NFSv4.1: Clean ups for the device id cache

The fact that the global device id cache holds a reference to the
nfs4_deviceid_node until it is invisible to rcu lookups implies that
we can always assume that the reference count is non-zero in
_find_get_deviceid.

Also clean up nfs4_put_deviceid_node and the removal of the device id
from the cache.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/pnfs.h

@@ -198,7 +198,6 @@ struct nfs4_deviceid_node {
 
 void nfs4_print_deviceid(const struct nfs4_deviceid *dev_id);
 struct nfs4_deviceid_node *nfs4_find_get_deviceid(const struct pnfs_layoutdriver_type *, const struct nfs_client *, const struct nfs4_deviceid *);
-struct nfs4_deviceid_node *nfs4_unhash_put_deviceid(const struct pnfs_layoutdriver_type *, const struct nfs_client *, const struct nfs4_deviceid *);
 void nfs4_delete_deviceid(const struct pnfs_layoutdriver_type *, const struct nfs_client *, const struct nfs4_deviceid *);
 void nfs4_init_deviceid_node(struct nfs4_deviceid_node *,
 			     const struct pnfs_layoutdriver_type *,

fs/nfs/pnfs_dev.c

@@ -100,8 +100,8 @@ _find_get_deviceid(const struct pnfs_layoutdriver_type *ld,
 
 	rcu_read_lock();
 	d = _lookup_deviceid(ld, clp, id, hash);
-	if (d && !atomic_inc_not_zero(&d->ref))
-		d = NULL;
+	if (d != NULL)
+		atomic_inc(&d->ref);
 	rcu_read_unlock();
 	return d;
 }
@@ -115,15 +115,15 @@ nfs4_find_get_deviceid(const struct pnfs_layoutdriver_type *ld,
 EXPORT_SYMBOL_GPL(nfs4_find_get_deviceid);
 
 /*
- * Unhash and put deviceid
+ * Remove a deviceid from cache
  *
  * @clp nfs_client associated with deviceid
  * @id the deviceid to unhash
  *
  * @ret the unhashed node, if found and dereferenced to zero, NULL otherwise.
  */
-struct nfs4_deviceid_node *
-nfs4_unhash_put_deviceid(const struct pnfs_layoutdriver_type *ld,
+void
+nfs4_delete_deviceid(const struct pnfs_layoutdriver_type *ld,
 			 const struct nfs_client *clp, const struct nfs4_deviceid *id)
 {
 	struct nfs4_deviceid_node *d;
@@ -134,7 +134,7 @@ nfs4_unhash_put_deviceid(const struct pnfs_layoutdriver_type *ld,
 	rcu_read_unlock();
 	if (!d) {
 		spin_unlock(&nfs4_deviceid_lock);
-		return NULL;
+		return;
 	}
 	hlist_del_init_rcu(&d->node);
 	spin_unlock(&nfs4_deviceid_lock);
@@ -142,28 +142,7 @@ nfs4_unhash_put_deviceid(const struct pnfs_layoutdriver_type *ld,
 
 	/* balance the initial ref set in pnfs_insert_deviceid */
 	if (atomic_dec_and_test(&d->ref))
-		return d;
-
-	return NULL;
-}
-EXPORT_SYMBOL_GPL(nfs4_unhash_put_deviceid);
-
-/*
- * Delete a deviceid from cache
- *
- * @clp struct nfs_client qualifying the deviceid
- * @id deviceid to delete
- */
-void
-nfs4_delete_deviceid(const struct pnfs_layoutdriver_type *ld,
-		     const struct nfs_client *clp, const struct nfs4_deviceid *id)
-{
-	struct nfs4_deviceid_node *d;
-
-	d = nfs4_unhash_put_deviceid(ld, clp, id);
-	if (!d)
-		return;
-	d->ld->free_deviceid_node(d);
+		d->ld->free_deviceid_node(d);
 }
 EXPORT_SYMBOL_GPL(nfs4_delete_deviceid);
 
@@ -221,16 +200,15 @@ EXPORT_SYMBOL_GPL(nfs4_insert_deviceid_node);
  *
  * @d deviceid node to put
  *
- * @ret true iff the node was deleted
+ * return true iff the node was deleted
+ * Note that since the test for d->ref == 0 is sufficient to establish
+ * that the node is no longer hashed in the global device id cache.
  */
 bool
 nfs4_put_deviceid_node(struct nfs4_deviceid_node *d)
 {
-	if (!atomic_dec_and_lock(&d->ref, &nfs4_deviceid_lock))
+	if (!atomic_dec_and_test(&d->ref))
 		return false;
-	hlist_del_init_rcu(&d->node);
-	spin_unlock(&nfs4_deviceid_lock);
-	synchronize_rcu();
 	d->ld->free_deviceid_node(d);
 	return true;
 }