Re: ont out of 6 bcache devices does not register automatically

[Stefan Priebe - Profihost AG <s.priebe@profihost.ag>]

Am 22.11.2017 um 22:03 schrieb Michael Lyle:
> On 11/22/2017 12:56 PM, Stefan Priebe - Profihost AG wrote:
>>
>> Am 22.11.2017 um 21:44 schrieb Michael Lyle:
>>> On 11/22/2017 12:36 PM, Stefan Priebe - Profihost AG wrote:
>>>> Am 22.11.2017 um 21:22 schrieb Michael Lyle:
>>> mlyle@midnight:~/Downloads$ blkid 8k
>>> 8k: UUID="65811163-4ffc-4823-ad72-bae10ce85b63" TYPE="bcache"
>>> mlyle@midnight:~/Downloads$ blkid --version
>>> blkid from util-linux 2.30.1  (libblkid 2.30.1, 20-Jul-2017)
>>>
>>> I don't understand, it seems OK.
>> i think i remember that the xfs external log superblock is NOT at the
>> beginning. Not sure where it is and yes there's an XFS on top of bcache...
>>
>> Greets,
>> Stefan
> 
> It shouldn't be an issue because: A) blkid should "favor" bcache, and B)
> the other filesystem data structures should be offset and not at the
> position that blkid will be looking for them.  Can you check your blkid
> version?

If you strace blkid you see that it seeks several positions and reads them.

Exmaple:
read(3,
"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
4096) = 4096
lseek(3, 0, SEEK_SET)                   = 0
read(3,
"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
1024) = 1024
lseek(3, 1024, SEEK_SET)                = 1024
read(3,
"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
1024) = 1024
lseek(3, 1048576, SEEK_SET)             = 1048576
read(3,
"ABTB\0\0\1\36\0\0\1\310\0\0\0\215\0029\335\334\0\0\0070\0029\355\f\0\0\4\0"...,
1024) = 1024
lseek(3, 3072, SEEK_SET)                = 3072
read(3,
"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
1024) = 1024
lseek(3, 7168, SEEK_SET)                = 7168
read(3,
"\0\0\232\352\0\0\0\26\0\0\233\301\0\0\0\20\0\0\234\21\0\0\0\34\0\0\234.\0\0\0\1"...,
1024) = 1024
lseek(3, 15360, SEEK_SET)               = 15360
read(3,
"\0\0'\353\0\0\0\1\0\0'\353\0\0\0\1\0\0'\353\0\0\0\1\0\0'\353\0\0\0\1"...,
1024) = 1024
lseek(3, 31744, SEEK_SET)               = 31744
read(3,
"\0\10\340\346\0\0\0\30\0\10\340\346\0\0\0\30drmtwsS0l\n1gKn80"...,
1024) = 1024
lseek(3, 64512, SEEK_SET)               = 64512
read(3,
"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
1024) = 1024
lseek(3, 0, SEEK_SET)                   = 0
mmap(NULL, 266240, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1,
0) = 0x7efe60612000
read(3,
"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
262144) = 262144
lseek(3, 393216, SEEK_SET)              = 393216

> 
> Mike
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