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Date: Wed, 31 May 2017 16:02:39 -0400
From: Jeff Layton <jlayton@...hat.com>
To: Eduardo Valentin <eduval@...zon.com>
Cc: fstests@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>,
Al Viro <viro@...IV.linux.org.uk>, Jan Kara <jack@...e.cz>,
tytso@....edu, axboe@...nel.dk, mawilcox@...rosoft.com,
ross.zwisler@...ux.intel.com, corbet@....net, dhowells@...hat.com,
linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
linux-doc@...r.kernel.org
Subject: Re: [xfstests PATCH v3 1/5] generic: add a writeback error handling
test
On Wed, 2017-05-31 at 11:59 -0700, Eduardo Valentin wrote:
> Hello,
>
> On Wed, May 31, 2017 at 09:08:16AM -0400, Jeff Layton wrote:
> > I'm working on a set of kernel patches to change how writeback errors
> > are handled and reported in the kernel. Instead of reporting a
> > writeback error to only the first fsync caller on the file, I aim
> > to make the kernel report them once on every file description.
> >
> > This patch adds a test for the new behavior. Basically, open many fds
> > to the same file, turn on dm_error, write to each of the fds, and then
> > fsync them all to ensure that they all get an error back.
> >
> > To do that, I'm adding a new tools/dmerror script that the C program
> > can use to load the error table. For now, that's all it can do, but
> > we can fill it out with other commands as necessary.
> >
> > Signed-off-by: Jeff Layton <jlayton@...hat.com>
> > ---
> > common/dmerror | 13 ++--
> > doc/auxiliary-programs.txt | 8 +++
> > src/Makefile | 2 +-
> > src/fsync-err.c | 161 +++++++++++++++++++++++++++++++++++++++++++++
> > tests/generic/999 | 76 +++++++++++++++++++++
> > tests/generic/999.out | 3 +
> > tests/generic/group | 1 +
> > tools/dmerror | 44 +++++++++++++
> > 8 files changed, 302 insertions(+), 6 deletions(-)
> > create mode 100644 src/fsync-err.c
> > create mode 100755 tests/generic/999
> > create mode 100644 tests/generic/999.out
> > create mode 100755 tools/dmerror
> >
> > diff --git a/common/dmerror b/common/dmerror
> > index d46c5d0b7266..238baa213b1f 100644
> > --- a/common/dmerror
> > +++ b/common/dmerror
> > @@ -23,22 +23,25 @@ if [ $? -eq 0 ]; then
> > _notrun "Cannot run tests with DAX on dmerror devices"
> > fi
> >
> > -_dmerror_init()
> > +_dmerror_setup()
> > {
> > local dm_backing_dev=$SCRATCH_DEV
> >
> > - $DMSETUP_PROG remove error-test > /dev/null 2>&1
> > -
> > local blk_dev_size=`blockdev --getsz $dm_backing_dev`
> >
> > DMERROR_DEV='/dev/mapper/error-test'
> >
> > DMLINEAR_TABLE="0 $blk_dev_size linear $dm_backing_dev 0"
> >
> > + DMERROR_TABLE="0 $blk_dev_size error $dm_backing_dev 0"
> > +}
> > +
> > +_dmerror_init()
> > +{
> > + _dmerror_setup
> > + $DMSETUP_PROG remove error-test > /dev/null 2>&1
> > $DMSETUP_PROG create error-test --table "$DMLINEAR_TABLE" || \
> > _fatal "failed to create dm linear device"
> > -
> > - DMERROR_TABLE="0 $blk_dev_size error $dm_backing_dev 0"
> > }
> >
> > _dmerror_mount()
> > diff --git a/doc/auxiliary-programs.txt b/doc/auxiliary-programs.txt
> > index 21ef118596b6..191ac0596511 100644
> > --- a/doc/auxiliary-programs.txt
> > +++ b/doc/auxiliary-programs.txt
> > @@ -16,6 +16,7 @@ note the dependency with:
> > Contents:
> >
> > - af_unix -- Create an AF_UNIX socket
> > + - fsync-err -- tests fsync error reporting after failed writeback
> > - open_by_handle -- open_by_handle_at syscall exercise
> > - stat_test -- statx syscall exercise
> > - t_dir_type -- print directory entries and their file type
> > @@ -30,6 +31,13 @@ af_unix
> >
> > The af_unix program creates an AF_UNIX socket at the given location.
> >
> > +fsync-err
> > + Specialized program for testing how the kernel reports errors that
> > + occur during writeback. Works in conjunction with the dmerror script
> > + in tools/ to write data to a device, and then force it to fail
> > + writeback and test that errors are reported during fsync and cleared
> > + afterward.
