[PATCH] fstests: generic test for preadv2 behavior on linux

[Milosz Tanski]

preadv2 is a new syscall introduced that is like preadv2 but with flag
argument. The first use case of this is to let us add a flag to perform a
non-blocking file using the page cache.
---
 src/Makefile           |   2 +-
 src/preadv2-pwritev2.h |  52 +++++++++++++++++
 src/preadv2.c          | 150 +++++++++++++++++++++++++++++++++++++++++++++++++
 tests/generic/067      |  85 ++++++++++++++++++++++++++++
 tests/generic/067.out  |   9 +++
 tests/generic/group    |   1 +
 6 files changed, 298 insertions(+), 1 deletion(-)
 create mode 100644 src/preadv2-pwritev2.h
 create mode 100644 src/preadv2.c
 create mode 100755 tests/generic/067
 create mode 100644 tests/generic/067.out

diff --git a/src/Makefile b/src/Makefile
index 4781736..f7d3681 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -19,7 +19,7 @@ LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \
 	bulkstat_unlink_test_modified t_dir_offset t_futimens t_immutable \
 	stale_handle pwrite_mmap_blocked t_dir_offset2 seek_sanity_test \
 	seek_copy_test t_readdir_1 t_readdir_2 fsync-tester nsexec cloner \
-	renameat2 t_getcwd e4compact
+	renameat2 t_getcwd e4compact preadv2
 
