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Date: Mon, 16 Mar 2015 15:07:46 -0600
From: Andreas Dilger <adilger@...ger.ca>
To: Milosz Tanski <milosz@...in.com>
Cc: linux-kernel@...r.kernel.org,
Christoph Hellwig <hch@...radead.org>,
linux-fsdevel@...r.kernel.org, linux-aio@...ck.org,
Mel Gorman <mgorman@...e.de>,
Volker Lendecke <Volker.Lendecke@...net.de>,
Tejun Heo <tj@...nel.org>, Jeff Moyer <jmoyer@...hat.com>,
Theodore Ts'o <tytso@....edu>,
Al Viro <viro@...iv.linux.org.uk>, linux-api@...r.kernel.org,
Michael Kerrisk <mtk.manpages@...il.com>,
linux-arch@...r.kernel.org, Dave Chinner <david@...morbit.com>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] fstests: generic test for preadv2 behavior on linux
> On Mar 16, 2015, at 12:34 PM, Milosz Tanski <milosz@...in.com> wrote:
>
> preadv2 is a new syscall introduced that is like preadv2 but with flag
Sorry, "preadv2 ... is like preadv2"?
> argument. The first use case of this is to let us add a flag to perform a
> non-blocking file using the page cache.
This is also missing a Signed-off-by: line.
Cheers, Andreas
> ---
> 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@...il.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
>
> --
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Cheers, Andreas
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