Use containers procfs to parse mountinfo

Usually the mount is the first line making parsing way
faster than going through entire system mounts list.

Signed-off-by: Mrunal Patel <[email protected]>

container_layers.py

@@ -6,54 +6,65 @@
 import subprocess
 import sys
 
+
 def get_container_layers(id):
-        try:
-                container_status = subprocess.check_output(["runc", "state", container_id])
-        except subprocess.CalledProcessError:
-                print "container not found; probably exited"
-                sys.exit(0)
-
-        status_json = json.loads(container_status)
-        if status_json['status'] == "stopped":
-                print "container already stopped"
-                sys.exit(0)
-
-        rootfs_path = status_json['rootfs']
-        dir_path = os.path.dirname(rootfs_path)
-        top_layer_id = os.path.basename(dir_path)
-        container_mount_output = subprocess.check_output("mount | grep " + top_layer_id, shell=True)
-
-        if container_mount_output == "":
-                print "container not found; probably exited"
-                sys.exit(0)
-
-        layers = []
-        m = re.search('lowerdir=(.*),upperdir', container_mount_output)
-        if m:
-                lowerdirs = m.group(1).split(':')
-                for l in lowerdirs:
-                        layers.append(l)
-        else:
-                print "Unable to find lowerdir in mount output: ", container_mount_output
-                sys.exit(1)
-
-        m = re.search('upperdir=(.*),workdir', container_mount_output)
-        if m:
-                upperdir = m.group(1)
-                layers.append(upperdir)
-        else:
-                print "Unable to find upperdir in mount output: ", container_mount_output
-                sys.exit(1)
-
-        return layers
+    try:
+        container_status = subprocess.check_output(
+            ["runc", "state", container_id])
+    except subprocess.CalledProcessError:
+        print "container not found; probably exited"
+        sys.exit(0)
+
+    status_json = json.loads(container_status)
+    if status_json['status'] == "stopped":
+        print "container already stopped"
+        sys.exit(0)
+
+    rootfs_path = status_json['rootfs']
+    dir_path = os.path.dirname(rootfs_path)
+    top_layer_id = os.path.basename(dir_path)
+    container_pid = status_json['pid']
+
+    # Note: os.path.join failed for some reason on RHCOS
+    countainer_mounts_path = "/proc/" + str(container_pid) + "/mountinfo"
+    container_mount_output = ""
+    with open(countainer_mounts_path, "r") as f:
+        for line in f:
+            if re.search(top_layer_id, line):
+                container_mount_output = line
+                break
+
+    if container_mount_output == "":
+        print "container mount not found; probably exited"
+        sys.exit(0)
+
+    layers = []
+    m = re.search('lowerdir=(.*),upperdir', container_mount_output)
+    if m:
+        lowerdirs = m.group(1).split(':')
+        for l in lowerdirs:
+            layers.append(l)
+    else:
+        print "Unable to find lowerdir in mount output: ", container_mount_output
+        sys.exit(1)
+
+    m = re.search('upperdir=(.*),workdir', container_mount_output)
+    if m:
+        upperdir = m.group(1)
+        layers.append(upperdir)
+    else:
+        print "Unable to find upperdir in mount output: ", container_mount_output
+        sys.exit(1)
+
+    return layers
 
 
 if __name__ == "__main__":
-        if len(sys.argv) < 2:
-                print "Usage: sys.argv[0] <container_id>"
-                sys.exit(1)
-
-        container_id = sys.argv[1]
-        layers = get_container_layers(container_id)
-        for l in layers:
-                print l
+    if len(sys.argv) < 2:
+        print "Usage: sys.argv[0] <container_id>"
+        sys.exit(1)
+
+    container_id = sys.argv[1]
+    layers = get_container_layers(container_id)
+    for l in layers:
+        print l