> > +
> > open_by_handle
> >
> > The open_by_handle program exercises the open_by_handle_at() system
> > diff --git a/src/Makefile b/src/Makefile
> > index 4ec01975f8f7..b79c4d84d31b 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_cow_race fsync-err
> >
> > 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/fsync-err.c b/src/fsync-err.c
> > new file mode 100644
> > index 000000000000..cbeb37fb1790
> > --- /dev/null
> > +++ b/src/fsync-err.c
> > @@ -0,0 +1,161 @@
> > +/*
> > + * fsync-err.c: test whether writeback errors are reported to all open fds
> > + * and properly cleared as expected after being seen once on each
> > + *
> > + * Copyright (c) 2017: Jeff Layton <jlayton@...hat.com>
> > + */
> > +#include <sys/types.h>
> > +#include <sys/stat.h>
> > +#include <errno.h>
> > +#include <fcntl.h>
> > +#include <stdlib.h>
> > +#include <stdio.h>
> > +#include <string.h>
> > +#include <unistd.h>
> > +
> > +/*
> > + * btrfs has a fixed stripewidth of 64k, so we need to write enough data to
> > + * ensure that we hit both stripes.
> > + *
> > + * FIXME: have the test script pass in the length?
> > + */
> > +#define BUFSIZE (65 * 1024)
> > +
> > +/* FIXME: should this be tunable */
> > +#define NUM_FDS 10
> > +
> > +static void usage() {
> > + fprintf(stderr, "Usage: fsync-err <filename>\n");
> > +}
>
> Just to follow the same style as your main:
>
> +static void usage()
> +{
> + fprintf(stderr, "Usage: fsync-err <filename>\n");
> +}
>
> > +
> > +int main(int argc, char **argv)
> > +{
> > + int fd[NUM_FDS], ret, i;
> > + char *fname, *buf;
> > +
> > + if (argc < 1) {
> > + usage();
> > + return 1;
> > + }
> > +
> > + /* First argument is filename */
> > + fname = argv[1];
> > +
> > + for (i = 0; i < NUM_FDS; ++i) {
> > + fd[i] = open(fname, O_WRONLY | O_CREAT | O_TRUNC, 0644);
> > + if (fd[i] < 0) {
> > + printf("open of fd[%d] failed: %m\n", i);
> > + return 1;
> > + }
> > + }
> > +
> > + buf = malloc(BUFSIZE);
> > + if (!buf) {
> > + printf("malloc failed: %m\n");
> > + return 1;
> > + }
> > +
> > + memset(buf, 0x7c, BUFSIZE);
> > +
> > + for (i = 0; i < NUM_FDS; ++i) {
> > + ret = write(fd[i], buf, BUFSIZE);
> > + if (ret < 0) {
> > + printf("First write on fd[%d] failed: %m\n", i);
> > + return 1;
> > + }
> > + }
> > +
> > + for (i = 0; i < NUM_FDS; ++i) {
> > + ret = fsync(fd[i]);
> > + if (ret < 0) {
> > + printf("First fsync on fd[%d] failed: %m\n", i);
> > + return 1;
> > + }
> > + }
> > +
> > + /* flip the device to non-working mode */
> > + ret = system("./tools/dmerror load_error_table");
>
> Just assuming a hardcoded relative path?
>
The callers in tests/ call commands with hardcoded paths like "src/", so
I figured that was OK here.
Is there some other way we should do this? I'd prefer to shell out to
the dmerror tool than reimplement it here.
> > + if (ret) {
> > + if (WIFEXITED(ret))
> > + printf("system: program exited: %d\n",
> > + WEXITSTATUS(ret));
> > + else
> > + printf("system: 0x%x\n", (int)ret);
> > +
> > + return 1;
> > + }
> > +
> > + for (i = 0; i < NUM_FDS; ++i) {
> > + ret = write(fd[i], buf, strlen(buf) + 1);
>
> Why not BUFSIZE here?
>
Good catch. It should be BUFSIZE.
> > + if (ret < 0) {
> > + printf("Second write on fd[%d] failed: %m\n", i);
> > + return 1;
> > + }
> > + }
> > +
> > + for (i = 0; i < NUM_FDS; ++i) {
> > + ret = fsync(fd[i]);
> > + /* Now, we EXPECT the error! */
> > + if (ret >= 0) {
> > + printf("Success on second fsync on fd[%d]!\n", i);
> > + return 1;
> > + }
> > + }
> > +
> > + for (i = 0; i < NUM_FDS; ++i) {
> > + ret = fsync(fd[i]);
> > + if (ret < 0) {
> > + /* Now the error should be clear */
> > + printf("Third fsync on fd[%d] failed: %m\n", i);
> > + return 1;
> > + }
> > + }
> > +
> > + /* flip the device to working mode */
> > + ret = system("./tools/dmerror load_working_table");
> > + if (ret) {
> > + if (WIFEXITED(ret))
> > + printf("system: program exited: %d\n",
> > + WEXITSTATUS(ret));
> > + else
> > + printf("system: 0x%x\n", (int)ret);
> > +
> > + return 1;
> > + }
> > +
> > + for (i = 0; i < NUM_FDS; ++i) {
> > + ret = fsync(fd[i]);
> > + if (ret < 0) {
> > + /* The error should still be clear */
> > + printf("fsync after healing device on fd[%d] failed: %m\n", i);
> > + return 1;
> > + }
> > + }
> > +
> > + /*
> > + * reopen each file one at a time to ensure the same inode stays
> > + * in core. fsync each one to make sure we see no errors on a fresh
> > + * open of the inode.
