linux-kernel - [PATCH] mm/mmap.c: logic of find_vma_intersection repeated in __do

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Date:   Fri,  9 Apr 2021 13:21:26 -0300
From:   Gonzalo Matias Juarez Tello <gmjuareztello@...il.com>
To:     linux-mm@...ck.org
Cc:     Gonzalo Matias Juarez Tello <gmjuareztello@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] mm/mmap.c: logic of find_vma_intersection repeated in __do_munmap

Logic of find_vma_intersection() (which is an inline fc) is
repeated in __do_munmap().
Besides, prev is assigned a value before checking vma->vm_start >= end
which might end up on a return statement making that assignment useless.

Calling find_vma_intersection() checks that condition and returns NULL if
no vma is found, hence only the !vma check is needed in __do_munmap().

Signed-off-by: Gonzalo Matias Juarez Tello <gmjuareztello@...il.com>
---
 mm/mmap.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 3f287599a7a3..59ceaa474a00 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2822,16 +2822,11 @@ int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
 	 */
 	arch_unmap(mm, start, end);
 
-	/* Find the first overlapping VMA */
-	vma = find_vma(mm, start);
+	/* Find the first overlapping VMA where start < vma->vm_end */
+	vma = find_vma_intersection(mm, start, end);
 	if (!vma)
 		return 0;
 	prev = vma->vm_prev;
-	/* we have  start < vma->vm_end  */
-
-	/* if it doesn't overlap, we have nothing.. */
-	if (vma->vm_start >= end)
-		return 0;
 
 	/*
 	 * If we need to split any vma, do it now to save pain later.
-- 
2.31.1