[PATCH v2][memcg+dirtylimit] Fix overwriting global vm dirty limit setting by memcg (Re: [PATCH v3 00/11] memcg: per cgroup dirty page accounting

[Minchan Kim]

On Wed, Oct 20, 2010 at 02:02:55PM +0900, KAMEZAWA Hiroyuki wrote:
> Fixed one here.
> ==
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu at jp.fujitsu.com>
> 
> Now, at calculating dirty limit, vm_dirty_param() is called.
> This function returns dirty-limit related parameters considering
> memory cgroup settings.
> 
> Now, assume that vm_dirty_bytes=100M (global dirty limit) and
> memory cgroup has 1G of pages and 40 dirty_ratio, dirtyable memory is
> 500MB.
> 
> In this case, global_dirty_limits will consider dirty_limt as
> 500 *0.4 = 200MB. This is bad...memory cgroup is not back door.
> 
> This patch limits the return value of vm_dirty_param() considring
> global settings.
> 
> Changelog:
>  - fixed an argument "mem" int to u64
>  - fixed to use global available memory to cap memcg's value.
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu at jp.fujitsu.com>
Reviewed-by: Minchan Kim <minchan.kim at gmail.com>

It should have written this on Documentation.
"memcg dirty limit can't exceed global dirty limit"

-- 
Kind regards,
Minchan Kim