memcg: swap cgroup for remembering usage

For accounting swap, we need a record per swap entry, at least.

This patch adds following function.
  - swap_cgroup_swapon() .... called from swapon
  - swap_cgroup_swapoff() ... called at the end of swapoff.

  - swap_cgroup_record() .... record information of swap entry.
  - swap_cgroup_lookup() .... lookup information of swap entry.

This patch just implements "how to record information".  No actual method
for limit the usage of swap.  These routine uses flat table to record and
lookup.  "wise" lookup system like radix-tree requires requires memory
allocation at new records but swap-out is usually called under memory
shortage (or memcg hits limit.) So, I used static allocation.  (maybe
dynamic allocation is not very hard but it adds additional memory
allocation in memory shortage path.)

Note1: In this, we use pointer to record information and this means
      8bytes per swap entry. I think we can reduce this when we
      create "id of cgroup" in the range of 0-65535 or 0-255.

Reported-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Tested-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Reported-by: Hugh Dickins <hugh@veritas.com>
Reported-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Pavel Emelianov <xemul@openvz.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/mm/swapfile.c b/mm/swapfile.c
index ddc6d92be2cb..1e7a715a3866 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -33,6 +33,7 @@
 #include <asm/pgtable.h>
 #include <asm/tlbflush.h>
 #include <linux/swapops.h>
+#include <linux/page_cgroup.h>
 
 static DEFINE_SPINLOCK(swap_lock);
 static unsigned int nr_swapfiles;
@@ -1494,6 +1495,9 @@ asmlinkage long sys_swapoff(const char __user * specialfile)
         spin_unlock(&swap_lock);
         mutex_unlock(&swapon_mutex);
         vfree(swap_map);
+        /* Destroy swap account informatin */
+        swap_cgroup_swapoff(type);
+
         inode = mapping->host;
         if (S_ISBLK(inode->i_mode)) {
                 struct block_device *bdev = I_BDEV(inode);
@@ -1811,6 +1815,11 @@ asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
                 }
                 swap_map[page_nr] = SWAP_MAP_BAD;
         }
+
+        error = swap_cgroup_swapon(type, maxpages);
+        if (error)
+                goto bad_swap;
+
         nr_good_pages = swap_header->info.last_page -
                         swap_header->info.nr_badpages -
                         1 /* header page */;
@@ -1882,6 +1891,7 @@ bad_swap:
                 bd_release(bdev);
         }
         destroy_swap_extents(p);
+        swap_cgroup_swapoff(type);
 bad_swap_2:
         spin_lock(&swap_lock);
         p->swap_file = NULL;