On Fri, 08/04 16:49, Daniel P. Berrange wrote: > This is odd. In the bdrv_aligned_readv() it looks very much like > we'll reference qiov->niov, if bytes != 0, so if qiov was NULL we > would crash.
It doesn't make sense if read doesn't have an iov, where should the data be placed? :) > > In bdrv_aligned_writev(), qiov->niov is also refernced if bytes != 0, > *unless* flags contains BDRV_REQ_ZERO_WRITE, in which case we'll > invoke bdrv_co_do_pwrite_zeroes() instead. This is intended. Zero-write doesn't need qiov, hence the BDRV_REQ_ZERO_WRITE branch. Otherwise, we can assert qiov != NULL. > > So unless I'm missing something, bdrv_co_preadv|writev cannot be > called with a NULL qiov, and bdrv_aligned_writev|readv might > need their assertions tightened up. bdrv_co_pwritev _is_ called with a NULL qiov from blk_aio_pwrite_zeroes. Your other reasonings are right. So for write we cannot remove the bytes parameter. Fam
