diff mbox

[fstests,2/2] generic/999: test DAX DMA vs truncate/hole-punch

Message ID 20180620225147.12151-2-ross.zwisler@linux.intel.com (mailing list archive)
State New, archived
Headers show

Commit Message

Ross Zwisler June 20, 2018, 10:51 p.m. UTC 
This adds a regression test for the following series:

https://lists.01.org/pipermail/linux-nvdimm/2018-June/016431.html

which added synchronization between DAX DMA in ext4 and
truncate/hole-punch.  The intention of the test is to test those specific
changes, but it runs fine both with XFS and without DAX, so I've put it in
the generic tests instead of ext4 and not restricted it to only DAX
configurations.

When run with v4.18-rc1 + DAX + ext4, this test will hit the following
WARN_ON_ONCE() in dax_disassociate_entry():

	WARN_ON_ONCE(trunc && page_ref_count(page) > 1);

If you change this to a WARN_ON() instead, you can see that each of the
four paths being exercised in this test hits that condition many times in
the one second that the subtest is being run.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
---
 .gitignore             |   1 +
 src/Makefile           |   2 +-
 src/t_mmap_collision.c | 208 +++++++++++++++++++++++++++++++++++++++++++++++++
 tests/generic/999      |  50 ++++++++++++
 tests/generic/999.out  |   2 +
 tests/generic/group    |   1 +
 6 files changed, 263 insertions(+), 1 deletion(-)
 create mode 100644 src/t_mmap_collision.c
 create mode 100755 tests/generic/999
 create mode 100644 tests/generic/999.out

Comments

Dave Chinner June 21, 2018, 2:18 a.m. UTC | #1 
On Wed, Jun 20, 2018 at 04:51:47PM -0600, Ross Zwisler wrote:
> diff --git a/src/t_mmap_collision.c b/src/t_mmap_collision.c
> new file mode 100644
> index 00000000..f652e913
> --- /dev/null
> +++ b/src/t_mmap_collision.c
> @@ -0,0 +1,208 @@
> +#include <errno.h>
> +#include <fcntl.h>
> +#include <pthread.h>
> +#include <stdbool.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <sys/mman.h>
> +#include <sys/stat.h>
> +#include <sys/types.h>
> +#include <unistd.h>

No license (SPDX), no copyright, no comments explaining what the
code is for, what bug/API it is trying to exercise how it works,
command line usage, etc.

> +++ b/tests/generic/999
> @@ -0,0 +1,50 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2018 Intel Corporation.  All Rights Reserved.
> +#
> +# FS QA Test generic/999
> +#
> +# This is a regression test for kernel patch:
> +#   ext4: handle layout changes to pinned DAX mapping
> +# created by Ross Zwisler <ross.zwisler@linux.intel.com>

Author information is stored in the git tree, not the code.

> +rm -f $seqres.full
> +
> +# Modify as appropriate.
> +_supported_fs generic
> +_supported_os Linux
> +_require_test
> +_require_test_program "t_mmap_collision"
> +
> +# turn off DAX on our scratch device so we can get normal O_DIRECT behavior
> +export MOUNT_OPTIONS=""
> +_scratch_unmount >> $seqres.full 2>&1
> +_scratch_mount >> $seqres.full 2>&1

_exclude_scratch_mount_option "dax"

i.e. we skip the test if "-o dax" is in the mount options. We try
not to turn off all mount options, because then we never exercise
any filesystem configuration other than mount defaults, regardless of
what other mount options the tester has specified on the CLI or
in config files...

> +Silence is golden
> diff --git a/tests/generic/group b/tests/generic/group
> index 83a6fdab..793f71ed 100644
> --- a/tests/generic/group
> +++ b/tests/generic/group
> @@ -501,3 +501,4 @@
>  496 auto quick swap
>  497 auto quick swap collapse
>  498 auto quick log
> +999 auto quick dax

Why should this be in a "dax" group when the test explicitly turns
off the the DAX mount option?

