Re: [Qemu-devel] [PATCH] qcow2: Replace align_offset() with ROUND_UP()

[Eric Blake <eblake@redhat.com>]

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On 01/30/2018 09:04 AM, Alberto Garcia wrote:
> The align_offset() function is equivalent to the ROUND_UP() macro so
> there's no need to use the former. The ROUND_UP() name is also a bit
> more explicit.
> 
> This patch uses ROUND_UP() instead of the slower QEMU_ALIGN_UP()
> because align_offset() already requires that the second parameter is a
> power of two.

(Presumably, for the cases where the second argument is a compile-time
constant, the compiler emits the same code for either macro - but I
agree that QEMU_ALIGN_UP can be slower where the compiler can't see it
is a power of 2)

> 
> Signed-off-by: Alberto Garcia <berto@igalia.com>
> ---
> +++ b/block/qcow2-bitmap.c
> @@ -413,7 +413,7 @@ static inline void bitmap_dir_entry_to_be(Qcow2BitmapDirEntry *entry)
>  
>  static inline int calc_dir_entry_size(size_t name_size, size_t extra_data_size)
>  {
> -    return align_offset(sizeof(Qcow2BitmapDirEntry) +
> +    return ROUND_UP(sizeof(Qcow2BitmapDirEntry) +
>                          name_size + extra_data_size, 8);

Indentation alignment is now off.


> +++ b/block/qcow2.c

> @@ -3681,7 +3681,7 @@ static BlockMeasureInfo *qcow2_measure(QemuOpts *opts, BlockDriverState *in_bs,
>      has_backing_file = !!optstr;
>      g_free(optstr);
>  
> -    virtual_size = align_offset(qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0),
> +    virtual_size = ROUND_UP(qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0),
>                                  cluster_size);

and again.

With the whitespace fixed,
Reviewed-by: Eric Blake <eblake@redhat.com>

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


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