fuse(4): add tests for FUSE_READ

PR:		236379
PR:		236466
PR:		236472
Sponsored by:	The FreeBSD Foundation

tests/sys/fs/fuse/Makefile

@@ -13,6 +13,7 @@ ATF_TESTS_CXX+=	lookup
 ATF_TESTS_CXX+=	mkdir
 ATF_TESTS_CXX+=	mknod
 ATF_TESTS_CXX+=	open
+ATF_TESTS_CXX+=	read
 ATF_TESTS_CXX+=	readlink
 ATF_TESTS_CXX+=	release
 ATF_TESTS_CXX+=	rename
@@ -68,6 +69,11 @@ SRCS.open+=	mockfs.cc
 SRCS.open+=	open.cc
 SRCS.open+=	utils.cc
 
+SRCS.read+=	getmntopts.c
+SRCS.read+=	mockfs.cc
+SRCS.read+=	read.cc
+SRCS.read+=	utils.cc
+
 SRCS.readlink+=	getmntopts.c
 SRCS.readlink+=	mockfs.cc
 SRCS.readlink+=	readlink.cc

tests/sys/fs/fuse/mockfs.cc

@@ -165,12 +165,13 @@ void debug_fuseop(const mockfs_buf_in *in)
 	printf("\n");
 }
 
-MockFS::MockFS() {
+MockFS::MockFS(int max_readahead) {
 	struct iovec *iov = NULL;
 	int iovlen = 0;
 	char fdstr[15];
 
 	m_daemon_id = NULL;
+	m_maxreadahead = max_readahead;
 	quit = 0;
 
 	/*
@@ -247,8 +248,7 @@ void MockFS::init() {
 	m_max_write = MIN(default_max_write, MAXPHYS / 2);
 	out->body.init.max_write = m_max_write;
 
-	/* Default max_readahead is UINT_MAX, though it can be lowered */
+	out->body.init.max_readahead = m_maxreadahead;
-	out->body.init.max_readahead = UINT_MAX;
 	SET_OUT_HEADER_LEN(out, init);
 	write(m_fuse_fd, out, out->header.len);
 

tests/sys/fs/fuse/mockfs.hh

@@ -99,7 +99,7 @@ union fuse_payloads_out {
 	fuse_attr_out		attr;
 	fuse_create_out		create;
 	/* The protocol places no limits on the size of bytes */
-	uint8_t			bytes[0x2000];
+	uint8_t			bytes[0x20000];
 	fuse_entry_out		entry;
 	fuse_init_out		init;
 	fuse_open_out		open;
@@ -152,6 +152,9 @@ class MockFS {
 	/* file descriptor of /dev/fuse control device */
 	int m_fuse_fd;
 	
+	/* The max_readahead filesystem option */
+	uint32_t m_maxreadahead;
+
 	/* pid of the test process */
 	pid_t m_pid;
 
@@ -175,7 +178,7 @@ class MockFS {
 	uint32_t m_max_write;
 
 	/* Create a new mockfs and mount it to a tempdir */
-	MockFS();
+	MockFS(int max_readahead);
 	virtual ~MockFS();
 
