nfs: track whether server sets MAY_NOTIFY_LOCK flag

We want to handle the two cases differently, such that we poll more
aggressively when we don't expect a callback.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/nfs4_fs.h

@@ -157,6 +157,7 @@ enum {
 	NFS_STATE_RECLAIM_NOGRACE,	/* OPEN stateid needs to recover state */
 	NFS_STATE_POSIX_LOCKS,		/* Posix locks are supported */
 	NFS_STATE_RECOVERY_FAILED,	/* OPEN stateid state recovery failed */
+	NFS_STATE_MAY_NOTIFY_LOCK,	/* server may CB_NOTIFY_LOCK */
 };
 
 struct nfs4_state {

fs/nfs/nfs4proc.c

@@ -2537,6 +2537,8 @@ static int _nfs4_open_and_get_state(struct nfs4_opendata *opendata,
 		goto out;
 	if (server->caps & NFS_CAP_POSIX_LOCK)
 		set_bit(NFS_STATE_POSIX_LOCKS, &state->flags);
+	if (opendata->o_res.rflags & NFS4_OPEN_RESULT_MAY_NOTIFY_LOCK)
+		set_bit(NFS_STATE_MAY_NOTIFY_LOCK, &state->flags);
 
 	dentry = opendata->dentry;
 	if (d_really_is_negative(dentry)) {