On Mon, Nov 14, 2011 at 4:50 PM, Kevin Wolf <kw...@redhat.com> wrote:
> Am 14.11.2011 04:04, schrieb Zhi Yong Wu:
>> 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?
>
> No, they are needed. We want to wait until the whole operation has
> completed, but qemu_coroutine_enter() returns after the first
> qemu_coroutine_yield().
got it. thanks.
>
> Kevin
>
--
Regards,
Zhi Yong Wu
