Still seeing hangs in xlog_grant_log_space

[Mark Tinguely]

On 06/05/12 18:54, Dave Chinner wrote:


>> Reading bug #922 I see your test case reproduces in recent kernels, so
>> there must be a newer problem also.
>
> Right, that's what we need to find - it appears to be a CIL
> stall/accounting leak, completely unrelated to all the other AIL/log
> space stalls that have been occurring. Last thing is that I was
> waiting for more information on the stall that mark T @ sgi was able
> to reproduce. I haven't heard anything from him since I asked for
> more information on May 23....
>
...

>
> Cheers,
>
> Dave.

I am using the test instructions/programs in the above bug report

  1) Linux 3.5rc1
  2) temporary band-aid of performing a xfs_log_force() before the
     xfs_fs_log_dummy() in the xfs_sync_worker().
   a) Even with a xfs_log_force(), it is still possible to hang the sync
      worker.
   b) or replacing the band-aid with Brian Foster's "xfs: check for stale
      inode before acquiring iflock on push" patch also resulted in a
      quick hard hang.
      i) side note, printk routines in Linux 3.5rc1 has a "struct log"
        item that crash wants to use instead of XFS's "struct log". I
  3) small log (576K)
   a) size of the log in important. The smaller the log, the easier it
      is to hang. 2+MB logs are much harder to hang.
  4) perl program that has multiple workers doing cp/rm.

Sorry Dave, I did not realize you were waiting for more information from 
me. I thought the fixing the sync worker was more important.
I also was hoping empty AIL hang was a result of the band-aid
xfs_log_force() and not a second problem.

I will use the above to try to recreate and core the hang on Linux 
3.5rc1 where the AIL is empty.



Thanks.

--Mark Tinguely.