[PATCH v4 2/3] selftests/mm: add memory failure clean pagecache test

[Miaohe Lin <linmiaohe@huawei.com>]

This patch adds a new testcase to validate memory failure handling for
clean pagecache. This test performs similar operations as anonymous
pages except allocating memory using mmap() with a file fd.

This test helps ensure that memory failure handling for clean pagecache
works correctly, including unchanged page content, page isolation, and
recovery paths.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202601221142.mDWA1ucw-lkp@intel.com/
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
 tools/testing/selftests/mm/memory-failure.c | 66 +++++++++++++++++++++
 1 file changed, 66 insertions(+)

diff --git a/tools/testing/selftests/mm/memory-failure.c b/tools/testing/selftests/mm/memory-failure.c
index 37806a58f4b4..3aa624db9577 100644
--- a/tools/testing/selftests/mm/memory-failure.c
+++ b/tools/testing/selftests/mm/memory-failure.c
@@ -10,10 +10,14 @@
 #include <sys/mman.h>
 #include <linux/mman.h>
 #include <linux/string.h>
+#include <unistd.h>
 #include <signal.h>
 #include <setjmp.h>
 #include <unistd.h>
 #include <fcntl.h>
+#include <sys/vfs.h>
+#include <linux/magic.h>
+#include <errno.h>
 
 #include "vm_util.h"
 
@@ -24,7 +28,9 @@ enum inject_type {
 
 enum result_type {
 	MADV_HARD_ANON,
+	MADV_HARD_CLEAN_PAGECACHE,
 	MADV_SOFT_ANON,
+	MADV_SOFT_CLEAN_PAGECACHE,
 };
 
 static jmp_buf signal_jmp_buf;
@@ -154,6 +160,8 @@ static void check(struct __test_metadata *_metadata, FIXTURE_DATA(memory_failure
 
 	switch (type) {
 	case MADV_SOFT_ANON:
+	case MADV_HARD_CLEAN_PAGECACHE:
+	case MADV_SOFT_CLEAN_PAGECACHE:
 		/* It is not expected to receive a SIGBUS signal. */
 		ASSERT_EQ(setjmp, 0);
 
@@ -236,4 +244,62 @@ TEST_F(memory_failure, anon)
 	ASSERT_EQ(munmap(addr, self->page_size), 0);
 }
 
+/* Borrowed from mm/gup_longterm.c. */
+static int get_fs_type(int fd)
+{
+	struct statfs fs;
+	int ret;
+
+	do {
+		ret = fstatfs(fd, &fs);
+	} while (ret && errno == EINTR);
+
+	return ret ? 0 : (int)fs.f_type;
+}
+
+TEST_F(memory_failure, clean_pagecache)
+{
+	const char *fname = "./clean-page-cache-test-file";
+	int fd;
+	char *addr;
+	int ret;
+	int fs_type;
+
+	fd = open(fname, O_RDWR | O_CREAT, 0664);
+	if (fd < 0)
+		SKIP(return, "failed to open test file.\n");
+	unlink(fname);
+	ftruncate(fd, self->page_size);
+	fs_type = get_fs_type(fd);
+	if (!fs_type || fs_type == TMPFS_MAGIC)
+		SKIP(return, "unsupported filesystem :%x\n", fs_type);
+
+	addr = mmap(0, self->page_size, PROT_READ | PROT_WRITE,
+		    MAP_SHARED, fd, 0);
+	if (addr == MAP_FAILED)
+		SKIP(return, "mmap failed, not enough memory.\n");
+	memset(addr, 0xce, self->page_size);
+	fsync(fd);
+
+	prepare(_metadata, self, addr);
+
+	ret = sigsetjmp(signal_jmp_buf, 1);
+	if (!self->triggered) {
+		self->triggered = true;
+		ASSERT_EQ(variant->inject(self, addr), 0);
+		FORCE_READ(*addr);
+	}
+
+	if (variant->type == MADV_HARD)
+		check(_metadata, self, addr, MADV_HARD_CLEAN_PAGECACHE, ret);
+	else
+		check(_metadata, self, addr, MADV_SOFT_CLEAN_PAGECACHE, ret);
+
+	cleanup(_metadata, self, addr);
+
+	ASSERT_EQ(munmap(addr, self->page_size), 0);
+
+	ASSERT_EQ(close(fd), 0);
+}
+
 TEST_HARNESS_MAIN
-- 
2.33.0