nfs: Fix ugly referral attributes

nfs: Fix ugly referral attributes

BugLink: http://bugs.launchpad.net/bugs/1744873
commit c05cefcc72416a37eba5a2b35f0704ed758a9145 upstream.

Before traversing a referral and performing a mount, the mounted-on
directory looks strange:

dr-xr-xr-x. 2 4294967294 4294967294 0 Dec 31  1969 dir.0

nfs4_get_referral is wiping out any cached attributes with what was
returned via GETATTR(fs_locations), but the bit mask for that
operation does not request any file attributes.

Retrieve owner and timestamp information so that the memcpy in
nfs4_get_referral fills in more attributes.

Changes since v1:
- Don't request attributes that the client unconditionally replaces
- Request only MOUNTED_ON_FILEID or FILEID attribute, not both
- encode_fs_locations() doesn't use the third bitmask word

Fixes: 6b97fd3da1ea ("NFSv4: Follow a referral")
Suggested-by: Pradeep Thomas <pradeepthomas@gmail.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>