[Libguestfs] nbdkit test-checkwrite.sh failing occasionally on ppc64le

[Laszlo Ersek]

On 07/13/22 13:27, Richard W.M. Jones wrote:
> 
> It's not 100% reproducible, but it seems to happen reasonably often.
> Unfortunately it only happens on ppc64le (so far).  The error message
> lacks sufficient detail to tell what's going on.
> 
> nbdkit: backend.c:624: backend_pread: Assertion `backend_valid_range (c, offset, count)' failed.
> nbdkit: backend.c:624: backend_pread: Assertion `backend_valid_range (c, offset, count)' failed.
> 
> Full log attached.

"tests/disk" has size 105923072.

Considering all the count=... offset=... lines in the last section of
the log, there isn't one line where backend_valid_range():

  return count > 0 && offset <= c->exportsize &&
    offset + count <= c->exportsize;

would return false.

I've printed a table, with offset, count, and offset+count colums, from
the log entries, then sorted the table three times separately, each time
by a different column. I got the following min and max elements:

offset    count     offset+count
--------- --------- -----------
        0 105923072   105923072 (min by offset)
105906176     16896   105923072 (max by offset)
        0      4096        4096 (min by count)
        0 105923072   105923072 (max by count)
        0      4096        4096 (min by end)
105906176     16896   105923072 (max by end)

All of these look valid... I think you'll have to look at the coredump
with gdb.

Laszlo