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

Milosz Tanski
2015-03-16T18:34:28Z

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@gmail.com>. 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