> > + */
> > + for (i = 0; i < NUM_FDS; ++i) {
> > + ret = close(fd[i]);
> > + if (ret < 0) {
> > + printf("Close of fd[%d] returned unexpected error: %m\n", i);
> > + return 1;
> > + }
> > + fd[i] = open(fname, O_WRONLY | O_CREAT | O_TRUNC, 0644);
> > + if (fd[i] < 0) {
> > + printf("Second open of fd[%d] failed: %m\n", i);
> > + return 1;
> > + }
> > + ret = fsync(fd[i]);
> > + if (ret < 0) {
> > + /* New opens should not return an error */
> > + printf("First fsync after reopen of fd[%d] failed: %m\n", i);
> > + return 1;
> > + }
> > + }
> > +
> > + printf("Test passed!\n");
> > + return 0;
> > +}
> > diff --git a/tests/generic/999 b/tests/generic/999
> > new file mode 100755
> > index 000000000000..6de143d1149e
> > --- /dev/null
> > +++ b/tests/generic/999
> > @@ -0,0 +1,76 @@
> > +#! /bin/bash
> > +# FS QA Test No. 999
> > +#
> > +# Open a file several times, write to it, fsync on all fds and make sure that
> > +# they all return 0. Change the device to start throwing errors. Write again
> > +# on all fds and fsync on all fds. Ensure that we get errors on all of them.
> > +# Then fsync on all one last time and verify that all return 0.
> > +#
> > +#-----------------------------------------------------------------------
> > +# Copyright (c) 2017, Jeff Layton <jlayton@...hat.com>
> > +#
> > +# 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
> > +#-----------------------------------------------------------------------
>
> Sure you want to track the address? Maybe just remove it?
>
Will do. I ended up copying and pasting instead of doing the "new"
script like I probably should have. I'll go back and read the docs and
make sure I get the boilerplate stuff right.
> > +
>
>
>
> > +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 -rf $tmp.* $testdir
> > + _dmerror_cleanup
> > +}
> > +
> > +# get standard environment, filters and checks
> > +. ./common/rc
> > +. ./common/filter
> > +. ./common/dmerror
> > +
> > +# real QA test starts here
> > +_supported_os Linux
> > +_require_scratch
> > +_require_logdev
> > +_require_dm_target error
> > +_require_test_program fsync-err
> > +
> > +rm -f $seqres.full
> > +
> > +echo "Format and mount"
> > +$XFS_IO_PROG -d -c "pwrite -S 0x7c -b 1048576 0 $((64 * 1048576))" $SCRATCH_DEV >> $seqres.full
> > +_scratch_mkfs > $seqres.full 2>&1
> > +_dmerror_init
> > +_dmerror_mount >> $seqres.full 2>&1
> > +_dmerror_unmount
> > +_dmerror_mount
> > +
> > +_require_fs_space $SCRATCH_MNT 8192
> > +
> > +testfile=$SCRATCH_MNT/fsync-err-test
> > +
> > +$here/src/fsync-err $testfile
> > +
> > +# success, all done
> > +_dmerror_load_working_table
> > +_dmerror_unmount
> > +_dmerror_cleanup
> > +_repair_scratch_fs >> $seqres.full
> > +status=0
> > +exit
> > diff --git a/tests/generic/999.out b/tests/generic/999.out
> > new file mode 100644
> > index 000000000000..2e48492ff6d1
> > --- /dev/null
> > +++ b/tests/generic/999.out
> > @@ -0,0 +1,3 @@
> > +QA output created by 999
> > +Format and mount
> > +Test passed!
> > diff --git a/tests/generic/group b/tests/generic/group
> > index 438c299030f2..39f7b14657f1 100644
> > --- a/tests/generic/group
> > +++ b/tests/generic/group
> > @@ -440,3 +440,4 @@
> > 435 auto encrypt
> > 436 auto quick rw
> > 437 auto quick
> > +999 auto quick
> > diff --git a/tools/dmerror b/tools/dmerror
> > new file mode 100755
> > index 000000000000..4aaf682ee5f9
> > --- /dev/null
> > +++ b/tools/dmerror
> > @@ -0,0 +1,44 @@
> > +#!/bin/bash
> > +#-----------------------------------------------------------------------
> > +# Copyright (c) 2017, Jeff Layton <jlayton@...hat.com>
> > +#
> > +# 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
> > +#-----------------------------------------------------------------------
> > +
> > +. ./common/config
> > +. ./common/dmerror
> > +
> > +_dmerror_setup
> > +
> > +case $1 in
> > +cleanup)
> > + _dmerror_cleanup
> > + ;;
> > +init)
> > + _dmerror_init
> > + ;;
> > +load_error_table)
> > + _dmerror_load_error_table
> > + ;;
> > +load_working_table)
> > + _dmerror_load_working_table
> > + ;;
> > +*)
> > + echo "Usage: $0 {init|cleanup|load_error_table|load_working_table}"
> > + exit 1
> > + ;;
> > +esac
> > +
> > +status=0
> > +exit
> > --
> > 2.9.4
> >
> >
>
>
Thanks for the review!
--
Jeff Layton <jlayton@...hat.com>
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