On Tue, Jul 10, 2012 at 08:21:04AM +0200, Michal Hocko wrote:

On Tue 10-07-12 14:10:21, Wanpeng Li wrote:

quoted

On Mon, Jul 09, 2012 at 05:20:58PM +0200, Michal Hocko wrote:

quoted

On Thu 05-07-12 02:45:00, Johannes Weiner wrote:

quoted

It does not matter to __mem_cgroup_try_charge() if the passed mm is
NULL or init_mm, it will charge the root memcg in either case.

You can also change the comment in __mem_cgroup_try_charge :

"if so charge the init_mm" => "if so charge the root memcg"

This is already in place:
"
If mm is NULL and the caller doesn't pass a valid memcg pointer, that is
treated as a charge to root_mem_cgroup.
"

IIUC, if still keep comment "if so charge the init_mm" is not correct,
since pages in pagecache aren't mapped into any processes' ptes, 
so mm is NULL, and these pages which in pagecache are not belong 
to init_mm, the comment should be changed. :-)

quoted

quoted

quoted

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

Acked-by: Michal Hocko <redacted>

quoted

---
 mm/memcontrol.c |    5 -----
 1 files changed, 0 insertions(+), 5 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 418b47d..6fe4101 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c

@@ -2766,8 +2766,6 @@ int mem_cgroup_try_charge_swapin(struct mm_struct *mm,
 		ret = 0;
 	return ret;
 charge_cur_mm:
-	if (unlikely(!mm))
-		mm = &init_mm;
 	ret = __mem_cgroup_try_charge(mm, mask, 1, memcgp, true);
 	if (ret == -EINTR)
 		ret = 0;

@@ -2832,9 +2830,6 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
 	if (PageCompound(page))
 		return 0;
 
-	if (unlikely(!mm))
-		mm = &init_mm;
-
 	if (!PageSwapCache(page))
 		ret = mem_cgroup_charge_common(page, mm, gfp_mask, type);
 	else { /* page is swapcache/shmem */

-- 
1.7.7.6

-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic

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