi_align_munmap(struct vma_iterator
 	/* Statistics and freeing VMAs */
 	mas_set(&mas_detach, start);
 	remove_mt(mm, &mas_detach);
-	__mt_destroy(&mt_detach);
 	validate_mm(mm);
 	if (unlock)
 		mmap_read_unlock(mm);
 
+	__mt_destroy(&mt_detach);
 	return 0;
 
 clear_tree_failed:
_

Patches currently in -mm which might be from Liam.Howlett@oracle.com are

mm-mlock-fix-vma-iterator-conversion-of-apply_vma_lock_flags.patch
maple_tree-fix-32-bit-mas_next-testing.patch
maple_tree-fix-node-allocation-testing-on-32-bit.patch
mm-mmap-clean-up-validate_mm-calls.patch
maple_tree-relax-lockdep-checks-for-on-stack-trees.patch
mm-mmap-change-detached-vma-locking-scheme.patch
maple_tree-be-more-strict-about-locking.patch