bitbake: fetch2: Add NFS Stale file exception handling

- In some cases the file descriptor
  is held by nfs client and none of os.path.* is catching
  that, it could mean that error is not doled out because
  client has cached the stat info. In this case we are
  out of luck. Needed to catch IOError, which would be
  causing the Stale error.

- In download method, update_stamp is invoked
  md5sum validation which is found to be throwing
  Stale errors.
- Added error handling to fix the stale errors.

(Bitbake rev: 5a53e7d7b017769a6eb0f0a6335735a1fe51a5ec)

Signed-off-by: Balaji Punnuru <balaji_punnuru@cable.comcast.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/fetch2/__init__.py

@@ -35,6 +35,7 @@ import operator
 import collections
 import subprocess
 import pickle
+import errno
 import bb.persist_data, bb.utils
 import bb.checksum
 from bb import data
@@ -998,6 +999,12 @@ def try_mirror_url(fetch, origud, ud, ld, check = False):
     except bb.fetch2.NetworkAccess:
         raise
 
+    except IOError as e:
+        if e.errno in [os.errno.ESTALE]:
+            logger.warn("Stale Error Observed %s." % ud.url)
+            return False
+        raise
+
     except bb.fetch2.BBFetchException as e:
         if isinstance(e, ChecksumError):
             logger.warning("Mirror checksum failure for url %s (original url: %s)\nCleaning and trying again." % (ud.url, origud.url))
@@ -1646,6 +1653,11 @@ class Fetch(object):
 
                 update_stamp(ud, self.d)
 
+            except IOError as e:
+                if e.errno in [os.errno.ESTALE]:
+                    logger.error("Stale Error Observed %s." % u)
+                    raise ChecksumError("Stale Error Detected")
+
             except BBFetchException as e:
                 if isinstance(e, ChecksumError):
                     logger.error("Checksum failure fetching %s" % u)