Re: [patch v2 4/6] memcg: simplify mem_cgroup_iter
On Tue, Dec 11, 2012 at 8:01 AM, Michal Hocko wrote:
> On Mon 10-12-12 20:35:20, Ying Han wrote:
>> On Mon, Nov 26, 2012 at 10:47 AM, Michal Hocko wrote:
>> > Current implementation of mem_cgroup_iter has to consider both css and
>> > memcg to find out whether no group has been found (css==NULL - aka the
>> > loop is completed) and that no memcg is associated with the found node
>> > (!memcg - aka css_tryget failed because the group is no longer alive).
>> > This leads to awkward tweaks like tests for css && !memcg to skip the
>> > current node.
>> >
>> > It will be much easier if we got rid off css variable altogether and
>> > only rely on memcg. In order to do that the iteration part has to skip
>> > dead nodes. This sounds natural to me and as a nice side effect we will
>> > get a simple invariant that memcg is always alive when non-NULL and all
>> > nodes have been visited otherwise.
>> >
>> > We could get rid of the surrounding while loop but keep it in for now to
>> > make review easier. It will go away in the following patch.
>> >
>> > Signed-off-by: Michal Hocko
>> > ---
>> > mm/memcontrol.c | 56
>> > +++
>> > 1 file changed, 27 insertions(+), 29 deletions(-)
>> >
>> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> > index 6bcc97b..d1bc0e8 100644
>> > --- a/mm/memcontrol.c
>> > +++ b/mm/memcontrol.c
>> > @@ -1086,7 +1086,6 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup
>> > *root,
>> > rcu_read_lock();
>> > while (!memcg) {
>> > struct mem_cgroup_reclaim_iter *uninitialized_var(iter);
>> > - struct cgroup_subsys_state *css = NULL;
>> >
>> > if (reclaim) {
>> > int nid = zone_to_nid(reclaim->zone);
>> > @@ -1112,53 +,52 @@ struct mem_cgroup *mem_cgroup_iter(struct
>> > mem_cgroup *root,
>> > * explicit visit.
>> > */
>> > if (!last_visited) {
>
> here
>
>> > - css = &root->css;
>> > + memcg = root;
>> > } else {
>> > struct cgroup *prev_cgroup, *next_cgroup;
>> >
>> > prev_cgroup = (last_visited == root) ? NULL
>> > : last_visited->css.cgroup;
>> > - next_cgroup =
>> > cgroup_next_descendant_pre(prev_cgroup,
>> > - root->css.cgroup);
>> > - if (next_cgroup)
>> > - css = cgroup_subsys_state(next_cgroup,
>> > - mem_cgroup_subsys_id);
>> > - }
>> > +skip_node:
>> > + next_cgroup = cgroup_next_descendant_pre(
>> > + prev_cgroup, root->css.cgroup);
>> >
>> > - /*
>> > -* Even if we found a group we have to make sure it is
>> > alive.
>> > -* css && !memcg means that the groups should be skipped
>> > and
>> > -* we should continue the tree walk.
>> > -* last_visited css is safe to use because it is protected
>> > by
>> > -* css_get and the tree walk is rcu safe.
>> > -*/
>> > - if (css == &root->css || (css && css_tryget(css)))
>> > - memcg = mem_cgroup_from_css(css);
>> > + /*
>> > +* Even if we found a group we have to make sure
>> > it is
>> > +* alive. css && !memcg means that the groups
>> > should be
>> > +* skipped and we should continue the tree walk.
>> > +* last_visited css is safe to use because it is
>> > +* protected by css_get and the tree walk is rcu
>> > safe.
>> > +*/
>> > + if (next_cgroup) {
>> > + struct mem_cgroup *mem =
>> > mem_cgroup_from_cont(
>> > + next_cgroup);
>> > + if (css_tryget(&mem->css))
>> > + memcg = mem;
>>
>> I see a functional change after this, where we now hold a refcnt of
>> css if memcg is root. It is not the case before this change.
>
> I know it is a bit obscure but this is not the case.
