> -----Original Message-----
> From: Eric Blake [mailto:[email protected]]
> Sent: Wednesday, October 09, 2013 11:49 AM
> To: Chen Hanxiao
> Cc: [email protected]
> Subject: Re: [libvirt] [PATCH 1/2]cgroup: introduce kernel version check
> function
> for cgroup
>
> On 10/08/2013 02:38 AM, Chen Hanxiao wrote:
> > From: Chen Hanxiao <[email protected]>
> >
> > Some cgroup value range may change
>
> s/range/ranges/
>
> > in the further kernel.
>
> s/the further kernel/future kernels/
>
> > Introduce kernel version check function for cgroup.
> > This will be helpful to determine the proper values.
>
> I'm half-inclined to NACK. Version checks are lousy, as features may be
> backported to a distro-style kernel that reports an older version
> number. Is there any way you can probe for an actual feature, rather
> than relying on brittle version number checks?
>
Maybe we could leave this job to kernel.
> > +
> > +static bool virCgroupVersionCheck(const char * dstVersion)
>
> Style: no space after '*' in pointer type declarations.
>
> > +{
> > + unsigned long currentVersion;
> > + unsigned long version;
> > +
> > + if (virCgroupGetKernelVersion(¤tVersion) < 0) {
> > + return -1;
> > + }
> > +
> > + if (virParseVersionString(dstVersion, &version, true) < 0) {
> > + return -1;
> > + }
> > +
> > + return (((long long)currentVersion - (long long)version) >= 0) ? true :
> false;
>
> The casts are pointless. Either we're on a 64-bit platform where it
> adds no precision, or we're on a 32-bit platform where the extra
> precision slows us down; but either way the version number already fits
> within a long.
>
> Style: 'bool_expr ? true: false' is wasteful; just write 'bool_expr'.
>
> Thus, this would be:
>
> return currentVersion >= version;
Thanks for your explanation.
>
> if we still determine we need this function.
>
> --
> Eric Blake eblake redhat com +1-919-301-3266
> Libvirt virtualization library http://libvirt.org
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