[PATCH v2 2/2] generic: test race when checking i_size on direct i/o read

[Eryu Guan <eguan@redhat.com>]

From: Zheng Liu <wenqing.lz@taobao.com>

In this commit a new test case is added to test that i_size races
don't occur under dio reads/writes.  We add a program in /src dir,
which has a writer to issue some append dio writes.  Meanwhile it
has a reader in this test to do some dio reads.  As we expect,
reader should read nothing or data with 'a'. But it might read some
data with '0'.

The bug can be reproduced by this test case [1].

1.  http://patchwork.ozlabs.org/patch/311761/

This ostensibly tests commit:
9fe55eea7 Fix race when checking i_size on direct i/o read

Update by Eric Sandeen:
- update to recent xfstests
- update commit log

Update by Eryu Guan:
- add aio-dio support to the test and add 'aio' group
- add ability to test different alignments
- move test from src/ to src/aio-dio-regress/
- add .gitignore entry
- rebase against latest xfstests with various minor fixes & cleanups
- update commit log

Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>
---
v2:
- start background reader in a thread first then start writer only after
  reader starts issuing reads

Confirmed that v2 still reproduces the bug reliably with unpatched
kernel and test passed with v4.14-rc3 kernel. 

Eric's original post
http://www.spinics.net/lists/fstests/msg06978.html

 .gitignore                                         |   1 +
 .../aio-dio-append-write-read-race.c               | 230 +++++++++++++++++++++
 tests/generic/464                                  |  75 +++++++
 tests/generic/464.out                              |   3 +
 tests/generic/group                                |   1 +
 5 files changed, 310 insertions(+)
 create mode 100644 src/aio-dio-regress/aio-dio-append-write-read-race.c
 create mode 100755 tests/generic/464
 create mode 100644 tests/generic/464.out

