Re: [Qemu-block] [Qemu-devel] [PATCH 2/4] block: Guarantee that *file is set on bdrv_get_block_status()

[Eric Blake]

On 05/18/2017 09:32 PM, Eric Blake wrote:
> We document that *file is valid if the return is not an error and
> includes BDRV_BLOCK_OFFSET_VALID, but forgot to obey this contract
> when a driver (such as blkdebug) lacks a callback.  Broken in
> commit 67a0fd2 (v2.6), when we added the file parameter.
> 

> +++ b/block/io.c
> @@ -1749,6 +1749,7 @@ static int64_t coroutine_fn 
> bdrv_co_get_block_status(BlockDriverState *bs,
>      int64_t n;
>      int64_t ret, ret2;
> 
> +    *file = NULL;
>      total_sectors = bdrv_nb_sectors(bs);
>      if (total_sectors < 0) {
>          return total_sectors;
> @@ -1769,6 +1770,7 @@ static int64_t coroutine_fn 
> bdrv_co_get_block_status(BlockDriverState *bs,
>          ret = BDRV_BLOCK_DATA | BDRV_BLOCK_ALLOCATED;
>          if (bs->drv->protocol_name) {
>              ret |= BDRV_BLOCK_OFFSET_VALID | (sector_num * BDRV_SECTOR_SIZE);
> +            *file = bs;
>          }
>          return ret;
>      }

Continuing context:

    *file = NULL;
    ret = bs->drv->bdrv_co_get_block_status(bs, sector_num, nb_sectors,
pnum,
                                            file);


Guess I need a v2, to remove the now-redundant second initialization of
*file.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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