Re: [Qemu-devel] [PATCH] block/vpc: fix get_sector_offset for vpc_read

[Max Reitz <mreitz@redhat.com>]

On 2015-02-23 at 10:01, Peter Lieven wrote:
> VHD images contain a bitmap at the beginning of each data block
> to indicate the allocation status of each sector in the data block.
>
> vpc_read currently checks the allocation status of the first sector
> in a data block it is going to read and then assumes the same allocation
> status for the whole remainder of the data block. This might end up
> in incorrect zero sectors if the first sector is unallocated.
>
> To fix this indiciate a sector is allocated as soon as its
> data block has a valid page table index.

Hm, as far as I can see, this patch just removes unused code. How does 
this correspond to the commit message?

Max

> CC: qemu-stable@nongnu.org
> Signed-off-by: Peter Lieven <pl@kamp.de>
> ---
>   block/vpc.c |   32 --------------------------------
>   1 file changed, 32 deletions(-)
>
> diff --git a/block/vpc.c b/block/vpc.c
> index 46803b1..9a75334 100644
> --- a/block/vpc.c
> +++ b/block/vpc.c
> @@ -376,38 +376,6 @@ static inline int64_t get_sector_offset(BlockDriverState *bs,
>           bdrv_pwrite_sync(bs->file, bitmap_offset, bitmap, s->bitmap_size);
>       }
>   
> -//    printf("sector: %" PRIx64 ", index: %x, offset: %x, bioff: %" PRIx64 ", bloff: %" PRIx64 "\n",
> -//	sector_num, pagetable_index, pageentry_index,
> -//	bitmap_offset, block_offset);
> -
> -// disabled by reason
> -#if 0
> -#ifdef CACHE
> -    if (bitmap_offset != s->last_bitmap)
> -    {
> -	lseek(s->fd, bitmap_offset, SEEK_SET);
> -
> -	s->last_bitmap = bitmap_offset;
> -
> -	// Scary! Bitmap is stored as big endian 32bit entries,
> -	// while we used to look it up byte by byte
> -	read(s->fd, s->pageentry_u8, 512);
> -	for (i = 0; i < 128; i++)
> -	    be32_to_cpus(&s->pageentry_u32[i]);
> -    }
> -
> -    if ((s->pageentry_u8[pageentry_index / 8] >> (pageentry_index % 8)) & 1)
> -	return -1;
> -#else
> -    lseek(s->fd, bitmap_offset + (pageentry_index / 8), SEEK_SET);
> -
> -    read(s->fd, &bitmap_entry, 1);
> -
> -    if ((bitmap_entry >> (pageentry_index % 8)) & 1)
> -	return -1; // not allocated
> -#endif
> -#endif
> -
>       return block_offset;
>   }
>