On Thu, Aug 15, 2024 at 10:26 PM David Hildenbrand <david@xxxxxxxxxx> wrote:
>
> >>> +static inline int get_order_from_str(const char *size_str)
> >>> +{
> >>> + unsigned long size;
> >>> + char *endptr;
> >>> + int order;
> >>> +
> >>> + size = memparse(size_str, &endptr);
> >>
> >> Do we have to also test if is_power_of_2(), and refuse if not? For
> >> example, what if someone would pass 3K, would the existing check catch it?
> >
> > no, the existing check can't catch it.
> >
> > I passed thp_anon=15K-64K:always, then I got 16K enabled:
> >
> > / # cat /sys/kernel/mm/transparent_hugepage/hugepages-16kB/enabled
> > [always] inherit madvise never
> >
>
> Okay, so we should document then that start/end of the range must be
> valid THP sizes.
Ack
>
> > I can actually check that by:
> >
> > static inline int get_order_from_str(const char *size_str)
> > {
> > unsigned long size;
> > char *endptr;
> > int order;
> >
> > size = memparse(size_str, &endptr);
> >
> > if (!is_power_of_2(size >> PAGE_SHIFT))
>
> No need for the shift.
>
> if (!is_power_of_2(size))
>
> Is likely even more correct if someone would manage to pass something
> stupid like
>
> 16385 (16K + 1)
Ack
>
> > goto err;
> > order = get_order(size);
> > if ((1 << order) & ~THP_ORDERS_ALL_ANON)
> > goto err;
> >
> > return order;
> > err:
> > pr_err("invalid size %s in thp_anon boot parameter\n", size_str);
> > return -EINVAL;
> > }
> >
> >>
> >>> + order = fls(size >> PAGE_SHIFT) - 1;
> >>
> >> Is this a fancy way of writing
> >>
> >> order = log2(size >> PAGE_SHIFT);
> >>
> >> ? :)
> >
> > I think ilog2 is implemented by fls ?
>
> Yes, so we should have used that instead. But get_order()
> is even better.
>
> >
> >>
> >> Anyhow, if get_order() wraps that, all good.
> >
> > I guess it doesn't check power of 2?
> >
> >>
> >>> + if ((1 << order) & ~THP_ORDERS_ALL_ANON) {
> >>> + pr_err("invalid size %s(order %d) in thp_anon boot parameter\n",
> >>> + size_str, order);
> >>> + return -EINVAL;
> >>> + }
> >>> +
> >>> + return order;
> >>> +}
> >>
> >> Apart from that, nothing jumped at me.
> >
> > Please take a look at the new get_order_from_str() before I
> > send v5 :-)
>
> Besides the shift for is_power_of_2(), LGTM, thanks!
Thanks, David!
Hi Andrew,
Apologies for sending another squash request. If you'd
prefer me to send a new v5 that includes all the changes,
please let me know.
Don't shift the size, as it can still detect invalid sizes
like 16K+1. Also, document that the size must be a valid THP
size.
diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
index 15404f06eefd..4468851b6ecb 100644
--- a/Documentation/admin-guide/mm/transhuge.rst
+++ b/Documentation/admin-guide/mm/transhuge.rst
@@ -294,8 +294,9 @@ kernel command line.
Alternatively, each supported anonymous THP size can be controlled by
passing ``thp_anon=<size>,<size>[KMG]:<state>;<size>-<size>[KMG]:<state>``,
-where ``<size>`` is the THP size and ``<state>`` is one of ``always``,
-``madvise``, ``never`` or ``inherit``.
+where ``<size>`` is the THP size (must be a power of 2 of PAGE_SIZE and
+supported anonymous THP) and ``<state>`` is one of ``always``, ``madvise``,
+``never`` or ``inherit``.
For example, the following will set 16K, 32K, 64K THP to ``always``,
set 128K, 512K to ``inherit``, set 256K to ``madvise`` and 1M, 2M
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index d6dade8ac5f6..903b47f2b2db 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -953,7 +953,7 @@ static inline int get_order_from_str(const char *size_str)
size = memparse(size_str, &endptr);
- if (!is_power_of_2(size >> PAGE_SHIFT))
+ if (!is_power_of_2(size))
goto err;
order = get_order(size);
if ((1 << order) & ~THP_ORDERS_ALL_ANON)
>
> --
> Cheers,
>
> David / dhildenb
>
Thanks
Barry
