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 bbb7b04..5d0de96 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) {