Re: [RFC PATCH] generic: test splice() with pipes

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Mon, Sep 02, 2019 at 10:20:52AM +0800, Zorro Lang wrote:
> On Thu, Aug 29, 2019 at 05:44:07PM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > Andreas Grünbacher reports that on the two filesystems that support
> > iomap directio, it's possible for splice() to return -EAGAIN (instead of
> > a short splice) if the pipe being written to has less space available in
> > its pipe buffers than the length supplied by the calling process.
> > 
> > This is a regression test to check for correct operation.
> > 
> > XXX Andreas: Since you wrote the C reproducer, can you send me the
> > proper copyright and author attribution statement for the C program?
> > 
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > ---
> 
> Hi Darrick,
> 
> I tried to add a splice_f operation into xfs_io long time ago:
> https://marc.info/?l=linux-xfs&m=155828702128047&w=2
> 
> For we can easily write more splice related test case later, I'd like to have
> a xfs_io to help that (if it can). Would you like to help to review that patch,
> if it can match your requirement to write this case? Or it can be improved to
> cover more testing conditions? I'm really appreciate that:)

Yeah, I'll try to have a look this week.

(FWIW I think Eric is backed up with dozens of xfsprogs patches...)

--D

> Thanks,
> Zorro
> 
> >  .gitignore            |    1 
> >  src/Makefile          |    2 -
> >  src/splice-test.c     |  173 +++++++++++++++++++++++++++++++++++++++++++++++++
> >  tests/generic/720     |   41 ++++++++++++
> >  tests/generic/720.out |    7 ++
> >  tests/generic/group   |    1 
> >  6 files changed, 224 insertions(+), 1 deletion(-)
> >  create mode 100644 src/splice-test.c
> >  create mode 100755 tests/generic/720
> >  create mode 100644 tests/generic/720.out
> > 
> > diff --git a/.gitignore b/.gitignore
> > index c8c815f9..26d4da11 100644
> > --- a/.gitignore
> > +++ b/.gitignore
> > @@ -112,6 +112,7 @@
> >  /src/runas
> >  /src/seek_copy_test
> >  /src/seek_sanity_test
> > +/src/splice-test
> >  /src/stale_handle
> >  /src/stat_test
> >  /src/swapon
> > diff --git a/src/Makefile b/src/Makefile
> > index c4fcf370..2920dfb1 100644
> > --- a/src/Makefile
> > +++ b/src/Makefile
> > @@ -28,7 +28,7 @@ LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \
> >  	attr-list-by-handle-cursor-test listxattr dio-interleaved t_dir_type \
> >  	dio-invalidate-cache stat_test t_encrypted_d_revalidate \
> >  	attr_replace_test swapon mkswap t_attr_corruption t_open_tmpfiles \
> > -	fscrypt-crypt-util bulkstat_null_ocount
> > +	fscrypt-crypt-util bulkstat_null_ocount splice-test
> >  
> >  SUBDIRS = log-writes perf
> >  
> > diff --git a/src/splice-test.c b/src/splice-test.c
> > new file mode 100644
> > index 00000000..d3c12075
> > --- /dev/null
> > +++ b/src/splice-test.c
> > @@ -0,0 +1,173 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + * Copyright (C) 2019 ?????????????????????????????
> > + * Author: 
> > + *
> > + * Make sure that reading and writing to a pipe via splice.
> > + */
> > +#include <sys/types.h>
> > +#include <sys/stat.h>
> > +#include <sys/wait.h>
> > +#include <unistd.h>
> > +#include <fcntl.h>
> > +#include <err.h>
> > +
> > +#include <stdlib.h>
> > +#include <stdio.h>
> > +#include <stdbool.h>
> > +#include <string.h>
> > +#include <errno.h>
> > +
> > +#define SECTOR_SIZE 512
> > +#define BUFFER_SIZE (150 * SECTOR_SIZE)
> > +
> > +void read_from_pipe(int fd, const char *filename, size_t size)
> > +{
> > +	char buffer[SECTOR_SIZE];
> > +	size_t sz;
> > +	ssize_t ret;
> > +
> > +	while (size) {
> > +		sz = size;
> > +		if (sz > sizeof buffer)
> > +			sz = sizeof buffer;
> > +		ret = read(fd, buffer, sz);
> > +		if (ret < 0)
> > +			err(1, "read: %s", filename);
> > +		if (ret == 0) {
> > +			fprintf(stderr, "read: %s: unexpected EOF\n", filename);
> > +			exit(1);
> > +		}
> > +		size -= sz;
> > +	}
> > +}
> > +
> > +void do_splice1(int fd, const char *filename, size_t size)
> > +{
> > +	bool retried = false;
> > +	int pipefd[2];
> > +
> > +	if (pipe(pipefd) == -1)
> > +		err(1, "pipe");
> > +	while (size) {
> > +		ssize_t spliced;
> > +
> > +		spliced = splice(fd, NULL, pipefd[1], NULL, size, SPLICE_F_MOVE);
> > +		if (spliced == -1) {
> > +			if (errno == EAGAIN && !retried) {
> > +				retried = true;
> > +				fprintf(stderr, "retrying splice\n");
> > +				sleep(1);