Cheers,

Dave.
Eryu Guan June 21, 2018, 2:40 a.m. UTC | #2 
On Wed, Jun 20, 2018 at 04:51:47PM -0600, Ross Zwisler wrote:
> This adds a regression test for the following series:
> 
> https://lists.01.org/pipermail/linux-nvdimm/2018-June/016431.html
> 
> which added synchronization between DAX DMA in ext4 and
> truncate/hole-punch.  The intention of the test is to test those specific
> changes, but it runs fine both with XFS and without DAX, so I've put it in
> the generic tests instead of ext4 and not restricted it to only DAX
> configurations.
> 
> When run with v4.18-rc1 + DAX + ext4, this test will hit the following
> WARN_ON_ONCE() in dax_disassociate_entry():
> 
> 	WARN_ON_ONCE(trunc && page_ref_count(page) > 1);
> 
> If you change this to a WARN_ON() instead, you can see that each of the
> four paths being exercised in this test hits that condition many times in
> the one second that the subtest is being run.
> 
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>

I haven't tested it yet, just a few quick comments below.

> ---
>  .gitignore             |   1 +
>  src/Makefile           |   2 +-
>  src/t_mmap_collision.c | 208 +++++++++++++++++++++++++++++++++++++++++++++++++
>  tests/generic/999      |  50 ++++++++++++
>  tests/generic/999.out  |   2 +
>  tests/generic/group    |   1 +
>  6 files changed, 263 insertions(+), 1 deletion(-)
>  create mode 100644 src/t_mmap_collision.c
>  create mode 100755 tests/generic/999
>  create mode 100644 tests/generic/999.out
> 
> diff --git a/.gitignore b/.gitignore
> index efc73a7c..936955e0 100644
> --- a/.gitignore
> +++ b/.gitignore
> @@ -126,6 +126,7 @@
>  /src/t_immutable
>  /src/t_locks_execve
>  /src/t_mmap_cow_race
> +/src/t_mmap_collision

Looks like this should go before t_mmap_cow_race?

>  /src/t_mmap_dio
>  /src/t_mmap_fallocate
>  /src/t_mmap_stale_pmd
> diff --git a/src/Makefile b/src/Makefile
> index b06b7e25..2dbe5e7e 100644
> --- a/src/Makefile
> +++ b/src/Makefile
> @@ -15,7 +15,7 @@ TARGETS = dirstress fill fill2 getpagesize holes lstat64 \
>  	holetest t_truncate_self t_mmap_dio af_unix t_mmap_stale_pmd \
>  	t_mmap_cow_race t_mmap_fallocate fsync-err t_mmap_write_ro \
>  	t_ext4_dax_journal_corruption t_ext4_dax_inline_corruption \
> -	t_ofd_locks t_locks_execve
> +	t_ofd_locks t_locks_execve t_mmap_collision
>  
>  LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \
>  	preallo_rw_pattern_writer ftrunc trunc fs_perms testx looptest \
> diff --git a/src/t_mmap_collision.c b/src/t_mmap_collision.c
> new file mode 100644
> index 00000000..f652e913
> --- /dev/null
> +++ b/src/t_mmap_collision.c
> @@ -0,0 +1,208 @@

Please add copyright and licence statements to c file too, use the new
SPDX tag :)

(Refer to Dave's pending patch "src/: spdx license conversion" in
patchset "fstests: SPDX license conversion round 2").

