linux-kernel - Re: [RFC 5/4] mm, page_alloc: fix premature OOM due to vma mempolicy update

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Date:   Wed, 18 Jan 2017 17:23:38 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Mel Gorman <mgorman@...hsingularity.net>,
        Ganapatrao Kulkarni <gpkulkarni@...il.com>
Cc:     Michal Hocko <mhocko@...nel.org>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [RFC 5/4] mm, page_alloc: fix premature OOM due to vma mempolicy
 update

On 01/18/2017 05:20 PM, Vlastimil Babka wrote:
> By changing the LTP cpuset01 testcase (will post patch as a reply) this was
> confirmed and the problem is also older than the changes in 4.7.

-----8<-----
diff --git a/testcases/kernel/mem/cpuset/cpuset01.c b/testcases/kernel/mem/cpuset/cpuset01.c
index 558420f72f9b..ef673366e15e 100644
--- a/testcases/kernel/mem/cpuset/cpuset01.c
+++ b/testcases/kernel/mem/cpuset/cpuset01.c
@@ -40,6 +40,7 @@
 #include <fcntl.h>
 #include <math.h>
 #if HAVE_NUMAIF_H
+#include <linux/mempolicy.h>
 #include <numaif.h>
 #endif
 #include <signal.h>
@@ -61,6 +62,7 @@ volatile int end;
 static int *nodes;
 static int nnodes;
 static long ncpus;
+static unsigned long nmask[MAXNODES / BITS_PER_LONG] = { 0 };
 
 static void testcpuset(void);
 static void sighandler(int signo LTP_ATTRIBUTE_UNUSED);
@@ -89,7 +91,6 @@ static void testcpuset(void)
 {
 	int lc;
 	int child, i, status;
-	unsigned long nmask[MAXNODES / BITS_PER_LONG] = { 0 };
 	char mems[BUFSIZ], buf[BUFSIZ];
 
 	read_cpuset_files(CPATH, "cpus", buf);
@@ -105,6 +106,7 @@ static void testcpuset(void)
 		for (i = 0; i < nnodes; i++) {
 			if (nodes[i] >= MAXNODES)
 				continue;
+			printf("bind to node %d\n", nodes[i]);
 			set_node(nmask, nodes[i]);
 		}
 		if (set_mempolicy(MPOL_BIND, nmask, MAXNODES) == -1)
@@ -163,6 +165,8 @@ static int mem_hog(void)
 			tst_resm(TFAIL | TERRNO, "mmap");
 			break;
 		}
+		if (mbind(addr, pagesize * 10, MPOL_BIND, nmask, MAXNODES, 0) == -1)
+			tst_brkm(TBROK | TERRNO, cleanup, "set_mempolicy");
 		memset(addr, 0xF7, pagesize * 10);
 		munmap(addr, pagesize * 10);
 	}