Re: [PATCH 1/9] common: extract rt extent size for _get_file_block_size

[Christoph Hellwig <hch@infradead.org>]

On Tue, Oct 27, 2020 at 12:01:35PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> _get_file_block_size is intended to return the size (in bytes) of the
> fundamental allocation unit for a file.  This is required for remapping
> operations like fallocate and reflink, which can only operate on
> allocation units.  Since the XFS realtime volume can be configure for
> allocation units larger than 1 fs block, we need to factor that in here.

Should this also cover the ext4 bigalloc clusters?  Or do they not
matter for fallocate?

> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  common/rc  |   13 ++++++++++---
>  common/xfs |   20 ++++++++++++++++++++
>  2 files changed, 30 insertions(+), 3 deletions(-)
> 
> 
> diff --git a/common/rc b/common/rc
> index 27a27ea3..41f93047 100644
> --- a/common/rc
> +++ b/common/rc
> @@ -3974,11 +3974,18 @@ _get_file_block_size()
>  		echo "Missing mount point argument for _get_file_block_size"
>  		exit 1
>  	fi
> -	if [ "$FSTYP" = "ocfs2" ]; then
> +
> +	case "$FSTYP" in
> +	"ocfs2")
>  		stat -c '%o' $1
> -	else
> +		;;
> +	"xfs")
> +		_xfs_get_file_block_size $1
> +		;;
> +	*)
>  		_get_block_size $1
> -	fi
> +		;;
> +	esac
>  }
>  
>  # Get the minimum block size of an fs.
> diff --git a/common/xfs b/common/xfs
> index 79dab058..3f5c14ba 100644
> --- a/common/xfs
> +++ b/common/xfs
> @@ -174,6 +174,26 @@ _scratch_mkfs_xfs()
>  	return $mkfs_status
>  }
>  
> +# Get the size of an allocation unit of a file.  Normally this is just the
> +# block size of the file, but for realtime files, this is the realtime extent
> +# size.
> +_xfs_get_file_block_size()
> +{
> +	local path="$1"
> +
> +	if ! ($XFS_IO_PROG -c "stat -v" "$path" 2>&1 | egrep -q '(rt-inherit|realtime)'); then
> +		_get_block_size "$path"
> +		return
> +	fi
> +
> +	# Otherwise, call xfs_info until we find a mount point or the root.
> +	path="$(readlink -m "$path")"
> +	while ! $XFS_INFO_PROG "$path" &>/dev/null && [ "$path" != "/" ]; do
> +		path="$(dirname "$path")"
> +	done
> +	$XFS_INFO_PROG "$path" | grep realtime | sed -e 's/^.*extsz=\([0-9]*\).*$/\1/g'
> +}
> +
>  # xfs_check script is planned to be deprecated. But, we want to
>  # be able to invoke "xfs_check" behavior in xfstests in order to
>  # maintain the current verification levels.
> 
---end quoted text---