xfersize (int)     = -1808
(size_t)xfersize   = 0xfffffffffffff8f0 (18446744073709549808)
uio_resid          = 16
LINE 294: uio_resid < xfersize is TRUE (size_t promotion)
LINE 295: xfersize = uio_resid = 16
xfersize after clamp = 16 (POSITIVE -- OOB path defeated)
balloc: blkoffset + xfersize = 10000 + 16 = 10016 > fs_bsize=8192 => PANIC 'blk too big'