> cgroup_next_descendant_pre never visits its root. That's why we have
> that if (!last_visited) test above. We have to handle it separately.
>
> Makes sense?
Ah, OK. The code is more readable after this patch then
--Ying
>
>>
>> --Ying
> [...]
> --
> Michal Hocko
> SUSE Labs
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Please
Re: [patch v2 4/6] memcg: simplify mem_cgroup_iter
On Mon 10-12-12 20:35:20, Ying Han wrote:
> On Mon, Nov 26, 2012 at 10:47 AM, Michal Hocko wrote:
> > Current implementation of mem_cgroup_iter has to consider both css and
> > memcg to find out whether no group has been found (css==NULL - aka the
> > loop is completed) and that no memcg is associated with the found node
> > (!memcg - aka css_tryget failed because the group is no longer alive).
> > This leads to awkward tweaks like tests for css && !memcg to skip the
> > current node.
> >
> > It will be much easier if we got rid off css variable altogether and
> > only rely on memcg. In order to do that the iteration part has to skip
> > dead nodes. This sounds natural to me and as a nice side effect we will
> > get a simple invariant that memcg is always alive when non-NULL and all
> > nodes have been visited otherwise.
> >
> > We could get rid of the surrounding while loop but keep it in for now to
> > make review easier. It will go away in the following patch.
> >
> > Signed-off-by: Michal Hocko
> > ---
> > mm/memcontrol.c | 56
> > +++
> > 1 file changed, 27 insertions(+), 29 deletions(-)
> >
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index 6bcc97b..d1bc0e8 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -1086,7 +1086,6 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup
> > *root,
> > rcu_read_lock();
> > while (!memcg) {
> > struct mem_cgroup_reclaim_iter *uninitialized_var(iter);
> > - struct cgroup_subsys_state *css = NULL;
> >
> > if (reclaim) {
> > int nid = zone_to_nid(reclaim->zone);
> > @@ -1112,53 +,52 @@ struct mem_cgroup *mem_cgroup_iter(struct
> > mem_cgroup *root,
> > * explicit visit.
> > */
> > if (!last_visited) {
here
> > - css = &root->css;
> > + memcg = root;
> > } else {
> > struct cgroup *prev_cgroup, *next_cgroup;
> >
> > prev_cgroup = (last_visited == root) ? NULL
> > : last_visited->css.cgroup;
> > - next_cgroup =
> > cgroup_next_descendant_pre(prev_cgroup,
> > - root->css.cgroup);
> > - if (next_cgroup)
> > - css = cgroup_subsys_state(next_cgroup,
> > - mem_cgroup_subsys_id);
> > - }
> > +skip_node:
> > + next_cgroup = cgroup_next_descendant_pre(
> > + prev_cgroup, root->css.cgroup);
> >
> > - /*
> > -* Even if we found a group we have to make sure it is
> > alive.
> > -* css && !memcg means that the groups should be skipped and
> > -* we should continue the tree walk.
> > -* last_visited css is safe to use because it is protected
> > by
> > -* css_get and the tree walk is rcu safe.
> > -*/
> > - if (css == &root->css || (css && css_tryget(css)))
> > - memcg = mem_cgroup_from_css(css);
> > + /*
> > +* Even if we found a group we have to make sure it
> > is
> > +* alive. css && !memcg means that the groups
> > should be
> > +* skipped and we should continue the tree walk.
> > +* last_visited css is safe to use because it is
> > +* protected by css_get and the tree walk is rcu
> > safe.
> > +*/
> > + if (next_cgroup) {
> > + struct mem_cgroup *mem =
> > mem_cgroup_from_cont(
> > + next_cgroup);
> > + if (css_tryget(&mem->css))
> > + memcg = mem;
>
> I see a functional change after this, where we now hold a refcnt of
> css if memcg is root. It is not the case before this change.
I know it is a bit obscure but this is not the case.
cgroup_next_descendant_pre never visits its root. That's why we have
that if (!last_visited) test above. We have to handle it separately.
