[patch 39/56] mm: remove UP version of lru_add_drain_all()

Greg KH
2009-02-11T00:42:12Z

[-- Attachment #1: mm-remove-up-version-of-lru_add_drain_all.patch --]
[-- Type: text/plain, Size: 2199 bytes --]

2.6.27-stable review patch. If anyone has any objections, please let us know.
------------------

From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>

commit 6841c8e26357904ef462650273f5d5015f7bb370 upstream.

Currently, lru_add_drain_all() has two version.
(1) use schedule_on_each_cpu()
(2) don't use schedule_on_each_cpu()

Gerald Schaefer reported it doesn't work well on SMP (not NUMA) S390
machine.

offline_pages() calls lru_add_drain_all() followed by drain_all_pages().
While drain_all_pages() works on each cpu, lru_add_drain_all() only runs
on the current cpu for architectures w/o CONFIG_NUMA. This let us run
into the BUG_ON(!PageBuddy(page)) in __offline_isolated_pages() during
memory hotplug stress test on s390. The page in question was still on the
pcp list, because of a race with lru_add_drain_all() and drain_all_pages()
on different cpus.

Actually, Almost machine has CONFIG_UNEVICTABLE_LRU=y. Then almost machine use
(1) version lru_add_drain_all although the machine is UP.

Then this ifdef is not valueable.
simple removing is better.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Acked-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nick Piggin <npiggin@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
mm/swap.c | 13 -------------
1 file changed, 13 deletions(-)

--- a/mm/swap.c
+++ b/mm/swap.c
@@ -244,7 +244,6 @@ void lru_add_drain(void)
put_cpu();
}

-#ifdef CONFIG_NUMA
static void lru_add_drain_per_cpu(struct work_struct *dummy)
{
lru_add_drain();
@@ -258,18 +257,6 @@ int lru_add_drain_all(void)
return schedule_on_each_cpu(lru_add_drain_per_cpu);
}

-#else
-
-/*
- * Returns 0 for success
- */
-int lru_add_drain_all(void)
-{
- lru_add_drain();
- return 0;
-}
-#endif
-
/*
* Batched page_cache_release(). Decrement the reference count on all the
* passed pages. If it fell to zero then remove the page from the LRU and