memcg: move charge swapin under lock
KAMEZAWA Hiroyuki [Sun, 19 Oct 2008 03:28:08 +0000 (20:28 -0700)]
While page-cache's charge/uncharge is done under page_lock(), swap-cache
isn't.  (anonymous page is charged when it's newly allocated.)

This patch moves do_swap_page()'s charge() call under lock.  I don't see
any bad problem *now* but this fix will be good for future for avoiding
unnecessary racy state.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memory.c

index ba86b43..54cf20e 100644 (file)
@@ -2326,16 +2326,17 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
                count_vm_event(PGMAJFAULT);
        }
 
+       mark_page_accessed(page);
+
+       lock_page(page);
+       delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
+
        if (mem_cgroup_charge(page, mm, GFP_KERNEL)) {
-               delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
                ret = VM_FAULT_OOM;
+               unlock_page(page);
                goto out;
        }
 
-       mark_page_accessed(page);
-       lock_page(page);
-       delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
-
        /*
         * Back out if somebody else already faulted in this pte.
         */