diff --git a/.gitignore b/.gitignore
index ae7ef87ab384..2dface41d485 100644
--- a/.gitignore
+++ b/.gitignore
@@ -142,6 +142,7 @@
 /src/writemod
 /src/writev_on_pagefault
 /src/xfsctl
+/src/aio-dio-regress/aio-dio-append-write-read-race
 /src/aio-dio-regress/aio-dio-cycle-write
 /src/aio-dio-regress/aio-dio-eof-race
 /src/aio-dio-regress/aio-dio-extend-stat
diff --git a/src/aio-dio-regress/aio-dio-append-write-read-race.c b/src/aio-dio-regress/aio-dio-append-write-read-race.c
new file mode 100644
index 000000000000..2956599c1474
--- /dev/null
+++ b/src/aio-dio-regress/aio-dio-append-write-read-race.c
@@ -0,0 +1,230 @@
+/*
+ * Copyright (c) 2013 Alibaba Group.
+ * Copyright (c) 2017 Red Hat Inc.
+ * 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
+ */
+
+/*
+ * This is a normal case that we do some append dio writes and meanwhile
+ * we do some dio reads.  Currently in vfs we don't ensure that i_size
+ * is updated properly.  Hence the reader will read some data with '0'.
+ * But we expect that the reader should read nothing or data with 'a'.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+
+#include <libaio.h>
+#include <pthread.h>
+
+struct io_data {
+	int fd;
+	size_t blksize;
+	off_t offset;
+	char *buf;
+	int use_aio;
+};
+
+int reader_ready = 0;
+
+static void usage(const char *prog)
+{
+	fprintf(stderr, "usage: %s [-a] <file>\n", prog);
+	fprintf(stderr, "\t-a\tuse aio-dio\n");
+	exit(EXIT_FAILURE);
+}
+
+static void *reader(void *arg)
+{
+	struct io_data *data = (struct io_data *)arg;
+	int ret;
+
+	memset(data->buf, 'b', data->blksize);
+	do {
+		ret = pread(data->fd, data->buf, data->blksize, data->offset);
+		if (ret < 0)
+			perror("read file");
+		if (!reader_ready)
+			reader_ready = 1;
+	} while (ret <= 0);
+
+	return NULL;
+}
+
+static void *writer(struct io_data *data)
+{
+	int ret;
+
+	while (!reader_ready)
+		usleep(1);
+
+	if (data->use_aio) {
+		struct io_context *ctx = NULL;
+		struct io_event evs[1];
+		struct iocb iocb;
+		struct iocb *iocbs[] = { &iocb };
+
+		ret = io_setup(1, &ctx);
+		if (ret) {
+			fprintf(stderr, "error %s during io_setup\n",
+				strerror(ret));
+			return NULL;
+		}
+		io_prep_pwrite(&iocb, data->fd, data->buf, data->blksize, data->offset);
+		ret = io_submit(ctx, 1, iocbs);
+		if (ret != 1) {
+			fprintf(stderr, "error %s during io_submit\n",
+				strerror(ret));
+			return NULL;
+		}
+		ret = io_getevents(ctx, 1, 1, evs, NULL);
+		if (ret != 1) {
+			fprintf(stderr, "error %s during io_getevents\n",
+				strerror(ret));
+			return NULL;
+		}
+	} else {
+		ret = pwrite(data->fd, data->buf, data->blksize, data->offset);
+		if (ret < 0)
+			perror("write file failed");
+	}
+
+	reader_ready = 0;
+	return NULL;
+}
+
+int main(int argc, char *argv[])
+{
+	pthread_t tid;
+	struct io_data wdata;
+	struct io_data rdata;
+	size_t max_blocks = 128;		/* 128 */
+	size_t blksize = 1 * 1024 * 1024;	/* 1M */
+	char *rbuf = NULL, *wbuf = NULL;
+	int rfd = 0, wfd = 0;
+	int i, j, c;
+	int use_aio = 1;
+	int ret = 0;
+	int io_align = 4096;
+	char *prog;
+	char *testfile;
+
+
+	prog = basename(argv[0]);
+
+	while ((c = getopt(argc, argv, "a:d")) != -1) {
+		switch (c) {
+		case 'a':
+			io_align = strtol(optarg, NULL, 0);
+			break;
+		case 'd':
+			use_aio = 0;
+			break;
+		default:
+			usage(prog);
+		}
+	}
+	if (optind != argc - 1)
+		usage(prog);
+	testfile = argv[optind];
+
+	wfd = open(testfile, O_CREAT|O_DIRECT|O_WRONLY|O_TRUNC, 0644);
+	if (wfd < 0) {
+		perror("open for write");
+		exit(1);
+	}
+
+	rfd = open(testfile, O_DIRECT|O_RDONLY, 0644);
+	if (rfd < 0) {
+		perror("open for read");
+		ret = 1;
+		goto err;
+	}
+
+	ret = posix_memalign((void **)&wbuf, io_align, blksize);
+	if (ret) {
+		fprintf(stderr, "failed to alloc memory: %s\n", strerror(ret));
+		ret = 1;
+		goto err;
+	}
+
+	ret = posix_memalign((void **)&rbuf, io_align, blksize);
+	if (ret) {
+		fprintf(stderr, "failed to alloc memory: %s\n", strerror(ret));
+		ret = 1;
+		goto err;
+	}
+
+	memset(wbuf, 'a', blksize);
+	wdata.fd = wfd;
+	wdata.blksize = blksize;
+	wdata.buf = wbuf;
+	wdata.use_aio = use_aio;
+	rdata.fd = rfd;
+	rdata.blksize = blksize;
+	rdata.buf = rbuf;
+
+	for (i = 0; i < max_blocks; i++) {
+		wdata.offset = rdata.offset = i * blksize;
+
+		ret = pthread_create(&tid, NULL, reader, &rdata);
+		if (ret) {
+			fprintf(stderr, "create reader thread failed: %s\n",
+				strerror(ret));
+			ret = 1;
+			goto err;
+		}
+
+		writer(&wdata);
+
+		ret = pthread_join(tid, NULL);
+		if (ret) {
+			fprintf(stderr, "pthread join reader failed: %s\n",
+				strerror(ret));
+			ret = 1;
+			goto err;
+		}
+
+		for (j = 0; j < blksize; j++) {
+			if (rdata.buf[j] != 'a') {
+				fprintf(stderr, "encounter an error: "
+					"block %d offset %d, content %x\n",
+					i, j, rbuf[j]);
+				ret = 1;
+				goto err;
+			}
+		}
+	}
+
+err:
+	if (rfd)
+		close(rfd);
+	if (wfd)
+		close(wfd);
+	if (rbuf)
+		free(rbuf);
+	if (wbuf)
+		free(wbuf);
+
+	exit(ret);
+}
diff --git a/tests/generic/464 b/tests/generic/464
new file mode 100755
index 000000000000..b0423c91a7cf
--- /dev/null
+++ b/tests/generic/464
@@ -0,0 +1,75 @@
+#! /bin/bash
+# FS QA Test No. 464
+#
+# Test i_size is updated properly under dio read/write
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2013 Alibaba Group.  All Rights Reserved.
+# Copyright (c) 2017 Red Hat Inc. 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/$$
+status=1	# failure is the default!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+	cd /
+	rm -f $tmp.* $testfile.*
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+# real QA test starts here
+_supported_fs generic
+_supported_os Linux
+
+_require_aiodio aio-dio-append-write-read-race
+_require_test_program "feature"
+
+testfile=$TEST_DIR/$seq.$$
+min_dio_align=`_min_dio_alignment $TEST_DEV`
+page_size=`$here/src/feature -s`
+
+rm -f $seqres.full
+
+echo "non-aio dio test"
+align=$min_dio_align
+while [ $align -le $page_size ]; do
+	echo "$AIO_TEST -a $align -d $testfile.$align" >> $seqres.full
+	$AIO_TEST -a $align -d $testfile.$align 2>&1 | tee -a $seqres.full
+	align=$((align * 2))
+done
+
+echo "aio-dio test"
+align=$min_dio_align
+while [ $align -le $page_size ]; do
+	echo "$AIO_TEST -a $align $testfile.$align" >> $seqres.full
+	$AIO_TEST -a $align $testfile.$align 2>&1 | tee -a $seqres.full
+	align=$((align * 2))
+done
+
+# success, all done
+status=0
+exit
diff --git a/tests/generic/464.out b/tests/generic/464.out
new file mode 100644
index 000000000000..14e66fe7d778
--- /dev/null
+++ b/tests/generic/464.out
@@ -0,0 +1,3 @@
+QA output created by 464
+non-aio dio test
+aio-dio test
diff --git a/tests/generic/group b/tests/generic/group
index 9f173e7a63c9..556add16286b 100644
--- a/tests/generic/group
+++ b/tests/generic/group
@@ -466,3 +466,4 @@
 461 auto shutdown stress
 462 auto quick dax
 463 auto rw
+464 auto rw quick aio
-- 
2.13.6