On 06/10/2016 10:05 AM, Kevin Wolf wrote: > We don't really want to go through the block layer in order to read from > or write to the vmstate in a qcow2 image. Doing so required a few ugly > hacks like saving and restoring the old image size (because writing to > vmstate offsets would increase the image size) or disabling the "reads > after EOF = zeroes" logic. When calling the right functions directly, > these hacks aren't necessary any more. > > Note that .bdrv_vmstate_load/save() return 0 instead of the number of > bytes in case of success now. > > Signed-off-by: Kevin Wolf <[email protected]> > --- > block/qcow2.c | 24 ++++-------------------- > 1 file changed, 4 insertions(+), 20 deletions(-) >
> +++ b/block/qcow2.c
> @@ -2903,36 +2903,20 @@ static int qcow2_save_vmstate(BlockDriverState *bs,
> QEMUIOVector *qiov,
> int64_t pos)
> {
> BDRVQcow2State *s = bs->opaque;
> - int64_t total_sectors = bs->total_sectors;
> - bool zero_beyond_eof = bs->zero_beyond_eof;
> - int ret;
>
> BLKDBG_EVENT(bs->file, BLKDBG_VMSTATE_SAVE);
> - bs->zero_beyond_eof = false;
> - ret = bdrv_pwritev(bs, qcow2_vm_state_offset(s) + pos, qiov);
> - bs->zero_beyond_eof = zero_beyond_eof;
> -
> - /* bdrv_co_do_writev will have increased the total_sectors value to
> include
> - * the VM state - the VM state is however not an actual part of the block
> - * device, therefore, we need to restore the old value. */
> - bs->total_sectors = total_sectors;
> -
> - return ret;
> + return bs->drv->bdrv_co_pwritev(bs, qcow2_vm_state_offset(s) + pos,
> + qiov->size, qiov, 0);
> }
bs->drv->bdrv_co_pwritev() is an optional interface; not all the drivers
have it yet. Should you be asserting that it exists, and/or returning
an error if it does not?
>
> static int qcow2_load_vmstate(BlockDriverState *bs, QEMUIOVector *qiov,
> int64_t pos)
> {
> BDRVQcow2State *s = bs->opaque;
> - bool zero_beyond_eof = bs->zero_beyond_eof;
> - int ret;
>
> BLKDBG_EVENT(bs->file, BLKDBG_VMSTATE_LOAD);
> - bs->zero_beyond_eof = false;
> - ret = bdrv_preadv(bs, qcow2_vm_state_offset(s) + pos, qiov);
> - bs->zero_beyond_eof = zero_beyond_eof;
> -
> - return ret;
> + return bs->drv->bdrv_co_preadv(bs, qcow2_vm_state_offset(s) + pos,
> + qiov->size, qiov, 0);
Ditto.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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