Makes sense?
>
> --Ying
[...]
--
Michal Hocko
SUSE Labs
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Re: [patch v2 4/6] memcg: simplify mem_cgroup_iter
On Sun 09-12-12 09:01:48, Ying Han wrote:
> On Mon, Nov 26, 2012 at 10:47 AM, Michal Hocko wrote:
> > Current implementation of mem_cgroup_iter has to consider both css and
> > memcg to find out whether no group has been found (css==NULL - aka the
> > loop is completed) and that no memcg is associated with the found node
> > (!memcg - aka css_tryget failed because the group is no longer alive).
> > This leads to awkward tweaks like tests for css && !memcg to skip the
> > current node.
> >
> > It will be much easier if we got rid off css variable altogether and
> > only rely on memcg. In order to do that the iteration part has to skip
> > dead nodes. This sounds natural to me and as a nice side effect we will
> > get a simple invariant that memcg is always alive when non-NULL and all
> > nodes have been visited otherwise.
> >
> > We could get rid of the surrounding while loop but keep it in for now to
> > make review easier. It will go away in the following patch.
> >
> > Signed-off-by: Michal Hocko
> > ---
> > mm/memcontrol.c | 56
> > +++
> > 1 file changed, 27 insertions(+), 29 deletions(-)
> >
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index 6bcc97b..d1bc0e8 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -1086,7 +1086,6 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup
> > *root,
> > rcu_read_lock();
here
> > while (!memcg) {
> > struct mem_cgroup_reclaim_iter *uninitialized_var(iter);
> > - struct cgroup_subsys_state *css = NULL;
> >
> > if (reclaim) {
> > int nid = zone_to_nid(reclaim->zone);
[...]
> > +skip_node:
> > + next_cgroup = cgroup_next_descendant_pre(
> > + prev_cgroup, root->css.cgroup);
> >
> > - /*
> > -* Even if we found a group we have to make sure it is
> > alive.
> > -* css && !memcg means that the groups should be skipped and
> > -* we should continue the tree walk.
> > -* last_visited css is safe to use because it is protected
> > by
> > -* css_get and the tree walk is rcu safe.
> > -*/
> > - if (css == &root->css || (css && css_tryget(css)))
> > - memcg = mem_cgroup_from_css(css);
> > + /*
> > +* Even if we found a group we have to make sure it
> > is
> > +* alive. css && !memcg means that the groups
> > should be
> > +* skipped and we should continue the tree walk.
> > +* last_visited css is safe to use because it is
> > +* protected by css_get and the tree walk is rcu
> > safe.
> > +*/
> > + if (next_cgroup) {
> > + struct mem_cgroup *mem =
> > mem_cgroup_from_cont(
> > + next_cgroup);
> > + if (css_tryget(&mem->css))
> > + memcg = mem;
> > + else {
> > + prev_cgroup = next_cgroup;
>
> I might be missing something here, but the comment says the
> last_visited is safe to use but not the next_cgroup. What is
> preventing it to be
> removed ?
rcu_read_lock. cgroup cannot disappear inside rcu.
>
> --Ying
[...]
--
Michal Hocko
SUSE Labs
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Re: [patch v2 4/6] memcg: simplify mem_cgroup_iter
On Mon, Nov 26, 2012 at 10:47 AM, Michal Hocko wrote:
> Current implementation of mem_cgroup_iter has to consider both css and
> memcg to find out whether no group has been found (css==NULL - aka the
> loop is completed) and that no memcg is associated with the found node
> (!memcg - aka css_tryget failed because the group is no longer alive).
> This leads to awkward tweaks like tests for css && !memcg to skip the
> current node.
>
> It will be much easier if we got rid off css variable altogether and
> only rely on memcg. In order to do that the iteration part has to skip
> dead nodes. This sounds natural to me and as a nice side effect we will
> get a simple invariant that memcg is always alive when non-NULL and all
> nodes have been visited otherwise.
>
> We could get rid of the surrounding while loop but keep it in for now to
> make review easier. It will go away in the following patch.
