f2fs: fix tracking parent inode number

Previously, f2fs didn't track the parent inode number correctly which is stored
in each f2fs_inode. In the case of the following scenario, a bug can be occured.

Let's suppose there are one directory, "/b", and two files, "/a" and "/b/a".
 - pino of "/a" is ROOT_INO.
 - pino of "/b/a" is DIR_B_INO.

Then,
 # sync
  : The inode pages of "/a" and "/b/a" contain the parent inode numbers as
    ROOT_INO and DIR_B_INO respectively.
 # mv /a /b/a
  : The parent inode number of "/a" should be changed to DIR_B_INO, but f2fs
    didn't do that. Ref. f2fs_set_link().

In order to fix this clearly, I added i_pino in f2fs_inode_info, and whenever
it needs to be changed like in f2fs_add_link() and f2fs_set_link(), it is
updated temporarily in f2fs_inode_info.

And later, f2fs_write_inode() stores the latest information to the inode pages.
For power-off-recovery, f2fs_sync_file() triggers simply f2fs_write_inode().
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/dir.c

@@ -256,13 +256,16 @@ void f2fs_set_link(struct inode *dir, struct f2fs_dir_entry *de,
 	set_page_dirty(page);
 	dir->i_mtime = dir->i_ctime = CURRENT_TIME;
 	mark_inode_dirty(dir);
+
+	/* update parent inode number before releasing dentry page */
+	F2FS_I(inode)->i_pino = dir->i_ino;
+
 	f2fs_put_page(page, 1);
 	mutex_unlock_op(sbi, DENTRY_OPS);
 }
 
 void init_dent_inode(struct dentry *dentry, struct page *ipage)
 {
-	struct inode *dir = dentry->d_parent->d_inode;
 	struct f2fs_node *rn;
 
 	if (IS_ERR(ipage))
@@ -272,7 +275,6 @@ void init_dent_inode(struct dentry *dentry, struct page *ipage)
 
 	/* copy dentry info. to this inode page */
 	rn = (struct f2fs_node *)page_address(ipage);
-	rn->i.i_pino = cpu_to_le32(dir->i_ino);
 	rn->i.i_namelen = cpu_to_le32(dentry->d_name.len);
 	memcpy(rn->i.i_name, dentry->d_name.name, dentry->d_name.len);
 	set_page_dirty(ipage);
@@ -444,7 +446,11 @@ int f2fs_add_link(struct dentry *dentry, struct inode *inode)
 	for (i = 0; i < slots; i++)
 		test_and_set_bit_le(bit_pos + i, &dentry_blk->dentry_bitmap);
 	set_page_dirty(dentry_page);
+
 	update_parent_metadata(dir, inode, current_depth);
+
+	/* update parent inode number before releasing dentry page */
+	F2FS_I(inode)->i_pino = dir->i_ino;
 fail:
 	kunmap(dentry_page);
 	f2fs_put_page(dentry_page, 1);

fs/f2fs/f2fs.h

@@ -136,6 +136,7 @@ struct f2fs_inode_info {
 	unsigned long i_flags;		/* keep an inode flags for ioctl */
 	unsigned char i_advise;		/* use to give file attribute hints */
 	unsigned int i_current_depth;	/* use only in directory structure */
+	unsigned int i_pino;		/* parent inode number */
 	umode_t i_acl_mode;		/* keep file acl mode temporarily */
 
 	/* Use below internally in f2fs*/

fs/f2fs/inode.c

@@ -107,6 +107,7 @@ static int do_read_inode(struct inode *inode)
 	fi->flags = 0;
 	fi->data_version = le64_to_cpu(F2FS_CKPT(sbi)->checkpoint_ver) - 1;
 	fi->i_advise = ri->i_advise;
+	fi->i_pino = le32_to_cpu(ri->i_pino);
 	get_extent_info(&fi->ext, ri->i_ext);
 	f2fs_put_page(node_page, 1);
 	return 0;
@@ -200,6 +201,7 @@ void update_inode(struct inode *inode, struct page *node_page)
 	ri->i_current_depth = cpu_to_le32(F2FS_I(inode)->i_current_depth);
 	ri->i_xattr_nid = cpu_to_le32(F2FS_I(inode)->i_xattr_nid);
 	ri->i_flags = cpu_to_le32(F2FS_I(inode)->i_flags);
+	ri->i_pino = cpu_to_le32(F2FS_I(inode)->i_pino);
 	ri->i_generation = cpu_to_le32(inode->i_generation);
 	set_page_dirty(node_page);
 }