Re: Shutdown preventing umount

[Dave Chinner <david@fromorbit.com>]

On Sat, Mar 14, 2020 at 06:31:10AM -0700, Andi Kleen wrote:
> 
> Hi,
> 
> I had a cable problem on a USB connected XFS file system, triggering 
> some IO errors, and the result was that any access to the mount point
> resulted in EIO. This prevented unmounting the file system to recover
> from the problem. 

Full dmesg output, please.

> I also tried xfs_io with shutdown -f, but it had the same problem
> because xfs_io couldn't access anything on the file system.

Because the IO errors had already shut the filesystem down, as
per the dmesg output you quoted below.

> How is that supposed to work? Having to reboot just to recover
> from IO errors doesn't seem to be very available.
> 
> I don't think shutdown should prevent unmounting.

It doesn't. Something was leaked or not cleaned up properly,
preventing the filesytem from being unmounted. You know, a bug...

> From googling I found some old RHEL bugzilla that such a problem
> was fixed in some RHEL release. Is that a regression? 

RHEL has an upstream first policy, so whatever bug fix you find in
a RHEL kernel is already in the upstream kernels.

> This was on a 5.4.10 kernel.
> 
> I got lots of:
> 
>  XFS (...): metadata I/O error in "xfs_trans_read_buf_map" at daddr
>  0x4a620288 len 8 error 5
> 
> Then some
> 
> XFS (...): writeback error on sector 7372099184
> 
> And finally:
> 
> XFS (...): log I/O error -5
>  XFS (...): xfs_do_force_shutdown(0x2)
> called from line 1250 of file fs/xfs/xfs_log.c. Return address =
> 00000000f7956130
> XFS (...): Log I/O Error Detected.
> Shutting down filesystem
> XFS (...): Please unmount the filesystem
> and rectify the problem(s)
> 
> (very funny XFS!)
> 
> XFS (...): log I/O error -5
> 
> scsi 7:0:0:0: rejecting I/O to dead device

Where is unmount stuck? 'echo w > /proc/sysrq-trigger' output if it
is hung, 'echo l > /proc/sysrq-trigger' if it is spinning, please?

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com