Re: [Qemu-devel] [PATCH] block: Fix bdrv_is_allocated() for short backing files

[Max Reitz <mreitz@redhat.com>]

On 06.05.2014 15:30, Kevin Wolf wrote:
> bdrv_is_allocated() shouldn't return true for sectors that are
> unallocated, but after the end of a short backing file, even though
> such sectors are (correctly) marked as containing zeros.
>
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>   block.c               |  8 +++++---
>   include/block/block.h | 11 +++++++----
>   2 files changed, 12 insertions(+), 7 deletions(-)
>
> diff --git a/block.c b/block.c
> index c90c71a..d3a9906 100644
> --- a/block.c
> +++ b/block.c
> @@ -3883,6 +3883,10 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs,
>                                        *pnum, pnum);
>       }
>   
> +    if (ret & (BDRV_BLOCK_DATA | BDRV_BLOCK_ZERO)) {
> +        ret |= BDRV_BLOCK_ALLOCATED;
> +    }
> +

Shouldn't BDRV_BLOCK_ALLOCATED be set in the 
!bs->drv->bdrv_co_get_block_status case as well?

>       if (!(ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO)) {
>           if (bdrv_unallocated_blocks_are_zero(bs)) {
>               ret |= BDRV_BLOCK_ZERO;
> @@ -3959,9 +3963,7 @@ int coroutine_fn bdrv_is_allocated(BlockDriverState *bs, int64_t sector_num,
>       if (ret < 0) {
>           return ret;
>       }
> -    return
> -        (ret & BDRV_BLOCK_DATA) ||
> -        ((ret & BDRV_BLOCK_ZERO) && !bdrv_has_zero_init(bs));
> +    return (ret & BDRV_BLOCK_ALLOCATED);
>   }
>   
>   /*
> diff --git a/include/block/block.h b/include/block/block.h
> index 2fda81c..ad4c7e8 100644
> --- a/include/block/block.h
> +++ b/include/block/block.h
> @@ -116,6 +116,8 @@ typedef enum {
>   /* BDRV_BLOCK_DATA: data is read from bs->file or another file
>    * BDRV_BLOCK_ZERO: sectors read as zero
>    * BDRV_BLOCK_OFFSET_VALID: sector stored in bs->file as raw data
> + * BDRV_BLOCK_ALLOCATED: the content of the block is determined by this
> + *                       layer (as opposed to the backing file)

I guess this is above BDRV_BLOCK_RAW (albeit having a greater value) 
because it is not only used internally? (to pick up on the topic of OCD :-P)

Max

>    * BDRV_BLOCK_RAW: used internally to indicate that the request
>    *                 was answered by the raw driver and that one
>    *                 should look in bs->file directly.
> @@ -137,10 +139,11 @@ typedef enum {
>    *  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_RAW          8
> +#define BDRV_BLOCK_DATA         0x01
> +#define BDRV_BLOCK_ZERO         0x02
> +#define BDRV_BLOCK_OFFSET_VALID 0x04
> +#define BDRV_BLOCK_RAW          0x08
> +#define BDRV_BLOCK_ALLOCATED    0x10
>   #define BDRV_BLOCK_OFFSET_MASK  BDRV_SECTOR_MASK
>   
>   typedef enum {