Re: [PATCH] hugetlb_cgroup: convert comma to semicolon

[Matthew Wilcox]

On Wed, Aug 19, 2020 at 10:14:11AM +0200, Giuseppe Scrivano wrote:
> >> -  cft->file_offset = offsetof(struct hugetlb_cgroup, events_file[idx]),
> >> +  cft->file_offset = offsetof(struct hugetlb_cgroup, events_file[idx]);
> >>    cft->flags = CFTYPE_NOT_ON_ROOT;
> 
> I think in this case having two expressions as part of the same
> statement is equivalent to having two separate statements.  Both
> cft->file_offset and cft->flags get the expected value.

That's not how the comma operator works.

It will evaluate offsetof(struct hugetlb_cgroup, events_file[idx]) and
then discard the result.  Since it has no side-effects, this is effectively
doing:

        cft->file_offset = cft->flags = CFTYPE_NOT_ON_ROOT;