[PATCH] xfs: shutdown xfs_sync_worker before the log

[Mark Tinguely]

On 06/11/12 15:45, Ben Myers wrote:
...

> That sounds pretty good.  In particular, I think that making the start
> and stop of the workqueues correct should be the high priority.  I'm not
> as concerned about the accuracy of the names, or cleaning up xfs_sync.c
> and xfs_iget.c, but cleanups are worth doing too.
>
> I hit a crash related to the xfslogd workqueue awhile back.  Mark has
> taken it up, so there might be a little coordination to do with him.
>
> Regards,
> 	Ben

To not leave a teaser out there:

PID: 25879  TASK: ffff88012ac20340  CPU: 3   COMMAND: "kworker/3:3"
  #0 [ffff8801a72af920] machine_kexec at ffffffff810244e9
  #1 [ffff8801a72af990] crash_kexec at ffffffff8108d053
  #2 [ffff8801a72afa60] oops_end at ffffffff813ad1b8
  #3 [ffff8801a72afa90] no_context at ffffffff8102bd48
  #4 [ffff8801a72afae0] __bad_area_nosemaphore at ffffffff8102c04d
  #5 [ffff8801a72afb30] bad_area_nosemaphore at ffffffff8102c12e
  #6 [ffff8801a72afb40] do_page_fault at ffffffff813afaee
  #7 [ffff8801a72afc50] page_fault at ffffffff813ac635
     [exception RIP: xlog_assign_tail_lsn_locked+72]
     RIP: ffffffffa040da68  RSP: ffff8801a72afd00  RFLAGS: 00010246
     RAX: 0000000000000000  RBX: 0000000000000000  RCX: dead000000200200
     RDX: ffff88013b32d550  RSI: dead000000100100  RDI: ffff88013b32d550
     RBP: ffff8801a72afd10   R8: ffff8801a72ae000   R9: 0000000000000000
     R10: 0000000000000000  R11: 0000000000000000  R12: ffff88013b32d568
     R13: 0000000000000001  R14: ffff8801a72afd90  R15: ffff88013b32d540
     ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
  #8 [ffff8801a72afd18] xfs_trans_ail_delete_bulk at ffffffffa0414b2a [xfs]
  #9 [ffff8801a72afd78] xfs_buf_iodone at ffffffffa04119c7 [xfs]
#10 [ffff8801a72afdb8] xfs_buf_do_callbacks at ffffffffa041166c [xfs]
#11 [ffff8801a72afdd8] xfs_buf_iodone_callbacks at ffffffffa04117de [xfs]
#12 [ffff8801a72afdf8] xfs_buf_iodone_work at ffffffffa03ad7e1 [xfs]
#13 [ffff8801a72afe18] process_one_work at ffffffff8104c53b
#14 [ffff8801a72afe68] worker_thread at ffffffff8104f0e3
#15 [ffff8801a72afee8] kthread at ffffffff8105395e
#16 [ffff8801a72aff48] kernel_thread_helper at ffffffff813b3ae4

I am just digging through that crash. It appears that xfs_umountfs() did 
a good job in cleaning the AIL and the m_ddev_targp, but it needs to 
wait for the xfslogd to be finished before deallocating the log.

Since workqueues are cheap, maybe it would be smart to have a 
per-filesystem xfslogd too.

--Mark.