> +#include <errno.h>
> +#include <fcntl.h>
> +#include <pthread.h>
> +#include <stdbool.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <sys/mman.h>
> +#include <sys/stat.h>
> +#include <sys/types.h>
> +#include <unistd.h>
> +
> +#define PAGE(a) ((a)*0x1000)
> +#define FILE_SIZE PAGE(4)
> +
> +void *dax_data;
> +int nodax_fd;
> +int dax_fd;
> +bool done;
> +
> +#define err_exit(op)                                                          \
> +{                                                                             \
> +	fprintf(stderr, "%s %s: %s\n", __func__, op, strerror(errno));        \
> +	exit(1);                                                              \
> +}                                                                             \
> +
> +void punch_hole_fn(void *ptr)
> +{
> +	ssize_t read;
> +	int rc;
> +
> +	while (!done) {
> +		read = 0;
> +
> +		do {
> +			rc = pread(nodax_fd, dax_data + read, FILE_SIZE - read,
> +					read);
> +			if (rc > 0)
> +				read += rc;
> +		} while (rc > 0);
> +
> +		if (read != FILE_SIZE || rc != 0)
> +			err_exit("pread");
> +
> +		rc = fallocate(dax_fd,
> +				FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
> +				0, FILE_SIZE);
> +		if (rc < 0)
> +			err_exit("fallocate");
> +
> +		usleep(rand() % 1000);
> +	}
> +}
> +
> +void zero_range_fn(void *ptr)
> +{
> +	ssize_t read;
> +	int rc;
> +
> +	while (!done) {
> +		read = 0;
> +
> +		do {
> +			rc = pread(nodax_fd, dax_data + read, FILE_SIZE - read,
> +					read);
> +			if (rc > 0)
> +				read += rc;
> +		} while (rc > 0);
> +
> +		if (read != FILE_SIZE || rc != 0)
> +			err_exit("pread");
> +
> +		rc = fallocate(dax_fd,
> +				FALLOC_FL_ZERO_RANGE | FALLOC_FL_KEEP_SIZE,
> +				0, FILE_SIZE);
> +		if (rc < 0)
> +			err_exit("fallocate");
> +
> +		usleep(rand() % 1000);
> +	}
> +}
> +
> +void truncate_down_fn(void *ptr)
> +{
> +	ssize_t read;
> +	int rc;
> +
> +	while (!done) {
> +		read = 0;
> +
> +		if (ftruncate(dax_fd, 0) < 0)
> +			err_exit("ftruncate");
> +		if (fallocate(dax_fd, 0, 0, FILE_SIZE) < 0)
> +			err_exit("fallocate");
> +
> +		do {
> +			rc = pread(nodax_fd, dax_data + read, FILE_SIZE - read,
> +					read);
> +			if (rc > 0)
> +				read += rc;
> +		} while (rc > 0);
> +
> +		/*
> +		 * For this test we ignore errors from pread().  These errors
> +		 * can happen if we try and read while the other thread has
> +		 * made the file size 0.
> +		 */
> +
> +		usleep(rand() % 1000);
> +	}
> +}
> +
> +void collapse_range_fn(void *ptr)
> +{
> +	ssize_t read;
> +	int rc;
> +
> +	while (!done) {
> +		read = 0;
> +
> +		if (fallocate(dax_fd, 0, 0, FILE_SIZE) < 0)
> +			err_exit("fallocate 1");
> +		if (fallocate(dax_fd, FALLOC_FL_COLLAPSE_RANGE, 0, PAGE(1)) < 0)
> +			err_exit("fallocate 2");
> +		if (fallocate(dax_fd, 0, 0, FILE_SIZE) < 0)
> +			err_exit("fallocate 3");
> +
> +		do {
> +			rc = pread(nodax_fd, dax_data + read, FILE_SIZE - read,
> +					read);
> +			if (rc > 0)
> +				read += rc;
> +		} while (rc > 0);
> +
> +		/* For this test we ignore errors from pread. */
> +
> +		usleep(rand() % 1000);
> +	}
> +}
> +
> +void run_test(void (*test_fn)(void *))
> +{
> +	const int NUM_THREADS = 2;
> +	pthread_t worker_thread[NUM_THREADS];
> +	int i;
> +
> +	done = 0;
> +	for (i = 0; i < NUM_THREADS; i++)
> +		pthread_create(&worker_thread[i], NULL, (void*)test_fn, NULL);
> +
> +	sleep(1);
> +	done = 1;
> +
> +	for (i = 0; i < NUM_THREADS; i++)
> +		pthread_join(worker_thread[i], NULL);
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +	int err;
> +
> +	if (argc != 3) {
> +		printf("Usage: %s <dax file> <non-dax file>\n",
> +				basename(argv[0]));
> +		exit(0);
> +	}
> +
> +	dax_fd = open(argv[1], O_RDWR|O_CREAT, S_IRUSR|S_IWUSR);
> +	if (dax_fd < 0)
> +		err_exit("dax_fd open");
> +
> +	nodax_fd = open(argv[2], O_RDWR|O_CREAT|O_DIRECT, S_IRUSR|S_IWUSR);
> +	if (nodax_fd < 0)
> +		err_exit("nodax_fd open");
> +
> +	if (ftruncate(dax_fd, 0) < 0)
> +		err_exit("dax_fd ftruncate");
> +	if (fallocate(dax_fd, 0, 0, FILE_SIZE) < 0)
> +		err_exit("dax_fd fallocate");
> +
> +	if (ftruncate(nodax_fd, 0) < 0)
> +		err_exit("nodax_fd ftruncate");
> +	if (fallocate(nodax_fd, 0, 0, FILE_SIZE) < 0)
> +		err_exit("nodax_fd fallocate");
> +
> +	dax_data = mmap(NULL, FILE_SIZE, PROT_READ|PROT_WRITE, MAP_SHARED,
> +			dax_fd, 0);
> +	if (dax_data == MAP_FAILED)
> +		err_exit("mmap");
> +
> +	run_test(&punch_hole_fn);
> +	run_test(&zero_range_fn);
> +	run_test(&truncate_down_fn);
> +	run_test(&collapse_range_fn);

