[PATCH v4 4/4] mm, shmem, selftests: add tmpfs memcg= mount option tests

[Mina Almasry]

- Test mounting and remounting with memcg= succeeds.
- Test that simple writes in this file system are charged to the correct
  memecg.
- Test that on non-pagefault paths the calling process gets an ENOSPC.
- Test that in pagefault paths the calling process gets a SIGBUS.

Signed-off-by: Mina Almasry <almasrymina@xxxxxxxxxx>

---

Changes in v4:

- Convert tests to expect ENOSPC/SIGBUS rather than ENOMEM oom behavior.
- Added remount test.

---
 tools/testing/selftests/vm/.gitignore     |   1 +
 tools/testing/selftests/vm/mmap_write.c   | 103 +++++++++++++++++++
 tools/testing/selftests/vm/tmpfs-memcg.sh | 116 ++++++++++++++++++++++
 3 files changed, 220 insertions(+)
 create mode 100644 tools/testing/selftests/vm/mmap_write.c
 create mode 100755 tools/testing/selftests/vm/tmpfs-memcg.sh

diff --git a/tools/testing/selftests/vm/.gitignore b/tools/testing/selftests/vm/.gitignore
index 2e7e86e852828..cb229974c5f15 100644
--- a/tools/testing/selftests/vm/.gitignore
+++ b/tools/testing/selftests/vm/.gitignore
@@ -19,6 +19,7 @@ madv_populate
 userfaultfd
 mlock-intersect-test
 mlock-random-test
+mmap_write
 virtual_address_range
 gup_test
 va_128TBswitch
diff --git a/tools/testing/selftests/vm/mmap_write.c b/tools/testing/selftests/vm/mmap_write.c
new file mode 100644
index 0000000000000..88a8468f2128c
--- /dev/null
+++ b/tools/testing/selftests/vm/mmap_write.c
@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * This program faults memory in tmpfs
+ */
+
+#include <err.h>
+#include <errno.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <sys/shm.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+
+/* Global definitions. */
+
+/* Global variables. */
+static const char *self;
+static char *shmaddr;
+static int shmid;
+
+/*
+ * Show usage and exit.
+ */
+static void exit_usage(void)
+{
+	printf("Usage: %s -p <path to tmpfs file> -s <size to map>\n", self);
+	exit(EXIT_FAILURE);
+}
+
+int main(int argc, char **argv)
+{
+	int fd = 0;
+	int key = 0;
+	int *ptr = NULL;
+	int c = 0;
+	int size = 0;
+	char path[256] = "";
+	int want_sleep = 0, private = 0;
+	int populate = 0;
+	int write = 0;
+	int reserve = 1;
+
+	/* Parse command-line arguments. */
+	setvbuf(stdout, NULL, _IONBF, 0);
+	self = argv[0];
+
+	while ((c = getopt(argc, argv, ":s:p:")) != -1) {
+		switch (c) {
+		case 's':
+			size = atoi(optarg);
+			break;
+		case 'p':
+			strncpy(path, optarg, sizeof(path));
+			break;
+		default:
+			errno = EINVAL;
+			perror("Invalid arg");
+			exit_usage();
+		}
+	}
+
+	printf("%s\n", path);
+	if (strncmp(path, "", sizeof(path)) != 0) {
+		printf("Writing to this path: %s\n", path);
+	} else {
+		errno = EINVAL;
+		perror("path not found");
+		exit_usage();
+	}
+
+	if (size != 0) {
+		printf("Writing this size: %d\n", size);
+	} else {
+		errno = EINVAL;
+		perror("size not found");
+		exit_usage();
+	}
+
+	fd = open(path, O_CREAT | O_RDWR, 0777);
+	if (fd == -1)
+		err(1, "Failed to open file.");
+
+	if (ftruncate(fd, size))
+		err(1, "failed to ftruncate %s", path);
+
+	ptr = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	if (ptr == MAP_FAILED) {
+		close(fd);
+		err(1, "Error mapping the file");
+	}
+
+	printf("Writing to memory.\n");
+	memset(ptr, 1, size);
+	printf("Done writing to memory.\n");
+	close(fd);
+
+	return 0;
+}
