Re: [PATCH 11/8] common/inject: refactor helpers to use new errortag interface

[Brian Foster <bfoster@redhat.com>]

On Thu, Jun 29, 2017 at 09:13:08PM -0700, Darrick J. Wong wrote:
> Refactor the XFS error injection helpers to use the new errortag
> interface to configure error injection.  If that isn't present, fall
> back either to the xfs_io/ioctl based injection or the older sysfs
> knobs.  Refactor existing testcases to use the new helpers.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  common/inject |   62 +++++++++++++++++++++++++++++++++++++++++++++++++++++++--
>  tests/xfs/051 |    7 ++++--
>  tests/xfs/141 |    5 +++--
>  tests/xfs/196 |   17 ++++++----------
>  4 files changed, 73 insertions(+), 18 deletions(-)
> 
> diff --git a/common/inject b/common/inject
> index 8ecc290..1f12a2b 100644
> --- a/common/inject
> +++ b/common/inject
> @@ -35,10 +35,50 @@ _require_error_injection()
>  	esac
>  }
>  
> +# Find a given xfs mount's errortag injection knob in sysfs
> +_find_xfs_errortag_knob()
> +{
> +	dev="$1"
> +	knob="$2"
> +	shortdev="$(_short_dev "${dev}")"
> +	tagfile="/sys/fs/xfs/${shortdev}/errortag/${knob}"
> +
> +	# Some of the new sysfs errortag knobs were previously available via
> +	# another sysfs path.
> +	case "${knob}" in
> +	"log_bad_crc")
> +		if [ ! -w "${tagfile}" ]; then
> +			tagfile="/sys/fs/xfs/${shortdev}/log/log_badcrc_factor"
> +		fi
> +		;;
> +	"drop_writes")
> +		if [ ! -w "${tagfile}" ]; then
> +			tagfile="/sys/fs/xfs/${shortdev}/drop_writes"
> +		fi
> +		if [ ! -w "${tagfile}" ]; then
> +			tagfile="/sys/fs/xfs/${shortdev}/fail_writes"
> +		fi
> +		;;
> +	"log_recovery_delay"|"bug_on_assert")

What's the purpose for having these here? I'm not sure that either is
really related to error injection (which I find a little confusing
despite that this code can be reused to generically send a value to a
sysfs knob).

> +		# These apply to all xfs filesystems
> +		tagfile="/sys/fs/xfs/debug/${knob}"
> +		;;
> +	*)
> +		;;
> +	esac
> +
> +	echo "${tagfile}"
> +}
> +
>  # Requires that xfs_io inject command knows about this error type
>  _require_xfs_io_error_injection()
>  {
>  	type="$1"
> +
> +	# Can we find the error injection knobs via the new errortag
> +	# configuration mechanism?
> +	test -w "$(_find_xfs_errortag_knob "${TEST_DEV}" "${type}")" && return
> +
>  	_require_error_injection
>  
>  	# NOTE: We can't actually test error injection here because xfs
...
> diff --git a/tests/xfs/196 b/tests/xfs/196
> index e9b0649..5afc343 100755
> --- a/tests/xfs/196
> +++ b/tests/xfs/196
...
> @@ -53,13 +54,7 @@ rm -f $seqres.full
>  _supported_fs generic
>  _supported_os Linux
>  _require_scratch
> -
> -DROP_WRITES="drop_writes"
> -# replace "drop_writes" with "fail_writes" for old kernel
> -if [ -f /sys/fs/xfs/$(_short_dev $TEST_DEV)/fail_writes ];then
> -	DROP_WRITES="fail_writes"
> -fi
> -_require_xfs_sysfs $(_short_dev $TEST_DEV)/${DROP_WRITES}
> +_require_xfs_io_error_injection "drop_writes"
>  
>  _scratch_mkfs >/dev/null 2>&1
>  _scratch_mount
> @@ -72,7 +67,7 @@ bytes=$((64 * 1024))
>  $XFS_IO_PROG -f -c "pwrite 0 $bytes" $file >> $seqres.full 2>&1
>  
>  # Enable write drops. All buffered writes are dropped from this point on.
> -echo 1 > /sys/fs/xfs/$sdev/$DROP_WRITES
> +_scratch_inject_error "drop_writes"

I'd prefer to keep the parameter in this case (and below) just as a
defense against future changes in the default value. Otherwise the rest
looks pretty good.

Brian

>  
>  # Write every other 4k range to split the larger delalloc extent into many more
>  # smaller extents. Use pwrite because with write failures enabled, all
> @@ -89,7 +84,7 @@ for i in $(seq 4096 8192 $endoff); do
>  	$XFS_IO_PROG -c "pwrite $i 4k" $file >> $seqres.full 2>&1
>  done
>  
> -echo 0 > /sys/fs/xfs/$sdev/$DROP_WRITES
> +_scratch_inject_error "drop_writes" 0
>  
>  _scratch_cycle_mount
>  $XFS_IO_PROG -c 'bmap -vp' $file | _filter_bmap
> @@ -104,9 +99,9 @@ for offset in $(seq 0 100 500); do
>  	$XFS_IO_PROG -fc "pwrite ${offset}m 100m" $file >> $seqres.full 2>&1
>  
>  	punchoffset=$((offset + 75))
> -	echo 1 > /sys/fs/xfs/$sdev/$DROP_WRITES
> +	_scratch_inject_error "drop_writes"
>  	$XFS_IO_PROG -c "pwrite ${punchoffset}m 4k" $file >> $seqres.full 2>&1
> -	echo 0 > /sys/fs/xfs/$sdev/$DROP_WRITES
> +	_scratch_inject_error "drop_writes" 0
>  done
>  
>  echo "Silence is golden."
> --
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