> On Aug 15, 2017, at 11:36 AM, Shaohua Li <shli@xxxxxxxxxx> wrote:
>
> On Tue, Aug 15, 2017 at 05:24:53PM +0800, Guoqing Jiang wrote:
>>
>>
>> On 08/14/2017 01:29 AM, Stephane Thiell wrote:
>>> Also known as "kernel BUG at drivers/md/raid5.c:527!"
>>>
>>> I’m still struggling with this issue in raid5.c. I currently have one crash per week in average on a system using Lustre and 24 x 10-disk raid6 per server. It did happen with or without check running. I now think there is a race at some point where a released stripe head (batched) is added to conf->inactive_list without sh->batch_head being set back to NULL.
>>>
>>> Because sh->batch_head is only being set back to NULL in a single function, break_stripe_batch_list(), my guess is that a call to raid5_release_stripe() on the head stripe is performed elsewhere. I didn’t find where this could come from yet. So perhaps sh->batch_head should be just set to NULL in do_release_stripe(), before being added to the inactive list?
>>>
>>> Alternatively, I wonder if it would make more sense to set batch_head to NULL where sh->overwrite_disks is also set back to 0 (like in ops_run_biodrain() today).
>>>
>>> Because sh->overwrite_disks is also set to 0 in init_stripe(), my current plan is to try this change, at least as a workaround: remove the BUG_ON(sh->batch_head) from init_stripe() and set sh->batch_head = NULL (I don’t think I need to lock on sh->stripe_lock there?). I will get new hardware soon so I will give it a try on a test system. Any suggestions welcomed…
>>>
>>> Quick analysis of the last vmcore:
>>>
>>> crash> ps | grep ">"
>>> ...
>>>> 16119 16111 22 ffff881f93bace70 RU 0.0 150772 10748 e2label
>>>> 151448 2 34 ffff881ff753bec0 RU 0.0 0 0 [kiblnd_sd_00_00]
>>>> 151449 2 2 ffff881ff753edd0 RU 0.0 0 0 [kiblnd_sd_00_01]
>>>> 154637 2 29 ffff881f776b1f60 RU 0.0 0 0 [md32_raid6]
>>>> 163643 2 11 ffff8820d200bec0 UN 0.0 0 0 [ll_ost_io01_008]
>>>> 164083 2 13 ffff8820d2753ec0 UN 0.0 0 0 [ll_ost_io01_034]
>>>> 171389 2 5 ffff883fd072de20 UN 0.0 0 0 [ll_ost_io01_058]
>>>> 171391 2 17 ffff883fd072ce70 UN 0.0 0 0 [ll_ost_io01_060]
>>>> 171399 2 33 ffff883fd9e9ce70 UN 0.0 0 0 [ll_ost_io01_068]
>>>> 237019 2 15 ffff882715628fb0 UN 0.0 0 0 [ll_ost_io01_084]
>>>> 237033 2 3 ffff881fb0250fb0 UN 0.0 0 0 [ll_ost_io01_098]
>>> ...
>>>
>>> crash> bt 237033
>>> PID: 237033 TASK: ffff881fb0250fb0 CPU: 3 COMMAND: "ll_ost_io01_098"
>>> #0 [ffff8826fa3e7240] machine_kexec at ffffffff81059bdb
>>> #1 [ffff8826fa3e72a0] __crash_kexec at ffffffff811057c2
>>> #2 [ffff8826fa3e7370] crash_kexec at ffffffff811058b0
>>> #3 [ffff8826fa3e7388] oops_end at ffffffff8168fac8
>>> #4 [ffff8826fa3e73b0] die at ffffffff8102e93b
>>> #5 [ffff8826fa3e73e0] do_trap at ffffffff8168f180
>>> #6 [ffff8826fa3e7430] do_invalid_op at ffffffff8102b144
>>> #7 [ffff8826fa3e74e0] invalid_op at ffffffff81698b5e
>>> [exception RIP: raid5_get_active_stripe+1809]
>>> RIP: ffffffffa0fefd71 RSP: ffff8826fa3e7590 RFLAGS: 00010086
>>> RAX: 0000000000000000 RBX: ffff883df051641c RCX: dead000000000200
>>> RDX: 0000000000000000 RSI: 0000000000000005 RDI: ffff881e08d54d30
