linux-kernel - [PATCH v6 67/71] nommu: Remove uses of VMA linked list

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Message-ID: <20220215144241.3812052-67-Liam.Howlett@oracle.com>
Date:   Tue, 15 Feb 2022 14:43:28 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH v6 67/71] nommu: Remove uses of VMA linked list

From: "Matthew Wilcox (Oracle)" <willy@...radead.org>

Use the maple tree or VMA iterator instead.  This is faster and will
allow us to shrink the VMA.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
Acked-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/nommu.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/mm/nommu.c b/mm/nommu.c
index f500c57a59f3..13028f93dfd9 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1370,6 +1370,7 @@ static int shrink_vma(struct mm_struct *mm,
  */
 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, struct list_head *uf)
 {
+	MA_STATE(mas, &mm->mm_mt, start, start);
 	struct vm_area_struct *vma;
 	unsigned long end;
 	int ret;
@@ -1381,7 +1382,7 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, struct list
 	end = start + len;
 
 	/* find the first potentially overlapping VMA */
-	vma = find_vma(mm, start);
+	vma = mas_find(&mas, end - 1);
 	if (!vma) {
 		static int limit;
 		if (limit < 5) {
@@ -1400,7 +1401,7 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, struct list
 				return -EINVAL;
 			if (end == vma->vm_end)
 				goto erase_whole_vma;
-			vma = vma->vm_next;
+			vma = mas_next(&mas, end - 1);
 		} while (vma);
 		return -EINVAL;
 	} else {
@@ -1449,6 +1450,7 @@ SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
  */
 void exit_mmap(struct mm_struct *mm)
 {
+	VMA_ITERATOR(vmi, mm, 0);
 	struct vm_area_struct *vma;
 
 	if (!mm)
@@ -1456,12 +1458,17 @@ void exit_mmap(struct mm_struct *mm)
 
 	mm->total_vm = 0;
 
-	while ((vma = mm->mmap)) {
-		mm->mmap = vma->vm_next;
+	/*
+	 * Lock the mm to avoid assert complaining even though this is the only
+	 * user of the mm
+	 */
+	mmap_write_lock(mm);
+	for_each_vma(vmi, vma) {
 		delete_vma_from_mm(vma);
 		delete_vma(mm, vma);
 		cond_resched();
 	}
+	mmap_write_unlock(mm);
 	__mt_destroy(&mm->mm_mt);
 }
 
-- 
2.34.1