NFSv4.x: Directory delegations don't require any state recovery

The state recovery code in nfs_end_delegation_return() is intended to
allow regular files to recover cached open and lock state. It has no
function for directory delegations, and may cause corruption.

Fixes: 156b09482933 ("NFS: Request a directory delegation on ACCESS, CREATE, and UNLINK")
Signed-off-by: Trond Myklebust <[e-mail]>

fs/nfs/delegation.c

···
 	if (delegation == NULL)
 		return 0;
 
+	/* Directory delegations don't require any state recovery */
+	if (!S_ISREG(inode->i_mode))
+		goto out_return;
+
 	if (!issync)
 		mode |= O_NONBLOCK;
 	/* Recall of any remaining application leases */
···
 		goto out;
 	}
 
+out_return:
 	err = nfs_do_return_delegation(inode, delegation, issync);
 out:
 	/* Refcount matched in nfs_start_delegation_return_locked() */

fs/nfs/nfs4state.c

···
 	struct nfs4_state *state;
 	bool found = false;
 
+	if (!S_ISREG(inode->i_mode))
+		goto out;
 	rcu_read_lock();
 	list_for_each_entry_rcu(ctx, &nfsi->open_files, list) {
 		state = ctx->state;
···
 			found = true;
 	}
 	rcu_read_unlock();
-
+out:
 	nfs_inode_find_delegation_state_and_recover(inode, stateid);
 	if (found)
 		nfs4_schedule_state_manager(clp);
···
 	struct nfs_inode *nfsi = NFS_I(inode);
 	struct nfs_open_context *ctx;
 
+	if (!S_ISREG(inode->i_mode))
+		return;
 	rcu_read_lock();
 	list_for_each_entry_rcu(ctx, &nfsi->open_files, list) {
 		if (ctx->state != state)