 	/* Kill the filesystem daemon without unmounting the filesystem */

tests/sys/fs/fuse/read.cc

@@ -0,0 +1,566 @@
+/*-
+ * Copyright (c) 2019 The FreeBSD Foundation
+ *
+ * This software was developed by BFF Storage Systems, LLC under sponsorship
+ * from the FreeBSD Foundation.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+extern "C" {
+#include <sys/types.h>
+#include <sys/mman.h>
+#include <sys/socket.h>
+#include <sys/sysctl.h>
+#include <sys/uio.h>
+
+#include <aio.h>
+#include <fcntl.h>
+#include <unistd.h>
+}
+
+#include "mockfs.hh"
+#include "utils.hh"
+
+using namespace testing;
+
+class Read: public FuseTest {
+
+public:
+const static uint64_t FH = 0xdeadbeef1a7ebabe;
+void expect_getattr(uint64_t ino, uint64_t size)
+{
+	/* Until the attr cache is working, we may send an additional GETATTR */
+	EXPECT_CALL(*m_mock, process(
+		ResultOf([=](auto in) {
+			return (in->header.opcode == FUSE_GETATTR &&
+				in->header.nodeid == ino);
+		}, Eq(true)),
+		_)
+	).WillRepeatedly(Invoke([=](auto in, auto out) {
+		out->header.unique = in->header.unique;
+		SET_OUT_HEADER_LEN(out, attr);
+		out->body.attr.attr.ino = ino;	// Must match nodeid
+		out->body.attr.attr.mode = S_IFREG | 0644;
+		out->body.attr.attr.size = size;
+	}));
+
+}
+
+void expect_lookup(const char *relpath, uint64_t ino)
+{
+	EXPECT_LOOKUP(1, relpath).WillRepeatedly(Invoke([=](auto in, auto out) {
+		out->header.unique = in->header.unique;
+		SET_OUT_HEADER_LEN(out, entry);
+		out->body.entry.attr.mode = S_IFREG | 0644;
+		out->body.entry.nodeid = ino;
+		out->body.entry.attr_valid = UINT64_MAX;
+	}));
+}
+
+void expect_open(uint64_t ino, uint32_t flags, int times)
+{
+	EXPECT_CALL(*m_mock, process(
+		ResultOf([=](auto in) {
+			return (in->header.opcode == FUSE_OPEN &&
+				in->header.nodeid == ino);
+		}, Eq(true)),
+		_)
+	).Times(times)
+	.WillRepeatedly(Invoke([=](auto in, auto out) {
+		out->header.unique = in->header.unique;
+		out->header.len = sizeof(out->header);
+		SET_OUT_HEADER_LEN(out, open);
+		out->body.open.fh = Read::FH;
+		out->body.open.open_flags = flags;
+	}));
+}
+
+void expect_read(uint64_t ino, uint64_t offset, uint64_t isize, uint64_t osize,
+		const void *contents)
+{
+	EXPECT_CALL(*m_mock, process(
+		ResultOf([=](auto in) {
+			return (in->header.opcode == FUSE_READ &&
+				in->header.nodeid == ino &&
+				in->body.read.fh == Read::FH &&
+				in->body.read.offset == offset &&
+				in->body.read.size == isize);
+		}, Eq(true)),
+		_)
+	).WillOnce(Invoke([=](auto in, auto out) {
+		out->header.unique = in->header.unique;
+		out->header.len = sizeof(struct fuse_out_header) + osize;
+		memmove(out->body.bytes, contents, osize);
+	})).RetiresOnSaturation();
+}
+};
+
+class AioRead: public Read {
+virtual void SetUp() {
+	const char *node = "vfs.aio.enable_unsafe";
+	int val = 0;
+	size_t size = sizeof(val);
+
+	ASSERT_EQ(0, sysctlbyname(node, &val, &size, NULL, 0))
+		<< strerror(errno);
+	// TODO: With GoogleTest 1.8.2, use SKIP instead
+	if (!val)
+		FAIL() << "vfs.aio.enable_unsafe must be set for this test";
+	FuseTest::SetUp();
+}
+};
+
+class ReadAhead: public Read, public WithParamInterface<uint32_t> {
+	virtual void SetUp() {
+		m_maxreadahead = GetParam();
+		Read::SetUp();
+	}
+};
