[PATCH] mm/mmap/vma_merge: set mid to NULL if not applicable-fix

[Vlastimil Babka]

Adjust/add comments as suggested by Lorenzo.

Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
---
 mm/mmap.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 3396c9b13f1c..cd0b0d1f4aeb 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -848,8 +848,9 @@ can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
  *
  * The following mprotect cases have to be considered, where AAAA is
  * the area passed down from mprotect_fixup, never extending beyond one
- * vma, PPPPPP is the prev vma specified, NNNN is a vma that overlaps
- * the area AAAA and XXXXXX the next vma after AAAA:
+ * vma, PPPP is the previous vma, NNNN is a vma that starts at the same
+ * address as AAAA and is of the same or larger span, and XXXX the next
+ * vma after AAAA:
  *
  *     AAAA             AAAA                   AAAA
  *    PPPPPPXXXXXX    PPPPPPXXXXXX       PPPPPPNNNNNN
@@ -920,6 +921,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
 	else
 		next = mid;
 
+	/* In cases 1 - 4 there's no NNNN vma */
 	if (mid && end <= mid->vm_start)
 		mid = NULL;
 
-- 
2.39.2