NFSv4: Optimise away forced revalidation when we know the attributes are OK

The NFS_INO_REVAL_FORCED flag needs to be set if we just got a delegation,
and we see that there might still be some ambiguity as to whether or not
our attribute or data cache are valid.
In practice, this means that a call to nfs_check_inode_attributes() will
have noticed a discrepancy between cached attributes and measured ones,
so let's move the setting of NFS_INO_REVAL_FORCED to there.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/delegation.c

@@ -391,10 +391,6 @@ int nfs_inode_set_delegation(struct inode *inode, struct rpc_cred *cred, struct
 	rcu_assign_pointer(nfsi->delegation, delegation);
 	delegation = NULL;
 
-	/* Ensure we revalidate the attributes and page cache! */
-	spin_lock(&inode->i_lock);
-	nfsi->cache_validity |= NFS_INO_REVAL_FORCED;
-	spin_unlock(&inode->i_lock);
 	trace_nfs4_set_delegation(inode, res->delegation_type);
 
 out:

fs/nfs/inode.c

@@ -1317,7 +1317,7 @@ static int nfs_check_inode_attributes(struct inode *inode, struct nfs_fattr *fat
 		invalid |= NFS_INO_INVALID_ATIME;
 
 	if (invalid != 0)
-		nfs_set_cache_invalid(inode, invalid);
+		nfs_set_cache_invalid(inode, invalid | NFS_INO_REVAL_FORCED);
 
 	nfsi->read_cache_jiffies = fattr->time_start;
 	return 0;