+
+/* AIO reads need to set the header's pid field correctly */
+/* https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=236379 */
+TEST_F(AioRead, aio_read)
+{
+	const char FULLPATH[] = "mountpoint/some_file.txt";
+	const char RELPATH[] = "some_file.txt";
+	const char *CONTENTS = "abcdefgh";
+	uint64_t ino = 42;
+	int fd;
+	ssize_t bufsize = strlen(CONTENTS);
+	char buf[bufsize];
+	struct aiocb iocb, *piocb;
+
+	expect_lookup(RELPATH, ino);
+	expect_open(ino, 0, 1);
+	expect_getattr(ino, bufsize);
+	expect_read(ino, 0, bufsize, bufsize, CONTENTS);
+
+	fd = open(FULLPATH, O_RDONLY);
+	ASSERT_LE(0, fd) << strerror(errno);
+
+	iocb.aio_nbytes = bufsize;
+	iocb.aio_fildes = fd;
+	iocb.aio_buf = buf;
+	iocb.aio_offset = 0;
+	iocb.aio_sigevent.sigev_notify = SIGEV_NONE;
+	ASSERT_EQ(0, aio_read(&iocb)) << strerror(errno);
+	ASSERT_EQ(bufsize, aio_waitcomplete(&piocb, NULL)) << strerror(errno);
+	ASSERT_EQ(0, memcmp(buf, CONTENTS, bufsize));
+	/* Deliberately leak fd.  close(2) will be tested in release.cc */
+}
+
+/* 0-length reads shouldn't cause any confusion */
+TEST_F(Read, direct_io_read_nothing)
+{
+	const char FULLPATH[] = "mountpoint/some_file.txt";
+	const char RELPATH[] = "some_file.txt";
+	uint64_t ino = 42;
+	int fd;
+	uint64_t offset = 100;
+	char buf[80];
+
+	expect_lookup(RELPATH, ino);
+	expect_open(ino, FOPEN_DIRECT_IO, 1);
+	expect_getattr(ino, offset + 1000);
+
+	fd = open(FULLPATH, O_RDONLY);
+	ASSERT_LE(0, fd) << strerror(errno);
+
+	ASSERT_EQ(0, pread(fd, buf, 0, offset)) << strerror(errno);
+	/* Deliberately leak fd.  close(2) will be tested in release.cc */
+}
+
+/* 
+ * With direct_io, reads should not fill the cache.  They should go straight to
+ * the daemon
+ */
+TEST_F(Read, direct_io_pread)
+{
+	const char FULLPATH[] = "mountpoint/some_file.txt";
+	const char RELPATH[] = "some_file.txt";
+	const char *CONTENTS = "abcdefgh";
+	uint64_t ino = 42;
+	int fd;
+	uint64_t offset = 100;
+	ssize_t bufsize = strlen(CONTENTS);
+	char buf[bufsize];
+
+	expect_lookup(RELPATH, ino);
+	expect_open(ino, FOPEN_DIRECT_IO, 1);
+	expect_getattr(ino, offset + bufsize);
+	expect_read(ino, offset, bufsize, bufsize, CONTENTS);
+
+	fd = open(FULLPATH, O_RDONLY);
+	ASSERT_LE(0, fd) << strerror(errno);
+
+	ASSERT_EQ(bufsize, pread(fd, buf, bufsize, offset)) << strerror(errno);
+	ASSERT_EQ(0, memcmp(buf, CONTENTS, bufsize));
+	/* Deliberately leak fd.  close(2) will be tested in release.cc */
+}
+
+/* 
+ * With direct_io, filesystems are allowed to return less data than is
+ * requested.  fuse(4) should return a short read to userland.
+ */
+TEST_F(Read, direct_io_short_read)
+{
+	const char FULLPATH[] = "mountpoint/some_file.txt";
+	const char RELPATH[] = "some_file.txt";
+	const char *CONTENTS = "abcdefghijklmnop";
+	uint64_t ino = 42;
+	int fd;
+	uint64_t offset = 100;
+	ssize_t bufsize = strlen(CONTENTS);
+	ssize_t halfbufsize = bufsize / 2;
+	char buf[bufsize];
+
+	expect_lookup(RELPATH, ino);
+	expect_open(ino, FOPEN_DIRECT_IO, 1);
+	expect_getattr(ino, offset + bufsize);
+	expect_read(ino, offset, bufsize, halfbufsize, CONTENTS);
+
+	fd = open(FULLPATH, O_RDONLY);
+	ASSERT_LE(0, fd) << strerror(errno);
+
+	ASSERT_EQ(halfbufsize, pread(fd, buf, bufsize, offset))
+		<< strerror(errno);
