linux-kernel - [PATCH v4 34/49] mm: Remove unnecessary write to vma iterator in __vma

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Message-Id: <20230120162650.984577-35-Liam.Howlett@oracle.com>
Date:   Fri, 20 Jan 2023 11:26:35 -0500
From:   "Liam R. Howlett" <Liam.Howlett@...cle.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        maple-tree@...ts.infradead.org
Cc:     "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>
Subject: [PATCH v4 34/49] mm: Remove unnecessary write to vma iterator in __vma_adjust()

From: "Liam R. Howlett" <Liam.Howlett@...cle.com>

If the vma start address is going to change due to an insert, then it is
safe to not write the vma to the tree.  The write of the insert vma will
alter the tree as necessary.

Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 mm/mmap.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 5f03c8f3f407..58b2187b447b 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -722,10 +722,12 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	}
 
 	if (start != vma->vm_start) {
-		if ((vma->vm_start < start) &&
-		    (!insert || (insert->vm_end != start))) {
-			vma_iter_clear(vmi, vma->vm_start, start);
-			VM_WARN_ON(insert && insert->vm_start > vma->vm_start);
+		if (vma->vm_start < start) {
+			if (!insert || (insert->vm_end != start)) {
+				vma_iter_clear(vmi, vma->vm_start, start);
+				vma_iter_set(vmi, start);
+				VM_WARN_ON(insert && insert->vm_start > vma->vm_start);
+			}
 		} else {
 			vma_changed = true;
 		}
-- 
2.35.1