>
> Signed-off-by: Michal Hocko
> ---
> mm/memcontrol.c | 56
> +++
> 1 file changed, 27 insertions(+), 29 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 6bcc97b..d1bc0e8 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1086,7 +1086,6 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup
> *root,
> rcu_read_lock();
> while (!memcg) {
> struct mem_cgroup_reclaim_iter *uninitialized_var(iter);
> - struct cgroup_subsys_state *css = NULL;
>
> if (reclaim) {
> int nid = zone_to_nid(reclaim->zone);
> @@ -1112,53 +,52 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup
> *root,
> * explicit visit.
> */
> if (!last_visited) {
> - css = &root->css;
> + memcg = root;
> } else {
> struct cgroup *prev_cgroup, *next_cgroup;
>
> prev_cgroup = (last_visited == root) ? NULL
> : last_visited->css.cgroup;
> - next_cgroup = cgroup_next_descendant_pre(prev_cgroup,
> - root->css.cgroup);
> - if (next_cgroup)
> - css = cgroup_subsys_state(next_cgroup,
> - mem_cgroup_subsys_id);
> - }
> +skip_node:
> + next_cgroup = cgroup_next_descendant_pre(
> + prev_cgroup, root->css.cgroup);
>
> - /*
> -* Even if we found a group we have to make sure it is alive.
> -* css && !memcg means that the groups should be skipped and
> -* we should continue the tree walk.
> -* last_visited css is safe to use because it is protected by
> -* css_get and the tree walk is rcu safe.
> -*/
> - if (css == &root->css || (css && css_tryget(css)))
> - memcg = mem_cgroup_from_css(css);
> + /*
> +* Even if we found a group we have to make sure it is
> +* alive. css && !memcg means that the groups should
> be
> +* skipped and we should continue the tree walk.
> +* last_visited css is safe to use because it is
> +* protected by css_get and the tree walk is rcu safe.
> +*/
> + if (next_cgroup) {
> + struct mem_cgroup *mem = mem_cgroup_from_cont(
> + next_cgroup);
> + if (css_tryget(&mem->css))
> + memcg = mem;
I see a functional change after this, where we now hold a refcnt of
css if memcg is root. It is not the case before this change.
--Ying
> + else {
> + prev_cgroup = next_cgroup;
> + goto skip_node;
> + }
> + }
> + }
>
> if (reclaim) {
> - struct mem_cgroup *curr = memcg;
> -
> if (last_visited)
> css_put(&last_visited->css);
>
> - if (css && !memcg)
> - curr = mem_cgroup_from_css(css);
> -
> /* make sure that the cached memcg is not removed */
> - if (curr)
> - css_get(&curr->css);
> - iter->last_visited = curr;
> + if (memcg)
> + css_get(&memcg->css);
> + iter->last_visited = memcg;
>
> - if (!
Re: [patch v2 4/6] memcg: simplify mem_cgroup_iter
On Mon, Nov 26, 2012 at 10:47 AM, Michal Hocko wrote:
> Current implementation of mem_cgroup_iter has to consider both css and
> memcg to find out whether no group has been found (css==NULL - aka the
> loop is completed) and that no memcg is associated with the found node
> (!memcg - aka css_tryget failed because the group is no longer alive).
> This leads to awkward tweaks like tests for css && !memcg to skip the
> current node.
>
> It will be much easier if we got rid off css variable altogether and
> only rely on memcg. In order to do that the iteration part has to skip
> dead nodes. This sounds natural to me and as a nice side effect we will
> get a simple invariant that memcg is always alive when non-NULL and all
> nodes have been visited otherwise.
>
> We could get rid of the surrounding while loop but keep it in for now to
> make review easier. It will go away in the following patch.