+	ASSERT_EQ(0, memcmp(buf, CONTENTS, halfbufsize));
+	/* Deliberately leak fd.  close(2) will be tested in release.cc */
+}
+
+TEST_F(Read, eio)
+{
+	const char FULLPATH[] = "mountpoint/some_file.txt";
+	const char RELPATH[] = "some_file.txt";
+	const char *CONTENTS = "abcdefgh";
+	uint64_t ino = 42;
+	int fd;
+	ssize_t bufsize = strlen(CONTENTS);
+	char buf[bufsize];
+
+	expect_lookup(RELPATH, ino);
+	expect_open(ino, 0, 1);
+	expect_getattr(ino, bufsize);
+	EXPECT_CALL(*m_mock, process(
+		ResultOf([=](auto in) {
+			return (in->header.opcode == FUSE_READ);
+		}, Eq(true)),
+		_)
+	).WillOnce(Invoke(ReturnErrno(EIO)));
+
+	fd = open(FULLPATH, O_RDONLY);
+	ASSERT_LE(0, fd) << strerror(errno);
+
+	ASSERT_EQ(-1, read(fd, buf, bufsize)) << strerror(errno);
+	ASSERT_EQ(EIO, errno);
+	/* Deliberately leak fd.  close(2) will be tested in release.cc */
+}
+
+TEST_F(Read, mmap)
+{
+	const char FULLPATH[] = "mountpoint/some_file.txt";
+	const char RELPATH[] = "some_file.txt";
+	const char *CONTENTS = "abcdefgh";
+	uint64_t ino = 42;
+	int fd;
+	ssize_t len;
+	ssize_t bufsize = strlen(CONTENTS);
+	void *p;
+	//char buf[bufsize];
+
+	len = getpagesize();
+
+	expect_lookup(RELPATH, ino);
+	expect_open(ino, 0, 1);
+	expect_getattr(ino, bufsize);
+	/* mmap may legitimately try to read more data than is available */
+	EXPECT_CALL(*m_mock, process(
+		ResultOf([=](auto in) {
+			return (in->header.opcode == FUSE_READ &&
+				in->header.nodeid == ino &&
+				in->body.read.fh == Read::FH &&
+				in->body.read.offset == 0 &&
+				in->body.read.size >= bufsize);
+		}, Eq(true)),
+		_)
+	).WillOnce(Invoke([=](auto in, auto out) {
+		out->header.unique = in->header.unique;
+		out->header.len = sizeof(struct fuse_out_header) + bufsize;
+		memmove(out->body.bytes, CONTENTS, bufsize);
+	}));
+
+	fd = open(FULLPATH, O_RDONLY);
+	ASSERT_LE(0, fd) << strerror(errno);
+
+	p = mmap(NULL, len, PROT_READ, MAP_SHARED, fd, 0);
+	ASSERT_NE(MAP_FAILED, p) << strerror(errno);
+
+	ASSERT_EQ(0, memcmp(p, CONTENTS, bufsize));
+
+	ASSERT_EQ(0, munmap(p, len)) << strerror(errno);
+	/* Deliberately leak fd.  close(2) will be tested in release.cc */
+}
+
+/*
+ * Just as when FOPEN_DIRECT_IO is used, reads with O_DIRECT should bypass
+ * cache and to straight to the daemon
+ */
+TEST_F(Read, o_direct)
+{
+	const char FULLPATH[] = "mountpoint/some_file.txt";
+	const char RELPATH[] = "some_file.txt";
+	const char *CONTENTS = "abcdefgh";
+	uint64_t ino = 42;
+	int fd;
+	ssize_t bufsize = strlen(CONTENTS);
+	char buf[bufsize];
+
+	expect_lookup(RELPATH, ino);
+	expect_open(ino, 0, 1);
+	expect_getattr(ino, bufsize);
+	expect_read(ino, 0, bufsize, bufsize, CONTENTS);
+
+	fd = open(FULLPATH, O_RDONLY);
+	ASSERT_LE(0, fd) << strerror(errno);
+
+	// Fill the cache
+	ASSERT_EQ(bufsize, read(fd, buf, bufsize)) << strerror(errno);
+	ASSERT_EQ(0, memcmp(buf, CONTENTS, bufsize));
+
+	// Reads with o_direct should bypass the cache
+	expect_read(ino, 0, bufsize, bufsize, CONTENTS);
+	ASSERT_EQ(0, fcntl(fd, F_SETFL, O_DIRECT)) << strerror(errno);
+	ASSERT_EQ(0, lseek(fd, 0, SEEK_SET)) << strerror(errno);
+	ASSERT_EQ(bufsize, read(fd, buf, bufsize)) << strerror(errno);
+	ASSERT_EQ(0, memcmp(buf, CONTENTS, bufsize));
+	
+	/* Deliberately leak fd.  close(2) will be tested in release.cc */
