f2fs: find parent dentry correctly

If dotdot directory is corrupted, its slot may be ocupied by another
file. In this case, dentry[1] is not the parent directory. Rename and
cross-rename will update the inode in dentry[1] incorrectly.   This
patch finds dotdot dentry by name.
Signed-off-by: Sheng Yong <shengyong1@huawei.com>
[Jaegeuk Kim: remove wron bug_on]
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/dir.c

@@ -267,22 +267,9 @@ struct f2fs_dir_entry *f2fs_find_entry(struct inode *dir,
 
 struct f2fs_dir_entry *f2fs_parent_dir(struct inode *dir, struct page **p)
 {
-	struct page *page;
-	struct f2fs_dir_entry *de;
-	struct f2fs_dentry_block *dentry_blk;
-
-	if (f2fs_has_inline_dentry(dir))
-		return f2fs_parent_inline_dir(dir, p);
-
-	page = get_lock_data_page(dir, 0, false);
-	if (IS_ERR(page))
-		return NULL;
+	struct qstr dotdot = QSTR_INIT("..", 2);
 
-	dentry_blk = kmap(page);
-	de = &dentry_blk->dentry[1];
-	*p = page;
-	unlock_page(page);
-	return de;
+	return f2fs_find_entry(dir, &dotdot, p);
 }
 
 ino_t f2fs_inode_by_name(struct inode *dir, struct qstr *qstr)

fs/f2fs/f2fs.h

@@ -2275,7 +2275,6 @@ int f2fs_write_inline_data(struct inode *, struct page *);
 bool recover_inline_data(struct inode *, struct page *);
 struct f2fs_dir_entry *find_in_inline_dir(struct inode *,
 				struct fscrypt_name *, struct page **);
-struct f2fs_dir_entry *f2fs_parent_inline_dir(struct inode *, struct page **);
 int make_empty_inline_dir(struct inode *inode, struct inode *, struct page *);
 int f2fs_add_inline_entry(struct inode *, const struct qstr *, struct inode *,
 						nid_t, umode_t);

fs/f2fs/inline.c

@@ -306,25 +306,6 @@ struct f2fs_dir_entry *find_in_inline_dir(struct inode *dir,
 	return de;
 }
 
-struct f2fs_dir_entry *f2fs_parent_inline_dir(struct inode *dir,
-							struct page **p)
-{
-	struct f2fs_sb_info *sbi = F2FS_I_SB(dir);
-	struct page *ipage;
-	struct f2fs_dir_entry *de;
-	struct f2fs_inline_dentry *dentry_blk;
-
-	ipage = get_node_page(sbi, dir->i_ino);
-	if (IS_ERR(ipage))
-		return NULL;
-
-	dentry_blk = inline_data_addr(ipage);
-	de = &dentry_blk->dentry[1];
-	*p = ipage;
-	unlock_page(ipage);
-	return de;
-}
-
 int make_empty_inline_dir(struct inode *inode, struct inode *parent,
 							struct page *ipage)
 {