fusefs: fix the tests for a wider range of maxphys

maxphys is now a tunable, ever since r368124.  The default value is also
larger than it used to be.  That broke several fusefs tests that made
assumptions about maxphys.

* WriteCluster.clustering used the MAXPHYS compile-time constant.

* WriteBackAsync.direct_io_partially_overlaps_cached_block implicitly
  depended on the default value of maxphys.  Fix it by making the
  dependency explicit.

* Write.write_large implicitly assumed that maxphys would be no more
  than twice maxbcachebuf.  Fix it by explicitly setting m_max_write.

* WriteCluster.clustering and several others failed because the MockFS
  module did not work for max_write > 128KB (which most tests would set
  when maxphys > 256KB).  Limit max_write accordingly.  This is the same
  as fusefs-libs's behavior.

* Bmap's tests were originally written for MAXPHYS=128KB.  With larger
  values, the simulated file size was too small.

PR:		252096
Reviewed by:	emaste
Differential Revision:	https://reviews.freebsd.org/D27769

tests/sys/fs/fusefs/bmap.cc

@@ -83,10 +83,14 @@ void expect_lookup(const char *relpath, uint64_t ino, off_t size)
 TEST_F(Bmap, bmap)
 {
 	struct fiobmap2_arg arg;
-	const off_t filesize = 1 << 20;
-	const ino_t ino = 42;
-	int64_t lbn = 10;
+	/*
+	 * Pick fsize and lbn large enough that max length runs won't reach
+	 * either beginning or end of file
+	 */
+	const off_t filesize = 1 << 30;
+	int64_t lbn = 100;
 	int64_t pbn = 12345;
+	const ino_t ino = 42;
 	int fd;
 
 	expect_lookup(RELPATH, 42, filesize);
@@ -112,7 +116,7 @@ TEST_F(Bmap, bmap)
 TEST_F(Bmap, default_)
 {
 	struct fiobmap2_arg arg;
-	const off_t filesize = 1 << 20;
+	const off_t filesize = 1 << 30;
 	const ino_t ino = 42;
 	int64_t lbn;
 	int fd;

tests/sys/fs/fusefs/mockfs.cc

@@ -365,7 +365,7 @@ MockFS::MockFS(int max_readahead, bool allow_other, bool default_permissions,
 	m_daemon_id = NULL;
 	m_kernel_minor_version = kernel_minor_version;
 	m_maxreadahead = max_readahead;
-	m_maxwrite = max_write;
+	m_maxwrite = MIN(max_write, max_max_write);
 	m_nready = -1;
 	m_pm = pm;
 	m_time_gran = time_gran;

tests/sys/fs/fusefs/mockfs.hh

@@ -72,6 +72,14 @@ extern "C" {
 
 extern int verbosity;
 
+/*
+ * The maximum that a test case can set max_write, limited by the buffer
+ * supplied when reading from /dev/fuse.  This limitation is imposed by
+ * fusefs-libs, but not by the FUSE protocol.
+ */
+const uint32_t max_max_write = 0x20000;
+
+
 /* This struct isn't defined by fuse_kernel.h or libfuse, but it should be */
 struct fuse_create_out {
 	struct fuse_entry_out	entry;
@@ -138,8 +146,17 @@ struct fuse_init_out_7_22 {
 union fuse_payloads_in {
 	fuse_access_in	access;
 	fuse_bmap_in	bmap;
-	/* value is from fuse_kern_chan.c in fusefs-libs */
-	uint8_t		bytes[0x21000 - sizeof(struct fuse_in_header)];
+	/*
+	 * In fusefs-libs 3.4.2 and below the buffer size is fixed at 0x21000
+	 * minus the header sizes.  fusefs-libs 3.4.3 (and FUSE Protocol 7.29)
+	 * add a FUSE_MAX_PAGES option that allows it to be greater.
+	 *
+	 * See fuse_kern_chan.c in fusefs-libs 2.9.9 and below, or
+	 * FUSE_DEFAULT_MAX_PAGES_PER_REQ in fusefs-libs 3.4.3 and above.
+	 */
+	uint8_t		bytes[
+	    max_max_write + 0x1000 - sizeof(struct fuse_in_header)
+	];
 	fuse_create_in	create;
 	fuse_flush_in	flush;
 	fuse_fsync_in	fsync;

tests/sys/fs/fusefs/utils.cc

@@ -59,13 +59,6 @@ using namespace testing;
  */
 const uint32_t libfuse_max_write = 32 * getpagesize() + 0x1000 - 4096;
 
