linux-kernel - [PATCH v2 3/4] mm/mmap: Change detached vma locking scheme

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Message-Id: <20230714195551.894800-4-Liam.Howlett@oracle.com>
Date:   Fri, 14 Jul 2023 15:55:50 -0400
From:   "Liam R. Howlett" <Liam.Howlett@...cle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     maple-tree@...ts.infradead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>
Subject: [PATCH v2 3/4] mm/mmap: Change detached vma locking scheme

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.

Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 mm/mmap.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 7b70379a8b3e..ab6cb00d377a 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2427,7 +2427,7 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	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 *vmi, struct vm_area_struct *vma,
 	/* 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:
-- 
2.39.2