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

[Kamezawa Hiroyuki]

(2012/06/20 8:58), Andrew Morton wrote:
> On Mon, 18 Jun 2012 20:59:44 +0900
> Kamezawa Hiroyuki<kamezawa.hiroyu@xxxxxxxxxxxxxx>  wrote:
>
> > By commit "memcg: move charges to root cgroup if use_hierarchy=0"
> > mem_cgroup_move_parent() only returns -EBUSY, -EINVAL.
> > So, we can remove -ENOMEM and -EINTR checks.
> >
> > Signed-off-by: KAMEZAWA Hiroyuki<kamezawa.hiroyu@xxxxxxxxxxxxxx>
> > ---
> >   mm/memcontrol.c |    5 -----
> >   1 files changed, 0 insertions(+), 5 deletions(-)
> >
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index cf8a0f6..726b7c6 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -3847,8 +3847,6 @@ static int mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
> >   		pc = lookup_page_cgroup(page);
> >
> >   		ret = mem_cgroup_move_parent(page, pc, memcg, GFP_KERNEL);
> > -		if (ret == -ENOMEM || ret == -EINTR)
> > -			break;
> >
> >   		if (ret == -EBUSY || ret == -EINVAL) {
>
> This looks a bit fragile - if mem_cgroup_move_parent() is later changed
> (intentionally or otherwise!) to return -Esomethingelse then
> mem_cgroup_force_empty_list() will subtly break.  Why not just do
>
> 		if (ret<  0)

You're right. I'm sorry I haven't done enough clean-ups.
I made 2 more patches...I'll repost/remake all paches if it's better.
one more patch will follow this email.
==
From eee5f31fc6378da19705de7187bb3f219ef6d7f6 Mon Sep 17 00:00:00 2001
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Date: Thu, 21 Jun 2012 17:25:04 +0900
Subject: [PATCH 1/2] mem_cgroup_move_parent() doesn't need gfp_mask.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
---
 mm/memcontrol.c |    5 ++---
 1 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 76d83a5..90a2ad4 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2662,8 +2662,7 @@ out:
 
 static int mem_cgroup_move_parent(struct page *page,
 				  struct page_cgroup *pc,
-				  struct mem_cgroup *child,
-				  gfp_t gfp_mask)
+				  struct mem_cgroup *child)
 {
 	struct mem_cgroup *parent;
 	unsigned int nr_pages;
@@ -3837,7 +3836,7 @@ static int mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
 
 		pc = lookup_page_cgroup(page);
 
-		ret = mem_cgroup_move_parent(page, pc, memcg, GFP_KERNEL);
+		ret = mem_cgroup_move_parent(page, pc, memcg);
 
 		if (ret == -EBUSY || ret == -EINVAL) {
 			/* found lock contention or "pc" is obsolete. */
--
1.7.4.1











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