f2fs: sync dir->i_size with its block allocation

If new dentry block is allocated and its i_size is updated, we should update
its inode block together in order to sync i_size and its block allocation.
Otherwise, we can loose additional dentry block due to the unconsistent i_size.

Errorneous Scenario
-------------------

In the recovery routine,
 - recovery_dentry
 | - __f2fs_add_link
 | | - get_new_data_page
 | | | - i_size_write(new_i_size)
 | | | - mark_inode_dirty_sync(dir)
 | | - update_parent_metadata
 | | | - mark_inode_dirty(dir)
 |
 - write_checkpoint
   - sync_dirty_dir_inodes
     - filemap_flush(dentry_blocks)
       - f2fs_write_data_page
         - skip to write the last dentry block due to index < i_size

In the above flow, new_i_size is not updated to its inode block so that the
last dentry block will be lost accordingly.
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/data.c

@@ -339,6 +339,8 @@ struct page *get_new_data_page(struct inode *inode,
 	if (new_i_size &&
 		i_size_read(inode) < ((index + 1) << PAGE_CACHE_SHIFT)) {
 		i_size_write(inode, ((index + 1) << PAGE_CACHE_SHIFT));
+		/* Only the directory inode sets new_i_size */
+		set_inode_flag(F2FS_I(inode), FI_UPDATE_DIR);
 		mark_inode_dirty_sync(inode);
 	}
 	return page;

fs/f2fs/dir.c

@@ -370,22 +370,20 @@ static struct page *init_inode_metadata(struct inode *inode,
 static void update_parent_metadata(struct inode *dir, struct inode *inode,
 						unsigned int current_depth)
 {
-	bool need_dir_update = false;
-
 	if (is_inode_flag_set(F2FS_I(inode), FI_NEW_INODE)) {
 		if (S_ISDIR(inode->i_mode)) {
 			inc_nlink(dir);
-			need_dir_update = true;
+			set_inode_flag(F2FS_I(dir), FI_UPDATE_DIR);
 		}
 		clear_inode_flag(F2FS_I(inode), FI_NEW_INODE);
 	}
 	dir->i_mtime = dir->i_ctime = CURRENT_TIME;
 	if (F2FS_I(dir)->i_current_depth != current_depth) {
 		F2FS_I(dir)->i_current_depth = current_depth;
-		need_dir_update = true;
+		set_inode_flag(F2FS_I(dir), FI_UPDATE_DIR);
 	}
 
-	if (need_dir_update)
+	if (is_inode_flag_set(F2FS_I(dir), FI_UPDATE_DIR))
 		update_inode_page(dir);
 	else
 		mark_inode_dirty(dir);
@@ -502,6 +500,7 @@ int __f2fs_add_link(struct inode *dir, const struct qstr *name, struct inode *in
 
 	update_parent_metadata(dir, inode, current_depth);
 fail:
+	clear_inode_flag(F2FS_I(dir), FI_UPDATE_DIR);
 	kunmap(dentry_page);
 	f2fs_put_page(dentry_page, 1);
 	return err;

fs/f2fs/f2fs.h

@@ -859,6 +859,7 @@ enum {
 	FI_INC_LINK,		/* need to increment i_nlink */
 	FI_ACL_MODE,		/* indicate acl mode */
 	FI_NO_ALLOC,		/* should not allocate any blocks */
+	FI_UPDATE_DIR,		/* should update inode block for consistency */
 	FI_DELAY_IPUT,		/* used for the recovery */
 };