[PATCH v2 3/5] common/rc: introduce new helper function _fs_type_dev_dir()

[Mauricio Faria de Oliveira <mfo@canonical.com>]

In order to determine the fs type on fuse-overlayfs (coming)
we need to search for the mount point/directory; the device
is not enough. (details in the next patch.)

Thus the _fs_type() function is insufficient to determine
the filesystem type, as it only searches for mount device.

So, introduce the _fs_type_dev_dir() function, which also
searches for the mountpoint/dir in addition to the device.

The fs type fix-up sed script goes into a common function.

P.S.: there might be other sites that need similar changes,
since the mount device is also checked elsewhere, but just
with this bit tests can run, so it is good enough for now.)

Signed-off-by: Mauricio Faria de Oliveira <mfo@canonical.com>
---
 common/rc | 36 ++++++++++++++++++++++++++++--------
 1 file changed, 28 insertions(+), 8 deletions(-)

diff --git a/common/rc b/common/rc
index 1feae1a94f9e..5711eca2a1d2 100644
--- a/common/rc
+++ b/common/rc
@@ -1262,6 +1262,19 @@ _used()
     _df_device $1 | $AWK_PROG '{ sub("%", "") ; print $6 }'
 }
 
+# fix filesystem type up
+#
+_fix_fs_type()
+{
+    #
+    # The Linux kernel shows NFSv4 filesystems in df output as
+    # filesystem type nfs4, although we mounted it as nfs earlier.
+    # Fix the filesystem type up here so that the callers don't
+    # have to bother with this quirk.
+    #
+    sed -e 's/nfs4/nfs/' -e 's/fuse.glusterfs/glusterfs/'
+}
+
 # return the FS type of a mounted device
 #
 _fs_type()
@@ -1272,14 +1285,21 @@ _fs_type()
 	exit 1
     fi
 
-    #
-    # The Linux kernel shows NFSv4 filesystems in df output as
-    # filesystem type nfs4, although we mounted it as nfs earlier.
-    # Fix the filesystem type up here so that the callers don't
-    # have to bother with this quirk.
-    #
-    _df_device $1 | $AWK_PROG '{ print $2 }' | \
-        sed -e 's/nfs4/nfs/' -e 's/fuse.glusterfs/glusterfs/'
+    _df_device $1 | $AWK_PROG '{ print $2 }' | _fix_fs_type
+}
+
+# return the FS type of a mounted device
+# on a mount point directory (check both)
+#
+_fs_type_dev_dir()
+{
+    if [ $# -ne 2 ]
+    then
+	echo "Usage: _fs_type_dev_dir device directory" 1>&2
+	exit 1
+    fi
+
+    _df_dir $2 | $AWK_PROG -v what=$1 '($1==what) { print $2 }' | _fix_fs_type
 }
 
 # return the FS mount options of a mounted device
-- 
2.20.1