mm/mmap.c: extract __vma_unlink_list() as counterpart for __vma_link_list()

Just make the code a little easier to read.

Link: http://lkml.kernel.org/r/20191006012636.31521-3-richardw.yang@linux.intel.comSigned-off-by: Wei Yang <richardw.yang@linux.intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/internal.h

@@ -291,6 +291,7 @@ static inline bool is_data_mapping(vm_flags_t flags)
 /* mm/util.c */
 void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
 		struct vm_area_struct *prev, struct rb_node *rb_parent);
+void __vma_unlink_list(struct mm_struct *mm, struct vm_area_struct *vma);
 
 #ifdef CONFIG_MMU
 extern long populate_vma_page_range(struct vm_area_struct *vma,

mm/mmap.c

@@ -686,18 +686,8 @@ static __always_inline void __vma_unlink_common(struct mm_struct *mm,
 						struct vm_area_struct *vma,
 						struct vm_area_struct *ignore)
 {
-	struct vm_area_struct *prev, *next;
-
 	vma_rb_erase_ignore(vma, &mm->mm_rb, ignore);
-	next = vma->vm_next;
-	prev = vma->vm_prev;
-	if (prev)
-		prev->vm_next = next;
-	else
-		mm->mmap = next;
-	if (next)
-		next->vm_prev = prev;
-
+	__vma_unlink_list(mm, vma);
 	/* Kill the cache */
 	vmacache_invalidate(mm);
 }

mm/nommu.c

@@ -684,13 +684,7 @@ static void delete_vma_from_mm(struct vm_area_struct *vma)
 	/* remove from the MM's tree and list */
 	rb_erase(&vma->vm_rb, &mm->mm_rb);
 
-	if (vma->vm_prev)
-		vma->vm_prev->vm_next = vma->vm_next;
-	else
-		mm->mmap = vma->vm_next;
-
-	if (vma->vm_next)
-		vma->vm_next->vm_prev = vma->vm_prev;
+	__vma_unlink_list(mm, vma);
 }
 
 /*

mm/util.c

@@ -292,6 +292,20 @@ void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
 		next->vm_prev = vma;
 }
 
+void __vma_unlink_list(struct mm_struct *mm, struct vm_area_struct *vma)
+{
+	struct vm_area_struct *prev, *next;
+
+	next = vma->vm_next;
+	prev = vma->vm_prev;
+	if (prev)
+		prev->vm_next = next;
+	else
+		mm->mmap = next;
+	if (next)
+		next->vm_prev = prev;
+}
+
 /* Check if the vma is being used as a stack by this task */
 int vma_is_stack_for_current(struct vm_area_struct *vma)
 {