Hi everyone,
just wanted to check if this was the expected behavior -- it doesn't
look like it would be, to me.
What I do is create a 1G RBD, and just for the heck of it, make an XFS on it:
root@alice:~# rbd create xfsdev --size 1024
root@alice:~# rbd map xfsdev
root@alice:~# rbd showmapped
id pool image snap device
0 rbd xfsdev - /dev/rbd0
root@alice:~# mkfs -t xfs /dev/rbd/rbd/xfsdev
log stripe unit (4194304 bytes) is too large (maximum is 256KiB)
log stripe unit adjusted to 32KiB
meta-data=/dev/rbd/rbd/xfsdev isize=256 agcount=9, agsize=31744 blks
= sectsz=512 attr=2, projid32bit=0
data = bsize=4096 blocks=262144, imaxpct=25
= sunit=1024 swidth=1024 blks
naming =version 2 bsize=4096 ascii-ci=0
log =internal log bsize=4096 blocks=2560, version=2
= sectsz=512 sunit=8 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
I double check to see if there's an XFS signature on the device:
root@alice:~# xxd /dev/rbd/rbd/xfsdev | head
0000000: 5846 5342 0000 1000 0000 0000 0004 0000 XFSB............
0000010: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0000020: 17bb f4df b1f3 444b bc01 3b3e f827 8fef ......DK..;>.'..
0000030: 0000 0000 0002 0008 0000 0000 0000 4000 ..............@.
0000040: 0000 0000 0000 4001 0000 0000 0000 4002 ......@.......@.
0000050: 0000 0001 0000 7c00 0000 0009 0000 0000 ......|.........
0000060: 0000 0a00 b5a4 0200 0100 0010 0000 0000 ................
0000070: 0000 0000 0000 0000 0c09 0804 0f00 0019 ................
0000080: 0000 0000 0000 0040 0000 0000 0000 003d .......@.......=
0000090: 0000 0000 0003 f5d8 0000 0000 0000 0000 ................
Now, I try to remove the device while it's mapped:
root@alice:~# rbd rm xfsdev
Removing image: 99% complete...2012-07-02 06:52:57.386040 b6c8d710 -1
librbd: error removing header: (16) Device or resource busy
Removing image: 99% complete...failed.
delete error: image still has watchers
This means the image is still open or the client using it crashed. Try
again after closing/unmapping it or waiting 30s for the crashed client
to timeout.
That sounds reasonable, except that the data has already been nuked:
root@alice:~# xxd /dev/rbd/rbd/xfsdev | head
0000000: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0000010: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0000020: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0000030: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0000040: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0000050: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0000060: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0000070: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0000080: 0000 0000 0000 0000 0000 0000 0000 0000 ................
0000090: 0000 0000 0000 0000 0000 0000 0000 0000 ................
After unmapping, the device removal proceeds just fine.
root@alice:~# rbd unmap /dev/rbd0
root@alice:~# rbd rm xfsdev
Removing image: 100% complete...done.
Now if the RBD is capable of detecting that it's being watched, why
not fail the removal _before_ wiping data, potentially with an
override with a --force flag?
Cheers,
Florian
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