From: Liam R. Howlett <Liam.Howlett@Oracle.com>
Date: Wed, 25 Nov 2020 01:23:48 +0000 (-0500)
Subject: mmap: Avoid modifying maple tree in __vma_adjust more than necessary
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=d06a7bb52d132ca937beb46739531873cf420481;p=users%2Fjedix%2Flinux-maple.git

mmap: Avoid modifying maple tree in __vma_adjust more than necessary

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

diff --git a/mm/mmap.c b/mm/mmap.c
index e20403ad4aed..5d7d798fb82f 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -743,7 +743,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
 	struct rb_root_cached *root = NULL;
 	struct anon_vma *anon_vma = NULL;
 	struct file *file = vma->vm_file;
-	bool start_changed = false, end_changed = false;
+	bool vma_changed = false;
 	long adjust_next = 0;
 	int remove_next = 0;
 
@@ -872,21 +872,21 @@ again:
 	}
 
 	if (start != vma->vm_start) {
-		unsigned long old_start = vma->vm_start;
+		if (vma->vm_start < start)
+			vma_mt_szero(mm, vma->vm_start, start);
+		else
+			vma_changed = true;
 		vma->vm_start = start;
-		if (old_start < start)
-			vma_mt_szero(mm, old_start, start);
-		start_changed = true;
 	}
 	if (end != vma->vm_end) {
-		unsigned long old_end = vma->vm_end;
+		if (vma->vm_end > end)
+			vma_mt_szero(mm, end, vma->vm_end);
+		else
+			vma_changed = true;
 		vma->vm_end = end;
-		if (old_end > end)
-			vma_mt_szero(mm, end, old_end);
-		end_changed = true;
 	}
 
-	if (end_changed || start_changed)
+	if (vma_changed)
 		vma_mt_store(mm, vma);
 
 	vma->vm_pgoff = pgoff;
@@ -914,7 +914,7 @@ again:
 		 * (it may either follow vma or precede it).
 		 */
 		__insert_vm_struct(mm, insert);
-	} else if (end_changed && !next) {
+	} else if (vma_changed && !next) {
 		mm->highest_vm_end = vm_end_gap(vma);
 	}