>
> Signed-off-by: Michal Hocko
> ---
> mm/memcontrol.c | 56
> +++
> 1 file changed, 27 insertions(+), 29 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 6bcc97b..d1bc0e8 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1086,7 +1086,6 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup
> *root,
> rcu_read_lock();
> while (!memcg) {
> struct mem_cgroup_reclaim_iter *uninitialized_var(iter);
> - struct cgroup_subsys_state *css = NULL;
>
> if (reclaim) {
> int nid = zone_to_nid(reclaim->zone);
> @@ -1112,53 +,52 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup
> *root,
> * explicit visit.
> */
> if (!last_visited) {
> - css = &root->css;
> + memcg = root;
> } else {
> struct cgroup *prev_cgroup, *next_cgroup;
>
> prev_cgroup = (last_visited == root) ? NULL
> : last_visited->css.cgroup;
> - next_cgroup = cgroup_next_descendant_pre(prev_cgroup,
> - root->css.cgroup);
> - if (next_cgroup)
> - css = cgroup_subsys_state(next_cgroup,
> - mem_cgroup_subsys_id);
> - }
> +skip_node:
> + next_cgroup = cgroup_next_descendant_pre(
> + prev_cgroup, root->css.cgroup);
>
> - /*
> -* Even if we found a group we have to make sure it is alive.
> -* css && !memcg means that the groups should be skipped and
> -* we should continue the tree walk.
> -* last_visited css is safe to use because it is protected by
> -* css_get and the tree walk is rcu safe.
> -*/
> - if (css == &root->css || (css && css_tryget(css)))
> - memcg = mem_cgroup_from_css(css);
> + /*
> +* Even if we found a group we have to make sure it is
> +* alive. css && !memcg means that the groups should
> be
> +* skipped and we should continue the tree walk.
> +* last_visited css is safe to use because it is
> +* protected by css_get and the tree walk is rcu safe.
> +*/
> + if (next_cgroup) {
> + struct mem_cgroup *mem = mem_cgroup_from_cont(
> + next_cgroup);
> + if (css_tryget(&mem->css))
> + memcg = mem;
> + else {
> + prev_cgroup = next_cgroup;
I might be missing something here, but the comment says the
last_visited is safe to use but not the next_cgroup. What is
preventing it to be
removed ?
--Ying
> + goto skip_node;
> + }
> + }
> + }
>
> if (reclaim) {
> - struct mem_cgroup *curr = memcg;
> -
> if (last_visited)
> css_put(&last_visited->css);
>
> - if (css && !memcg)
> - curr = mem_cgroup_from_css(css);
> -
> /* make sure that the cached memcg is not removed */
> - if (curr)
> - css_get(&curr->css);
> - iter->last_visited = curr;
> + if (memcg)
> + css_get(&memcg->css);
> + iter->last_visited = memcg;
>
> -
Re: [patch v2 4/6] memcg: simplify mem_cgroup_iter
(2012/11/27 3:47), Michal Hocko wrote: > Current implementation of mem_cgroup_iter has to consider both css and > memcg to find out whether no group has been found (css==NULL - aka the > loop is completed) and that no memcg is associated with the found node > (!memcg - aka css_tryget failed because the group is no longer alive). > This leads to awkward tweaks like tests for css && !memcg to skip the > current node. > > It will be much easier if we got rid off css variable altogether and > only rely on memcg. In order to do that the iteration part has to skip > dead nodes. This sounds natural to me and as a nice side effect we will > get a simple invariant that memcg is always alive when non-NULL and all > nodes have been visited otherwise. > > We could get rid of the surrounding while loop but keep it in for now to > make review easier. It will go away in the following patch. > > Signed-off-by: Michal Hocko Acked-by: KAMEZAWA Hiroyuki -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch v2 4/6] memcg: simplify mem_cgroup_iter
(2012/11/27 3:47), Michal Hocko wrote: > Current implementation of mem_cgroup_iter has to consider both css and > memcg to find out whether no group has been found (css==NULL - aka the > loop is completed) and that no memcg is associated with the found node > (!memcg - aka css_tryget failed because the group is no longer alive). > This leads to awkward tweaks like tests for css && !memcg to skip the > current node. > > It will be much easier if we got rid off css variable altogether and > only rely on memcg. In order to do that the iteration part has to skip > dead nodes. This sounds natural to me and as a nice side effect we will > get a simple invariant that memcg is always alive when non-NULL and all > nodes have been visited otherwise. > > We could get rid of the surrounding while loop but keep it in for now to > make review easier. It will go away in the following patch. > > Signed-off-by: Michal Hocko seems nice clean up. I'll ack when I ack 3/6 and we make agreement on that iterator will skip dead node. Thanks, -Kame -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[patch v2 4/6] memcg: simplify mem_cgroup_iter
Current implementation of mem_cgroup_iter has to consider both css and
memcg to find out whether no group has been found (css==NULL - aka the
loop is completed) and that no memcg is associated with the found node
(!memcg - aka css_tryget failed because the group is no longer alive).