>>> RBP: ffff8826fa3e7638 R8: ffff881e08d54d40 R9: 0000000000000080
>>> R10: 0000000000000000 R11: 0000000000000000 R12: ffff883df0516400
>>> R13: ffff881e08d54d30 R14: 0000000000000000 R15: 0000000000000000
>>> ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
>>> #8 [ffff8826fa3e7640] raid5_make_request at ffffffffa0feff55 [raid456]
>>> #9 [ffff8826fa3e7730] md_make_request at ffffffff814f838c
>>> #10 [ffff8826fa3e7790] generic_make_request at ffffffff812eedc9
>>> #11 [ffff8826fa3e77d8] submit_bio at ffffffff812eef11
>>> #12 [ffff8826fa3e7830] osd_submit_bio at ffffffffa10cdbcc [osd_ldiskfs]
>>> #13 [ffff8826fa3e7840] osd_do_bio at ffffffffa10d03c1 [osd_ldiskfs]
>>> #14 [ffff8826fa3e7960] osd_write_commit at ffffffffa10d0b94 [osd_ldiskfs]
>>> #15 [ffff8826fa3e7a00] ofd_commitrw_write at ffffffffa120c734 [ofd]
>>> #16 [ffff8826fa3e7a78] ofd_commitrw at ffffffffa120ff07 [ofd]
>>> #17 [ffff8826fa3e7b08] obd_commitrw at ffffffffa0c7dc22 [ptlrpc]
>>> #18 [ffff8826fa3e7b70] tgt_brw_write at ffffffffa0c55fc1 [ptlrpc]
>>> #19 [ffff8826fa3e7cd8] tgt_request_handle at ffffffffa0c52275 [ptlrpc]
>>> #20 [ffff8826fa3e7d20] ptlrpc_server_handle_request at ffffffffa0bfe1fb [ptlrpc]
>>> #21 [ffff8826fa3e7de8] ptlrpc_main at ffffffffa0c022b0 [ptlrpc]
>>> #22 [ffff8826fa3e7ec8] kthread at ffffffff810b0a4f
>>> #23 [ffff8826fa3e7f50] ret_from_fork at ffffffff81697218
>>>
>>>
>>> After some disassembly work, I found out that all active tasks are working on the same md (all are raid6):
>>>
>>> md32’s (struct r5conf *) is 0xffff883df0516400
>>>
>>> Our crashed task:
>>>
>>> crash> printf "%s", ((struct r5conf)*0xffff883df0516400).cache_name[0]
>>> raid6-md32
>>>
>>> Example for md32_raid6 task in release_inactive_stripe_list:
>>>
>>> crash> bt 154637
>>> PID: 154637 TASK: ffff881f776b1f60 CPU: 29 COMMAND: "md32_raid6"
>>> #0 [ffff883ffc985e48] crash_nmi_callback at ffffffff8104d2e2
>>> #1 [ffff883ffc985e58] nmi_handle at ffffffff8168fc77
>>> #2 [ffff883ffc985eb0] do_nmi at ffffffff8168fe83
>>> #3 [ffff883ffc985ef0] end_repeat_nmi at ffffffff8168f093
>>> [exception RIP: _raw_spin_lock_irqsave+64]
>>> RIP: ffffffff8168e5f0 RSP: ffff881e8d0cbc60 RFLAGS: 00000006
>>> RAX: 00000000000031bb RBX: ffff883df0516740 RCX: 000000000000009a
>>> RDX: 0000000000000098 RSI: 000000000000009a RDI: ffff883df051641c
>>> RBP: ffff881e8d0cbc60 R8: 0000000000000206 R9: 0000000000000000
>>> R10: 0000000000000000 R11: 0000000000000007 R12: ffff883df0516400
>>> R13: ffff883df051641c R14: 0000000000000006 R15: 0000000000000005
>>> ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
>>> --- <NMI exception stack> ---
>>> #4 [ffff881e8d0cbc60] _raw_spin_lock_irqsave at ffffffff8168e5f0
>>> #5 [ffff881e8d0cbc68] release_inactive_stripe_list at ffffffffa0fe5500 [raid456]
>>> #6 [ffff881e8d0cbcb0] handle_active_stripes at ffffffffa0ff34c2 [raid456]
>>> #7 [ffff881e8d0cbd60] raid5d at ffffffffa0ff3c28 [raid456]
>>> #8 [ffff881e8d0cbe50] md_thread at ffffffff814fb745
>>> #9 [ffff881e8d0cbec8] kthread at ffffffff810b0a4f
>>> #10 [ffff881e8d0cbf50] ret_from_fork at ffffffff81697218
>>>
>>>