+}
+
+TEST_F(Read, pread)
+{
+	const char FULLPATH[] = "mountpoint/some_file.txt";
+	const char RELPATH[] = "some_file.txt";
+	const char *CONTENTS = "abcdefgh";
+	uint64_t ino = 42;
+	int fd;
+	/* 
+	 * Set offset to a maxbcachebuf boundary so we'll be sure what offset
+	 * to read from.  Without this, the read might start at a lower offset.
+	 */
+	uint64_t offset = m_maxbcachebuf;
+	ssize_t bufsize = strlen(CONTENTS);
+	char buf[bufsize];
+
+	expect_lookup(RELPATH, ino);
+	expect_open(ino, 0, 1);
+	expect_getattr(ino, offset + bufsize);
+	expect_read(ino, offset, bufsize, bufsize, CONTENTS);
+
+	fd = open(FULLPATH, O_RDONLY);
+	ASSERT_LE(0, fd) << strerror(errno);
+
+	ASSERT_EQ(bufsize, pread(fd, buf, bufsize, offset)) << strerror(errno);
+	ASSERT_EQ(0, memcmp(buf, CONTENTS, bufsize));
+	/* Deliberately leak fd.  close(2) will be tested in release.cc */
+}
+
+TEST_F(Read, read)
+{
+	const char FULLPATH[] = "mountpoint/some_file.txt";
+	const char RELPATH[] = "some_file.txt";
+	const char *CONTENTS = "abcdefgh";
+	uint64_t ino = 42;
+	int fd;
+	ssize_t bufsize = strlen(CONTENTS);
+	char buf[bufsize];
+
+	expect_lookup(RELPATH, ino);
+	expect_open(ino, 0, 1);
+	expect_getattr(ino, bufsize);
+	expect_read(ino, 0, bufsize, bufsize, CONTENTS);
+
+	fd = open(FULLPATH, O_RDONLY);
+	ASSERT_LE(0, fd) << strerror(errno);
+
+	ASSERT_EQ(bufsize, read(fd, buf, bufsize)) << strerror(errno);
+	ASSERT_EQ(0, memcmp(buf, CONTENTS, bufsize));
+	/* Deliberately leak fd.  close(2) will be tested in release.cc */
+}
+
+/* If the filesystem allows it, the kernel should try to readahead */
+TEST_F(Read, default_readahead)
+{
+	const char FULLPATH[] = "mountpoint/some_file.txt";
+	const char RELPATH[] = "some_file.txt";
+	const char *CONTENTS0 = "abcdefghijklmnop";
+	uint64_t ino = 42;
+	int fd;
+	ssize_t bufsize = 8;
+	/* hard-coded in fuse_internal.c */
+	size_t default_maxreadahead = 65536;
+	ssize_t filesize = default_maxreadahead * 2;
+	char *contents;
+	char buf[bufsize];
+	const char *contents1 = CONTENTS0 + bufsize;
+
+	contents = (char*)calloc(1, filesize);
+	ASSERT_NE(NULL, contents);
+	memmove(contents, CONTENTS0, strlen(CONTENTS0));
+
+	expect_lookup(RELPATH, ino);
+	expect_open(ino, 0, 1);
+	expect_getattr(ino, filesize);
+	expect_read(ino, 0, default_maxreadahead, default_maxreadahead,
+		contents);
+
+	fd = open(FULLPATH, O_RDONLY);
+	ASSERT_LE(0, fd) << strerror(errno);
+
+	ASSERT_EQ(bufsize, read(fd, buf, bufsize)) << strerror(errno);
+	ASSERT_EQ(0, memcmp(buf, CONTENTS0, bufsize));
+
+	/* A subsequent read should be serviced by cache */
+	ASSERT_EQ(bufsize, read(fd, buf, bufsize)) << strerror(errno);
+	ASSERT_EQ(0, memcmp(buf, contents1, bufsize));
+	/* Deliberately leak fd.  close(2) will be tested in release.cc */
+}
+
+/* Reading with sendfile should work (though it obviously won't be 0-copy) */
+TEST_F(Read, sendfile)
+{
+	const char FULLPATH[] = "mountpoint/some_file.txt";
+	const char RELPATH[] = "some_file.txt";
+	const char *CONTENTS = "abcdefgh";
+	uint64_t ino = 42;
+	int fd;
+	ssize_t bufsize = strlen(CONTENTS);
+	char buf[bufsize];
+	int sp[2];
+	off_t sbytes;
+
+	expect_lookup(RELPATH, ino);
+	expect_open(ino, 0, 1);
+	expect_getattr(ino, bufsize);
