>From e20cd50a8f612dbc720d31d269e748215607a0b8 Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shute...@linux.intel.com>
Date: Fri, 29 Jan 2016 14:55:40 +0300
Subject: [PATCH 1/2] mm: fix bogus VM_BUG_ON_PAGE() in isolate_lru_page()

We don't care if there's a tail pages which is not on LRU. We are not
going to isolate them anyway.

Testcase:

        #include <fcntl.h>
        #include <unistd.h>
        #include <stdio.h>
        #include <sys/mman.h>
        #include <numaif.h>

        #define SIZE 0x2000

        int foo;

        int main()
        {
                int fd;
                char *p;
                unsigned long mask = 2;

                fd = open("/dev/sg0", O_RDWR);
                p = mmap(NULL, SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 
0);
                /* Faultin pages */
                foo = p[0] + p[0x1000];
                mbind(p, SIZE, MPOL_BIND, &mask, 4, MPOL_MF_MOVE | 
MPOL_MF_STRICT);
                return 0;
        }

MPOL_MF_STRICT makes queue_pages_test_walk() ignore !vma_megratable()
and we try to queue such pages for migration. It's good question why we
ignore !vma_megratable() for MPOL_MF_STRICT, but it's subject for a
separate patch.

Signed-off-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
Reported-by: Dmitry Vyukov <dvyu...@google.com>
Fixes: bb5b8589767a ("mm: make sure isolate_lru_page() is never called for tail 
page")
---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index eb3dd37ccd7c..492fbe73420b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1443,7 +1443,7 @@ int isolate_lru_page(struct page *page)
        int ret = -EBUSY;
 
        VM_BUG_ON_PAGE(!page_count(page), page);
-       VM_BUG_ON_PAGE(PageTail(page), page);
+       VM_BUG_ON_PAGE(PageLRU(page) && PageTail(page), page);
 
        if (PageLRU(page)) {
                struct zone *zone = page_zone(page);
-- 
2.7.0.rc3

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