Re: [Qemu-devel] [PATCH v3 16/22] block: Wording tweaks to write zeroes limits

[Fam Zheng]

On Thu, 06/23 16:37, Eric Blake wrote:
> Improve the documentation of the write zeroes limits, to mention
> additional constraints that drivers should observe.  Worth squashing
> into commit cf081fca, if that hadn't been pushed already :)
> 
> Signed-off-by: Eric Blake <address@hidden>
> 
> ---
> v3: new patch, split off from "block: Switch discard length bounds..."
> ---
>  include/block/block_int.h | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/include/block/block_int.h b/include/block/block_int.h
> index 7d2b152..7a4a00f 100644
> --- a/include/block/block_int.h
> +++ b/include/block/block_int.h
> @@ -331,11 +331,14 @@ typedef struct BlockLimits {
>      int64_t discard_alignment;
> 
>      /* maximum number of bytes that can zeroized at once (since it is
> -     * signed, it must be < 2G, if set) */
> +     * signed, it must be < 2G, if set), should be multiple of
> +     * pwrite_zeroes_alignment. May be 0 if no inherent 32-bit limit */

"inherent 32-bit limit"? What is special about 32-bit other than this field is
32-bit? Anyway,

Reviewed-by: Fam Zheng <address@hidden>

>      int32_t max_pwrite_zeroes;
> 
>      /* optimal alignment for write zeroes requests in bytes, must be
> -     * power of 2, and less than max_pwrite_zeroes if that is set */
> +     * power of 2, less than max_pwrite_zeroes if that is set, and
> +     * multiple of bs->request_alignment. May be 0 if
> +     * bs->request_alignment is good enough */
>      uint32_t pwrite_zeroes_alignment;
> 
>      /* optimal transfer length in bytes (must be power of 2, and
> -- 
> 2.5.5
>