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>

1 files changed, 59 insertions, 37 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 53eb30ebdb4..e5277e8a42a 100644
--- 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)