On Mon 12 Feb 2018 02:14:01 PM CET, Anton Nefedov wrote: > The normal bdrv_co_pwritev() use is either > - BDRV_REQ_ZERO_WRITE clear and iovector provided > - BDRV_REQ_ZERO_WRITE set and iovector == NULL > > while > - the flag clear and iovector == NULL is an assertion failure > in bdrv_co_do_zero_pwritev() > - the flag set and iovector provided is in fact allowed > (the flag prevails and zeroes are written) > > However the alignment logic does not support the latter case so the > padding areas get overwritten with zeroes.
Oh, so this doesn't simply write zeroes in [offset, offset+bytes), but also in the head and tail areas, instead of keeping the previous contents. This is a pretty serious bug, but I assume it can't be triggered (bdrv_pwrite_zeroes() is used in complete clusters). Did you check if there was any other scenario where this could happen? > Signed-off-by: Anton Nefedov <anton.nefe...@virtuozzo.com> > Reviewed-by: Eric Blake <ebl...@redhat.com> Reviewed-by: Alberto Garcia <be...@igalia.com> Berto
