[PATCH] test race when checking i_size on direct i/o read

[Eric Sandeen <sandeen@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

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Rich Johnston <rjohnston@sgi.com>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
[sandeen: update to recent xfstests, update commitlog]
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---

This test was originally titled:

 xfstests: add a new test case to test i_size updated properly under dio

but I think the issue is more of when and how it's tested, not how
it's updated.

Note, this passes on xfs on 4.10, but fails on 4.12.
ext4 on 4.10 passes as well but is very slow.

iomap dio maybe?  Not sure yet.

changelog v3:
 * rebase against latest xfstests/master branch
 * update commit log

changelog v2:
 * add '-lpthread' into LLDLIBS

diff --git a/configure.ac b/configure.ac
index 57092f1..4663004 100644
--- a/configure.ac
+++ b/configure.ac
@@ -59,6 +59,7 @@ AC_PACKAGE_NEED_GETXATTR_LIBATTR
 AC_PACKAGE_NEED_SYS_ACL_H
 AC_PACKAGE_NEED_ACL_LIBACL_H
 AC_PACKAGE_NEED_ACLINIT_LIBACL
+AC_PACKAGE_NEED_PTHREADMUTEXINIT
 
 AC_PACKAGE_WANT_GDBM
 AC_PACKAGE_WANT_AIO
diff --git a/include/builddefs.in b/include/builddefs.in
index cb52b99..fcc8b90 100644
--- a/include/builddefs.in
+++ b/include/builddefs.in
@@ -25,6 +25,7 @@ LIBGDBM = @libgdbm@
 LIBUUID = @libuuid@
 LIBHANDLE = @libhdl@
 LIBDM = @libdm@
+LIBPTHREAD = @libpthread@
 LIBTEST = $(TOPDIR)/lib/libtest.la
 prefix = @prefix@
 
diff --git a/src/Makefile b/src/Makefile
index b8aff49..e9419bd 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -23,7 +23,7 @@ LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \
 	seek_copy_test t_readdir_1 t_readdir_2 fsync-tester nsexec cloner \
 	renameat2 t_getcwd e4compact test-nextquota punch-alternating \
 	attr-list-by-handle-cursor-test listxattr dio-interleaved t_dir_type \
-	dio-invalidate-cache stat_test t_encrypted_d_revalidate
+	dio-invalidate-cache stat_test t_encrypted_d_revalidate diotest
 
 SUBDIRS =
 
diff --git a/src/diotest.c b/src/diotest.c
new file mode 100644
index 0000000..7d2378f
--- /dev/null
+++ b/src/diotest.c
@@ -0,0 +1,166 @@
+/*
+ * Copyright (c) 2013 Alibaba Group.
+ * 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 <pthread.h>
+
+static char *prog;
+
+struct writer_data {
+	int fd;
+	size_t blksize;
+	char *buf;
+};
+
+static void usage(void)
+{
+	fprintf(stderr, "usage: %s [FILE]\n", prog);
+}
+
+static void *writer(void *arg)
+{
+	struct writer_data *data = (struct writer_data *)arg;
+	int ret;
+
+	ret = write(data->fd, data->buf, data->blksize);
+	if (ret < 0)
+		fprintf(stderr, "write file failed: %s\n", strerror(errno));
+
+	return NULL;
+}
+
+int main(int argc, char *argv[])
+{
+	pthread_t tid;
+	struct writer_data wdata;
+	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;
+	int ret = 0;
+
+	prog = basename(argv[0]);
+
+	if (argc != 2) {
+		usage();
+		exit(1);
+	}
+
+	wfd = open(argv[1], O_CREAT|O_DIRECT|O_WRONLY|O_APPEND|O_TRUNC, S_IRWXU);
+	if (wfd < 0) {
+		fprintf(stderr, "failed to open write file: %s\n",
+			strerror(errno));
+		exit(1);
+	}
+
+	rfd = open(argv[1], O_DIRECT|O_RDONLY, S_IRWXU);
+	if (wfd < 0) {
+		fprintf(stderr, "failed to open read file: %s\n",
+			strerror(errno));
+		ret = 1;
+		goto err;
+	}
+
+	/*
+	 * We set 1024 as an alignment size for write buf.  Feel free to change
+	 * it with 4096.  But the problem is also hitted.
+	 */
+	if (posix_memalign((void **)&wbuf, 1024, blksize)) {
+		fprintf(stderr, "failed to alloc memory: %s\n", strerror(errno));
+		ret = 1;
+		goto err;
+	}
+
+	if (posix_memalign((void **)&rbuf, 4096, blksize)) {
+		fprintf(stderr, "failed to alloc memory: %s\n", strerror(errno));
+		ret = 1;
+		goto err;
+	}
+
+	memset(wbuf, 'a', blksize);
+	wdata.fd = wfd;
+	wdata.blksize = blksize;
+	wdata.buf = wbuf;
+
+	for (i = 0; i < max_blocks; i++) {
+		void *retval;
+
+		if (pthread_create(&tid, NULL, writer, &wdata)) {
+			fprintf(stderr, "create thread failed: %s\n",
+				strerror(errno));
+			ret = 1;
+			goto err;
+		}
+
+		memset(rbuf, 'b', blksize);
+		do {
+			ret = pread(rfd, rbuf, blksize, i * blksize);
+			if (ret < 0)
+				fprintf(stderr, "read file failed: %s\n",
+					strerror(errno));
+		} while (ret <= 0);
+
+		if (pthread_join(tid, &retval)) {
+			fprintf(stderr, " pthread join failed: %s\n",
+				strerror(errno));
+			ret = 1;
+			goto err;
+		}
+
+		if (ret >= 0) {
+			for (j = 0; j < ret; j ++) {
+				if (rbuf[j] != 'a') {
+					fprintf(stderr, "encounter an error: "
+						"offset %d content %c\n",
+						i, rbuf[j]);
+					ret = 1;
+					goto err;
+				}
+			}
+		}
+	}
+
+err:
+	if (rfd)
+		close(rfd);
+	if (wfd)
+		close(wfd);
+	if (rbuf)
+		free(rbuf);
+	if (wbuf)
+		free(wbuf);
+
+	return ret;
+}
diff --git a/tests/generic/450 b/tests/generic/450
new file mode 100755
index 0000000..cfb424c
--- /dev/null
+++ b/tests/generic/450
@@ -0,0 +1,56 @@
+#! /bin/bash
+# FS QA Test No. 450
+#
+# Test i_size is updated properly under dio read/write
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2013 Alibaba Group.  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/$$
+status=1	# failure is the default!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+    cd /
+    rm -f $tmp.* $testfile
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+# real QA test starts here
+_supported_fs generic
+_supported_os Linux
+
+testfile=$TEST_DIR/$seq.$$
+
+[ -x $here/src/diotest ] || _notrun "diotest not built"
+
+$here/src/diotest $testfile # > $seqres.full 2>&1 ||
+	# _fail "i_size isn't update properly!"
+
+# success, all done
+status=0
+exit
diff --git a/tests/generic/450.out b/tests/generic/450.out
new file mode 100644
index 0000000..734761a
--- /dev/null
+++ b/tests/generic/450.out
@@ -0,0 +1 @@
+QA output created by 450
diff --git a/tests/generic/group b/tests/generic/group
index b9cd0e8..a555fa0 100644
--- a/tests/generic/group
+++ b/tests/generic/group
@@ -452,3 +452,4 @@
 447 auto quick clone
 448 auto quick rw
 449 auto quick acl enospc
+450 auto rw quick