Re: bad CRC in data error on ARM

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On 15 May 2015 at 00:51, huang jun <hjwsm1989@xxxxxxxxx> wrote:
> hi,all

Hi HuangJun,

>
> We run ceph cluster on ARM platform (arm64, linux kernel 3.14, OS
> ubuntu 14.10), and use "dd if=/dev/zero of=/mnt/test bs=4M count=125"
> to write data.  On the osd side, we got bad data CRC error.
>
> The kclient log: (tid=6)
> May 14 17:21:08 node103 kernel: [  180.194312] CPU[0] libceph:
> send_request ffffffc8d252f000 tid-6 to osd0 flags 36 pg 1.9aae829f req
> data size is 4194304
> May 14 17:21:08 node103 kernel: [  180.194316] CPU[0] libceph: tid-6
> ----- ffffffc0702f66c8 to osd0 42=osd_op len 197+0+4194304 -----
> libceph: tid-6 front_crc is 388648745 middle_crc is 0 data_crc is 3036014994
>
> The OSD-0 log:
> 2015-05-13 08:12:50.049345 7f378d8d8700  0 seq  3 tid 6 front_len 197
> mid_len 0 data_len 4194304
> 2015-05-13 08:12:50.049348 7f378d8d8700  0 crc in front 388648745 exp 388648745
> 2015-05-13 08:12:50.049395 7f378d8d8700  0 crc in middle 0 exp 0
> 2015-05-13 08:12:50.049964 7f378d8d8700  0 crc in data 0 exp 3036014994
> 2015-05-13 08:12:50.050234 7f378d8d8700  0 bad crc in data 0 != exp 3036014994
>
> some considerations:
> 1) we use ceph 0.80.7 realse version and compile it on ARM, did this
> works? or  does ceph's code has ARM branch?

We did run a Ceph version close to that for 64-bit ARM, I'm checking
out 0.80.7 now to test.
In v9.0.0, there is some code to use the ARM optional crc32c
instructions, but this isn't in 0.80.7.

>
> 2) as we have write 125 objects, only few of them report CRC error,
> and the right object's data_crc is 0 both on osd and kclient. the
> wrong object's data_crc is not 0 on kclient, but osd calculate result
> 0. the object data came from /dev/zero, i think the data_crc should be
> 0, am i right?
>

If the initial CRC seed value is non-zero, then the CRC of a buffer
full of zeros won't be zero.
So ceph_crc32c(somethingnonzero, zerofilledbuffer, len), will be non-zero.

I would like to reproduce this problem here.
What steps did you take before this error occurred?
Is this a cephfs filesystem or something on top of an RBD image?
Which kernel are you running? Is it the one that comes with Ubuntu?
(If so which package version is it?)

Cheers,
--
Steve
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