[LTP] [PATCH] proc01: handle EOPNOTSUPP if !hugepages_supported()

[Cyril Hrubis]

Hi!
> This patch adds an entry to known issue list. These 2 proc files
> may return EOPNOTSUPP if CONFIG_HUGETLB_PAGE=Y and hugepages_supported()
> is false:
>   /proc/sys/vm/nr_hugepages: errno=EOPNOTSUPP(95): Operation not supported
>   /proc/sys/vm/nr_overcommit_hugepages: errno=EOPNOTSUPP(95): Operation not supported
> 
> from mm/hugetlb.c:
> --------------------------------- 8< ---------------------------------
> static int hugetlb_sysctl_handler_common(bool obey_mempolicy,
>                          struct ctl_table *table, int write,
>                          void __user *buffer, size_t *length, loff_t *ppos)
> {
>         struct hstate *h = &default_hstate;
>         unsigned long tmp = h->max_huge_pages;
>         int ret;
> 
>         if (!hugepages_supported())
>                 return -EOPNOTSUPP;
> --------------------------------- >8 ---------------------------------
> 
> I've noticed this issue on s390 only after this commit:
>   commit 7f9be77555bb2e52de84e9dddf7b4eb20cc6e171
>   Author: Dominik Dingel <dingel@linux.vnet.ibm.com>
>   Date:   Fri Jul 17 16:23:39 2015 -0700
>     s390/hugetlb: add hugepages_supported define
> 
> Also note, that kernel versions prior to 4.4 may fail with
> ENOTSUPP, which has been changed to EOPNOTSUPP by:
>   commit 86613628b3d367743f71b945c203774c522404f4
>   Author: Jan Stancek <jstancek@redhat.com>
>   Date:   Wed Mar 9 14:08:35 2016 -0800
>     mm/hugetlb: use EOPNOTSUPP in hugetlb sysctl handlers
> 
> Given that nobody complained running into this issue before,
> it's assumed that this is not common and therefore this patch
> adds only EOPNOTSUPP to list.

I've stumbled upon this failure as well, I was about to prod you to
submit exactly this patch. Acked, and thanks :).

-- 
Cyril Hrubis
chrubis@suse.cz