+	/* Like mmap, sendfile may request more data than is available */
+	EXPECT_CALL(*m_mock, process(
+		ResultOf([=](auto in) {
+			return (in->header.opcode == FUSE_READ &&
+				in->header.nodeid == ino &&
+				in->body.read.fh == Read::FH &&
+				in->body.read.offset == 0 &&
+				in->body.read.size >= bufsize);
+		}, Eq(true)),
+		_)
+	).WillOnce(Invoke([=](auto in, auto out) {
+		out->header.unique = in->header.unique;
+		out->header.len = sizeof(struct fuse_out_header) + bufsize;
+		memmove(out->body.bytes, CONTENTS, bufsize);
+	}));
+
+	ASSERT_EQ(0, socketpair(PF_LOCAL, SOCK_STREAM, 0, sp))
+		<< strerror(errno);
+	fd = open(FULLPATH, O_RDONLY);
+	ASSERT_LE(0, fd) << strerror(errno);
+
+	ASSERT_EQ(0, sendfile(fd, sp[1], 0, bufsize, NULL, &sbytes, 0))
+		<< strerror(errno);
+	ASSERT_EQ(bufsize, read(sp[0], buf, bufsize)) << strerror(errno);
+	ASSERT_EQ(0, memcmp(buf, CONTENTS, bufsize));
+
+	close(sp[1]);
+	close(sp[0]);
+	/* Deliberately leak fd.  close(2) will be tested in release.cc */
+}
+
+/* sendfile should fail gracefully if fuse declines the read */
+/* https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=236466 */
+TEST_F(Read, DISABLED_sendfile_eio)
+{
+	const char FULLPATH[] = "mountpoint/some_file.txt";
+	const char RELPATH[] = "some_file.txt";
+	const char *CONTENTS = "abcdefgh";
+	uint64_t ino = 42;
+	int fd;
+	ssize_t bufsize = strlen(CONTENTS);
+	int sp[2];
+	off_t sbytes;
+
+	expect_lookup(RELPATH, ino);
+	expect_open(ino, 0, 1);
+	expect_getattr(ino, bufsize);
+	EXPECT_CALL(*m_mock, process(
+		ResultOf([=](auto in) {
+			return (in->header.opcode == FUSE_READ);
+		}, Eq(true)),
+		_)
+	).WillOnce(Invoke(ReturnErrno(EIO)));
+
+	ASSERT_EQ(0, socketpair(PF_LOCAL, SOCK_STREAM, 0, sp))
+		<< strerror(errno);
+	fd = open(FULLPATH, O_RDONLY);
+	ASSERT_LE(0, fd) << strerror(errno);
+
+	ASSERT_NE(0, sendfile(fd, sp[1], 0, bufsize, NULL, &sbytes, 0));
+
+	close(sp[1]);
+	close(sp[0]);
+	/* Deliberately leak fd.  close(2) will be tested in release.cc */
+}
+
+/* fuse(4) should honor the filesystem's requested m_readahead parameter */
+/* https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=236472 */
+TEST_P(ReadAhead, DISABLED_readahead) {
+	const char FULLPATH[] = "mountpoint/some_file.txt";
+	const char RELPATH[] = "some_file.txt";
+	const char *CONTENTS0 = "abcdefghijklmnop";
+	uint64_t ino = 42;
+	int fd;
+	ssize_t bufsize = 8;
+	ssize_t filesize = m_maxbcachebuf * 2;
+	char *contents;
+	char buf[bufsize];
+
+	ASSERT_TRUE(GetParam() < (uint32_t)m_maxbcachebuf)
+		<< "Test assumes that max_readahead < maxbcachebuf";
+
+	contents = (char*)calloc(1, filesize);
+	ASSERT_NE(NULL, contents);
+	memmove(contents, CONTENTS0, strlen(CONTENTS0));
+
+	expect_lookup(RELPATH, ino);
+	expect_open(ino, 0, 1);
+	expect_getattr(ino, filesize);
+	/* fuse(4) should only read ahead the allowed amount */
+	expect_read(ino, 0, GetParam(), GetParam(), contents);
+
+	fd = open(FULLPATH, O_RDONLY);
+	ASSERT_LE(0, fd) << strerror(errno);
+
+	ASSERT_EQ(bufsize, read(fd, buf, bufsize)) << strerror(errno);
+	ASSERT_EQ(0, memcmp(buf, CONTENTS0, bufsize));
+
+	/* Deliberately leak fd.  close(2) will be tested in release.cc */
+}
+
+INSTANTIATE_TEST_CASE_P(RA, ReadAhead, ::testing::Values(0u, 2048u));

