From: Liam R. Howlett <Liam.Howlett@oracle.com>
Date: Mon, 6 Sep 2021 03:31:15 +0000 (-0400)
Subject: mmap: Change zeroing of maple tree in __vma_adjust
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=2876d6e06ecbcf6cc096d514f78bdd0392b355d2;p=users%2Fjedix%2Flinux-maple.git

mmap: Change zeroing of maple tree in __vma_adjust

Only write to the maple tree if we are not inserting or the insert isn't
going to overwrite the area to clear.  This avoids spanning writes and
node coealescing when unnecessary.

Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
---

diff --git a/mm/mmap.c b/mm/mmap.c
index e6e128c09b94..4308359ba3dc 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -615,6 +615,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
 	bool vma_changed = false;
 	long adjust_next = 0;
 	int remove_next = 0;
+	unsigned long old_start;
 
 	if (next && !insert) {
 		struct vm_area_struct *exporter = NULL, *importer = NULL;
@@ -740,25 +741,29 @@ again:
 			vma_interval_tree_remove(next, root);
 	}
 
+	old_start = vma->vm_start;
 	if (start != vma->vm_start) {
-		if (vma->vm_start < start)
-			vma_mt_szero(mm, vma->vm_start, start);
-		else
-			vma_changed = true;
+		vma_changed = true;
 		vma->vm_start = start;
 	}
 	if (end != vma->vm_end) {
-		if (vma->vm_end > end)
-			vma_mt_szero(mm, end, vma->vm_end);
-		else
+		if (vma->vm_end > end) {
+			if (!insert || (insert && (insert->vm_start != end)))
+				vma_mt_szero(mm, end, vma->vm_end);
+		} else
 			vma_changed = true;
 		vma->vm_end = end;
 		if (!next)
 			mm->highest_vm_end = vm_end_gap(vma);
 	}
 
-	if (vma_changed)
+	if (vma_changed) {
 		vma_store(mm, vma);
+		if (old_start < start) {
+			if (insert && (insert->vm_start != old_start))
+				vma_mt_szero(mm, old_start, start);
+		}
+	}
 
 	vma->vm_pgoff = pgoff;
 	if (adjust_next) {