Re: [PATCH v3] generic: test for seeing unseen fsync errors on newly open files

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On Sat, Apr 28, 2018 at 07:06:27PM -0400, Jeff Layton wrote:
> From: Jeff Layton <jlayton@xxxxxxxxxx>
> 
> This adds a regression test for the following kernel patch:
> 
>     errseq: Always report a writeback error once
> 
> This is motivated by some rather odd behavior done by the PostgreSQL
> project. The main database writers will offload the fsync calls to a
> separate process, which can open files after a writeback error has
> already occurred.
> 
> This used to work with older kernels that reported the error to only
> one fd, but with the errseq_t changes we lost the ability to see
> errors that occurred before the open. The above patch restores that
> behavior.
> 
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
>  tests/generic/999     | 95 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  tests/generic/999.out |  5 +++
>  tests/generic/group   |  1 +
>  3 files changed, 101 insertions(+)
>  create mode 100755 tests/generic/999
>  create mode 100644 tests/generic/999.out
> 
> diff --git a/tests/generic/999 b/tests/generic/999
> new file mode 100755
> index 000000000000..b816fd3bb423
> --- /dev/null
> +++ b/tests/generic/999
> @@ -0,0 +1,95 @@
> +#! /bin/bash
> +# FS QA Test No. XXX
                    ^^^ Need a test number here :)
> +#
> +# 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) 2018, Jeff Layton <jlayton@xxxxxxxxxx>
> +#
> +# 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 -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_nocheck
> +# This test uses "dm" without taking into account the data could be on
> +# realtime subvolume, thus the test will fail with rtinherit=1
> +_require_no_rtinherit
> +
> +_require_dm_target error
> +
> +rm -f $seqres.full
> +
> +echo "Format and mount"
> +_scratch_mkfs > $seqres.full 2>&1
> +_dmerror_init
> +_dmerror_mount
> +
> +datalen=65536
> +_require_fs_space $SCRATCH_MNT $datalen
> +
> +# use fd 5 to hold file open
> +testfile=$SCRATCH_MNT/fsync-open-after-err
> +exec 5>$testfile
> +
> +# write some data to file and fsync it out
> +$XFS_IO_PROG -c "pwrite -q 0 $datalen" -c fsync $testfile
> +
> +# flip device to non-working mode
> +_dmerror_load_error_table
> +
> +# rewrite the data, call sync to ensure it's written back w/o scraping error
> +$XFS_IO_PROG -c "pwrite -q 0 $datalen" -c sync $testfile
> +
> +# heal the device error
> +_dmerror_load_working_table
> +
> +# open again and call fsync
> +echo "The following fsync should fail with EIO:"
> +$XFS_IO_PROG -c fsync $testfile
> +echo "done"
                                                                                                                                                                                               
I built latest Linus tree, which should contain the mentioned fix, and I                                                                                                                       
saw different results on xfs, ext4 and btrfs.                                                                                                                                                  
                                                                                                                                                                                               
XFS fails the test as:                                                                                                                                                                         
    -fsync: Input/output error                                                                                                                                                                 
    +/mnt/scratch/fsync-open-after-err: Input/output error                                                                                                                                     
                                                                                                                                                                                               
While btrfs fails as:                                                                                                                                                                          
    -fsync: Input/output error                                                                                                                                                                 
    +/mnt/scratch/fsync-open-after-err: Read-only file system                                                                                                                                  
                                                                                                                                                                                               
And both XFS and btrfs behave in the same way no matter I have the fix                                                                                                                         
applied or not (tested on v4.16 kernel and v4.17-rc3+ kernel).                                                                                                                                 
                                                                                                                                                                                               
Only ext4 passes the test with v4.17-rc3+ kernel, and fails on v4.16                                                                                                                           
kernel as expected:                                                                                                                                                                            
    -fsync: Input/output error                                                                                                                                                                 
                                                                                                                                                                                               
Could you please take a look?                                                                                                                                                                  
                                                                                                                                                                                               
Thanks,                                                                                                                                                                                        
Eryu

> +
> +# close file
> +exec 5>&-
> +
> +# success, all done
> +_dmerror_unmount
> +_dmerror_cleanup
> +
> +status=0
> +exit
> diff --git a/tests/generic/999.out b/tests/generic/999.out
> new file mode 100644
> index 000000000000..38d2d7f6495f
> --- /dev/null
> +++ b/tests/generic/999.out
> @@ -0,0 +1,5 @@
> +QA output created by 999
> +Format and mount
> +The following fsync should fail with EIO:
> +fsync: Input/output error
> +done
> diff --git a/tests/generic/group b/tests/generic/group
> index ea8e51b35e79..48f491a5c32b 100644
> --- a/tests/generic/group
> +++ b/tests/generic/group
> @@ -486,3 +486,4 @@
>  481 auto quick log metadata
>  482 auto metadata replay
>  483 auto quick log metadata
> +999 auto quick
> -- 
> 2.14.3
> 
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