Re: [Qemu-devel] [PATCH][RFC] Add compare subcommand for qemu-img

[Stefan Hajnoczi]

On Wed, Aug 1, 2012 at 11:03 AM, Miroslav Rezanina <address@hidden> wrote:
> This patch adds compare subcommand that compares two images. Compare has 
> following criteria:
> - only data part is compared
> - unallocated sectors are not read
> - in case of different image size, exceeding part of bigger disk has to be 
> zeroed/unallocated to compare rest
> - qemu-img returns:
>    - 0 if images are identical
>    - 1 if images differ
>    - 2 on error

Please add qemu-img compare documentation to qemu-img.texi.
> @@ -652,6 +654,223 @@ static int compare_sectors(const uint8_t *buf1, const 
> uint8_t *buf2, int n,
>
>  #define IO_BUF_SIZE (2 * 1024 * 1024)
>
> +/*
> + * Get number of sectors that can be stored in IO buffer.
> + */
> +
> +static int64_t sectors_to_process(int64_t total, int64_t from)
> +{
> +  int64_t rv = total - from;
> +
> +  if (rv > (IO_BUF_SIZE >> BDRV_SECTOR_BITS))
> +     return IO_BUF_SIZE >> BDRV_SECTOR_BITS;

Please use git show | scripts/checkpatch.pl - to check coding style.

Stefan