 SUBDIRS =
 
diff --git a/src/preadv2-pwritev2.h b/src/preadv2-pwritev2.h
new file mode 100644
index 0000000..786e524
--- /dev/null
+++ b/src/preadv2-pwritev2.h
@@ -0,0 +1,52 @@
+#ifndef PREADV2_PWRITEV2_H
+#define PREADV2_PWRITEV2_H
+
+#include "global.h"
+
+#ifndef HAVE_PREADV2
+#include <sys/syscall.h>
+
+#if !defined(SYS_preadv2) && defined(__x86_64__)
+#define SYS_preadv2 323
+#define SYS_pwritev2 324
+#endif
+
+#if !defined (SYS_preadv2) && defined(__i386__)
+#define SYS_preadv2 359
+#define SYS_pwritev2 360
+#endif
+
+/* LO_HI_LONG taken from glibc */
+#define LO_HI_LONG(val)							\
+  (off_t) val,                                                          \
+  (off_t) ((((uint64_t) (val)) >> (sizeof (long) * 4)) >> (sizeof (long) * 4))
+
+static inline ssize_t
+preadv2(int fd, const struct iovec *iov, int iovcnt, off_t offset, int flags)
+{
+#ifdef SYS_preadv2
+        return syscall(SYS_preadv2, fd, iov, iovcnt, LO_HI_LONG(offset),
+		       flags);
+#else
+	errno = ENOSYS;
+	return -1;
+#endif
+}
+
+static inline ssize_t
+pwritev2(int fd, const struct iovec *iov, int iovcnt, off_t offset, int flags)
+{
+#ifdef SYS_pwritev2
+        return syscall(SYS_pwritev2, fd, iov, iovcnt, LO_HI_LONG(offset),
+		       flags);
+#else
+	errno = ENOSYS;
+	return -1;
+#endif
+}
+
+#define RWF_NONBLOCK	0x00000001
+#define RWF_DSYNC	0x00000002
+
+#endif /* HAVE_PREADV2 */
+#endif /* PREADV2_PWRITEV2_H */
diff --git a/src/preadv2.c b/src/preadv2.c
new file mode 100644
index 0000000..a4f89b5
--- /dev/null
+++ b/src/preadv2.c
@@ -0,0 +1,150 @@
+/*
+ * Copyright 2014 Red Hat, Inc.  All rights reserved.
+ * Copyright 2015 Milosz Tanski
+ *
+ * License: GPLv2
+ *
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <getopt.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <linux/fs.h> /* for RWF_NONBLOCK */
+
+/*
+ * Once preadv2 is part of the upstream kernel and there is glibc support for
+ * it. We'll add support for preadv2 to xfs_io and this will be unnecessary.
+ */
+#include "preadv2-pwritev2.h"
+
+/*
+ * Test to see if the system call is implemented.  If -EINVAL or -ENOSYS
+ * are returned, consider the call unimplemented.  All other errors are
+ * considered success.
+ *
+ * Returns: 0 if the system call is implemented, 1 if the system call
+ * is not implemented.
+ */
+int
+preadv2_check(int fd)
+{
+	int ret;
+	struct iovec iov[] = {};
+
+	/* 0 length read; just check iof the syscall is there.
+         *
+         * - 0 length iovec
+         * - Position is -1 (eg. use current position)
+         */
+	ret = preadv2(fd, iov, 0, -1, 0);
+
+	if (ret < 0) {
+		if (errno == ENOSYS || errno == EINVAL)
+			return 1;
+	}
+
+	return 0;
+}
+
+void
+usage(char *prog)
+{
+	fprintf(stderr, "Usage: %s [-v] [-ctdw] [-n] -p POS -l LEN <filename>\n\n", prog);
+	fprintf(stderr, "General arguments:\n");
+	fprintf(stderr, "  -v Verify that the syscall is supported and quit:\n");
+	fprintf(stderr, "\n");
+	fprintf(stderr, "Open arguments:\n");
+	fprintf(stderr, "  -c Open file with O_CREAT flag\n");
+	fprintf(stderr, "  -t Open file with O_TRUNC flag\n");
+	fprintf(stderr, "  -d Open file with O_DIRECT flag\n");
+	fprintf(stderr, "  -w Open file with O_RDWR flag vs O_RDONLY (default)\n");
+	fprintf(stderr, "\n");
+	fprintf(stderr, "preadv2 arguments:\n");
+	fprintf(stderr, "  -n use RWF_NONBLOCK when performing read\n");
+	fprintf(stderr, "  -p POS offset file to read at\n");
+	fprintf(stderr, "  -l LEN length of file data to read\n");
+	fprintf(stderr, "\n");
+	fflush(stderr);
+}
+
+int
+main(int argc, char **argv)
+{
+	int fd;
+	int ret;
+	int opt;
+	off_t pos = -1;
+	struct iovec iov = { NULL, 0 };
+	int o_flags = 0;
+	int r_flags = 0;
+	char *filename;
+
+	while ((opt = getopt(argc, argv, "vctdwnp:l:")) != -1) {
+		switch (opt) {
+		case 'v':
+			/*
+			 * See if we were called to check for availability of
+			 * sys_preadv2. STDIN is okay, since we do a zero
+			 * length read (see man 2 read).
+			 */
+			ret = preadv2_check(STDIN_FILENO);
+			exit(ret);
+		case 'c':
+			o_flags |= O_CREAT;
+			break;
+		case 't':
+			o_flags |= O_TRUNC;
+			break;
+		case 'd':
+			o_flags |= O_DIRECT;
+			break;
+		case 'w':
+			o_flags |= O_RDWR;
+			break;
+		case 'n':
+			r_flags |= RWF_NONBLOCK;
+			break;
+		case 'p':
+			pos = atoll(optarg);
+			break;
+		case 'l':
+			iov.iov_len = atoll(optarg);
+			break;
+		default:
+			fprintf(stderr, "invalid option: %c\n", opt);
+			usage(argv[0]);
+			exit(1);
+		}
+	}
+
+	if (optind >= argc) {
+		usage(argv[0]);
+		exit(1);
+	}
+
+	if ((o_flags & O_RDWR) != O_RDWR)
+		o_flags |= O_RDONLY;
+
+	if ((iov.iov_base = malloc(iov.iov_len)) == NULL) {
+		perror("malloc");
+		exit(1);
+	}
+
+	filename = argv[optind];
+	fd = open(filename, o_flags);
+
+	if (fd < 0) {
+		perror("open");
+		exit(1);
+	}
+
+	if ((ret = preadv2(fd, &iov, 1, pos, r_flags)) == -1) {
+		perror("preadv2");
+		exit(ret);
+	}
+
+	free(iov.iov_base);
+	exit(0);
+}
diff --git a/tests/generic/067 b/tests/generic/067
new file mode 100755
index 0000000..4cc58f8
--- /dev/null
+++ b/tests/generic/067
@@ -0,0 +1,85 @@
+#! /bin/bash
+# FS QA Test No. 067
+#
+# Test for the preadv2 syscall
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2015 Milosz Tanski <mtanski@xxxxxxxxx>.  All Rights Reserved.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it would be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write the Free Software Foundation,
+# Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+#-----------------------------------------------------------------------
+#
+
+seq=`basename $0`
+seqres=$RESULT_DIR/$seq
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1	# failure is the default!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+    cd /
+    rm -f $tmp.*
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+# real QA test starts here
+
+# Modify as appropriate.
+_supported_fs generic
+_supported_os Linux
+_require_test
+
+# test file we'll be using
+file=$SCRATCH_MNT/067.preadv2.$$
+
+# Create a file:
+# two regions of data and a hole in the middle
+# use O_DIRECT so it's not in the page cache
+echo "create file"
+$XFS_IO_PROG -t -f -d \
+	-c "pwrite 0 1024" \
+	-c "pwrite 2048 1024" \
+	$file > /dev/null
+
+# Make sure it returns EAGAIN on uncached data
+echo "uncached"
+$here/src/preadv2 -n -p 0 -l 1024 $file
+
+# Make sure we read in the whole file, after that RWF_NONBLOCK should return us all the data
+echo "cached"
+$XFS_IO_PROG -f $file -c "pread 0 4096" $file > /dev/null
+$here/src/preadv2 -n -p 0 -l 1024 $file
+
+# O_DIRECT and RWF_NONBLOCK should return EAGAIN always
+echo "O_DIRECT"
+$here/src/preadv2 -d -n -p 0 -l 1024 $file
+
+# Holes do not block
+echo "holes"
+$here/src/preadv2 -n -p 2048 -l 1024 $file
+
+# EOF behavior (no EAGAIN)
+echo "EOF"
+$here/src/preadv2 -n -p 3072 -l 1 $file
+
+# success, all done
+status=0
+exit
diff --git a/tests/generic/067.out b/tests/generic/067.out
new file mode 100644
index 0000000..6e3740f
--- /dev/null
+++ b/tests/generic/067.out
@@ -0,0 +1,9 @@
+QA output created by 067
+create file
+uncached
+preadv2: Resource temporarily unavailable
+cached
+O_DIRECT
+preadv2: Resource temporarily unavailable
+holes
+EOF
diff --git a/tests/generic/group b/tests/generic/group
index e5db772..91c5870 100644
--- a/tests/generic/group
+++ b/tests/generic/group
@@ -69,6 +69,7 @@
 064 auto quick prealloc
 065 metadata auto quick
 066 metadata auto quick
+067 auto quick rw
 068 other auto freeze dangerous stress
 069 rw udf auto quick
 070 attr udf auto quick stress
-- 
1.9.1

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