linux-kernel - [RFC PATCH 2/6] mm/mmap: Abstract vma clean up from exit

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Message-ID: <20250815191031.3769540-3-Liam.Howlett@oracle.com>
Date: Fri, 15 Aug 2025 15:10:27 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: David Hildenbrand <david@...hat.com>,
        Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: maple-tree@...ts.infradead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Vlastimil Babka <vbabka@...e.cz>,
        Mike Rapoport <rppt@...nel.org>,
        Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jann Horn <jannh@...gle.com>, Pedro Falcato <pfalcato@...e.de>,
        Charan Teja Kalla <quic_charante@...cinc.com>,
        shikemeng@...weicloud.com, kasong@...cent.com, nphamcs@...il.com,
        bhe@...hat.com, baohua@...nel.org, chrisl@...nel.org,
        Matthew Wilcox <willy@...radead.org>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>
Subject: [RFC PATCH 2/6] mm/mmap: Abstract vma clean up from exit_mmap()

Create the new function tear_down_vmas() to remove a range of vmas.
exit_mmap() will be removing all the vmas.

This is necessary for future patches.

No functional changes intended.

Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 mm/mmap.c | 37 ++++++++++++++++++++++++-------------
 1 file changed, 24 insertions(+), 13 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index c4c315b480af7..0995a48b46d59 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1250,6 +1250,29 @@ int vm_brk_flags(unsigned long addr, unsigned long request, vm_flags_t vm_flags)
 }
 EXPORT_SYMBOL(vm_brk_flags);
 
+static inline
+unsigned long tear_down_vmas(struct mm_struct *mm, struct vma_iterator *vmi,
+		struct vm_area_struct *vma, unsigned long max)
+{
+	unsigned long nr_accounted = 0;
+	int count = 0;
+
+	mmap_assert_write_locked(mm);
+	vma_iter_set(vmi, vma->vm_end);
+	do {
+		if (vma->vm_flags & VM_ACCOUNT)
+			nr_accounted += vma_pages(vma);
+		vma_mark_detached(vma);
+		remove_vma(vma);
+		count++;
+		cond_resched();
+		vma = vma_next(vmi);
+	} while (vma && vma->vm_end <= max);
+
+	BUG_ON(count != mm->map_count);
+	return nr_accounted;
+}
+
 /* Release all mmaps. */
 void exit_mmap(struct mm_struct *mm)
 {
@@ -1257,7 +1280,6 @@ void exit_mmap(struct mm_struct *mm)
 	struct vm_area_struct *vma;
 	unsigned long nr_accounted = 0;
 	VMA_ITERATOR(vmi, mm, 0);
-	int count = 0;
 
 	/* mm's last user has gone, and its about to be pulled down */
 	mmu_notifier_release(mm);
@@ -1297,18 +1319,7 @@ void exit_mmap(struct mm_struct *mm)
 	 * enabled, without holding any MM locks besides the unreachable
 	 * mmap_write_lock.
 	 */
-	vma_iter_set(&vmi, vma->vm_end);
-	do {
-		if (vma->vm_flags & VM_ACCOUNT)
-			nr_accounted += vma_pages(vma);
-		vma_mark_detached(vma);
-		remove_vma(vma);
-		count++;
-		cond_resched();
-		vma = vma_next(&vmi);
-	} while (vma && likely(!xa_is_zero(vma)));
-
-	BUG_ON(count != mm->map_count);
+	nr_accounted = tear_down_vmas(mm, &vmi, vma, ULONG_MAX);
 
 destroy:
 	__mt_destroy(&mm->mm_mt);
-- 
2.47.2