This leads to awkward tweaks like tests for css && !memcg to skip the
current node.
It will be much easier if we got rid off css variable altogether and
only rely on memcg. In order to do that the iteration part has to skip
dead nodes. This sounds natural to me and as a nice side effect we will
get a simple invariant that memcg is always alive when non-NULL and all
nodes have been visited otherwise.
We could get rid of the surrounding while loop but keep it in for now to
make review easier. It will go away in the following patch.
Signed-off-by: Michal Hocko
---
mm/memcontrol.c | 56 +++
1 file changed, 27 insertions(+), 29 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6bcc97b..d1bc0e8 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1086,7 +1086,6 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup
*root,
rcu_read_lock();
while (!memcg) {
struct mem_cgroup_reclaim_iter *uninitialized_var(iter);
- struct cgroup_subsys_state *css = NULL;
if (reclaim) {
int nid = zone_to_nid(reclaim->zone);
@@ -1112,53 +,52 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup
*root,
* explicit visit.
*/
if (!last_visited) {
- css = &root->css;
+ memcg = root;
} else {
struct cgroup *prev_cgroup, *next_cgroup;
prev_cgroup = (last_visited == root) ? NULL
: last_visited->css.cgroup;
- next_cgroup = cgroup_next_descendant_pre(prev_cgroup,
- root->css.cgroup);
- if (next_cgroup)
- css = cgroup_subsys_state(next_cgroup,
- mem_cgroup_subsys_id);
- }
+skip_node:
+ next_cgroup = cgroup_next_descendant_pre(
+ prev_cgroup, root->css.cgroup);
- /*
-* Even if we found a group we have to make sure it is alive.
-* css && !memcg means that the groups should be skipped and
-* we should continue the tree walk.
-* last_visited css is safe to use because it is protected by
-* css_get and the tree walk is rcu safe.
-*/
- if (css == &root->css || (css && css_tryget(css)))
- memcg = mem_cgroup_from_css(css);
+ /*
+* Even if we found a group we have to make sure it is
+* alive. css && !memcg means that the groups should be
+* skipped and we should continue the tree walk.
+* last_visited css is safe to use because it is
+* protected by css_get and the tree walk is rcu safe.
+*/
+ if (next_cgroup) {
+ struct mem_cgroup *mem = mem_cgroup_from_cont(
+ next_cgroup);
+ if (css_tryget(&mem->css))
+ memcg = mem;
+ else {
+ prev_cgroup = next_cgroup;
+ goto skip_node;
+ }
+ }
+ }
if (reclaim) {
- struct mem_cgroup *curr = memcg;
-
if (last_visited)
css_put(&last_visited->css);
- if (css && !memcg)
- curr = mem_cgroup_from_css(css);
-
/* make sure that the cached memcg is not removed */
- if (curr)
- css_get(&curr->css);
- iter->last_visited = curr;
+ if (memcg)
+ css_get(&memcg->css);
+ iter->last_visited = memcg;
- if (!css)
+ if (!memcg)
iter->generation++;
else if (!prev && memcg)
reclaim->generation = iter->generation;
spin_unlock(&iter->iter_lock);
- } else if (css && !memcg) {
- last_visited = mem_cgroup_from_css(css);
