memcg: fix shmem's swap accounting

Now, you can see following even when swap accounting is enabled.

 1. Create Group 01, and 02.
 2. allocate a "file" on tmpfs by a task under 01.
 3. swap out the "file" (by memory pressure)
 4. Read "file" from a task in group 02.
 5. the charge of "file" is moved to group 02.

This is not ideal behavior. This is because SwapCache which was loaded
by read-ahead is not taken into account..

This is a patch to fix shmem's swapcache behavior.
  - remove mem_cgroup_cache_charge_swapin().
  - Add SwapCache handler routine to mem_cgroup_cache_charge().
    By this, shmem's file cache is charged at add_to_page_cache()
    with GFP_NOWAIT.
  - pass the page of swapcache to shrink_mem_cgroup.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Paul Menage <menage@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 72 insertions, 92 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f50cb7b1efdb..93a792871804 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -893,6 +893,23 @@ nomem:
         return -ENOMEM;
 }
 
+static struct mem_cgroup *try_get_mem_cgroup_from_swapcache(struct page *page)
+{
+        struct mem_cgroup *mem;
+        swp_entry_t ent;
+
+        if (!PageSwapCache(page))
+                return NULL;
+
+        ent.val = page_private(page);
+        mem = lookup_swap_cgroup(ent);
+        if (!mem)
+                return NULL;
+        if (!css_tryget(&mem->css))
+                return NULL;
+        return mem;
+}
+
 /*
  * commit a charge got by __mem_cgroup_try_charge() and makes page_cgroup to be
  * USED state. If already USED, uncharge and return.
@@ -1084,6 +1101,9 @@ int mem_cgroup_newpage_charge(struct page *page,
 int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
                                 gfp_t gfp_mask)
 {
+        struct mem_cgroup *mem = NULL;
+        int ret;
+
         if (mem_cgroup_disabled())
                 return 0;
         if (PageCompound(page))
@@ -1096,6 +1116,8 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
          * For GFP_NOWAIT case, the page may be pre-charged before calling
          * add_to_page_cache(). (See shmem.c) check it here and avoid to call
          * charge twice. (It works but has to pay a bit larger cost.)
+         * And when the page is SwapCache, it should take swap information
+         * into account. This is under lock_page() now.
          */
         if (!(gfp_mask & __GFP_WAIT)) {
                 struct page_cgroup *pc;
@@ -1112,15 +1134,40 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
                 unlock_page_cgroup(pc);
         }
 
-        if (unlikely(!mm))
+        if (do_swap_account && PageSwapCache(page)) {
+                mem = try_get_mem_cgroup_from_swapcache(page);
+                if (mem)
+                        mm = NULL;
+                  else
+                        mem = NULL;
+                /* SwapCache may be still linked to LRU now. */
+                mem_cgroup_lru_del_before_commit_swapcache(page);
+        }
+
+        if (unlikely(!mm && !mem))
                 mm = &init_mm;
 
         if (page_is_file_cache(page))
                 return mem_cgroup_charge_common(page, mm, gfp_mask,
                                 MEM_CGROUP_CHARGE_TYPE_CACHE, NULL);
-        else
-                return mem_cgroup_charge_common(page, mm, gfp_mask,
-                                MEM_CGROUP_CHARGE_TYPE_SHMEM, NULL);
+
+        ret = mem_cgroup_charge_common(page, mm, gfp_mask,
+                                MEM_CGROUP_CHARGE_TYPE_SHMEM, mem);
+        if (mem)
+                css_put(&mem->css);
+        if (PageSwapCache(page))
+                mem_cgroup_lru_add_after_commit_swapcache(page);
+
+        if (do_swap_account && !ret && PageSwapCache(page)) {
+                swp_entry_t ent = {.val = page_private(page)};
+                /* avoid double counting */
+                mem = swap_cgroup_record(ent, NULL);
+                if (mem) {
+                        res_counter_uncharge(&mem->memsw, PAGE_SIZE);
+                        mem_cgroup_put(mem);
+                }
+        }
+        return ret;
 }
 
 /*
@@ -1134,7 +1181,6 @@ int mem_cgroup_try_charge_swapin(struct mm_struct *mm,
                                  gfp_t mask, struct mem_cgroup **ptr)
 {
         struct mem_cgroup *mem;
-        swp_entry_t     ent;
         int ret;
 
         if (mem_cgroup_disabled())
@@ -1142,7 +1188,6 @@ int mem_cgroup_try_charge_swapin(struct mm_struct *mm,
 
         if (!do_swap_account)
                 goto charge_cur_mm;
-
         /*
          * A racing thread's fault, or swapoff, may have already updated
          * the pte, and even removed page from swap cache: return success
@@ -1150,14 +1195,9 @@ int mem_cgroup_try_charge_swapin(struct mm_struct *mm,
          */
         if (!PageSwapCache(page))
                 return 0;
-
-        ent.val = page_private(page);
-
-        mem = lookup_swap_cgroup(ent);
+        mem = try_get_mem_cgroup_from_swapcache(page);
         if (!mem)
                 goto charge_cur_mm;
-        if (!css_tryget(&mem->css))
-                goto charge_cur_mm;
         *ptr = mem;
         ret = __mem_cgroup_try_charge(NULL, mask, ptr, true);
         /* drop extra refcnt from tryget */
@@ -1169,62 +1209,6 @@ charge_cur_mm:
         return __mem_cgroup_try_charge(mm, mask, ptr, true);
 }
 
