memcg: clean up move charge

This patch cleans up move charge code by:

- define functions to handle pte for each types, and make
  is_target_pte_for_mc() cleaner.

- instead of checking the MOVE_CHARGE_TYPE_ANON bit, define a function
  that checks the bit.

Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 53eb30e..e5277e8 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -266,6 +266,12 @@ static struct move_charge_struct {
        .waitq = __WAIT_QUEUE_HEAD_INITIALIZER(mc.waitq),
 };
 
+static bool move_anon(void)
+{
+       return test_bit(MOVE_CHARGE_TYPE_ANON,
+                                       &mc.to->move_charge_at_immigrate);
+}
+
 /*
  * Maximum loops in mem_cgroup_hierarchical_reclaim(), used for soft
  * limit reclaim to prevent infinite loops, if they ever occur.
@@ -4162,50 +4168,66 @@ enum mc_target_type {
        MC_TARGET_SWAP,
 };
 
-static int is_target_pte_for_mc(struct vm_area_struct *vma,
-               unsigned long addr, pte_t ptent, union mc_target *target)
+static struct page *mc_handle_present_pte(struct vm_area_struct *vma,
+                                               unsigned long addr, pte_t ptent)
 {
-       struct page *page = NULL;
-       struct page_cgroup *pc;
-       int ret = 0;
-       swp_entry_t ent = { .val = 0 };
-       int usage_count = 0;
-       bool move_anon = test_bit(MOVE_CHARGE_TYPE_ANON,
-                                       &mc.to->move_charge_at_immigrate);
+       struct page *page = vm_normal_page(vma, addr, ptent);
 
-       if (!pte_present(ptent)) {
-               /* TODO: handle swap of shmes/tmpfs */
-               if (pte_none(ptent) || pte_file(ptent))
-                       return 0;
-               else if (is_swap_pte(ptent)) {
-                       ent = pte_to_swp_entry(ptent);
-                       if (!move_anon || non_swap_entry(ent))
-                               return 0;
-                       usage_count = mem_cgroup_count_swap_user(ent, &page);
-               }
-       } else {
-               page = vm_normal_page(vma, addr, ptent);
-               if (!page || !page_mapped(page))
-                       return 0;
+       if (!page || !page_mapped(page))
+               return NULL;
+       if (PageAnon(page)) {
+               /* we don't move shared anon */
+               if (!move_anon() || page_mapcount(page) > 2)
+                       return NULL;
+       } else
                /*
                 * TODO: We don't move charges of file(including shmem/tmpfs)
                 * pages for now.
                 */
-               if (!move_anon || !PageAnon(page))
-                       return 0;
-               if (!get_page_unless_zero(page))
-                       return 0;
-               usage_count = page_mapcount(page);
-       }
-       if (usage_count > 1) {
-               /*
-                * TODO: We don't move charges of shared(used by multiple
-                * processes) pages for now.
-                */
+               return NULL;
+       if (!get_page_unless_zero(page))
+               return NULL;
+
+       return page;
+}
+
+static struct page *mc_handle_swap_pte(struct vm_area_struct *vma,
+                       unsigned long addr, pte_t ptent, swp_entry_t *entry)
+{
+       int usage_count;
+       struct page *page = NULL;
+       swp_entry_t ent = pte_to_swp_entry(ptent);
+
+       if (!move_anon() || non_swap_entry(ent))
+               return NULL;
+       usage_count = mem_cgroup_count_swap_user(ent, &page);
+       if (usage_count > 1) { /* we don't move shared anon */
                if (page)
                        put_page(page);
-               return 0;
+               return NULL;
        }
+       if (do_swap_account)
+               entry->val = ent.val;
+
+       return page;
+}
+
+static int is_target_pte_for_mc(struct vm_area_struct *vma,
+               unsigned long addr, pte_t ptent, union mc_target *target)
+{
+       struct page *page = NULL;
+       struct page_cgroup *pc;
+       int ret = 0;
+       swp_entry_t ent = { .val = 0 };
+
+       if (pte_present(ptent))
+               page = mc_handle_present_pte(vma, addr, ptent);
+       else if (is_swap_pte(ptent))
+               page = mc_handle_swap_pte(vma, addr, ptent, &ent);
+       /* TODO: handle swap of shmes/tmpfs */
+
+       if (!page && !ent.val)
+               return 0;
        if (page) {
                pc = lookup_page_cgroup(page);
                /*
@@ -4221,8 +4243,8 @@ static int is_target_pte_for_mc(struct vm_area_struct *vma,
                if (!ret || !target)
                        put_page(page);
        }
-       /* throught */
-       if (ent.val && do_swap_account && !ret &&
+       /* There is a swap entry and a page doesn't exist or isn't charged */
+       if (ent.val && !ret &&
                        css_id(&mc.from->css) == lookup_swap_cgroup(ent)) {
                ret = MC_TARGET_SWAP;
                if (target)