Re: Weird xfs_repair error

[Dave Chinner <david@fromorbit.com>]

On Thu, Jul 06, 2017 at 03:30:20PM +0200, Emmanuel Florac wrote:
> 
> After a RAID controller went bananas, I encountered an XFS corruption
> on a filesystem. Weirdly, the corruption seems to be mostly located in
> lost+found.
> 
> (I'm currently working on a metadump'd image of course, not the real
> thing; there are 90TB of data to be hopefully salvaged in there).
> 
> "ls /mnt/rescue/lost+found" gave this:
> 
> XFS (loop0): metadata I/O error: block 0x22b03f490
> ("xfs_trans_read_buf_map") error 117 numblks 16 
> XFS (loop0): xfs_imap_to_bp: xfs_trans_read_buf() returned error 117.
> XFS (loop0): Corruption detected. Unmount and run xfs_repair 
> XFS (loop0): Corruption detected. Unmount and run xfs_repair
> 
> I've run xfs_repair 4.9 on the xfs_mdrestored image. It dumps an insane
> lot of errors (the output log is 65MB)  and ends with this very strange
> message:
> 
> disconnected inode 26417467, moving to lost+found
> disconnected inode 26417468, moving to lost+found
> disconnected inode 26417469, moving to lost+found
> disconnected inode 26417470, moving to lost+found
> 
> fatal error -- name create failed in lost+found (117), filesystem may
> be out of space

Error 117. That's EFSCORRUPTED, not ENOSPC.  IOWs, lost+found was
corrupted as it was being modified by xfs_repair.

> Even stranger, after mounting back the image, there is no lost+found
> anywhere to be found! However the filesystem has lots of free space and
> free inodes, how come?

Because lost+found was corrupted.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com