Hi All,
I have modified mdb so that I can examine data structures on disk using
::print.
This works fine for disks containing ufs file systems. It also works
for zfs file systems, but...
I use the dva block number from the uberblock_t to print what is at the
block
on disk. The problem I am having is that I can not figure out what (if
any) structure to use.
All of the xxx_phys_t types that I try do not look right. So, the
question is, just what is
the structure that the uberblock_t dva's refer to on the disk?
Here is an example:
First, I use zdb to get the dva for the rootbp (should match the value
in the uberblock_t(?)).
# zdb -dddd usbhard | grep -i dva
Dataset mos [META], ID 0, cr_txg 4, 1003K, 167 objects, rootbp [L0 DMU
objset] 400L/200P DVA[0]=<0:111f79000:200> DVA[1]=<0:506bde00:200>
DVA[2]=<0:36a286e00:200> fletcher4 lzjb LE contiguous birth=621838
fill=167 cksum=84daa9667:365cb5b02b0:b4e531085e90:197eb9d99a3beb
bp = [L0 DMU objset] 400L/200P DVA[0]=<0:111f6ae00:200>
DVA[1]=<0:502efe00:200> DVA[2]=<0:36a284e00:200> fletcher4 lzjb LE
contiguous birth=621838 fill=34026
cksum=cd0d51959:4fef8f217c3:10036508a5cc4:2320f4b2cde529
Dataset usbhard [ZPL], ID 5, cr_txg 4, 15.7G, 34026 objects, rootbp [L0
DMU objset] 400L/200P DVA[0]=<0:111f6ae00:200> DVA[1]=<0:502efe00:200>
DVA[2]=<0:36a284e00:200> fletcher4 lzjb LE contiguous birth=621838
fill=34026 cksum=cd0d51959:4fef8f217c3:10036508a5cc4:2320f4b2cde529
first block: [L0 ZIL intent log] 9000L/9000P
DVA[0]=<0:36aef6000:9000> zilog uncompressed LE contiguous birth=263950
fill=0 cksum=97a624646cebdadb:fd7b50f37b55153b:5:1
^C
#
Then I run my modified mdb on the vdev containing the "usbhard" pool
# ./mdb /dev/rdsk/c4t0d0s0
I am using the DVA[0} for the META data set above. Note that I have
tried all of the xxx_phys_t structures
that I can find in zfs source, but none of them look right. Here is
example output dumping the data as a objset_phys_t.
(The shift by 9 and adding 400000 is from the zfs on-disk format paper,
I have tried without the addition, without the shift,
in all combinations, but the output still does not make sense).
> (111f79000<<9)+400000::print zfs`objset_phys_t
{
os_meta_dnode = {
dn_type = 0x4f
dn_indblkshift = 0x75
dn_nlevels = 0x82
dn_nblkptr = 0x25
dn_bonustype = 0x47
dn_checksum = 0x52
dn_compress = 0x1f
dn_flags = 0x82
dn_datablkszsec = 0x5e13
dn_bonuslen = 0x63c1
dn_pad2 = [ 0x2e, 0xb9, 0xaa, 0x22 ]
dn_maxblkid = 0x20a34fa97f3ff2a6
dn_used = 0xac2ea261cef045ff
dn_pad3 = [ 0x9c2b4541ab9f78c0, 0xdb27e70dce903053,
0x315efac9cb693387, 0x2d56c54db5da75bf ]
dn_blkptr = [
{
blk_dva = [
{
dva_word = [ 0x87c9ed7672454887,
0x760f569622246efe ]
}
{
dva_word = [ 0xce26ac20a6a5315c,
0x38802e5d7cce495f ]
}
{
dva_word = [ 0x9241150676798b95,
0x9c6985f95335742c ]
}
]
None of this looks believable. So, just what is the rootbp in the
uberblock_t referring to?
thanks,
max
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