[PATCH 2/13] memcg: account fault-in swap under lock.

[KAMEZAWA Hiroyuki]

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.
This is good for avoiding unnecessary slow-path in charge().

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>

 mm/memory.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

Index: mmotm-2.6.27-rc6+/mm/memory.c
===================================================================
--- mmotm-2.6.27-rc6+.orig/mm/memory.c
+++ mmotm-2.6.27-rc6+/mm/memory.c
@@ -2320,15 +2320,14 @@ static int do_swap_page(struct mm_struct
 		count_vm_event(PGMAJFAULT);
 	}
 
+	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;
 		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.

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