ext4: Handle non empty on-disk orphan link

In case of truncate errors we explicitly remove inode from in-core
orphan list via orphan_del(NULL, inode) without modifying the on-disk list.

But later on, the same inode may be inserted in the orphan list again
which will result the on-disk linked list getting corrupted.  If inode
i_dtime contains valid value, then skip on-disk list modification.
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/namei.c

@@ -2013,6 +2013,13 @@ int ext4_orphan_add(handle_t *handle, struct inode *inode)
 	err = ext4_reserve_inode_write(handle, inode, &iloc);
 	if (err)
 		goto out_unlock;
+	/*
+	 * Due to previous errors inode may be already a part of on-disk
+	 * orphan list. If so skip on-disk list modification.
+	 */
+	if (NEXT_ORPHAN(inode) && NEXT_ORPHAN(inode) <=
+		(le32_to_cpu(EXT4_SB(sb)->s_es->s_inodes_count)))
+			goto mem_insert;
 
 	/* Insert this inode at the head of the on-disk orphan list... */
 	NEXT_ORPHAN(inode) = le32_to_cpu(EXT4_SB(sb)->s_es->s_last_orphan);
@@ -2030,6 +2037,7 @@ int ext4_orphan_add(handle_t *handle, struct inode *inode)
 	 *
 	 * This is safe: on error we're going to ignore the orphan list
 	 * anyway on the next recovery. */
+mem_insert:
 	if (!err)
 		list_add(&EXT4_I(inode)->i_orphan, &EXT4_SB(sb)->s_orphan);