linux-kernel - [PATCH 1/2] mm/mmap: Add inline vma_next() for readability of mmap code

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Message-Id: <20200818154707.2515169-1-Liam.Howlett@Oracle.com>
Date:   Tue, 18 Aug 2020 11:47:06 -0400
From:   "Liam R. Howlett" <Liam.Howlett@...cle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Liam.Howlett@...cle.com
Subject: [PATCH 1/2] mm/mmap: Add inline vma_next() for readability of mmap code

There are three places that the next vma is required which uses the same
block of code.  Replace the block with a function and add comments on
what happens in the case where NULL is encountered.

Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 mm/mmap.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 40248d84ad5fb..6026353035966 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -560,6 +560,23 @@ static int find_vma_links(struct mm_struct *mm, unsigned long addr,
 	return 0;
 }
 
+/*
+ * vma_next() - Get the next VMA.
+ * @mm: The mm_struct.
+ * @vma: The current vma.
+ *
+ * If @vma is NULL, return the first vma in the mm.
+ *
+ * Returns: The next VMA after @vma.
+ */
+static inline struct vm_area_struct *vma_next(struct mm_struct *mm,
+					 struct vm_area_struct *vma)
+{
+	if (!vma)
+		return mm->mmap;
+
+	return vma->vm_next;
+}
 static unsigned long count_vma_pages_range(struct mm_struct *mm,
 		unsigned long addr, unsigned long end)
 {
@@ -1131,10 +1148,7 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm,
 	if (vm_flags & VM_SPECIAL)
 		return NULL;
 
-	if (prev)
-		next = prev->vm_next;
-	else
-		next = mm->mmap;
+	next = vma_next(mm, prev);
 	area = next;
 	if (area && area->vm_end == end)		/* cases 6, 7, 8 */
 		next = next->vm_next;
@@ -2625,7 +2639,7 @@ static void unmap_region(struct mm_struct *mm,
 		struct vm_area_struct *vma, struct vm_area_struct *prev,
 		unsigned long start, unsigned long end)
 {
-	struct vm_area_struct *next = prev ? prev->vm_next : mm->mmap;
+	struct vm_area_struct *next = vma_next(mm, prev);
 	struct mmu_gather tlb;
 
 	lru_add_drain();
@@ -2824,7 +2838,7 @@ int __do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
 		if (error)
 			return error;
 	}
-	vma = prev ? prev->vm_next : mm->mmap;
+	vma = vma_next(mm, prev);
 
 	if (unlikely(uf)) {
 		/*
-- 
2.28.0