mm: move ->mremap() from file_operations to vm_operations_struct

vma->vm_ops->mremap() looks more natural and clean in move_vma(), and this
way ->mremap() can have more users.  Say, vdso.

While at it, s/aio_ring_remap/aio_ring_mremap/.

Note: this is the minimal change before ->mremap() finds another user in
file_operations; this method should have more arguments, and it can be
used to kill arch_remap().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/aio.c

@@ -308,15 +308,9 @@ static void aio_free_ring(struct kioctx *ctx)
 	}
 }
 
-static int aio_ring_mmap(struct file *file, struct vm_area_struct *vma)
-{
-	vma->vm_flags |= VM_DONTEXPAND;
-	vma->vm_ops = &generic_file_vm_ops;
-	return 0;
-}
-
-static int aio_ring_remap(struct file *file, struct vm_area_struct *vma)
+static int aio_ring_mremap(struct vm_area_struct *vma)
 {
+	struct file *file = vma->vm_file;
 	struct mm_struct *mm = vma->vm_mm;
 	struct kioctx_table *table;
 	int i, res = -EINVAL;
@@ -342,9 +336,24 @@ static int aio_ring_remap(struct file *file, struct vm_area_struct *vma)
 	return res;
 }
 
+static const struct vm_operations_struct aio_ring_vm_ops = {
+	.mremap		= aio_ring_mremap,
+#if IS_ENABLED(CONFIG_MMU)
+	.fault		= filemap_fault,
+	.map_pages	= filemap_map_pages,
+	.page_mkwrite	= filemap_page_mkwrite,
+#endif
+};
+
+static int aio_ring_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	vma->vm_flags |= VM_DONTEXPAND;
+	vma->vm_ops = &aio_ring_vm_ops;
+	return 0;
+}
+
 static const struct file_operations aio_ring_fops = {
 	.mmap = aio_ring_mmap,
-	.mremap = aio_ring_remap,
 };
 
 #if IS_ENABLED(CONFIG_MIGRATION)

include/linux/fs.h

@@ -1612,7 +1612,6 @@ struct file_operations {
 	long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
 	long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
 	int (*mmap) (struct file *, struct vm_area_struct *);
-	int (*mremap)(struct file *, struct vm_area_struct *);
 	int (*open) (struct inode *, struct file *);
 	int (*flush) (struct file *, fl_owner_t id);
 	int (*release) (struct inode *, struct file *);

include/linux/mm.h

@@ -247,6 +247,7 @@ struct vm_fault {
 struct vm_operations_struct {
 	void (*open)(struct vm_area_struct * area);
 	void (*close)(struct vm_area_struct * area);
+	int (*mremap)(struct vm_area_struct * area);
 	int (*fault)(struct vm_area_struct *vma, struct vm_fault *vmf);
 	void (*map_pages)(struct vm_area_struct *vma, struct vm_fault *vmf);
 

mm/mremap.c

@@ -277,8 +277,8 @@ static unsigned long move_vma(struct vm_area_struct *vma,
 				     need_rmap_locks);
 	if (moved_len < old_len) {
 		err = -ENOMEM;
-	} else if (vma->vm_file && vma->vm_file->f_op->mremap) {
-		err = vma->vm_file->f_op->mremap(vma->vm_file, new_vma);
+	} else if (vma->vm_ops && vma->vm_ops->mremap) {
+		err = vma->vm_ops->mremap(new_vma);
 	}
 
 	if (unlikely(err)) {