lkml.org 
[lkml]   [2015]   [Oct]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] memcg: Fix thresholds for 32b architectures.
On Tue, Oct 27, 2015 at 11:37:14AM +0100, mhocko@kernel.org wrote:
> From: Michal Hocko <mhocko@suse.com>
>
> 424cdc141380 ("memcg: convert threshold to bytes") has fixed a
> regression introduced by 3e32cb2e0a12 ("mm: memcontrol: lockless page
> counters") where thresholds were silently converted to use page units
> rather than bytes when interpreting the user input.
>
> The fix is not complete, though, as properly pointed out by Ben
> Hutchings during stable backport review. The page count is converted
> to bytes but unsigned long is used to hold the value which would
> be obviously not sufficient for 32b systems with more than 4G
> thresholds. The same applies to usage as taken from mem_cgroup_usage
> which might overflow.
>
> Let's remove this bytes vs. pages internal tracking differences and
> handle thresholds in page units internally. Chage mem_cgroup_usage()
> to return the value in page units and revert 424cdc141380 because this
> should be sufficient for the consistent handling.
> mem_cgroup_read_u64 as the only users of mem_cgroup_usage outside of
> the threshold handling code is converted to give the proper in bytes
> result. It is doing that already for page_counter output so this is
> more consistent as well.
>
> The value presented to the userspace is still in bytes units.
>
> Fixes: 424cdc141380 ("memcg: convert threshold to bytes")
> Fixes: 3e32cb2e0a12 ("mm: memcontrol: lockless page counters")
> CC: stable@vger.kernel.org
> Reported-by: Ben Hutchings <ben@decadent.org.uk>
> Signed-off-by: Michal Hocko <mhocko@suse.com>

Acked-by: Johannes Weiner <hannes@cmpxchg.org>

> +++ b/mm/memcontrol.c
> @@ -2802,7 +2802,7 @@ static unsigned long tree_stat(struct mem_cgroup *memcg,
> return val;
> }
>
> -static inline u64 mem_cgroup_usage(struct mem_cgroup *memcg, bool swap)
> +static inline unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap)
> {
> u64 val;

Minor nit, but this should probably be unsigned long now.


\
 
 \ /
  Last update: 2015-10-27 17:41    [W:0.057 / U:0.892 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site