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>

1 files changed, 12 insertions, 18 deletions

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) {