-/* 
- * Set the default max_write to a distinct value from MAXPHYS to catch bugs
- * that confuse the two.
- */
-const uint32_t default_max_write = MIN(libfuse_max_write, MAXPHYS / 2);
-
-
 /* Check that fusefs(4) is accessible and the current user can mount(2) */
 void check_environment()
 {
@@ -156,6 +149,12 @@ void FuseTest::SetUp() {
 	ASSERT_EQ(0, sysctlbyname(maxphys_node, &val, &size, NULL, 0))
 		<< strerror(errno);
 	m_maxphys = val;
+	/*
+	 * Set the default max_write to a distinct value from MAXPHYS to catch
+	 * bugs that confuse the two.
+	 */
+	if (m_maxwrite == 0)
+		m_maxwrite = MIN(libfuse_max_write, (uint32_t)m_maxphys / 2);
 
 	try {
 		m_mock = new MockFS(m_maxreadahead, m_allow_other,

tests/sys/fs/fusefs/utils.hh

@@ -55,7 +55,6 @@ const char *cache_mode_to_s(enum cache_mode cm);
 bool is_unsafe_aio_enabled(void);
 
 extern const uint32_t libfuse_max_write;
-extern const uint32_t default_max_write;
 class FuseTest : public ::testing::Test {
 	protected:
 	uint32_t m_maxreadahead;
@@ -80,7 +79,7 @@ class FuseTest : public ::testing::Test {
 
 	FuseTest():
 		m_maxreadahead(0),
-		m_maxwrite(default_max_write),
+		m_maxwrite(0),
 		m_init_flags(0),
 		m_allow_other(false),
 		m_default_permissions(false),

tests/sys/fs/fusefs/write.cc

@@ -166,6 +166,7 @@ class WriteBackAsync: public WriteBack {
 public:
 virtual void SetUp() {
 	m_async = true;
+	m_maxwrite = 65536;
 	WriteBack::SetUp();
 }
 };
@@ -194,6 +195,19 @@ virtual void SetUp() {
 }
 };
 
+/* Tests relating to the server's max_write property */
+class WriteMaxWrite: public Write {
+public:
+virtual void SetUp() {
+	/*
+	 * For this test, m_maxwrite must be less than either m_maxbcachebuf or
+	 * maxphys.
+	 */
+	m_maxwrite = 32768;
+	Write::SetUp();
+}
+};
+
 void sigxfsz_handler(int __unused sig) {
 	Write::s_sigxfsz = 1;
 }
@@ -643,7 +657,7 @@ TEST_F(Write, write)
 }
 
 /* fuse(4) should not issue writes of greater size than the daemon requests */
-TEST_F(Write, write_large)
+TEST_F(WriteMaxWrite, write)
 {
 	const char FULLPATH[] = "mountpoint/some_file.txt";
 	const char RELPATH[] = "some_file.txt";
@@ -653,6 +667,8 @@ TEST_F(Write, write_large)
 	ssize_t halfbufsize, bufsize;
 
 	halfbufsize = m_mock->m_maxwrite;
+	if (halfbufsize >= m_maxbcachebuf || halfbufsize >= m_maxphys)
+		GTEST_SKIP() << "Must lower m_maxwrite for this test";
 	bufsize = halfbufsize * 2;
 	contents = (int*)malloc(bufsize);
 	ASSERT_NE(nullptr, contents);