Re: [PATCH] mm/hugetlb: use EOPNOTSUPP in hugetlb sysctl handlers

[Andrew Morton]

On Sat, 5 Mar 2016 03:09:50 -0500 (EST) Jan Stancek <jstancek@xxxxxxxxxx> wrote:

> > > Replace ENOTSUPP with EOPNOTSUPP. If hugepages are not supported,
> > > this value is propagated to userspace. EOPNOTSUPP is part of uapi
> > > and is widely supported by libc libraries.
> > 
> > hm, what is the actual user-visible effect of this change?  Does it fix
> > some misbehaviour?
> > 
> 
> It gives nicer message to user, rather than:
> # cat /proc/sys/vm/nr_hugepages
> cat: /proc/sys/vm/nr_hugepages: Unknown error 524
> 
> And also LTP's proc01 test was failing because this ret code (524)
> was unexpected:
> proc01      1  TFAIL  :  proc01.c:396: read failed: /proc/sys/vm/nr_hugepages: errno=???(524): Unknown error 524
> proc01      2  TFAIL  :  proc01.c:396: read failed: /proc/sys/vm/nr_hugepages_mempolicy: errno=???(524): Unknown error 524
> proc01      3  TFAIL  :  proc01.c:396: read failed: /proc/sys/vm/nr_overcommit_hugepages: errno=???(524): Unknown error 524
> 

Ah, OK, thanks.  "Unknown error 524" is rather rude.  I'll queue this
for 4.5.