diff --git a/tools/testing/selftests/vm/tmpfs-memcg.sh b/tools/testing/selftests/vm/tmpfs-memcg.sh
new file mode 100755
index 0000000000000..50876992107fd
--- /dev/null
+++ b/tools/testing/selftests/vm/tmpfs-memcg.sh
@@ -0,0 +1,116 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+CGROUP_PATH=/dev/cgroup/memory/tmpfs-memcg-test
+REMOUNT_CGROUP_PATH=/dev/cgroup/memory/remount-memcg-test
+
+function cleanup() {
+  rm -rf /mnt/tmpfs/*
+  umount /mnt/tmpfs
+  rm -rf /mnt/tmpfs
+
+  rmdir $CGROUP_PATH
+  rmdir $REMOUNT_CGROUP_PATH
+
+  echo CLEANUP DONE
+}
+
+function setup() {
+  mkdir -p $CGROUP_PATH
+  mkdir -p $REMOUNT_CGROUP_PATH
+  echo $((10 * 1024 * 1024)) > $CGROUP_PATH/memory.limit_in_bytes
+  echo 0 > $CGROUP_PATH/cpuset.cpus
+  echo 0 > $CGROUP_PATH/cpuset.mems
+
+  mkdir -p /mnt/tmpfs
+
+  echo SETUP DONE
+}
+
+function expect_equal() {
+  local expected="$1"
+  local actual="$2"
+  local error="$3"
+
+  if [[ "$actual" != "$expected" ]]; then
+    echo "expected ($expected) != actual ($actual): $3" >&2
+    cleanup
+    exit 1
+  fi
+}
+
+function expect_ge() {
+  local expected="$1"
+  local actual="$2"
+  local error="$3"
+
+  if [[ "$actual" -lt "$expected" ]]; then
+    echo "expected ($expected) < actual ($actual): $3" >&2
+    cleanup
+    exit 1
+  fi
+}
+
+cleanup
+setup
+
+mount -t tmpfs -o memcg=$REMOUNT_CGROUP_PATH tmpfs /mnt/tmpfs
+check=$(cat /proc/mounts | grep -i remount-memcg-test)
+if [ -z "$check" ]; then
+  echo "tmpfs memcg= was not mounted correctly:"
+  echo $check
+  echo "FAILED"
+  cleanup
+  exit 1
+fi
+
+mount -t tmpfs -o remount,memcg=$CGROUP_PATH tmpfs /mnt/tmpfs
+check=$(cat /proc/mounts | grep -i tmpfs-memcg-test)
+if [ -z "$check" ]; then
+  echo "tmpfs memcg= was not remounted correctly:"
+  echo $check
+  echo "FAILED"
+  cleanup
+  exit 1
+fi
+
+TARGET_MEMCG_USAGE=$(cat $CGROUP_PATH/memory.usage_in_bytes)
+expect_equal 0 "$TARGET_MEMCG_USAGE" "Before echo, memcg usage should be 0"
+
+# Echo to allocate a page in the tmpfs
+echo
+echo
+echo hello > /mnt/tmpfs/test
+TARGET_MEMCG_USAGE=$(cat $CGROUP_PATH/memory.usage_in_bytes)
+expect_ge 4096 "$TARGET_MEMCG_USAGE" "After echo, memcg usage should be greater than 4096"
+echo "Echo test succeeded"
+
+echo
+echo
+tools/testing/selftests/vm/mmap_write -p /mnt/tmpfs/test -s $((1 * 1024 * 1024))
+TARGET_MEMCG_USAGE=$(cat $CGROUP_PATH/memory.usage_in_bytes)
+expect_ge $((1 * 1024 * 1024)) "$TARGET_MEMCG_USAGE" "After mmap_write, memcg usage should greater than 1MB"
+echo "WRITE TEST SUCCEEDED"
+
+# SIGBUS the remote container on pagefault.
+echo
+echo
+echo "SIGBUS the process doing the remote charge on hitting the limit of the remote cgroup."
+echo "This will take a long time because the kernel goes through reclaim retries,"
+echo "but should eventually the write process should receive a SIGBUS"
+set +e
+tools/testing/selftests/vm/mmap_write -p /mnt/tmpfs/test -s $((11 * 1024 * 1024)) &
+wait $!
+expect_equal "$?" "135" "mmap_write should have exited with SIGBUS"
+set -e
+
+# ENOSPC the remote container on non pagefault.
+echo
+echo
+echo "OOMing the remote container using cat (non-pagefault)"
+echo "This will take a long time because the kernel goes through reclaim retries,"
+echo "but should eventually the cat command should receive an ENOSPC"
+cat /dev/random > /mnt/tmpfs/random || true
+
+cleanup
+echo TEST PASSED
--
2.34.0.rc2.393.gf8c9666880-goog