Am 22.11.2017 um 22:03 schrieb Michael Lyle:

On 11/22/2017 12:56 PM, Stefan Priebe - Profihost AG wrote:

quoted

Am 22.11.2017 um 21:44 schrieb Michael Lyle:

quoted

On 11/22/2017 12:36 PM, Stefan Priebe - Profihost AG wrote:

quoted

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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