-#ifdef CONFIG_SWAP
-
-int mem_cgroup_cache_charge_swapin(struct page *page,
-                        struct mm_struct *mm, gfp_t mask, bool locked)
-{
-        int ret = 0;
-
-        if (mem_cgroup_disabled())
-                return 0;
-        if (unlikely(!mm))
-                mm = &init_mm;
-        if (!locked)
-                lock_page(page);
-        /*
-         * If not locked, the page can be dropped from SwapCache until
-         * we reach here.
-         */
-        if (PageSwapCache(page)) {
-                struct mem_cgroup *mem = NULL;
-                swp_entry_t ent;
-
-                ent.val = page_private(page);
-                if (do_swap_account) {
-                        mem = lookup_swap_cgroup(ent);
-                        if (mem) {
-                                if (css_tryget(&mem->css))
-                                        mm = NULL; /* charge to recorded */
-                                else
-                                        mem = NULL; /* charge to current */
-                        }
-                }
-                /* SwapCache may be still linked to LRU now. */
-                mem_cgroup_lru_del_before_commit_swapcache(page);
-                ret = mem_cgroup_charge_common(page, mm, mask,
-                                MEM_CGROUP_CHARGE_TYPE_SHMEM, mem);
-                mem_cgroup_lru_add_after_commit_swapcache(page);
-                /* drop extra refcnt from tryget */
-                if (mem)
-                        css_put(&mem->css);
-
-                if (!ret && do_swap_account) {
-                        /* avoid double counting */
-                        mem = swap_cgroup_record(ent, NULL);
-                        if (mem) {
-                                res_counter_uncharge(&mem->memsw, PAGE_SIZE);
-                                mem_cgroup_put(mem);
-                        }
-                }
-        }
-        if (!locked)
-                unlock_page(page);
-
-        return ret;
-}
-#endif
-
 void mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr)
 {
         struct page_cgroup *pc;
@@ -1486,18 +1470,20 @@ void mem_cgroup_end_migration(struct mem_cgroup *mem,
  * This is typically used for page reclaiming for shmem for reducing side
  * effect of page allocation from shmem, which is used by some mem_cgroup.
  */
-int mem_cgroup_shrink_usage(struct mm_struct *mm, gfp_t gfp_mask)
+int mem_cgroup_shrink_usage(struct page *page,
+                            struct mm_struct *mm,
+                            gfp_t gfp_mask)
 {
-        struct mem_cgroup *mem;
+        struct mem_cgroup *mem = NULL;
         int progress = 0;
         int retry = MEM_CGROUP_RECLAIM_RETRIES;
 
         if (mem_cgroup_disabled())
                 return 0;
-        if (!mm)
-                return 0;
-
-        mem = try_get_mem_cgroup_from_mm(mm);
+        if (page)
+                mem = try_get_mem_cgroup_from_swapcache(page);
+        if (!mem && mm)
+                mem = try_get_mem_cgroup_from_mm(mm);
         if (unlikely(!mem))
                 return 0;
 
diff --git a/mm/shmem.c b/mm/shmem.c
index bbb7b043c986..5d0de96c9789 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -929,11 +929,11 @@ found:
         if (!inode)
                 goto out;
         /*
-         * Charge page using GFP_HIGHUSER_MOVABLE while we can wait.
-         * charged back to the user(not to caller) when swap account is used.
+         * Charge page using GFP_KERNEL while we can wait.
+         * Charged back to the user(not to caller) when swap account is used.
+         * add_to_page_cache() will be called with GFP_NOWAIT.
          */
-        error = mem_cgroup_cache_charge_swapin(page, current->mm, GFP_KERNEL,
-                                        true);
+        error = mem_cgroup_cache_charge(page, current->mm, GFP_KERNEL);
         if (error)
                 goto out;
         error = radix_tree_preload(GFP_KERNEL);
@@ -1270,16 +1270,6 @@ repeat:
                                 goto repeat;
                         }
                         wait_on_page_locked(swappage);
-                        /*
-                         * We want to avoid charge at add_to_page_cache().
-                         * charge against this swap cache here.
-                         */
-                        if (mem_cgroup_cache_charge_swapin(swappage,
-                                current->mm, gfp & GFP_RECLAIM_MASK, false)) {
-                                page_cache_release(swappage);
-                                error = -ENOMEM;
-                                goto failed;
-                        }
                         page_cache_release(swappage);
                         goto repeat;
                 }
@@ -1334,15 +1324,19 @@ repeat:
                 } else {
                         shmem_swp_unmap(entry);
                         spin_unlock(&info->lock);
-                        unlock_page(swappage);
-                        page_cache_release(swappage);
                         if (error == -ENOMEM) {
                                 /* allow reclaim from this memory cgroup */
-                                error = mem_cgroup_shrink_usage(current->mm,
+                                error = mem_cgroup_shrink_usage(swappage,
+                                                                current->mm,
                                                                 gfp);
-                                if (error)
+                                if (error) {
+                                        unlock_page(swappage);
+                                        page_cache_release(swappage);
                                         goto failed;
+                                }
                         }
+                        unlock_page(swappage);
+                        page_cache_release(swappage);
                         goto repeat;
                 }
         } else if (sgp == SGP_READ && !filepage) {