On Fri, 12 Apr 2013 17:11:08 +0900 Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx> wrote:
> > --- a/include/linux/res_counter.h
> > +++ b/include/linux/res_counter.h
> > @@ -54,7 +54,7 @@ struct res_counter {
> > struct res_counter *parent;
> > };
> >
> > -#define RESOURCE_MAX (unsigned long long)LLONG_MAX
> > +#define RESOURCE_MAX (unsigned long long)ULLONG_MAX
> >
>
> I don't think it's a good idea to change a user-visible value.
The old value was a mistake, surely.
RESOURCE_MAX shouldn't be in this header file - that is far too general
a name. I suggest the definition be moved to res_counter.c. And the
(unsigned long long) cast is surely unneeded if we're to use
ULLONG_MAX.
> > /**
> > * Helpers to interact with userspace
> > diff --git a/kernel/res_counter.c b/kernel/res_counter.c
> > index ff55247..6c35310 100644
> > --- a/kernel/res_counter.c
> > +++ b/kernel/res_counter.c
> > @@ -195,6 +195,12 @@ int res_counter_memparse_write_strategy(const char *buf,
> > if (*end != '\0')
> > return -EINVAL;
> >
> > - *res = PAGE_ALIGN(*res);
> > + /* Since PAGE_ALIGN is aligning up(the next page boundary),
> > + * check the left space to avoid overflow to 0. */
> > + if (RESOURCE_MAX - *res < PAGE_SIZE - 1)
> > + *res = RESOURCE_MAX;
> > + else
> > + *res = PAGE_ALIGN(*res);
> > +
>
> Current interface seems strange because we can set a bigger value than
> the value which means "unlimited".
I'm not sure what you mean by this?
> So, how about some thing like:
>
> if (*res > RESOURCE_MAX)
> return -EINVAL;
> if (*res > PAGE_ALIGN(RESOURCE_MAX) - PAGE_SIZE)
> *res = RESOURCE_MAX;
> else
> *res = PAGE_ALIGN(*res);
>
The first thing I'd do to res_counter_memparse_write_strategy() is to
rename its second arg to `resp' then add a local called `res'. Because
that function dereferences res far too often.
Then,
- *res = PAGE_ALIGN(*res);
if (PAGE_ALIGN(res) >= res)
res = PAGE_ALIGN(res);
else
res = RESOURCE_MAX; /* PAGE_ALIGN wrapped to zero */
*resp = res;
return 0;
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