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

From: Milosz Tanski <milosz@adfin.com>
To: Andreas Dilger <adilger@dilger.ca>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Christoph Hellwig <hch@infradead.org>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	"linux-aio@kvack.org" <linux-aio@kvack.org>,
	Mel Gorman <mgorman@suse.de>,
	Volker Lendecke <Volker.Lendecke@sernet.de>,
	Tejun Heo <tj@kernel.org>, Jeff Moyer <jmoyer@redhat.com>,
	"Theodore Ts'o" <tytso@mit.edu>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Linux API <linux-api@vger.kernel.org>,
	Michael Kerrisk <mtk.manpages@gmail.com>,
	linux-arch@vger.kernel.org, Dave Chinner <david@fromorbit.com>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] fstests: generic test for preadv2 behavior on linux
Date: Mon, 16 Mar 2015 18:03:26 -0400	[thread overview]
Message-ID: <CANP1eJGsmEOVxJQ5nN3RfoU8FVjumE=aAqzCXzDQ+iAHzTK0qA@mail.gmail.com> (raw)
In-Reply-To: <BF78A586-3F25-4434-B646-EEA9DB8E62B6@dilger.ca>

On Mon, Mar 16, 2015 at 5:07 PM, Andreas Dilger <adilger@dilger.ca> wrote:
>
>> On Mar 16, 2015, at 12:34 PM, Milosz Tanski <milosz@adfin.com> wrote:
>>
>> preadv2 is a new syscall introduced that is like preadv2 but with flag
>
> Sorry, "preadv2 ... is like preadv2"?

I already have a fix for in my branch. Robert Elliott was the first
one to notice that (via private email).

>
>> 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.

Good catch. I'm going to fix the above to issues, add a pre-test check
for preadv2 (I just noticed it's missing) and I'm going to resend this
patch.

>
> 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@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
>>
>> --
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>
>
> Cheers, Andreas
>
>
>
>
>

-- 
Milosz Tanski
CTO
16 East 34th Street, 15th floor
New York, NY 10016

p: 646-253-9055
e: milosz@adfin.com