NFSv4: Enable delegated opens even when reboot recovery is pending

Unlike the previous attempt, this takes into account the fact that
we may be calling it from the recovery thread itself. Detect this
by looking at what kind of open we're doing, and checking the state
of the NFS_DELEGATION_NEED_RECLAIM if it turns out we're doing a
reboot reclaim-type open.

Cc: Olga Kornievskaia <[e-mail]>
Signed-off-by: Trond Myklebust <[e-mail]>

fs/nfs/nfs4proc.c

···
 	return ret;
 }
 
-static int can_open_delegated(struct nfs_delegation *delegation, fmode_t fmode)
+static int can_open_delegated(struct nfs_delegation *delegation, fmode_t fmode,
+		enum open_claim_type4 claim)
 {
 	if (delegation == NULL)
 		return 0;
 	if ((delegation->type & fmode) != fmode)
 		return 0;
-	if (test_bit(NFS_DELEGATION_NEED_RECLAIM, &delegation->flags))
-		return 0;
 	if (test_bit(NFS_DELEGATION_RETURNING, &delegation->flags))
 		return 0;
+	switch (claim) {
+	case NFS4_OPEN_CLAIM_NULL:
+	case NFS4_OPEN_CLAIM_FH:
+		break;
+	case NFS4_OPEN_CLAIM_PREVIOUS:
+		if (!test_bit(NFS_DELEGATION_NEED_RECLAIM, &delegation->flags))
+			break;
+	default:
+		return 0;
+	}
 	nfs_mark_delegation_referenced(delegation);
 	return 1;
 }
···
 	struct nfs_delegation *delegation;
 	int open_mode = opendata->o_arg.open_flags;
 	fmode_t fmode = opendata->o_arg.fmode;
+	enum open_claim_type4 claim = opendata->o_arg.claim;
 	nfs4_stateid stateid;
 	int ret = -EAGAIN;
 
···
 		spin_unlock(&state->owner->so_lock);
 		rcu_read_lock();
 		delegation = rcu_dereference(nfsi->delegation);
-		if (!can_open_delegated(delegation, fmode)) {
+		if (!can_open_delegated(delegation, fmode, claim)) {
 			rcu_read_unlock();
 			break;
 		}
···
 	struct nfs4_opendata *data = calldata;
 	struct nfs4_state_owner *sp = data->owner;
 	struct nfs_client *clp = sp->so_server->nfs_client;
+	enum open_claim_type4 claim = data->o_arg.claim;
 
 	if (nfs_wait_on_sequence(data->o_arg.seqid, task) != 0)
 		goto out_wait;
···
 			goto out_no_action;
 		rcu_read_lock();
 		delegation = rcu_dereference(NFS_I(data->state->inode)->delegation);
-		if (data->o_arg.claim != NFS4_OPEN_CLAIM_DELEGATE_CUR &&
-		    data->o_arg.claim != NFS4_OPEN_CLAIM_DELEG_CUR_FH &&
-		    can_open_delegated(delegation, data->o_arg.fmode))
+		if (can_open_delegated(delegation, data->o_arg.fmode, claim))
 			goto unlock_no_action;
 		rcu_read_unlock();
 	}
 	/* Update client id. */
 	data->o_arg.clientid = clp->cl_clientid;
-	switch (data->o_arg.claim) {
+	switch (claim) {
+	default:
+		break;
 	case NFS4_OPEN_CLAIM_PREVIOUS:
 	case NFS4_OPEN_CLAIM_DELEG_CUR_FH:
 	case NFS4_OPEN_CLAIM_DELEG_PREV_FH:

include/linux/nfs_xdr.h

···
 	const struct nfs_server *server;	 /* Needed for ID mapping */
 	const u32 *		bitmask;
 	const u32 *		open_bitmap;
-	__u32			claim;
+	enum open_claim_type4	claim;
 	enum createmode4	createmode;
 	const struct nfs4_label *label;
 };