>>> crash> bt 163643 164083 171389 171391 171399 237019 237033 |grep "exception RIP:"
>>> [exception RIP: _raw_spin_lock_irq+63]
>>> [exception RIP: _raw_spin_lock_irq+63]
>>> [exception RIP: _raw_spin_lock_irq+58]
>>> [exception RIP: _raw_spin_lock_irq+63]
>>> [exception RIP: _raw_spin_lock_irq+58]
>>> [exception RIP: _raw_spin_lock_irq+63]
>>> [exception RIP: raid5_get_active_stripe+1809]
>>>
>>> crash> bt 163643 164083 171389 171391 171399 237019 237033 |grep "raid5_get_active_stripe"
>>> #5 [ffff883bcee93588] raid5_get_active_stripe at ffffffffa0fef6cb [raid456]
>>> #5 [ffff883ba4af7588] raid5_get_active_stripe at ffffffffa0fef6cb [raid456]
>>> #5 [ffff88390877b588] raid5_get_active_stripe at ffffffffa0fef6cb [raid456]
>>> #5 [ffff88390803b588] raid5_get_active_stripe at ffffffffa0fef6cb [raid456]
>>> #5 [ffff88390831f588] raid5_get_active_stripe at ffffffffa0fef6cb [raid456]
>>> #5 [ffff8826fa7f7588] raid5_get_active_stripe at ffffffffa0fef6cb [raid456]
>>> [exception RIP: raid5_get_active_stripe+1809]
>>>
>>> crash> bt 163643 164083 171389 171391 171399 237019 237033 |grep R12
>>> R10: 0000000000000003 R11: 0000000000000000 R12: ffff883df0516400
>>> R10: 0000000000000001 R11: 0000000000000000 R12: ffff883df0516400
>>> R10: 0000000000000005 R11: 0000000000000000 R12: ffff883df0516400
>>> R10: 0000000000000007 R11: 0000000000000000 R12: ffff883df0516400
>>> R10: 0000000000000009 R11: 0000000000000000 R12: ffff883df0516400
>>> R10: 0000000000000009 R11: 0000000000000000 R12: ffff883df0516400
>>> R10: 0000000000000000 R11: 0000000000000000 R12: ffff883df0516400
>>>
>>>
>>> The bad stripe_head (sh) is available at (usually in %r13):
>>>
>>> crash> p ((struct stripe_head)*0xffff881e08d54d30).raid_conf
>>> $98 = (struct r5conf *) 0xffff883df0516400
>>>
>>> and batch_head is not NULL... that's the issue:
>>>
>>> crash> p ((struct stripe_head)*0xffff881e08d54d30).batch_head
>>> $99 = (struct stripe_head *) 0xffff881e08d54d30
>>>
>>> Full struct dump below. We can see than overwrite_disks is set to 0, state is 0… but this batch_head not set to NULL makes it crash in init_stripe():
>>>
>>> crash> p ((struct stripe_head)*0xffff881e08d54d30)
>>> $6 = {
>>> hash = {
>>> next = 0x0,
>>> pprev = 0x0
>>> },
>>> lru = {
>>> next = 0xffff881e08d54d40,
>>> prev = 0xffff881e08d54d40
>>> },
>>> release_list = {
>>> next = 0xffff881dfe405cc0
>>> },
>>> raid_conf = 0xffff883df0516400,
>>> generation = 0,
>>> sector = 3701224808,
>>> pd_idx = 1,
>>> qd_idx = 2,
>>> ddf_layout = 0,
>>> hash_lock_index = 5,
>>> state = 0,
>>> count = {
>>> counter = 0
>>> },
>>> bm_seq = 22708787,
>>> disks = 10,
>>> overwrite_disks = 0,
>>> check_state = check_state_idle,
>>> reconstruct_state = reconstruct_state_idle,
>>> stripe_lock = {
>>> {
>>> rlock = {
>>> raw_lock = {
>>> {
>>> head_tail = 3709263126,
>>> tickets = {
>>> head = 56598,
>>> tail = 56598
>>> }
>>> }
>>> }
>>> }
>>> }
>>> },
>>> cpu = 15,
>>> group = 0x0,
>>> batch_head = 0xffff881e08d54d30,
>>> batch_lock = {
>>> {
>>> rlock = {
>>> raw_lock = {
>>> {
>>> head_tail = 9961624,
>>> tickets = {
>>> head = 152,
>>> tail = 152
>>> }
>>> }