Check for FALLOC_FL_* definition and compile
(punch_hole|zero_range|collapse_range)_fn out if the needed flag is not
defined?

> +
> +	if (munmap(dax_data, FILE_SIZE) != 0)
> +		err_exit("munmap");
> +
> +	err = close(dax_fd);
> +	if (err < 0)
> +		err_exit("dax_fd close");
> +
> +	err = close(nodax_fd);
> +	if (err < 0)
> +		err_exit("nodax_fd close");
> +
> +	return 0;
> +}
> diff --git a/tests/generic/999 b/tests/generic/999
> new file mode 100755
> index 00000000..8f488cb5
> --- /dev/null
> +++ b/tests/generic/999
> @@ -0,0 +1,50 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2018 Intel Corporation.  All Rights Reserved.
> +#
> +# FS QA Test generic/999
> +#
> +# This is a regression test for kernel patch:
> +#   ext4: handle layout changes to pinned DAX mapping
> +# created by Ross Zwisler <ross.zwisler@linux.intel.com>
> +#
> +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
> +
> +# remove previous $seqres.full before test
> +rm -f $seqres.full
> +
> +# Modify as appropriate.
> +_supported_fs generic
> +_supported_os Linux
> +_require_test
> +_require_test_program "t_mmap_collision"

_require_xfs_io_command "fpunch"
_require_xfs_io_command "fcollapse"
_require_xfs_io_command "fzero"

> +
> +# turn off DAX on our scratch device so we can get normal O_DIRECT behavior
> +export MOUNT_OPTIONS=""
> +_scratch_unmount >> $seqres.full 2>&1
> +_scratch_mount >> $seqres.full 2>&1
> +
> +# real QA test starts here
> +$here/src/t_mmap_collision $TEST_DIR/testfile $SCRATCH_MNT/testfile
> +
> +# success, all done
> +echo "Silence is golden"
> +status=0
> +exit
> diff --git a/tests/generic/999.out b/tests/generic/999.out
> new file mode 100644
> index 00000000..3b276ca8
> --- /dev/null
> +++ b/tests/generic/999.out
> @@ -0,0 +1,2 @@
> +QA output created by 999
> +Silence is golden
> diff --git a/tests/generic/group b/tests/generic/group
> index 83a6fdab..793f71ed 100644
> --- a/tests/generic/group
> +++ b/tests/generic/group
> @@ -501,3 +501,4 @@
>  496 auto quick swap
>  497 auto quick swap collapse
>  498 auto quick log
> +999 auto quick dax

Also need "punch collapse zero" groups.