> > +				continue;
> > +			}
> > +			err(1, "splice");
> > +		}
> > +		read_from_pipe(pipefd[0], filename, spliced);
> > +		size -= spliced;
> > +	}
> > +	close(pipefd[0]);
> > +	close(pipefd[1]);
> > +}
> > +
> > +void do_splice2(int fd, const char *filename, size_t size)
> > +{
> > +	bool retried = false;
> > +	int pipefd[2];
> > +	int pid;
> > +
> > +	if (pipe(pipefd) == -1)
> > +		err(1, "pipe");
> > +
> > +	pid = fork();
> > +	if (pid == 0) {
> > +		close(pipefd[1]);
> > +		read_from_pipe(pipefd[0], filename, size);
> > +		exit(0);
> > +	} else {
> > +		close(pipefd[0]);
> > +		while (size) {
> > +			ssize_t spliced;
> > +
> > +			spliced = splice(fd, NULL, pipefd[1], NULL, size, SPLICE_F_MOVE);
> > +			if (spliced == -1) {
> > +				if (errno == EAGAIN && !retried) {
> > +					retried = true;
> > +					fprintf(stderr, "retrying splice\n");
> > +					sleep(1);
> > +					continue;
> > +				}
> > +				err(1, "splice");
> > +			}
> > +			size -= spliced;
> > +		}
> > +		close(pipefd[1]);
> > +		waitpid(pid, NULL, 0);
> > +	}
> > +}
> > +
> > +void usage(const char *argv0)
> > +{
> > +	fprintf(stderr, "USAGE: %s [-rd] {filename}\n", basename(argv0));
> > +	exit(2);
> > +}
> > +
> > +int main(int argc, char *argv[])
> > +{
> > +	void (*do_splice)(int fd, const char *filename, size_t size);
> > +	const char *filename;
> > +	char *buffer;
> > +	int opt, open_flags, fd;
> > +	ssize_t ret;
> > +
> > +	do_splice = do_splice1;
> > +	open_flags = O_CREAT | O_TRUNC | O_RDWR | O_DIRECT;
> > +
> > +	while ((opt = getopt(argc, argv, "rd")) != -1) {
> > +		switch(opt) {
> > +		case 'r':
> > +			do_splice = do_splice2;
> > +			break;
> > +		case 'd':
> > +			open_flags &= ~O_DIRECT;
> > +			break;
> > +		default:  /* '?' */
> > +			usage(argv[0]);
> > +		}
> > +	}
> > +
> > +	if (optind >= argc)
> > +		usage(argv[0]);
> > +	filename = argv[optind];
> > +
> > +	printf("%s reader %s O_DIRECT\n",
> > +		   do_splice == do_splice1 ? "sequential" : "concurrent",
> > +		   (open_flags & O_DIRECT) ? "with" : "without");
> > +
> > +	buffer = aligned_alloc(SECTOR_SIZE, BUFFER_SIZE);
> > +	if (buffer == NULL)
> > +		err(1, "aligned_alloc");
> > +
> > +	fd = open(filename, open_flags, 0666);
> > +	if (fd == -1)
> > +		err(1, "open: %s", filename);
> > +
> > +	memset(buffer, 'x', BUFFER_SIZE);
> > +	ret = write(fd, buffer, BUFFER_SIZE);
> > +	if (ret < 0)
> > +		err(1, "write: %s", filename);
> > +	if (ret != BUFFER_SIZE) {
> > +		fprintf(stderr, "%s: short write\n", filename);
> > +		exit(1);
> > +	}
> > +
> > +	ret = lseek(fd, 0, SEEK_SET);
> > +	if (ret != 0)
> > +		err(1, "lseek: %s", filename);
> > +
> > +	do_splice(fd, filename, BUFFER_SIZE);
> > +
> > +	if (unlink(filename) == -1)
> > +		err(1, "unlink: %s", filename);
> > +
> > +	return 0;
> > +}
> > diff --git a/tests/generic/720 b/tests/generic/720
> > new file mode 100755
> > index 00000000..b7f09c40
> > --- /dev/null
> > +++ b/tests/generic/720
> > @@ -0,0 +1,41 @@
> > +#! /bin/bash
> > +# SPDX-License-Identifier: GPL-2.0-or-later
> > +# Copyright (c) 2019, Oracle and/or its affiliates.  All Rights Reserved.
> > +#
> > +# FS QA Test No. 720
> > +#
> > +# Test using splice() to read from pipes.
> > +
> > +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 $TEST_DIR/a
> > +}
> > +
> > +# get standard environment, filters and checks
> > +. ./common/rc
> > +
> > +# real QA test starts here
> > +_supported_os Linux
> > +_supported_fs generic
> > +_require_test
> > +
> > +rm -f $seqres.full
> > +
> > +src/splice-test -r $TEST_DIR/a
> > +src/splice-test -rd $TEST_DIR/a
> > +src/splice-test $TEST_DIR/a
> > +src/splice-test -d $TEST_DIR/a
> > +
> > +# success, all done
> > +status=0
> > +exit
> > diff --git a/tests/generic/720.out b/tests/generic/720.out
> > new file mode 100644
> > index 00000000..b0fc9935
> > --- /dev/null
> > +++ b/tests/generic/720.out
> > @@ -0,0 +1,7 @@
> > +QA output created by 720
> > +concurrent reader with O_DIRECT
> > +concurrent reader with O_DIRECT
> > +concurrent reader without O_DIRECT
> > +concurrent reader without O_DIRECT
> > +sequential reader with O_DIRECT
> > +sequential reader without O_DIRECT
> > diff --git a/tests/generic/group b/tests/generic/group
> > index cd418106..f75d4e60 100644
> > --- a/tests/generic/group
> > +++ b/tests/generic/group
> > @@ -569,3 +569,4 @@
> >  564 auto quick copy_range
> >  565 auto quick copy_range
> >  719 auto quick quota metadata
> > +720 auto quick rw pipe splice