[Android] remount file system as writeable when failing to push files to external storage

build/android/provision_devices.py

Index: build/android/provision_devices.py
diff --git a/build/android/provision_devices.py b/build/android/provision_devices.py
index faf980f73dfd14ed9c7e917294d0010421327618..8188803b31f5ac337ee49fab62f4f1326ca50c4a 100755
--- a/build/android/provision_devices.py
+++ b/build/android/provision_devices.py
@@ -16,6 +16,7 @@ import json
 import logging
 import os
 import posixpath
+import random
 import re
 import subprocess
 import sys
@@ -99,6 +100,7 @@ def ProvisionDevice(device, blacklist, options):
       device.adb.WaitForDevice()
 
   try:
+    CheckExternalStorage(device)
     if should_run_phase(_PHASES.WIPE):
       if options.chrome_specific_wipe:
         run_phase(WipeChromeData)
@@ -126,6 +128,24 @@ def ProvisionDevice(device, blacklist, options):
                       str(device))
     blacklist.Extend([str(device)])
 
+def CheckExternalStorage(device):
+  """Checks that storage is writable and if not makes it writable.
+
+  Arguments:
+    device: The device to check.
+  """
+  # Write a file with random name to $EXTERNAL_STORAGE to test writability.

[jbudorick, 2015/09/28 18:01:17]

Use DeviceTempFile with dir=device.GetExternalStoragePath()

[rnephew (Reviews Here), 2015/09/28 18:34:06]

Done.

+  file_path = (
+      device.GetExternalStoragePath() + '/' + str(random.randint(0, 9999999)))
+  try:
+    device.WriteFile(file_path, 'test')
+  except device_errors.CommandFailedError:
+    logging.info('External storage not writable. Remounting / as RW')
+    device.RunShellCommand(['mount', '-o', 'remount,rw', '/'],
+                           check_return=True, as_root=True)
+    device.WriteFile(file_path, 'test')
+  finally:
+    device.RunShellCommand(['rm', file_path], check_return=True)
 
 def WipeChromeData(device, options):
   """Wipes chrome specific data from device
@@ -392,7 +412,6 @@ def _LaunchHostHeartbeat():
   subprocess.Popen([os.path.join(constants.DIR_SOURCE_ROOT,
                                  'build/android/host_heartbeat.py')])
 
-
 def KillHostHeartbeat():
   ps = subprocess.Popen(['ps', 'aux'], stdout=subprocess.PIPE)
   stdout, _ = ps.communicate()
@@ -402,7 +421,6 @@ def KillHostHeartbeat():
     pid = re.findall(r'(\S+)', match)[1]
     subprocess.call(['kill', str(pid)])
 
-
 def main():
   # Recommended options on perf bots:
   # --disable-network