common: extract rt extent size for _get_file_block_size

_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.

Note that ext* with bigalloc does not allocations to be aligned to the
cluster size, so no update is needed there.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

common/rc

@@ -3991,11 +3991,18 @@ _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.

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.