[Jfs-discussion] Strange dir inode

[Felipe M. de C. <fel...@gm...>]

Hello,

I've been working hard to get jfs read support in my software, and I
try as hard as possible to figure out myself without asking question,
but there is a very strange point where I got stuck =( Its a dir
inode, which has 10.000 files inside it.

inode nr 12291 and offset 0x600460 presents us the following basic
inode information:

http://magnifier.sourceforge.net/tmp/jfs_inode_10k_files.png

di_fileset $10
di_number $303
di_gen $2A
di_size = $14000
di_nblocks = $140
di_nlink = 2
di_uid = 0
di_gid = 0
di_mode = $200041FF
di_next_index = $B0100
di_acltype = 0

dtroot_t
DASD = zeroes
flag = 0x85 = DXD_INDEX | BT_INTERNAL | BT_ROOT
nextindex = 1
freecnt: int8 = 7
freelistt: int8 = 2
idotdot = $3040
stbl = 1, 2, 4, 6, 8, 0, 0, 0

dir_table_slot[0]
dir_table_slot->rsrvd = 0
dir_table_slot->flag = 1 DIR_INDEX_VALID
dir_table_slot->slot = B
dir_table_slot->addr1 = 0
dir_table_slot->addr2 = $6023
dir_table_slot[1]
dir_table_slot = 0
dir_table_slot->flag = 1  DIR_INDEX_VALID
dir_table_slot->slot = 0
dir_table_slot->addr1 = 0
dir_table_slot->addr2 = $6023
dir_table_slot[2]
dir_table_slot->rsrvd = $85
dir_table_slot->flag = 1 DIR_INDEX_VALID
dir_table_slot->slot = 3
dir_table_slot->addr1 = 0
dir_table_slot->addr2 = 6
dir_table_slot[3]
dir_table_slot->rsrvd = 0
dir_table_slot->flag = 1 DIR_INDEX_VALID
dir_table_slot->slot = 2
dir_table_slot->addr1 = 0
dir_table_slot->addr2 = $6023
dir_table_slot[4]
dir_table_slot->rsrvd = 0
dir_table_slot->flag = 1 DIR_INDEX_VALID
dir_table_slot->slot = 3
dir_table_slot->addr1 = 0
dir_table_slot->addr2 = 0
dir_table_slot[5]
dir_table_slot->rsrvd = 1
dir_table_slot->flag = 0 DIR_INDEX_FREE
dir_table_slot->slot = 0
dir_table_slot->addr1 = 0
dir_table_slot->addr2= $801A
etc
etc

Which has the following problems:

1> If I believe in freecnt 7 items should be free and only 1 valid?
Which one? The first with address 0x6023? But in reality 0x6023
contains some files, while 0x801A constains a list of blocks, so it
cannot be that only 0x6023 is valid...

2> dir_table_slot[5] with addr 0x801A should be valid, because if it
is not, then I don't see how I could possibly have the names of all
10k files, since 0x6023 is filled with only some filenames, while
0x801A has links to many blocks of filenames. But 0x801A has
flag=0=DIR_INDEX_FREE, why?

3> dir_table_slot[2] has addr=6 which is obviously wrong, and this
block (offset 0x6000) contains only zeroes. But slot[2] is listed in
the stbl and even has flag = 1 = DIR_INDEX_VALID How to identify that
it is invalid then?

4> 801A is here: http://magnifier.sourceforge.net/tmp/jfs_block_801A.png

I assume that the structure is a xtpage_t followed by an array of xad:

xtpage_t->next = 0
xtpage_t->prev = 0
xtpage_t->flag = 2=BT_LEAF?
xtpage_t->rsrvd1 = 0
xtpage_t->nextindex= $16
xtpage_t->maxentry = $100
xtpage_t->rsrvd2 = 0

Strange here is the flag, I'd expect BT_INTERNAL, but it is BT_LEAF...

801A links to 602A which links to 6083 which finally is a leaf block.
But all 3 blocks have flag 2 set .... so how can I differentiate
between a leaf (which I think should contain filenames) and an
internal node (which I think should contain a list of blocks)?

5> In block 602A there are multiple xad's referring to the exact same
leaf blocks (0x6023 for example), the only difference between them
being the reserved field:

http://magnifier.sourceforge.net/tmp/jfs_block_602A.png

xad[2]
xad_t->flag = 0
xad_t->rsvrd= $301
xad_t->off1 = 0
xad_t->off2= $6023
xad_t->len = $60100
xad_t->addr1 = 0
xad_t->addr2 = $6023
xad[3]
xad_t->flag = 0
xad_t->rsvrd = $501
xad_t->off1 = 0
xad_t->off2= $6023
xad_t->len = $60100
xad_t->addr1 = 0
xad_t->addr2 = $6023

Is this information relevant for my software or should I just skip
repeated blocks?

thanks =)
-- 
Felipe Monteiro de Carvalho