On Fri, Nov 11, 2011 at 1:32 AM, Kevin Wolf <kw...@redhat.com> wrote:
> qcow2 has a writeback metadata cache, so flushing a qcow2 image actually
> consists of writing back that cache to the protocol and only then flushes the
> protocol in order to get everything stable on disk.
>
> This introduces a separate bdrv_co_flush_to_os to reflect the split.
>
> Signed-off-by: Kevin Wolf <kw...@redhat.com>
> ---
> block.c | 13 ++++++++++++-
> block/qcow2.c | 10 ++++++++--
> block_int.h | 7 +++++++
> 3 files changed, 27 insertions(+), 3 deletions(-)
>
> diff --git a/block.c b/block.c
> index d3042da..f81dd9f 100644
> --- a/block.c
> +++ b/block.c
> @@ -2782,11 +2782,22 @@ static void coroutine_fn bdrv_flush_co_entry(void
> *opaque)
>
> int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
> {
> + int ret;
> +
> if (bs->open_flags & BDRV_O_NO_FLUSH) {
> return 0;
> } else if (!bs->drv) {
> return 0;
> - } else if (bs->drv->bdrv_co_flush_to_disk) {
> + }
> +
> + if (bs->drv->bdrv_co_flush_to_os) {
> + ret = bs->drv->bdrv_co_flush_to_os(bs);
> + if (ret < 0) {
> + return ret;
> + }
> + }
> +
> + if (bs->drv->bdrv_co_flush_to_disk) {
> return bs->drv->bdrv_co_flush_to_disk(bs);
> } else if (bs->drv->bdrv_aio_flush) {
> BlockDriverAIOCB *acb;
> diff --git a/block/qcow2.c b/block/qcow2.c
> index f7f73fe..5c784ee 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -1105,7 +1105,7 @@ fail:
> return ret;
> }
>
> -static int qcow2_co_flush(BlockDriverState *bs)
> +static int qcow2_co_flush_to_os(BlockDriverState *bs)
> {
> BDRVQcowState *s = bs->opaque;
> int ret;
> @@ -1124,6 +1124,11 @@ static int qcow2_co_flush(BlockDriverState *bs)
> }
> qemu_co_mutex_unlock(&s->lock);
>
> + return 0;
> +}
> +
> +static int qcow2_co_flush_to_disk(BlockDriverState *bs)
> +{
> return bdrv_co_flush(bs->file);
> }
>
> @@ -1245,7 +1250,8 @@ static BlockDriver bdrv_qcow2 = {
>
> .bdrv_co_readv = qcow2_co_readv,
> .bdrv_co_writev = qcow2_co_writev,
> - .bdrv_co_flush_to_disk = qcow2_co_flush,
> + .bdrv_co_flush_to_os = qcow2_co_flush_to_os,
> + .bdrv_co_flush_to_disk = qcow2_co_flush_to_disk,
>
> .bdrv_co_discard = qcow2_co_discard,
> .bdrv_truncate = qcow2_truncate,
> diff --git a/block_int.h b/block_int.h
> index 5aadc1f..1ec4921 100644
> --- a/block_int.h
> +++ b/block_int.h
> @@ -93,6 +93,13 @@ struct BlockDriver {
> */
> int coroutine_fn (*bdrv_co_flush_to_disk)(BlockDriverState *bs);
>
> + /*
> + * Flushes all internal caches to the OS. The data may still sit in a
> + * writeback cache of the host OS, but it will survive a crash of the
> qemu
Sorry, How to use the data in cache of host OS to survive acrash of the qemu?
> + * process.
> + */
> + int coroutine_fn (*bdrv_co_flush_to_os)(BlockDriverState *bs);
> +
> int (*bdrv_aio_multiwrite)(BlockDriverState *bs, BlockRequest *reqs,
> int num_reqs);
> int (*bdrv_merge_requests)(BlockDriverState *bs, BlockRequest* a,
> --
> 1.7.6.4
>
>
>
--
Regards,
Zhi Yong Wu
