[2/3] ext4: test for DAX + journaling corruption

Add a regression test for the following kernel commit:

  ext4: prevent data corruption with journaling + DAX

The test passes if either we successfully compare the data between the mmap
with journaling turned on and the one with journaling turned off, or if we
fail the chattr command to turn on or off journaling.  The latter is how we
prevent this issue in the kernel.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
---
 .gitignore                          |  1 +
 src/Makefile                        |  2 +-
 src/t_ext4_dax_journal_corruption.c | 93 +++++++++++++++++++++++++++++++++++++
 tests/ext4/030                      | 68 +++++++++++++++++++++++++++
 tests/ext4/030.out                  |  2 +
 tests/ext4/group                    |  1 +
 6 files changed, 166 insertions(+), 1 deletion(-)
 create mode 100644 src/t_ext4_dax_journal_corruption.c
 create mode 100755 tests/ext4/030
 create mode 100644 tests/ext4/030.out

On Mon, Sep 11, 2017 at 10:45:20PM -0600, Ross Zwisler wrote:
> Add a regression test for the following kernel commit:
> 
>   ext4: prevent data corruption with journaling + DAX
> 
> The test passes if either we successfully compare the data between the mmap
> with journaling turned on and the one with journaling turned off, or if we
> fail the chattr command to turn on or off journaling.  The latter is how we
> prevent this issue in the kernel.

Yeah, I noticed that mounting ext4 with "-o dax,data=journal" is not
allowed, enabling data journaling on a dax mount should be stopped too.

> 
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> ---
>  .gitignore                          |  1 +
>  src/Makefile                        |  2 +-
>  src/t_ext4_dax_journal_corruption.c | 93 +++++++++++++++++++++++++++++++++++++
>  tests/ext4/030                      | 68 +++++++++++++++++++++++++++
>  tests/ext4/030.out                  |  2 +
>  tests/ext4/group                    |  1 +
>  6 files changed, 166 insertions(+), 1 deletion(-)
>  create mode 100644 src/t_ext4_dax_journal_corruption.c
>  create mode 100755 tests/ext4/030
>  create mode 100644 tests/ext4/030.out
> 
> diff --git a/.gitignore b/.gitignore
> index 2accc37..4bdc5bf 100644
> --- a/.gitignore
> +++ b/.gitignore
> @@ -154,6 +154,7 @@
>  /src/t_mmap_stale_pmd
>  /src/t_mmap_cow_race
>  /src/t_mmap_fallocate
> +/src/t_ext4_dax_journal_corruption

Better to add new entry in alphabetical order, I know there're already
some out-of-order entries there, but this one is not affected and better
to stop adding new ones :)

>  
>  # dmapi/ binaries
>  /dmapi/src/common/cmd/read_invis
> diff --git a/src/Makefile b/src/Makefile
> index b8aff49..e6558e2 100644
> --- a/src/Makefile
> +++ b/src/Makefile
> @@ -13,7 +13,7 @@ TARGETS = dirstress fill fill2 getpagesize holes lstat64 \
>  	multi_open_unlink dmiperf unwritten_sync genhashnames t_holes \
>  	t_mmap_writev t_truncate_cmtime dirhash_collide t_rename_overwrite \
>  	holetest t_truncate_self t_mmap_dio af_unix t_mmap_stale_pmd \
> -	t_mmap_cow_race t_mmap_fallocate fsync-err
> +	t_mmap_cow_race t_mmap_fallocate fsync-err t_ext4_dax_journal_corruption
>  
>  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_ext4_dax_journal_corruption.c b/src/t_ext4_dax_journal_corruption.c
> new file mode 100644
> index 0000000..e0d63f8
> --- /dev/null
> +++ b/src/t_ext4_dax_journal_corruption.c
> @@ -0,0 +1,93 @@
> +#include <errno.h>
> +#include <fcntl.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <sys/mman.h>
> +#include <sys/stat.h>
> +#include <sys/types.h>
> +#include <time.h>
> +#include <unistd.h>
> +
> +#define PAGE(a) ((a)*0x1000)
> +#define STRLEN 256
> +
> +void err_exit(char *op)
> +{
> +	fprintf(stderr, "%s: %s\n", op, strerror(errno));
> +	exit(1);
> +}
> +
> +void chattr_cmd(char *chattr, char *cmd, char *file)
> +{
> +	int ret;
> +	char command[STRLEN];
> +
> +	ret = snprintf(command, STRLEN, "%s %s %s 2>/dev/null", chattr, cmd, file);
> +	if (ret < 0)
> +		err_exit("snprintf");
> +
> +	ret = system(command);
> +	if (ret) /* Success - the kernel fix is to have this chattr fail */
> +		exit(77);
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +	int fd, err, len = PAGE(1);
> +	char *data, *dax_data, *chattr, *file;
> +	char string[STRLEN];
> +
> +	if (argc < 3) {
> +		printf("Usage: %s <chattr program> <file>\n", basename(argv[0]));
> +		exit(0);
> +	}
> +
> +	chattr = argv[1];
> +	file = argv[2];
> +
> +	srand(time(NULL));
> +	snprintf(string, STRLEN, "random number %d\n", rand());
> +
> +	fd = open(file, O_RDWR|O_CREAT, S_IRUSR|S_IWUSR);
> +	if (fd < 0)
> +		err_exit("fd");
> +
> +	/* begin with journaling off and DAX on */
> +	chattr_cmd(chattr, "-j", file);
> +
> +	ftruncate(fd, 0);
> +	fallocate(fd, 0, 0, len);
> +
> +	dax_data = mmap(NULL, len, PROT_READ, MAP_SHARED, fd, 0);
> +	if (!dax_data)
> +		err_exit("mmap dax_data");
> +
> +	/* turns on journaling, and turns off DAX */
> +	chattr_cmd(chattr, "+j", file);