Thanks,
Eryu

> -- 
> 2.14.4
>
Ross Zwisler June 21, 2018, 4:34 p.m. UTC | #3 
On Thu, Jun 21, 2018 at 12:18:42PM +1000, Dave Chinner wrote:
> On Wed, Jun 20, 2018 at 04:51:47PM -0600, Ross Zwisler wrote:
<>
> > +rm -f $seqres.full
> > +
> > +# Modify as appropriate.
> > +_supported_fs generic
> > +_supported_os Linux
> > +_require_test
> > +_require_test_program "t_mmap_collision"
> > +
> > +# turn off DAX on our scratch device so we can get normal O_DIRECT behavior
> > +export MOUNT_OPTIONS=""
> > +_scratch_unmount >> $seqres.full 2>&1
> > +_scratch_mount >> $seqres.full 2>&1
> 
> _exclude_scratch_mount_option "dax"
> 
> i.e. we skip the test if "-o dax" is in the mount options. We try
> not to turn off all mount options, because then we never exercise
> any filesystem configuration other than mount defaults, regardless of
> what other mount options the tester has specified on the CLI or
> in config files...
> 
> > +Silence is golden
> > diff --git a/tests/generic/group b/tests/generic/group
> > index 83a6fdab..793f71ed 100644
> > --- a/tests/generic/group
> > +++ b/tests/generic/group
> > @@ -501,3 +501,4 @@
> >  496 auto quick swap
> >  497 auto quick swap collapse
> >  498 auto quick log
> > +999 auto quick dax
> 
> Why should this be in a "dax" group when the test explicitly turns
> off the the DAX mount option?

Right, sorry, this is a bit confusing.  We only turn off dax for the scratch
device, but we use the full mount options for the test device.  To reproduce
the bug I'm looking for we would like those mount options to include -o dax
(hence the membership in the dax group), but the test runs fine without this
so I didn't want to require the dax mount option for the test to run.

I'll add comments to this effect, and I'll address the rest of your feedback
in v2.

Thank you for the review.
Ross Zwisler July 10, 2018, 9:15 p.m. UTC | #4 
On Thu, Jun 21, 2018 at 10:40:33AM +0800, Eryu Guan wrote:
> On Wed, Jun 20, 2018 at 04:51:47PM -0600, Ross Zwisler wrote:
<>

> > diff --git a/tests/generic/999 b/tests/generic/999
> > new file mode 100755
> > index 00000000..8f488cb5
> > --- /dev/null
> > +++ b/tests/generic/999
> > @@ -0,0 +1,50 @@
> > +#! /bin/bash
> > +# SPDX-License-Identifier: GPL-2.0
> > +# Copyright (c) 2018 Intel Corporation.  All Rights Reserved.
> > +#
> > +# FS QA Test generic/999
> > +#
> > +# This is a regression test for kernel patch:
> > +#   ext4: handle layout changes to pinned DAX mapping
> > +# created by Ross Zwisler <ross.zwisler@linux.intel.com>
> > +#
> > +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
> > +
> > +# remove previous $seqres.full before test
> > +rm -f $seqres.full
> > +
> > +# Modify as appropriate.
> > +_supported_fs generic
> > +_supported_os Linux
> > +_require_test
> > +_require_test_program "t_mmap_collision"
> 
> _require_xfs_io_command "fpunch"
> _require_xfs_io_command "fcollapse"
> _require_xfs_io_command "fzero"

I don't think I need these because I don't actually require this functionality
from xfs_io.  I did try and use xfs_io for this test, but the way the
threading needs to work I ended up having to write my own C program.  So,
even if xfs_io happens to be old and without fpunch, for example, as long as
fallocate can use FALLC_FL_PUNCH_HOLE I think the test should do the right
thing.

> > diff --git a/tests/generic/group b/tests/generic/group
> > index 83a6fdab..793f71ed 100644
> > --- a/tests/generic/group
> > +++ b/tests/generic/group
> > @@ -501,3 +501,4 @@
> >  496 auto quick swap
> >  497 auto quick swap collapse
> >  498 auto quick log
> > +999 auto quick dax
> 
> Also need "punch collapse zero" groups.

I'm assuming I should still add my test to these 3 groups, even though I'm not
getting this functionality via xfs_io?

Thank you for the review, I'll address the rest of your comments in v2.
diff mbox

Patch

diff --git a/.gitignore b/.gitignore
index efc73a7c..936955e0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -126,6 +126,7 @@ 
 /src/t_immutable
 /src/t_locks_execve
 /src/t_mmap_cow_race
+/src/t_mmap_collision
 /src/t_mmap_dio
 /src/t_mmap_fallocate
 /src/t_mmap_stale_pmd
diff --git a/src/Makefile b/src/Makefile
index b06b7e25..2dbe5e7e 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -15,7 +15,7 @@  TARGETS = dirstress fill fill2 getpagesize holes lstat64 \
 	holetest t_truncate_self t_mmap_dio af_unix t_mmap_stale_pmd \
 	t_mmap_cow_race t_mmap_fallocate fsync-err t_mmap_write_ro \
 	t_ext4_dax_journal_corruption t_ext4_dax_inline_corruption \
-	t_ofd_locks t_locks_execve
+	t_ofd_locks t_locks_execve t_mmap_collision
 
 LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \
 	preallo_rw_pattern_writer ftrunc trunc fs_perms testx looptest \
diff --git a/src/t_mmap_collision.c b/src/t_mmap_collision.c
new file mode 100644
index 00000000..f652e913
--- /dev/null
+++ b/src/t_mmap_collision.c
@@ -0,0 +1,208 @@ 
+#include <errno.h>
+#include <fcntl.h>
+#include <pthread.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#define PAGE(a) ((a)*0x1000)
+#define FILE_SIZE PAGE(4)
+
+void *dax_data;
+int nodax_fd;
+int dax_fd;
+bool done;
+
+#define err_exit(op)                                                          \
+{                                                                             \
+	fprintf(stderr, "%s %s: %s\n", __func__, op, strerror(errno));        \
+	exit(1);                                                              \
+}                                                                             \
+
+void punch_hole_fn(void *ptr)
+{
+	ssize_t read;
+	int rc;
+
+	while (!done) {
+		read = 0;
+
+		do {
+			rc = pread(nodax_fd, dax_data + read, FILE_SIZE - read,
+					read);
+			if (rc > 0)
+				read += rc;
+		} while (rc > 0);
+
+		if (read != FILE_SIZE || rc != 0)
+			err_exit("pread");
+
+		rc = fallocate(dax_fd,
+				FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
+				0, FILE_SIZE);
+		if (rc < 0)
+			err_exit("fallocate");
+
+		usleep(rand() % 1000);
+	}
+}
+
+void zero_range_fn(void *ptr)
+{
+	ssize_t read;
+	int rc;
+
+	while (!done) {
+		read = 0;
+
+		do {
+			rc = pread(nodax_fd, dax_data + read, FILE_SIZE - read,
+					read);
+			if (rc > 0)
+				read += rc;
+		} while (rc > 0);
+
+		if (read != FILE_SIZE || rc != 0)
+			err_exit("pread");
+
+		rc = fallocate(dax_fd,
+				FALLOC_FL_ZERO_RANGE | FALLOC_FL_KEEP_SIZE,
+				0, FILE_SIZE);
+		if (rc < 0)
+			err_exit("fallocate");
+
+		usleep(rand() % 1000);
+	}
+}
+
+void truncate_down_fn(void *ptr)
+{
+	ssize_t read;
+	int rc;
+
+	while (!done) {
+		read = 0;
+
+		if (ftruncate(dax_fd, 0) < 0)
+			err_exit("ftruncate");
+		if (fallocate(dax_fd, 0, 0, FILE_SIZE) < 0)
+			err_exit("fallocate");
+
+		do {
+			rc = pread(nodax_fd, dax_data + read, FILE_SIZE - read,
+					read);
+			if (rc > 0)
+				read += rc;
+		} while (rc > 0);
+
+		/*
+		 * For this test we ignore errors from pread().  These errors
+		 * can happen if we try and read while the other thread has
+		 * made the file size 0.
+		 */
+
+		usleep(rand() % 1000);
+	}
+}
+
+void collapse_range_fn(void *ptr)
+{
+	ssize_t read;
+	int rc;
+
+	while (!done) {
+		read = 0;
+
+		if (fallocate(dax_fd, 0, 0, FILE_SIZE) < 0)
+			err_exit("fallocate 1");
+		if (fallocate(dax_fd, FALLOC_FL_COLLAPSE_RANGE, 0, PAGE(1)) < 0)
+			err_exit("fallocate 2");
+		if (fallocate(dax_fd, 0, 0, FILE_SIZE) < 0)
+			err_exit("fallocate 3");
+
+		do {
+			rc = pread(nodax_fd, dax_data + read, FILE_SIZE - read,
+					read);
+			if (rc > 0)
+				read += rc;
+		} while (rc > 0);
+
+		/* For this test we ignore errors from pread. */
+
+		usleep(rand() % 1000);
+	}
