Re: [linux-yocto] [PATCH 1/1] 4.1.28 Fix bad backport of 8f182270dfec "mm/swap.c: flush lru, pvecs on compound page arrival"

[Bruce Ashfield]

On 2016-07-25 04:43 PM, Chris Sykes wrote:

 From 74225a4cbea38034034add5da67a2f7ee23251c0 Mon Sep 17 00:00:00 2001
From: Steven Rostedt <rost...@goodmis.org>

When I pulled in 4.1.28 into my stable 4.1-rt tree and ran the tests,
it crashed with a severe OOM killing everything. I then tested 4.1.28
without -rt and it had the same issue. I did a bisect between 4.1.27
and 4.1.28 and found that the bug started at:

commit 8f182270dfec "mm/swap.c: flush lru pvecs on compound page
arrival"

Looking at that patch and what's in mainline, I see that there's a
mismatch in one of the hunks:

I expect that 4.1.29 will drop any day now, but I went ahead and
integrated this change.

The patch was slightly corrupted, so I grabbed it directly off the
4.1.y stable queue.

SRCREV updates will be out shortly for this (but it is in the tree
now).

Bruce

Mainline:

@@ -391,9 +391,8 @@ static void __lru_cache_add(struct page *page)
         struct pagevec *pvec = &get_cpu_var(lru_add_pvec);

         get_page(page);
-       if (!pagevec_space(pvec))
+       if (!pagevec_add(pvec, page) || PageCompound(page))
                 __pagevec_lru_add(pvec);
-       pagevec_add(pvec, page);
         put_cpu_var(lru_add_pvec);
  }

Stable 4.1.28:

@@ -631,9 +631,8 @@ static void __lru_cache_add(struct page *page)
         struct pagevec *pvec = &get_cpu_var(lru_add_pvec);

         page_cache_get(page);
-       if (!pagevec_space(pvec))
+       if (!pagevec_space(pvec) || PageCompound(page))
                 __pagevec_lru_add(pvec);
-       pagevec_add(pvec, page);
         put_cpu_var(lru_add_pvec);
  }

Where mainline replace pagevec_space() with pagevec_add, and stable did
not.

Fixing this makes the OOM go away.

Note, 3.18 has the same bug.

Signed-off-by: Steven Rostedt <rost...@goodmis.org>
Signed-off-by: Sasha Levin <alexander.le...@verizon.com>
---
  mm/swap.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/swap.c b/mm/swap.c
index b523f0a..ab3b9c2 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -631,7 +631,7 @@ static void __lru_cache_add(struct page *page)
      struct pagevec *pvec = &get_cpu_var(lru_add_pvec);

      page_cache_get(page);
-    if (!pagevec_space(pvec) || PageCompound(page))
+    if (!pagevec_add(pvec, page) || PageCompound(page))
          __pagevec_lru_add(pvec);
      put_cpu_var(lru_add_pvec);
  }

--
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