[zfs-code] Space allocation failure

[Manoj Joseph]

Hi,

Trying to understand the zfs code, I was playing with libzpool - like 
ztest does.

What I am trying to do is create an object in a zfs filesystem. But I am 
seeing failures when I try to sync changes.

bash-3.00# ./udmu test Object 4 error: ZFS: I/O failure (write on 
<unknown> off 0: zio 81f5d00 [L0 unallocated] 200L/200P DVA[0]=<0:0:200> 
fletcher2 uncompressed LE contiguous birth=7 fill=0 
cksum=4141414141414141:4141:2828282828282820:82820): error 28
Abort (core dumped)

I can see that space does not get allocated and sync results in ENOSPC. 
There is plenty of space in the pool. So, that is not the issue. I guess 
I am missing the step of allocating space. Could someone help me figure 
out what it is?

I have tried to follow what ztest does. This is what I do:

<code snippet>
kernel_init(FREAD | FWRITE);
buf = malloc(BUF_SIZE);
memset(buf, 'A', BUF_SIZE);

error = dmu_objset_open(osname, DMU_OST_ZFS, DS_MODE_PRIMARY, &os);
if (error) {
        fprintf(stderr, "dmu_objset_open() = %d", error);
        return (error);
}
tx = dmu_tx_create(os);
dmu_tx_hold_write(tx, DMU_NEW_OBJECT, 0, BUF_SIZE);
// dmu_tx_hold_bonus(tx, DMU_NEW_OBJECT);

error = dmu_tx_assign(tx, TXG_WAIT);
if (error) {
        dmu_tx_abort(tx);
        return (error);
}

object = dmu_object_alloc(os, DMU_OT_UINT64_OTHER, 0,
     DMU_OT_NONE, 0, tx);

printf("Object %lld\n", object);

dmu_write(os, object, 0, BUF_SIZE, buf, tx);
dmu_tx_commit(tx);

txg_wait_synced(dmu_objset_pool(os), 0);
</code snippet>

It is interesting that the checksum that is reported is the pattern that 
I try to write.

This is the panic stack:
  d11d8e65 _lwp_kill (98, 6) + 15
  d1192102 raise    (6) + 22
  d1170dad abort    (81f5d00, d1354000, ce3fdcc8, ce3fdcbc, d13c0568, 
ce3fdcbc) + cd
  d131ed79 vpanic   (d1341dbc, ce3fdcc8) + 51
  d131ed9f panic    (d1341dbc, d135a384, d135a724, d133a630, 0, 0) + 1f
  d131921d zio_done (81f5d00) + 455
  d131c15d zio_next_stage (81f5d00) + 161
  d1318b92 zio_wait_for_children (81f5d00, 11, 81f5ef0) + 6a
  d1318c88 zio_wait_children_done (81f5d00) + 18
  d131c15d zio_next_stage (81f5d00) + 161
  d131ba83 zio_vdev_io_assess (81f5d00) + 183
  d131c15d zio_next_stage (81f5d00) + 161
  d1307011 vdev_mirror_io_done (81f5d00) + 421
  d131b8a2 zio_vdev_io_done (81f5d00, 0, d0e0ac00, d1210000, d11ba2df, 
3) + 36
  d131f585 taskq_thread (81809c0) + 89
  d11d7604 _thr_setup (d0e0ac00) + 52
  d11d7860 _lwp_start (d0e0ac00, 0, 0, 0, 0, 0)

Thanks in advance!

Regards,
Manoj