Based on
2.6.38-rc2 +
mm-memcontrolc-fix-uninitialized-variable-use-in-mem_cgroup_move_parent.patch
==
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
A fix up mem_cgroup_move_parent() which use compound_order() in
asynchrnous manner. This compound_order() may return unknown value
because we don't take lock. Use PageTransHuge() and HPAGE_SIZE instead of
it.
Also clean up for mem_cgroup_move_parent().
- remove unnecessary initialization of local variable.
- rename charge_size -> page_size
- remove unnecessary (wrong) comment.
- added a comment about THP.
Changelog:
- fixed page size calculation for avoiding race.
Note:
Current design take compound_page_lock() in caller of move_account().
This should be revisited when we implement direct move_task of hugepage
without splitting.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
---
mm/memcontrol.c | 25 ++++++++++++++++---------
1 file changed, 16 insertions(+), 9 deletions(-)
Index: linux-2.6.38-rc2/mm/memcontrol.c
===================================================================
--- linux-2.6.38-rc2.orig/mm/memcontrol.c
+++ linux-2.6.38-rc2/mm/memcontrol.c
@@ -2234,7 +2234,12 @@ static int mem_cgroup_move_account(struc
{
int ret = -EINVAL;
unsigned long flags;
-
+ /*
+ * The page is isolated from LRU. So, collapse function
+ * will not handle this page. But page splitting can happen.
+ * Do this check under compound_page_lock(). The caller should
+ * hold it.
+ */
if ((charge_size > PAGE_SIZE) && !PageTransHuge(pc->page))
return -EBUSY;
@@ -2266,7 +2271,7 @@ static int mem_cgroup_move_parent(struct
struct cgroup *cg = child->css.cgroup;
struct cgroup *pcg = cg->parent;
struct mem_cgroup *parent;
- int charge = PAGE_SIZE;
+ int page_size = PAGE_SIZE;
unsigned long flags;
int ret;
@@ -2279,22 +2284,24 @@ static int mem_cgroup_move_parent(struct
goto out;
if (isolate_lru_page(page))
goto put;
- /* The page is isolated from LRU and we have no race with splitting */
- charge = PAGE_SIZE << compound_order(page);
+
+ if (PageTransHuge(page))
+ page_size = HPAGE_SIZE;
parent = mem_cgroup_from_cont(pcg);
- ret = __mem_cgroup_try_charge(NULL, gfp_mask, &parent, false, charge);
+ ret = __mem_cgroup_try_charge(NULL, gfp_mask,
+ &parent, false, page_size);
if (ret || !parent)
goto put_back;
- if (charge > PAGE_SIZE)
+ if (page_size > PAGE_SIZE)
flags = compound_lock_irqsave(page);
- ret = mem_cgroup_move_account(pc, child, parent, true, charge);
+ ret = mem_cgroup_move_account(pc, child, parent, true, page_size);
if (ret)
- mem_cgroup_cancel_charge(parent, charge);
+ mem_cgroup_cancel_charge(parent, page_size);
- if (charge > PAGE_SIZE)
+ if (page_size > PAGE_SIZE)
compound_unlock_irqrestore(page, flags);
put_back:
putback_lru_page(page);
--
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