tests/sys/fs/fuse/utils.cc

@@ -65,6 +65,22 @@ class FuseEnv: public ::testing::Environment {
 	}
 };
 
+void FuseTest::SetUp() {
+	const char *node = "vfs.maxbcachebuf";
+	int val = 0;
+	size_t size = sizeof(val);
+
+	ASSERT_EQ(0, sysctlbyname(node, &val, &size, NULL, 0))
+		<< strerror(errno);
+	m_maxbcachebuf = val;
+
+	try {
+		m_mock = new MockFS(m_maxreadahead);
+	} catch (std::system_error err) {
+		FAIL() << err.what();
+	}
+}
+
 static void usage(char* progname) {
 	fprintf(stderr, "Usage: %s [-v]\n\t-v increase verbosity\n", progname);
 	exit(2);

tests/sys/fs/fuse/utils.hh

@@ -29,16 +29,20 @@
 
 class FuseTest : public ::testing::Test {
 	protected:
+	uint32_t m_maxreadahead;
 	MockFS *m_mock = NULL;
 
 	public:
-	virtual void SetUp() {
+	int m_maxbcachebuf;
-		try {
+
-			m_mock = new MockFS{};
+	/*
-		} catch (std::system_error err) {
+	 * libfuse's default max_readahead is UINT_MAX, though it can be
-			FAIL() << err.what();
+	 * lowered
-		}
+	 */
-	}
+	FuseTest(): FuseTest(UINT_MAX) {}
+	FuseTest(uint32_t maxreadahead): m_maxreadahead(maxreadahead) {}
+
+	virtual void SetUp();
 
 	virtual void TearDown() {
 		if (m_mock)

tests/sys/fs/fuse/write.cc

@@ -56,20 +56,6 @@ using namespace testing;
 class Write: public FuseTest {
 
 public:
-int m_maxbcachebuf;
-
-virtual void SetUp() {
-	const char *node = "vfs.maxbcachebuf";
-	int val = 0;
-	size_t size = sizeof(val);
-
-	ASSERT_EQ(0, sysctlbyname(node, &val, &size, NULL, 0))
-		<< strerror(errno);
-	m_maxbcachebuf = val;
-
-	FuseTest::SetUp();
-}
-
 const static uint64_t FH = 0xdeadbeef1a7ebabe;
 void expect_getattr(uint64_t ino, uint64_t size)
 {
@@ -137,7 +123,6 @@ void expect_read(uint64_t ino, uint64_t offset, uint64_t size,
 		out->header.len = sizeof(struct fuse_out_header) + size;
 		memmove(out->body.bytes, contents, size);
 	})).RetiresOnSaturation();
-
 }
 
 void expect_release(uint64_t ino, ProcessMockerT r)