common/xfs: Add _scratch_get_sfdir_prefix function

Move get_sfdir_prefix function from xfs/278 to commom/xfs
and rename it to _scratch_get_sfdir_prefix so it can be
used in other xfs tests.

This commit also changes xfs/278 to make use of
_scratch_get_sfdir_prefix instead previous one.

Signed-off-by: Marco Benatto <mbenatto@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

common/xfs

@@ -760,3 +760,18 @@ _require_xfs_spaceman_command()
 			_notrun "xfs_spaceman $command doesn't support $param"
 	fi
 }
+
+_scratch_get_sfdir_prefix() {
+	local dir_ino="$1"
+
+	for prefix in "u.sfdir3" "u.sfdir2" "u3.sfdir3"; do
+		if [ -n "$(_scratch_xfs_get_metadata_field \
+				"${prefix}.hdr.parent.i4" \
+				"inode ${dir_ino}")" ]; then
+			echo "${prefix}"
+			return 0
+		fi
+	done
+	_scratch_xfs_db -c "inode ${dir_ino}" -c 'p' >> $seqres.full
+	return 1
+}

tests/xfs/278

@@ -46,25 +46,11 @@ _scratch_unmount
 
 echo "Silence is goodness..."
 
-get_sfdir_prefix() {
-	local dir_ino="$1"
-
-	for prefix in "u.sfdir3" "u.sfdir2" "u3.sfdir3"; do
-		if [ -n "$(_scratch_xfs_get_metadata_field \
-				"${prefix}.hdr.parent.i4" \
-				"inode ${dir_ino}")" ]; then
-			echo "${prefix}"
-			return 0
-		fi
-	done
-	_scratch_xfs_db -c "inode ${dir_ino}" -c 'p' >> $seqres.full
-	return 1
-}
 set_ifield() {
 	_scratch_xfs_set_metadata_field "$1" 0 "inode $2" >> $seqres.full
 }
 
-sfdir_prefix="$(get_sfdir_prefix "$DIR_INO" || \
+sfdir_prefix="$(_scratch_get_sfdir_prefix "$DIR_INO" || \
 	_fail "Cannot determine sfdir prefix")"
 
 # Corrupt DIR