generic: Test races between mmap and normal write for prefaulted ranges

Add test which spawns two threads both writing one file via mmap which
has been previously prefaulted by reading. Do the same test when one
thread accesses the file via mmap and the other one via normal write.
This is mainly interesting to uncover races in DAX fault handling and
between DAX fault handling and write path.

Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

src/holetest.c

@@ -67,6 +67,7 @@
 long page_size;
 long page_offs[THREADS];
 int use_wr[THREADS];
+int prefault = 0;
 
 void *pt_page_marker(void *args)
 {
@@ -122,6 +123,16 @@ int test_this(int fd, loff_t sz)
 		exit(20);
 	}
 
+	if (prefault) {
+		for (i = 0; i < npages; i++) {
+			if (vastart[i * page_size] != 0) {
+				fprintf(stderr, "Prefaulting found non-zero "
+					"value in page %d: %d\n", i,
+					vastart[i * page_size]);
+			}
+		}
+	}
+
 	/* prepare the thread args */
 	for (i = 0; i < THREADS; i++) {
 		targs[i][0] = (void *)(long)fd;
@@ -185,7 +196,7 @@ int main(int argc, char **argv)
 	for (i = 1; i < THREADS; i++)
 		page_offs[i] = page_offs[i-1] + step;
 
-	while ((opt = getopt(argc, argv, "fw")) > 0) {
+	while ((opt = getopt(argc, argv, "fwr")) > 0) {
 		switch (opt) {
 		case 'f':
 			/* ignore errors */
@@ -195,6 +206,10 @@ int main(int argc, char **argv)
 			/* use writes instead of mmap for one thread */
 			use_wr[0] = 1;
 			break;
+		case 'r':
+			/* prefault mmapped area by reading it */
+			prefault = 1;
+			break;
 		default:
 			fprintf(stderr, "ERROR: Unknown option character.\n");
 			exit(1);
@@ -202,7 +217,7 @@ int main(int argc, char **argv)
 	}
 
 	if (optind != argc - 2) {
-		fprintf(stderr, "ERROR: usage: holetest [-fw] "
+		fprintf(stderr, "ERROR: usage: holetest [-fwr] "
 			"FILENAME FILESIZEinMB\n");
 		exit(1);
 	}

tests/generic/344

@@ -0,0 +1,60 @@
+#! /bin/bash
+# FSQA Test No. 344
+#
+# Test races between mmap from racing threads when pages are prefaulted,
+# Test races between mmap and buffered writes when pages are prefaulted.
+#
+#-----------------------------------------------------------------------
+#
+# Copyright (C) 2016 SUSE Linux Products GmbH. All Rights Reserved.
+# Author: Jan Kara <jack@suse.cz>
+#
+# 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"
+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 and checks
+. ./common/rc
+
+# real QA test starts here
+_supported_fs generic
+_supported_os Linux
+_require_scratch
+_require_test_program "holetest"
+
+rm -f $seqres.full
+
+_scratch_mkfs >>$seqres.full 2>&1
+_scratch_mount
+
+src/holetest -f -r $SCRATCH_MNT/testfile 16
+src/holetest -f -r $SCRATCH_MNT/testfile 256
+src/holetest -f -r -w $SCRATCH_MNT/testfile 16
+src/holetest -f -r -w $SCRATCH_MNT/testfile 256
+
+status=0
+exit

tests/generic/344.out

@@ -0,0 +1,73 @@
+QA output created by 344
+
+INFO: zero-filled test...
+INFO: sz = 16777216
+INFO: thread 0 created
+INFO: thread 1 created
+INFO: 0 error(s) detected
+
+INFO: posix_fallocate test...
+INFO: sz = 16777216
+INFO: thread 0 created
+INFO: thread 1 created
+INFO: 0 error(s) detected
+
+INFO: ftruncate test...
+INFO: sz = 16777216
+INFO: thread 0 created
+INFO: thread 1 created
+INFO: 0 error(s) detected
+
+INFO: zero-filled test...
+INFO: sz = 268435456
+INFO: thread 0 created
+INFO: thread 1 created
+INFO: 0 error(s) detected
+
+INFO: posix_fallocate test...
+INFO: sz = 268435456
+INFO: thread 0 created
+INFO: thread 1 created
+INFO: 0 error(s) detected
+
+INFO: ftruncate test...
+INFO: sz = 268435456
+INFO: thread 0 created
+INFO: thread 1 created
+INFO: 0 error(s) detected
+
+INFO: zero-filled test...
+INFO: sz = 16777216
+INFO: thread 0 created
+INFO: thread 1 created
+INFO: 0 error(s) detected
+
+INFO: posix_fallocate test...
+INFO: sz = 16777216
+INFO: thread 0 created
+INFO: thread 1 created
+INFO: 0 error(s) detected
+
+INFO: ftruncate test...
+INFO: sz = 16777216
+INFO: thread 0 created
+INFO: thread 1 created
+INFO: 0 error(s) detected
+
+INFO: zero-filled test...
+INFO: sz = 268435456
+INFO: thread 0 created
+INFO: thread 1 created
+INFO: 0 error(s) detected
+
+INFO: posix_fallocate test...
+INFO: sz = 268435456
+INFO: thread 0 created
+INFO: thread 1 created
+INFO: 0 error(s) detected
+
+INFO: ftruncate test...
+INFO: sz = 268435456
+INFO: thread 0 created
+INFO: thread 1 created
+INFO: 0 error(s) detected

tests/generic/group

@@ -346,6 +346,7 @@
 341 auto quick metadata
 342 auto quick metadata
 343 auto quick metadata
+344 auto
 346 auto
 705 blockdev quick rw
 706 blockdev quick rw