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Re: [PATCH] xfs: shutdown xfs_sync_worker before the log

To: Ben Myers <bpm@xxxxxxx>
Subject: Re: [PATCH] xfs: shutdown xfs_sync_worker before the log
From: Mark Tinguely <tinguely@xxxxxxx>
Date: Mon, 11 Jun 2012 16:11:28 -0500
Cc: Dave Chinner <david@xxxxxxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <20120611204516.GR4721@xxxxxxx>
References: <20120323174327.GU7762@xxxxxxx> <20120514203449.GE16099@xxxxxxx> <20120516015626.GN25351@dastard> <20120516170402.GD3963@xxxxxxx> <20120517071658.GP25351@dastard> <20120524223952.GU16099@xxxxxxx> <20120525204536.GA4721@xxxxxxx> <20120606042647.GK22848@dastard> <20120611204516.GR4721@xxxxxxx>
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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.

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