mm/nommu: use file_has_valid_mmap_hooks() helper

Since commit c84bf6d ("mm: introduce new .mmap_prepare() file
callback"), the f_op->mmap() hook has been deprecated in favour of
f_op->mmap_prepare().

Therefore, update the check for file operations supporting mmap() by using
the file_has_valid_mmap_hooks() helper function, which checks for either
f_op->mmap or f_op->mmap_prepare rather than checking only for f_op->mmap
directly.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Link: https://lore.kernel.org/5f120b644b5890d1b50202d0f0d4c9f0d6b62873.1750099179.git.lorenzo.stoakes@oracle.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: ljskernel

mm/nommu.c

@@ -719,7 +719,7 @@ static int validate_mmap_request(struct file *file,
 
 	if (file) {
 		/* files must support mmap */
-		if (!file->f_op->mmap)
+		if (!file_has_valid_mmap_hooks(file))
 			return -ENODEV;
 
 		/* work out if what we've got could possibly be shared