On Sat, Nov 12, 2011 at 12:47 AM, Stefan Hajnoczi
<stefa...@linux.vnet.ibm.com> wrote:
> This patch adds the .bdrv_co_is_allocated() interface which is identical
> to .bdrv_is_allocated() but runs in coroutine context. Running in
> coroutine context implies that other coroutines might be performing I/O
> at the same time. Therefore it must be safe to run while the following
> BlockDriver functions are in-flight:
>
> .bdrv_co_readv()
> .bdrv_co_writev()
> .bdrv_co_flush()
> .bdrv_co_is_allocated()
>
> The new .bdrv_co_is_allocated() interface is useful because it can be
> used when a VM is running, whereas .bdrv_is_allocated() is a synchronous
> interface that does not cope with parallel requests.
>
> Signed-off-by: Stefan Hajnoczi <stefa...@linux.vnet.ibm.com>
> ---
> block.c | 37 +++++++++++++++++++++++++++++++++++++
> block_int.h | 2 ++
> 2 files changed, 39 insertions(+), 0 deletions(-)
>
> diff --git a/block.c b/block.c
> index e6ac6d3..f8705b7 100644
> --- a/block.c
> +++ b/block.c
> @@ -1771,6 +1771,26 @@ int bdrv_has_zero_init(BlockDriverState *bs)
> return 1;
> }
>
> +typedef struct BdrvCoIsAllocatedData {
> + BlockDriverState *bs;
> + int64_t sector_num;
> + int nb_sectors;
> + int *pnum;
> + int ret;
> + bool done;
> +} BdrvCoIsAllocatedData;
> +
> +/* Coroutine wrapper for bdrv_is_allocated() */
> +static void coroutine_fn bdrv_is_allocated_co_entry(void *opaque)
> +{
> + BdrvCoIsAllocatedData *data = opaque;
> + BlockDriverState *bs = data->bs;
> +
> + data->ret = bs->drv->bdrv_co_is_allocated(bs, data->sector_num,
> + data->nb_sectors, data->pnum);
> + data->done = true;
> +}
> +
> /*
> * Returns true iff the specified sector is present in the disk image. Drivers
> * not implementing the functionality are assumed to not support backing
> files,
> @@ -1786,6 +1806,23 @@ int bdrv_is_allocated(BlockDriverState *bs, int64_t
> sector_num, int nb_sectors,
> int *pnum)
> {
> int64_t n;
> + if (bs->drv->bdrv_co_is_allocated) {
> + Coroutine *co;
> + BdrvCoIsAllocatedData data = {
> + .bs = bs,
> + .sector_num = sector_num,
> + .nb_sectors = nb_sectors,
> + .pnum = pnum,
> + .done = false,
> + };
> +
> + co = qemu_coroutine_create(bdrv_is_allocated_co_entry);
> + qemu_coroutine_enter(co, &data);
Since this main process will stop within qemu_coroutine_enter() until
bdrv_is_allocated_co_entry() is completed, three lines of condition
codes below are unnecessary, right?
> + while (!data.done) {
> + qemu_aio_wait();
> + }
> + return data.ret;
> + }
> if (!bs->drv->bdrv_is_allocated) {
> if (sector_num >= bs->total_sectors) {
> *pnum = 0;
> diff --git a/block_int.h b/block_int.h
> index f4547f6..1c1351c 100644
> --- a/block_int.h
> +++ b/block_int.h
> @@ -87,6 +87,8 @@ struct BlockDriver {
> int coroutine_fn (*bdrv_co_flush)(BlockDriverState *bs);
> int coroutine_fn (*bdrv_co_discard)(BlockDriverState *bs,
> int64_t sector_num, int nb_sectors);
> + int coroutine_fn (*bdrv_co_is_allocated)(BlockDriverState *bs,
> + int64_t sector_num, int nb_sectors, int *pnum);
>
> int (*bdrv_aio_multiwrite)(BlockDriverState *bs, BlockRequest *reqs,
> int num_reqs);
> --
> 1.7.7.1
>
>
>
--
Regards,
Zhi Yong Wu
