On Sun, Jan 27, 2019 at 12:51:44PM +0000, Stefan Hajnoczi wrote: > On Fri, Jan 25, 2019 at 05:18:13PM +0100, Stefano Garzarella wrote: > > On Fri, Jan 25, 2019 at 02:58:56PM +0000, Stefan Hajnoczi wrote: > > > On Thu, Jan 24, 2019 at 06:23:22PM +0100, Stefano Garzarella wrote: > > > > + virtio_error(vdev, "virtio-blk discard/wzeroes header too > > > > short"); > > > > + return -1; > > > > + } > > > > + > > > > + sector = virtio_ldq_p(VIRTIO_DEVICE(req->dev), > > > > &dwz_hdr.sector); > > > > + bytes = virtio_ldl_p(VIRTIO_DEVICE(req->dev), > > > > + &dwz_hdr.num_sectors) << BDRV_SECTOR_BITS; > > > > > > Please handle num_sectors << BDRV_SECTOR_BITS overflow so that we don't > > > need to worry about what happens with an overflowed value later on. > > > > > > > Should I also check if num_sectors is less than "max_discard_sectors" or > > "max_write_zeroes_sectors"? > > Yes, anything that virtio_blk_sect_range_ok() doesn't check needs to be > checked manually in this patch. I can't see a reason for allowing > requests through that exceed the limit. > > > Do you think make sense flush the MultiReqBuffer before call > > blk_aio_pdiscard() or blk_aio_pwrite_zeroes()? > > I don't think that is necessary since virtio-blk doesn't guarantee > ordering (the legacy barrier feature isn't supported by QEMU). > > Even the MultiReqBuffer is flushed, -drive aio=threads (the default > setting) could end up submitting discard/write zeroes before "earlier" > requests - it depends on host kernel thread scheduler decisions. >
Thanks for the details! Stefano
