Il 30/07/2013 16:40, Kevin Wolf ha scritto:
> Am 25.07.2013 um 16:23 hat Paolo Bonzini geschrieben:
>> Reviewed-by: Eric Blake <ebl...@redhat.com>
>> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
>> ---
>> block/cow.c | 8 +++++++-
>> block/qcow.c | 9 ++++++++-
>> block/qcow2.c | 16 ++++++++++++++--
>> block/qed.c | 35 ++++++++++++++++++++++++++++-------
>> block/sheepdog.c | 2 +-
>> block/vdi.c | 13 ++++++++++++-
>> block/vmdk.c | 19 ++++++++++++++++++-
>> block/vvfat.c | 11 ++++++-----
>> 8 files changed, 94 insertions(+), 19 deletions(-)
>>
>> diff --git a/block/cow.c b/block/cow.c
>> index e738b96..1e90413 100644
>> --- a/block/cow.c
>> +++ b/block/cow.c
>> @@ -194,7 +194,13 @@ static int coroutine_fn
>> cow_co_is_allocated(BlockDriverState *bs,
>> static int64_t coroutine_fn cow_co_get_block_status(BlockDriverState *bs,
>> int64_t sector_num, int nb_sectors, int *num_same)
>> {
>> - return cow_co_is_allocated(bs, sector_num, nb_sectors, num_same);
>> + BDRVCowState *s = bs->opaque;
>> + int ret = cow_co_is_allocated(bs, sector_num, nb_sectors, num_same);
>> + int64_t offset = s->cow_sectors_offset + (sector_num <<
>> BDRV_SECTOR_BITS);
>> + if (ret < 0) {
>> + return ret;
>> + }
>> + return (ret ? BDRV_BLOCK_DATA : 0) | offset | BDRV_BLOCK_OFFSET_VALID;
>> }
>>
>> static int cow_update_bitmap(BlockDriverState *bs, int64_t sector_num,
>> diff --git a/block/qcow.c b/block/qcow.c
>> index acd1aeb..1a65822 100644
>> --- a/block/qcow.c
>> +++ b/block/qcow.c
>> @@ -410,7 +410,14 @@ static int64_t coroutine_fn
>> qcow_co_get_block_status(BlockDriverState *bs,
>> if (n > nb_sectors)
>> n = nb_sectors;
>> *pnum = n;
>> - return (cluster_offset != 0);
>> + if (!cluster_offset) {
>> + return 0;
>
> If you take your comment in patch 11 serious, you should return
> bs->backing_hd ? 0 : BDRV_BLOCK_ZERO instead. (I think it would be
> useful behaviour, too, because knowing that a sector is zero enables
> optimisations in several places.)
>
> Of course, this is something that could be done in the block.c
> implementation of bdrv_co_get_block_status() instead of each single
> driver.
And it is, in patch 15 ("block: use bdrv_has_zero_init to return
BDRV_BLOCK_ZERO"). :) Should I reorder the patches?
Paolo
