Using zio_data_buf_alloc() to allocate the itx's may be unsafe
because the itx->itx_lr.lrc_reclen field is not constant from
allocation to free. Using a different itx->itx_lr.lrc_reclen
size in zio_data_buf_free() can result in the allocation being
returned to the wrong kmem cache.
This issue can be avoided entirely by storing the allocation size
in itx->itx_size and using that for zio_data_buf_free().
Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#6912
72841b9fd9