I'm a bit confused here, just from the test code, it's not obvious to me
how DAX is turned off. I looked at the kernel code and there's a comment
saying: "Update inode->i_flags after EXT4_INODE_JOURNAL_DATA was
updated. E.g. S_DAX may get cleared / set." But isn't the per-inode dax
flag proposal rejected?

Anyway, some comments to explain how is DAX being turned off would be
good here.

> +
> +	data = mmap(NULL, len, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
> +	if (!data)
> +		err_exit("mmap data");
> +
> +	/*
> +	 * Write the data using the non-DAX mapping, and try and read it back
> +	 * using the DAX mapping.
> +	 */
> +	strcpy(data, string);
> +	if (strcmp(dax_data, string) != 0)
> +		printf("Data miscompare\n");
> +
> +	err = munmap(data, len);
> +	if (err < 0)
> +		err_exit("munmap data");
> +
> +	err = munmap(dax_data, len);
> +	if (err < 0)
> +		err_exit("munmap dax_data");
> +
> +	err = close(fd);
> +	if (err < 0)
> +		err_exit("close");
> +	return 0;
> +}
> diff --git a/tests/ext4/030 b/tests/ext4/030
> new file mode 100755
> index 0000000..3ac4952
> --- /dev/null
> +++ b/tests/ext4/030
> @@ -0,0 +1,68 @@
> +#! /bin/bash
> +# FS QA Test ext4/030
> +#
> +# This is a regression test for kernel patch:
> +#   ext4: prevent data corruption with journaling + DAX
> +# created by Ross Zwisler <ross.zwisler@linux.intel.com>
> +#
> +#-----------------------------------------------------------------------
> +# Copyright (c) 2017 Intel Corporation.  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.*
> +}
> +
> +# get standard environment, filters and checks
> +. ./common/rc
> +. ./common/filter
> +
> +# remove previous $seqres.full before test
> +rm -f $seqres.full
> +
> +# Modify as appropriate.
> +_supported_os Linux
> +_supported_fs ext4
> +_require_scratch_dax
> +_require_test_program "t_ext4_dax_journal_corruption"

_require_command "$CHATTR_PROG" chattr

> +
> +# real QA test starts here
> +_scratch_mkfs > $seqres.full 2>&1
> +_scratch_mount "-o dax,nodelalloc" >> $seqres.full 2>&1

Hmm, why do we need nodelalloc, need some comments too.

> +
> +src/t_ext4_dax_journal_corruption $CHATTR_PROG $SCRATCH_MNT/testfile

Let's use "$here/src/t_...", Christoph pointed this out in another
thread so I pay attention to it in review now :)

Thanks,
Eryu

> +
> +if [[ $? != 0 && $? != 77 ]]; then
> +	echo "Test failed, status $?"
> +	exit 1
> +fi
> +
> +# success, all done
> +echo "Silence is golden"
> +status=0
> +exit
> diff --git a/tests/ext4/030.out b/tests/ext4/030.out
> new file mode 100644
> index 0000000..06a1c8f
> --- /dev/null
> +++ b/tests/ext4/030.out
> @@ -0,0 +1,2 @@
> +QA output created by 030
> +Silence is golden
> diff --git a/tests/ext4/group b/tests/ext4/group
> index 257bb64..ef768df 100644
> --- a/tests/ext4/group
> +++ b/tests/ext4/group
> @@ -32,6 +32,7 @@
>  027 auto quick fsmap
>  028 auto quick fsmap
>  029 auto quick fsmap
> +030 auto quick
>  271 auto rw quick
>  301 aio auto ioctl rw stress defrag
>  302 aio auto ioctl rw stress defrag
> -- 
> 2.9.5
>