Re: [PATCH v2] xfs/011: support byte-based grant heads are stored in bytes now

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On Mon, Jul 15, 2024 at 08:24:53AM +0200, Christoph Hellwig wrote:
> New kernels where reservation grant track the actual reservation space
> consumed in bytes instead of LSNs in cycle/block tuples export different
> sysfs files for this information.
> 
> Adapt the test to detect which version is exported, and simply check
> for a near-zero reservation space consumption for the byte based version.
> 
> Based on work from Dave Chinner.
> 
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>

Seems fine to me
Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>

--D

> ---
> 
> Changes since v1:
>  - rebased to latests xfstests for-next
>  - improve a comment based on a mail from Dave Chinner
> 
>  tests/xfs/011 | 77 ++++++++++++++++++++++++++++++++++++---------------
>  1 file changed, 54 insertions(+), 23 deletions(-)
> 
> diff --git a/tests/xfs/011 b/tests/xfs/011
> index f9303d594..df967f098 100755
> --- a/tests/xfs/011
> +++ b/tests/xfs/011
> @@ -11,7 +11,15 @@
>  . ./common/preamble
>  _begin_fstest auto freeze log metadata quick
>  
> -# Import common functions.
> +_require_scratch
> +_require_freeze
> +_require_xfs_sysfs $(_short_dev $TEST_DEV)/log
> +_require_command "$KILLALL_PROG" killall
> +
> +. ./common/filter
> +
> +devname=`_short_dev $SCRATCH_DEV`
> +attrprefix="/sys/fs/xfs/$devname/log"
>  
>  # Override the default cleanup function.
>  _cleanup()
> @@ -24,27 +32,40 @@ _cleanup()
>  	rm -f $tmp.*
>  }
>  
> -# Use the information exported by XFS to sysfs to determine whether the log has
> -# active reservations after a filesystem freeze.
> -_check_scratch_log_state()
> +#
> +# The grant heads record reservations in bytes.
> +#
> +# The value is not exactly zero for complex reason.  In short: we must always
> +# have space for at least one minimum sized log write between ailp->ail_head_lsn
> +# and log->l_tail_lsn, and that is what is showing up in the grant head
> +# reservation values.  We don't need to explicitly reserve it for the first
> +# iclog write after mount, but we always end up with it being present after the
> +# first checkpoint commits and the AIL returns the checkpoint's unused space
> +# back to the grant head.
> +#
> +# Hence just check the value is between 0 and the maximum iclog size (256kB).
> +#
> +_check_scratch_log_state_new()
>  {
> -	devname=`_short_dev $SCRATCH_DEV`
> -	attrpath="/sys/fs/xfs/$devname/log"
> -
> -	# freeze the fs to ensure data is synced and the log is flushed. this
> -	# means no outstanding transactions, and thus no outstanding log
> -	# reservations, should exist
> -	xfs_freeze -f $SCRATCH_MNT
> +	for attr in "reserve_grant_head_bytes" "write_grant_head_bytes"; do
> +		space=`cat $attrprefix/$attr`
> +		_within_tolerance $space 1024 0 $((256 * 1024))
> +	done
> +}
>  
> -	# the log head is exported in basic blocks and the log grant heads in
> -	# bytes. convert the log head to bytes for precise comparison
> -	log_head_cycle=`awk -F : '{ print $1 }' $attrpath/log_head_lsn`
> -	log_head_bytes=`awk -F : '{ print $2 }' $attrpath/log_head_lsn`
> +#
> +# The log head is exported in basic blocks and the log grant heads in bytes.
> +# Convert the log head to bytes for precise comparison.
> +#
> +_check_scratch_log_state_old()
> +{
> +	log_head_cycle=`awk -F : '{ print $1 }' $attrprefix/log_head_lsn`
> +	log_head_bytes=`awk -F : '{ print $2 }' $attrprefix/log_head_lsn`
>  	log_head_bytes=$((log_head_bytes * 512))
>  
>  	for attr in "reserve_grant_head" "write_grant_head"; do
> -		cycle=`cat $attrpath/$attr | awk -F : '{ print $1 }'`
> -		bytes=`cat $attrpath/$attr | awk -F : '{ print $2 }'`
> +		cycle=`cat $attrprefix/$attr | awk -F : '{ print $1 }'`
> +		bytes=`cat $attrprefix/$attr | awk -F : '{ print $2 }'`
>  
>  		if [ $cycle != $log_head_cycle ] ||
>  		   [ $bytes != $log_head_bytes ]
> @@ -54,15 +75,25 @@ _check_scratch_log_state()
>  				"possible leak detected."
>  		fi
>  	done
> -
> -	xfs_freeze -u $SCRATCH_MNT
>  }
>  
> +# Use the information exported by XFS to sysfs to determine whether the log has
> +# active reservations after a filesystem freeze.
> +_check_scratch_log_state()
> +{
> +	# freeze the fs to ensure data is synced and the log is flushed. this
> +	# means no outstanding transactions, and thus no outstanding log
> +	# reservations, should exist
> +	xfs_freeze -f $SCRATCH_MNT
> +
> +	if [ -f "${attrprefix}/reserve_grant_head_bytes" ]; then
> +	    _check_scratch_log_state_new
> +	else
> +	    _check_scratch_log_state_old
> +	fi
>  
> -_require_scratch
> -_require_freeze
> -_require_xfs_sysfs $(_short_dev $TEST_DEV)/log
> -_require_command "$KILLALL_PROG" killall
> +	xfs_freeze -u $SCRATCH_MNT
> +}
>  
>  echo "Silence is golden."
>  
> -- 
> 2.43.0
> 
> 




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