qstr: constify instances in f2fs

Signed-off-by: Al Viro <[e-mail]>

fs/f2fs/dir.c

···
  * Entry is guaranteed to be valid.
  */
 struct f2fs_dir_entry *f2fs_find_entry(struct inode *dir,
-			struct qstr *child, struct page **res_page)
+			const struct qstr *child, struct page **res_page)
 {
 	unsigned long npages = dir_blocks(dir);
 	struct f2fs_dir_entry *de = NULL;
···
 	return de;
 }
 
-ino_t f2fs_inode_by_name(struct inode *dir, struct qstr *qstr)
+ino_t f2fs_inode_by_name(struct inode *dir, const struct qstr *qstr)
 {
 	ino_t res = 0;
 	struct f2fs_dir_entry *de;

fs/f2fs/f2fs.h

···
 void update_parent_metadata(struct inode *, struct inode *, unsigned int);
 int room_for_filename(const void *, int, int);
 void f2fs_drop_nlink(struct inode *, struct inode *, struct page *);
-struct f2fs_dir_entry *f2fs_find_entry(struct inode *, struct qstr *,
+struct f2fs_dir_entry *f2fs_find_entry(struct inode *, const struct qstr *,
 							struct page **);
 struct f2fs_dir_entry *f2fs_parent_dir(struct inode *, struct page **);
-ino_t f2fs_inode_by_name(struct inode *, struct qstr *);
+ino_t f2fs_inode_by_name(struct inode *, const struct qstr *);
 void f2fs_set_link(struct inode *, struct f2fs_dir_entry *,
 				struct page *, struct inode *);
 int update_dent_inode(struct inode *, struct inode *, const struct qstr *);