>>> }
>>> }
>>> }
>>> },
>>> batch_list = {
>>> next = 0xffff881dfe405d28,
>>> prev = 0xffff881e0e2dec98
>>> },
>>> log_io = 0x0,
>>> log_list = {
>>> next = 0x0,
>>> prev = 0x0
>>> },
>>> ops = {
>>> target = 0,
>>> target2 = 0,
>>> zero_sum_result = (unknown: 0)
>>> },
>>> dev = {{
>>> req = {
>>> bi_sector = 0,
>>> bi_next = 0x0,
>>> bi_bdev = 0x0,
>>> bi_flags = 1,
>>> bi_rw = 0,
>>> bi_vcnt = 0,
>>> bi_idx = 0,
>>> bi_phys_segments = 0,
>>> bi_size = 0,
>>> bi_seg_front_size = 0,
>>> bi_seg_back_size = 0,
>>> bi_end_io = 0x0,
>>> bi_private = 0xffff881e08d54d30,
>>> bi_ioc = 0x0,
>>> bi_css = 0x0,
>>> bi_integrity = 0x0,
>>> bi_max_vecs = 1,
>>> bi_cnt = {
>>> counter = 1
>>> },
>>> bi_io_vec = 0xffff881e08d54f00,
>>> bi_pool = 0x0,
>>> {
>>> bio_aux = 0x0,
>>> __UNIQUE_ID_rh_kabi_hide15 = {
>>> rh_reserved1 = 0x0
>>> },
>>> {<No data fields>}
>>> },
>>> bi_inline_vecs = 0xffff881e08d54e78
>>> },
>>> rreq = {
>>> bi_sector = 0,
>>> bi_next = 0x0,
>>> bi_bdev = 0x0,
>>> bi_flags = 1,
>>> bi_rw = 0,
>>> bi_vcnt = 0,
>>> bi_idx = 0,
>>> bi_phys_segments = 0,
>>> bi_size = 0,
>>> bi_seg_front_size = 0,
>>> bi_seg_back_size = 0,
>>> bi_end_io = 0x0,
>>> bi_private = 0xffff881e08d54d30,
>>> bi_ioc = 0x0,
>>> bi_css = 0x0,
>>> bi_integrity = 0x0,
>>> bi_max_vecs = 1,
>>> bi_cnt = {
>>> counter = 1
>>> },
>>> bi_io_vec = 0xffff881e08d54f10,
>>> bi_pool = 0x0,
>>> {
>>> bio_aux = 0x0,
>>> __UNIQUE_ID_rh_kabi_hide15 = {
>>> rh_reserved1 = 0x0
>>> },
>>> {<No data fields>}
>>> },
>>> bi_inline_vecs = 0xffff881e08d54f00
>>> },
>>> vec = {
>>> bv_page = 0xffffea0078236080,
>>> bv_len = 4096,
>>> bv_offset = 0
>>> },
>>> rvec = {
>>> bv_page = 0x0,
>>> bv_len = 0,
>>> bv_offset = 0
>>> },
>>> page = 0xffffea0078236080,
>>> orig_page = 0xffffea0078236080,
>>> toread = 0x0,
>>> read = 0x0,
>>> towrite = 0x0,
>>> written = 0xffff8824832a7c00,
>>> sector = 29609798632,
>>> flags = 24,
>>
>> Seems the flags is R5_OVERWRITE | R5_Insync, handle_stripe_clean_event
>> only calls break_stripe_batch_list if do_endio is set to true.
>>
>> if (head_sh->batch_head && do_endio)
>> break_stripe_batch_list(head_sh, STRIPE_EXPAND_SYNC_FLAGS);
>>
>> And do_endio is set to true if we meet the below condition.
>>
>> if (!test_bit(R5_LOCKED, &dev->flags) &&
>> (test_bit(R5_UPTODATE, &dev->flags) ||
>> test_bit(R5_Discard, &dev->flags) ||
>> test_bit(R5_SkipCopy, &dev->flags))) {
>>
>> I guess it is why the batch_head is not null, just my 2 cents.
>
> this is strange. The bi_end_io == NULL, written != NULL and !R5_UPTODATE means
> we are do restruction and restruction isn't finished yet. But at that time, we
> should have R5_LOCKED set, which isn't true for this case.
>
> Did you enable skip_copy or discard?
Nope!
# cat /sys/block/md32/md/skip_copy
0
# cat /sys/block/md32/queue/discard_max_bytes
0
# cat /sys/block/md32/queue/discard_granularity
524288
# cat /sys/block/md32/queue/discard_zeroes_data
0
# cat /sys/block/md32/discard_alignment
524288
# cat /sys/module/raid456/parameters/devices_handle_discard_safely
N
Thanks!
Stephane
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