eCryptfs: Copy up lower inode attrs in getattr

The lower filesystem may do some type of inode revalidation during a
getattr call. eCryptfs should take advantage of that by copying the
lower inode attributes to the eCryptfs inode after a call to
vfs_getattr() on the lower inode.

I originally wrote this fix while working on eCryptfs on nfsv3 support,
but discovered it also fixed an eCryptfs on ext4 nanosecond timestamp
bug that was reported.

https://bugs.launchpad.net/bugs/613873

Cc: <stable@kernel.org>
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>

fs/ecryptfs/inode.c

@@ -1010,6 +1010,8 @@ int ecryptfs_getattr(struct vfsmount *mnt, struct dentry *dentry,
 	rc = vfs_getattr(ecryptfs_dentry_to_lower_mnt(dentry),
 			 ecryptfs_dentry_to_lower(dentry), &lower_stat);
 	if (!rc) {
+		fsstack_copy_attr_all(dentry->d_inode,
+				      ecryptfs_inode_to_lower(dentry->d_inode));
 		generic_fillattr(dentry->d_inode, stat);
 		stat->blocks = lower_stat.blocks;
 	}