+}
+
+void run_test(void (*test_fn)(void *))
+{
+	const int NUM_THREADS = 2;
+	pthread_t worker_thread[NUM_THREADS];
+	int i;
+
+	done = 0;
+	for (i = 0; i < NUM_THREADS; i++)
+		pthread_create(&worker_thread[i], NULL, (void*)test_fn, NULL);
+
+	sleep(1);
+	done = 1;
+
+	for (i = 0; i < NUM_THREADS; i++)
+		pthread_join(worker_thread[i], NULL);
+}
+
+int main(int argc, char *argv[])
+{
+	int err;
+
+	if (argc != 3) {
+		printf("Usage: %s <dax file> <non-dax file>\n",
+				basename(argv[0]));
+		exit(0);
+	}
+
+	dax_fd = open(argv[1], O_RDWR|O_CREAT, S_IRUSR|S_IWUSR);
+	if (dax_fd < 0)
+		err_exit("dax_fd open");
+
+	nodax_fd = open(argv[2], O_RDWR|O_CREAT|O_DIRECT, S_IRUSR|S_IWUSR);
+	if (nodax_fd < 0)
+		err_exit("nodax_fd open");
+
+	if (ftruncate(dax_fd, 0) < 0)
+		err_exit("dax_fd ftruncate");
+	if (fallocate(dax_fd, 0, 0, FILE_SIZE) < 0)
+		err_exit("dax_fd fallocate");
+
+	if (ftruncate(nodax_fd, 0) < 0)
+		err_exit("nodax_fd ftruncate");
+	if (fallocate(nodax_fd, 0, 0, FILE_SIZE) < 0)
+		err_exit("nodax_fd fallocate");
+
+	dax_data = mmap(NULL, FILE_SIZE, PROT_READ|PROT_WRITE, MAP_SHARED,
+			dax_fd, 0);
+	if (dax_data == MAP_FAILED)
+		err_exit("mmap");
+
+	run_test(&punch_hole_fn);
+	run_test(&zero_range_fn);
+	run_test(&truncate_down_fn);
+	run_test(&collapse_range_fn);
+
+	if (munmap(dax_data, FILE_SIZE) != 0)
+		err_exit("munmap");
+
+	err = close(dax_fd);
+	if (err < 0)
+		err_exit("dax_fd close");
+
+	err = close(nodax_fd);
+	if (err < 0)
+		err_exit("nodax_fd close");
+
+	return 0;
+}
diff --git a/tests/generic/999 b/tests/generic/999
new file mode 100755
index 00000000..8f488cb5
--- /dev/null
+++ b/tests/generic/999
@@ -0,0 +1,50 @@ 
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2018 Intel Corporation.  All Rights Reserved.
+#
+# FS QA Test generic/999
+#
+# This is a regression test for kernel patch:
+#   ext4: handle layout changes to pinned DAX mapping
+# created by Ross Zwisler <ross.zwisler@linux.intel.com>
+#
+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
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# Modify as appropriate.
+_supported_fs generic
+_supported_os Linux
+_require_test
+_require_test_program "t_mmap_collision"
+
+# turn off DAX on our scratch device so we can get normal O_DIRECT behavior
+export MOUNT_OPTIONS=""
+_scratch_unmount >> $seqres.full 2>&1
+_scratch_mount >> $seqres.full 2>&1
+
+# real QA test starts here
+$here/src/t_mmap_collision $TEST_DIR/testfile $SCRATCH_MNT/testfile
+
+# success, all done
+echo "Silence is golden"
+status=0
+exit
diff --git a/tests/generic/999.out b/tests/generic/999.out
new file mode 100644
index 00000000..3b276ca8
--- /dev/null
+++ b/tests/generic/999.out
@@ -0,0 +1,2 @@ 
+QA output created by 999
+Silence is golden
diff --git a/tests/generic/group b/tests/generic/group
index 83a6fdab..793f71ed 100644
--- a/tests/generic/group
+++ b/tests/generic/group
@@ -501,3 +501,4 @@ 
 496 auto quick swap
 497 auto quick swap collapse
 498 auto quick log
+999 auto quick dax