Re: [Xen-devel] [PATCH]libxl: rewrite libxl_cpumap_alloc()

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2012-05-18 at 03:53 +0100, Zhang, Yang Z wrote:
> Allow libxl_cpumap_alloc to allocate memory of specific size. 
> Max_cpus equals to zero means allocate the biggest possibly required map.

Can we get a comment to that effect in the header please.

> -    int max_cpus;
>      int sz;
> 
> -    max_cpus = libxl_get_max_cpus(ctx);
> -    if (max_cpus == 0)
> -        return ERROR_FAIL;
> +    if (max_cpus < 0) {
> +        return ERROR_INVAL;
> +    } else if (max_cpus == 0) {
> +        max_cpus = libxl_get_max_cpus(ctx);
> +        if (max_cpus == 0)
> +            return ERROR_FAIL;
> +    }

I would have written this as

+    if (max_cpus < 0)
+        return ERROR_INVAL;
+    if (max_cpus == 0)
+        max_cpus = libxl_get_max_cpus(ctx);
+    if (max_cpus == 0)
+        return ERROR_FAIL;

and avoided the nested if and ifelse logic.

> 
>      sz = (max_cpus + 7) / 8;
> -    cpumap->map = calloc(sz, sizeof(*cpumap->map));
> -    if (!cpumap->map)
> -        return ERROR_NOMEM;
> +    cpumap->map = libxl__zalloc(NULL, sz * sizeof(*cpumap->map));

You might as well use libxl__calloc here.

Should I be expecting a v3 of "libxl: allow to set more than 31 vcpus"
which uses this patch? If you already sent it then I may have missed it.

Cheers,
Ian.



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