Re: [PATCH 2/2] memcg: clean up force_empty_list() return value check

[Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>]

On Thu, 21 Jun 2012 17:17:01 +0900
Kamezawa Hiroyuki <kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org> wrote:

> Now, mem_cgroup_force_empty_list() just returns 0 or -EBUSY and
> -EBUSY is just indicating 'you need to retry.'.
> This patch makes mem_cgroup_force_empty_list() as boolean function and
> make the logic simpler.
> 

For some reason I'm having trouble applying these patches - many
rejects, need to massage it in by hand.

> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3797,7 +3797,7 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
>    * This routine traverse page_cgroup in given list and drop them all.
>    * *And* this routine doesn't reclaim page itself, just removes page_cgroup.
>    */
> -static int mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
> +static bool mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
>   				int node, int zid, enum lru_list lru)

Let's document the return value.  The mem_cgroup_force_empty_list()
comment is a mess so I tried to help it a bit.  How does this look?

--- a/mm/memcontrol.c~memcg-make-mem_cgroup_force_empty_list-return-bool-fix
+++ a/mm/memcontrol.c
@@ -3609,8 +3609,10 @@ unsigned long mem_cgroup_soft_limit_recl
 }
 
 /*
- * This routine traverse page_cgroup in given list and drop them all.
- * *And* this routine doesn't reclaim page itself, just removes page_cgroup.
+ * Traverse a specified page_cgroup list and try to drop them all.  This doesn't
+ * reclaim the pages page themselves - it just removes the page_cgroups.
+ * Returns true if some page_cgroups were not freed, indicating that the caller
+ * must retry this operation.
  */
 static bool mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
 				int node, int zid, enum lru_list lru)
_