nfsd: Convert delegation counter to an atomic_long_t type

We want to convert to an atomic type so that we don't need to lock
across the call to alloc_init_deleg(). Then convert to a long type so
that we match the size of 'max_delegations'.

None of this is a problem today, but it will be once we remove
client_mutex protection.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs4state.c

@@ -342,7 +342,7 @@ find_any_file(struct nfs4_file *f)
 	return ret;
 }
 
-static int num_delegations;
+static atomic_long_t num_delegations;
 unsigned long max_delegations;
 
 /*
@@ -582,22 +582,23 @@ static struct nfs4_delegation *
 alloc_init_deleg(struct nfs4_client *clp, struct nfs4_ol_stateid *stp, struct svc_fh *current_fh)
 {
 	struct nfs4_delegation *dp;
+	long n;
 
 	dprintk("NFSD alloc_init_deleg\n");
-	if (num_delegations > max_delegations)
-		return NULL;
+	n = atomic_long_inc_return(&num_delegations);
+	if (n < 0 || n > max_delegations)
+		goto out_dec;
 	if (delegation_blocked(&current_fh->fh_handle))
-		return NULL;
+		goto out_dec;
 	dp = delegstateid(nfs4_alloc_stid(clp, deleg_slab));
 	if (dp == NULL)
-		return dp;
+		goto out_dec;
 	/*
 	 * delegation seqid's are never incremented.  The 4.1 special
 	 * meaning of seqid 0 isn't meaningful, really, but let's avoid
 	 * 0 anyway just for consistency and use 1:
 	 */
 	dp->dl_stid.sc_stateid.si_generation = 1;
-	num_delegations++;
 	INIT_LIST_HEAD(&dp->dl_perfile);
 	INIT_LIST_HEAD(&dp->dl_perclnt);
 	INIT_LIST_HEAD(&dp->dl_recall_lru);
@@ -605,6 +606,9 @@ alloc_init_deleg(struct nfs4_client *clp, struct nfs4_ol_stateid *stp, struct sv
 	fh_copy_shallow(&dp->dl_fh, &current_fh->fh_handle);
 	INIT_WORK(&dp->dl_recall.cb_work, nfsd4_run_cb_recall);
 	return dp;
+out_dec:
+	atomic_long_dec(&num_delegations);
+	return NULL;
 }
 
 static void remove_stid(struct nfs4_stid *s)
@@ -627,7 +631,7 @@ nfs4_put_delegation(struct nfs4_delegation *dp)
 			put_nfs4_file(dp->dl_file);
 		remove_stid(&dp->dl_stid);
 		nfs4_free_stid(deleg_slab, &dp->dl_stid);
-		num_delegations--;
+		atomic_long_dec(&num_delegations);
 	}
 }