catch OSError to prevent breaking request /recon/diskusage

swift.common.utils.ismount maybe raise some OSError in some special
cases; and the request against /recon/diskusage doesn't handle it
before. This patch let output of mounted keyword is the error's message.

Change-Id: I5d9018f580181e618a3fa072b7a760d41795d8eb
Closes-Bug: #1249181

swift/common/middleware/recon.py

@@ -201,7 +201,14 @@ class ReconMiddleware(object):
         """get disk utilization statistics"""
         devices = []
         for entry in os.listdir(self.devices):
-            if check_mount(self.devices, entry):
+            try:
+                mounted = check_mount(self.devices, entry)
+            except OSError as err:
+                devices.append({'device': entry, 'mounted': str(err),
+                                'size': '', 'used': '', 'avail': ''})
+                continue
+
+            if mounted:
                 path = os.path.join(self.devices, entry)
                 disk = os.statvfs(path)
                 capacity = disk.f_bsize * disk.f_blocks

test/unit/common/middleware/test_recon.py

@@ -27,6 +27,10 @@ from swift.common.middleware import recon
 from swift.common.utils import json
 
 
+def fake_check_mount(a, b):
+    raise OSError('Input/Output Error')
+
+
 class FakeApp(object):
     def __call__(self, env, start_response):
         return "FAKE APP"
@@ -606,6 +610,14 @@ class TestReconSuccess(TestCase):
                           [(('/srv/node/canhazdrive1',), {})])
         self.assertEquals(rv, du_resp)
 
+    @mock.patch("swift.common.middleware.recon.check_mount", fake_check_mount)
+    def test_get_diskusage_oserror(self):
+        du_resp = [{'device': 'canhazdrive1', 'avail': '',
+                    'mounted': 'Input/Output Error', 'used': '', 'size': ''}]
+        self.mockos.ls_output = ['canhazdrive1']
+        rv = self.app.get_diskusage()
+        self.assertEquals(rv, du_resp)
+
     def test_get_quarantine_count(self):
         self.mockos.ls_output = ['sda']
         self.mockos.ismount_output = True