[PATCH] mm/selftest: Add MAP_POPULATE test

[Dmitry Safonov <dima@arista.com>]

As many other projects, we use some shmalloc allocator.
At some point we need to make a part of allocated pages back private to
process. And it should be populated straight away.
Check that (MAP_PRIVATE | MAP_POPULATE) actually copies the private page.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: Hua Zhong <hzhong@arista.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Stuart Ritchie <sritchie@arista.com>
Cc: linux-kselftest@vger.kernel.org
Signed-off-by: Dmitry Safonov <dima@arista.com>
---
 tools/testing/selftests/vm/.gitignore     |   1 +
 tools/testing/selftests/vm/Makefile       |   1 +
 tools/testing/selftests/vm/map_populate.c | 113 ++++++++++++++++++++++++++++++
 tools/testing/selftests/vm/run_vmtests    |  11 +++
 4 files changed, 126 insertions(+)
 create mode 100644 tools/testing/selftests/vm/map_populate.c

diff --git a/tools/testing/selftests/vm/.gitignore b/tools/testing/selftests/vm/.gitignore
index 342c7bc9dc8c..af5ff83f6d7f 100644
--- a/tools/testing/selftests/vm/.gitignore
+++ b/tools/testing/selftests/vm/.gitignore
@@ -1,6 +1,7 @@
 hugepage-mmap
 hugepage-shm
 map_hugetlb
+map_populate
 thuge-gen
 compaction_test
 mlock2-tests
diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
index fdefa2295ddc..9881876d2aa0 100644
--- a/tools/testing/selftests/vm/Makefile
+++ b/tools/testing/selftests/vm/Makefile
@@ -12,6 +12,7 @@ TEST_GEN_FILES += gup_benchmark
 TEST_GEN_FILES += hugepage-mmap
 TEST_GEN_FILES += hugepage-shm
 TEST_GEN_FILES += map_hugetlb
+TEST_GEN_FILES += map_populate
 TEST_GEN_FILES += mlock-random-test
 TEST_GEN_FILES += mlock2-tests
 TEST_GEN_FILES += on-fault-limit
diff --git a/tools/testing/selftests/vm/map_populate.c b/tools/testing/selftests/vm/map_populate.c
new file mode 100644
index 000000000000..df3eacc8eecb
--- /dev/null
+++ b/tools/testing/selftests/vm/map_populate.c
@@ -0,0 +1,113 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2018 Dmitry Safonov, Arista Networks
+ *
+ * MAP_POPULATE | MAP_PRIVATE should COW VMA pages.
+ */
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#ifndef MMAP_SZ
+#define MMAP_SZ		4096
+#endif
+
+#define BUG_ON(condition, description)					\
+	do {								\
+		if (condition) {					\
+			fprintf(stderr, "[FAIL]\t%s:%d\t%s:%s\n", __func__, \
+				__LINE__, (description), strerror(errno)); \
+			exit(1);					\
+		}							\
+	} while (0)
+
+static int parent_f(int sock, unsigned long *smap, int child)
+{
+	int status, ret;
+
+	ret = read(sock, &status, sizeof(int));
+	BUG_ON(ret <= 0, "read(sock)");
+
+	*smap = 0x22222BAD;
+	ret = msync(smap, MMAP_SZ, MS_SYNC);
+	BUG_ON(ret, "msync()");
+
+	ret = write(sock, &status, sizeof(int));
+	BUG_ON(ret <= 0, "write(sock)");
+
+	waitpid(child, &status, 0);
+	BUG_ON(!WIFEXITED(status), "child hasn't suicide by own will");
+
+	return WEXITSTATUS(status);
+}
+
+static int child_f(int sock, unsigned long *smap, int fd)
+{
+	int ret, buf = 0;
+
+	smap = mmap(0, MMAP_SZ, PROT_READ | PROT_WRITE,
+			MAP_PRIVATE | MAP_POPULATE, fd, 0);
+	BUG_ON(smap == MAP_FAILED, "mmap()");
+
+	BUG_ON(*smap != 0xdeadbabe, "MAP_PRIVATE | MAP_POPULATE changed file");
+
+	ret = write(sock, &buf, sizeof(int));
+	BUG_ON(ret <= 0, "write(sock)");
+
+	ret = read(sock, &buf, sizeof(int));
+	BUG_ON(ret <= 0, "read(sock)");
+
+	BUG_ON(*smap == 0x22222BAD, "MAP_POPULATE didn't COW private page");
+	BUG_ON(*smap != 0xdeadbabe, "mapping was corrupted");
+
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	int sock[2], child, ret;
+	FILE *ftmp;
+	unsigned long *smap;
+
+	ftmp = tmpfile();
+	BUG_ON(ftmp == 0, "tmpfile()");
+
+	ret = ftruncate(fileno(ftmp), MMAP_SZ);
+	BUG_ON(ret, "ftruncate()");
+
+	smap = mmap(0, MMAP_SZ, PROT_READ | PROT_WRITE,
+			MAP_SHARED, fileno(ftmp), 0);
+	BUG_ON(smap == MAP_FAILED, "mmap()");
+
+	*smap = 0xdeadbabe;
+	/* Probably unnecessary, but let it be. */
+	ret = msync(smap, MMAP_SZ, MS_SYNC);
+	BUG_ON(ret, "msync()");
+
+	ret = socketpair(PF_LOCAL, SOCK_SEQPACKET, 0, sock);
+	BUG_ON(ret, "socketpair()");
+
+	child = fork();
+	BUG_ON(child == -1, "fork()");
+
+	if (child) {
+		ret = close(sock[0]);
+		BUG_ON(ret, "close()");
+
+		return parent_f(sock[1], smap, child);
+	}
+
+	ret = close(sock[1]);
+	BUG_ON(ret, "close()");
+
+	return child_f(sock[0], smap, fileno(ftmp));
+}
diff --git a/tools/testing/selftests/vm/run_vmtests b/tools/testing/selftests/vm/run_vmtests
index 88cbe5575f0c..584a91ae4a8f 100755
--- a/tools/testing/selftests/vm/run_vmtests
+++ b/tools/testing/selftests/vm/run_vmtests
@@ -168,6 +168,17 @@ else
 fi
 
 echo "--------------------"
+echo "running map_populate"
+echo "--------------------"
+./map_populate
+if [ $? -ne 0 ]; then
+	echo "[FAIL]"
+	exitcode=1
+else
+	echo "[PASS]"
+fi
+
+echo "--------------------"
 echo "running mlock2-tests"
 echo "--------------------"
 ./mlock2-tests
-- 
2.13.6