vm_area_operations: kill ->migrate()

the only instance this method has ever grown was one in kernfs -
one that call ->migrate() of another vm_ops if it exists.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/kernfs/file.c

@@ -448,27 +448,6 @@ static struct mempolicy *kernfs_vma_get_policy(struct vm_area_struct *vma,
 	return pol;
 }
 
-static int kernfs_vma_migrate(struct vm_area_struct *vma,
-			      const nodemask_t *from, const nodemask_t *to,
-			      unsigned long flags)
-{
-	struct file *file = vma->vm_file;
-	struct kernfs_open_file *of = kernfs_of(file);
-	int ret;
-
-	if (!of->vm_ops)
-		return 0;
-
-	if (!kernfs_get_active(of->kn))
-		return 0;
-
-	ret = 0;
-	if (of->vm_ops->migrate)
-		ret = of->vm_ops->migrate(vma, from, to, flags);
-
-	kernfs_put_active(of->kn);
-	return ret;
-}
 #endif
 
 static const struct vm_operations_struct kernfs_vm_ops = {
@@ -479,7 +458,6 @@ static const struct vm_operations_struct kernfs_vm_ops = {
 #ifdef CONFIG_NUMA
 	.set_policy	= kernfs_vma_set_policy,
 	.get_policy	= kernfs_vma_get_policy,
-	.migrate	= kernfs_vma_migrate,
 #endif
 };
 

include/linux/migrate.h

@@ -36,9 +36,6 @@ extern int migrate_pages(struct list_head *l, new_page_t new, free_page_t free,
 
 extern int migrate_prep(void);
 extern int migrate_prep_local(void);
-extern int migrate_vmas(struct mm_struct *mm,
-		const nodemask_t *from, const nodemask_t *to,
-		unsigned long flags);
 extern void migrate_page_copy(struct page *newpage, struct page *page);
 extern int migrate_huge_page_move_mapping(struct address_space *mapping,
 				  struct page *newpage, struct page *page);
@@ -57,13 +54,6 @@ static inline int migrate_pages(struct list_head *l, new_page_t new,
 static inline int migrate_prep(void) { return -ENOSYS; }
 static inline int migrate_prep_local(void) { return -ENOSYS; }
 
-static inline int migrate_vmas(struct mm_struct *mm,
-		const nodemask_t *from, const nodemask_t *to,
-		unsigned long flags)
-{
-	return -ENOSYS;
-}
-
 static inline void migrate_page_copy(struct page *newpage,
 				     struct page *page) {}
 

include/linux/mm.h

@@ -286,8 +286,6 @@ struct vm_operations_struct {
 	 */
 	struct mempolicy *(*get_policy)(struct vm_area_struct *vma,
 					unsigned long addr);
-	int (*migrate)(struct vm_area_struct *vma, const nodemask_t *from,
-		const nodemask_t *to, unsigned long flags);
 #endif
 	/* called by sys_remap_file_pages() to populate non-linear mapping */
 	int (*remap_pages)(struct vm_area_struct *vma, unsigned long addr,

mm/mempolicy.c

@@ -1047,10 +1047,6 @@ int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,
 
 	down_read(&mm->mmap_sem);
 
-	err = migrate_vmas(mm, from, to, flags);
-	if (err)
-		goto out;
-
 	/*
 	 * Find a 'source' bit set in 'tmp' whose corresponding 'dest'
 	 * bit in 'to' is not also set in 'tmp'.  Clear the found 'source'
@@ -1130,7 +1126,6 @@ int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,
 		if (err < 0)
 			break;
 	}
-out:
 	up_read(&mm->mmap_sem);
 	if (err < 0)
 		return err;

mm/migrate.c

@@ -1536,27 +1536,6 @@ SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
 	return err;
 }
 
-/*
- * Call migration functions in the vma_ops that may prepare
- * memory in a vm for migration. migration functions may perform
- * the migration for vmas that do not have an underlying page struct.
- */
-int migrate_vmas(struct mm_struct *mm, const nodemask_t *to,
-	const nodemask_t *from, unsigned long flags)
-{
- 	struct vm_area_struct *vma;
- 	int err = 0;
-
-	for (vma = mm->mmap; vma && !err; vma = vma->vm_next) {
- 		if (vma->vm_ops && vma->vm_ops->migrate) {
- 			err = vma->vm_ops->migrate(vma, to, from, flags);
- 			if (err)
- 				break;
- 		}
- 	}
- 	return err;
-}
-
 #ifdef CONFIG_NUMA_BALANCING
 /*
  * Returns true if this is a safe migration target node for misplaced NUMA