Re: [PATCH] mm/mincore: allow for making sys_mincore() privileged

[Tejun Heo]

Hello, Linus.

On Sat, Jan 05, 2019 at 01:54:03PM -0800, Linus Torvalds wrote:
> And the first hit is 'fincore', which probably nobody cares about
> anyway, but it does
> 
>     fd = open (name, O_RDONLY)
>     ..
>     mmap(window, len, PROT_NONE, MAP_PRIVATE, ..

So, folks here have been using fincore(1) for diagnostic purposes and
are also looking to expand on it to investigate per-cgroup cache
usages (mmap -> mincore -> /proc/self/pagemap -> /proc/kpagecgroup ->
cgroup path).

These are all root-only usages to find out what's going on with the
whole page cache.  We aren't attached to doing things this particular
way but it'd suck if there's no way.

Thanks.

-- 
tejun