Am 03.07.2013 um 16:34 schrieb Paolo Bonzini <pbonz...@redhat.com>:
> Define the return value of get_block_status. Bits 0, 1, 2 and 8-62
> are valid; bit 63 (the sign bit) is reserved for errors. Bits 3-7
> are left for future extensions.
Is Bit 8 not also reserved for future use? BDRV_SECTOR_BITS is 9.
Can you explain which information is exactly returned in Bits 9-62?
Peter
>
> The return code is compatible with the old is_allocated API: returning
> just 0 or 1 (aka BDRV_BLOCK_DATA) will not cause any behavioral change
> in clients of is_allocated. We will return more precise information
> in the next patches.
>
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
> ---
> block.c | 7 +++++--
> include/block/block.h | 23 +++++++++++++++++++++++
> 2 files changed, 28 insertions(+), 2 deletions(-)
>
> diff --git a/block.c b/block.c
> index aa1a5f7..8931cac 100644
> --- a/block.c
> +++ b/block.c
> @@ -2976,7 +2976,7 @@ static int64_t coroutine_fn
> bdrv_co_get_block_status(BlockDriverState *bs,
>
> if (!bs->drv->bdrv_co_get_block_status) {
> *pnum = nb_sectors;
> - return 1;
> + return BDRV_BLOCK_DATA;
> }
>
> return bs->drv->bdrv_co_get_block_status(bs, sector_num, nb_sectors,
> pnum);
> @@ -3026,7 +3026,10 @@ int64_t bdrv_get_block_status(BlockDriverState *bs,
> int64_t sector_num,
> int coroutine_fn bdrv_is_allocated(BlockDriverState *bs, int64_t sector_num,
> int nb_sectors, int *pnum)
> {
> - return bdrv_get_block_status(bs, sector_num, nb_sectors, pnum);
> + int64_t ret = bdrv_get_block_status(bs, sector_num, nb_sectors, pnum);
> + return
> + (ret & BDRV_BLOCK_DATA) ||
> + ((ret & BDRV_BLOCK_ZERO) && !bdrv_has_zero_init(bs));
> }
>
> /*
> diff --git a/include/block/block.h b/include/block/block.h
> index 2b50b51..9e44bdd 100644
> --- a/include/block/block.h
> +++ b/include/block/block.h
> @@ -81,6 +81,29 @@ typedef struct BlockDevOps {
> #define BDRV_SECTOR_SIZE (1ULL << BDRV_SECTOR_BITS)
> #define BDRV_SECTOR_MASK ~(BDRV_SECTOR_SIZE - 1)
>
> +/* BDRV_BLOCK_DATA: data is read from bs->file or another file
> + * BDRV_BLOCK_ZERO: sectors read as zero
> + * BDRV_BLOCK_OFFSET_VALID: contents of sector available in bs->file at
> offset
> + *
> + * DATA == 0 && ZERO == 0 means that data is read from backing_hd if present.
> + *
> + * DATA ZERO OFFSET_VALID
> + * t t t sectors read as zero, bs->file is zero at offset
> + * t f t sectors read as valid from bs->file at offset
> + * f t t sectors preallocated, read as zero, bs->file not
> + * necessarily zero at offset
> + * f f t sectors preallocated but read from backing_hd,
> + * bs->file contains garbage at offset
> + * t t f sectors preallocated, read as zero, unknown offset
> + * t f f sectors read from unknown file or offset
> + * f t f not allocated or unknown offset, read as zero
> + * f f f not allocated or unknown offset, read from
> backing_hd
> + */
> +#define BDRV_BLOCK_DATA 1
> +#define BDRV_BLOCK_ZERO 2
> +#define BDRV_BLOCK_OFFSET_VALID 4
> +#define BDRV_BLOCK_OFFSET_MASK BDRV_SECTOR_MASK
> +
> typedef enum {
> BDRV_ACTION_REPORT, BDRV_ACTION_IGNORE, BDRV_ACTION_STOP
> } BlockErrorAction;
> --
> 1.8.2.1
>
>
