NFSv4.1: Convert pNFS deviceid to use kfree_rcu()

Use of synchronize_rcu() when unmounting and potentially freeing a lot
of deviceids is problematic. There really is no reason why we can't just
use kfree_rcu() here.

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

fs/nfs/blocklayout/dev.c

···
 		container_of(d, struct pnfs_block_dev, node);
 
 	bl_free_device(dev);
-	kfree(dev);
+	kfree_rcu(dev, node.rcu);
 }
 
 static int

fs/nfs/filelayout/filelayoutdev.c

···
 			nfs4_pnfs_ds_put(ds);
 	}
 	kfree(dsaddr->stripe_indices);
-	kfree(dsaddr);
+	kfree_rcu(dsaddr, id_node.rcu);
 }
 
 /* Decode opaque device data and return the result */

fs/nfs/flexfilelayout/flexfilelayoutdev.c

···
 {
 	nfs4_print_deviceid(&mirror_ds->id_node.deviceid);
 	nfs4_pnfs_ds_put(mirror_ds->ds);
-	kfree(mirror_ds);
+	kfree_rcu(mirror_ds, id_node.rcu);
 }
 
 /* Decode opaque device data and construct new_ds using it */

fs/nfs/objlayout/objio_osd.c

···
 
 	dprintk("%s: free od=%p\n", __func__, de->od.od);
 	osduld_put_device(de->od.od);
-	kfree(de);
+	kfree_rcu(d, rcu);
 }
 
 struct objio_segment {

fs/nfs/pnfs.h

···
 	unsigned long 			flags;
 	unsigned long			timestamp_unavailable;
 	struct nfs4_deviceid		deviceid;
+	struct rcu_head			rcu;
 	atomic_t			ref;
 };
 

fs/nfs/pnfs_dev.c

···
 	rcu_read_lock();
 	d = _lookup_deviceid(server->pnfs_curr_ld, server->nfs_client, id,
 			hash);
-	if (d != NULL)
-		atomic_inc(&d->ref);
+	if (d != NULL && !atomic_inc_not_zero(&d->ref))
+		d = NULL;
 	rcu_read_unlock();
 	return d;
 }
···
 	}
 	hlist_del_init_rcu(&d->node);
 	spin_unlock(&nfs4_deviceid_lock);
-	synchronize_rcu();
 
 	/* balance the initial ref set in pnfs_insert_deviceid */
 	if (atomic_dec_and_test(&d->ref))
···
 	if (hlist_empty(&tmp))
 		return;
 
-	synchronize_rcu();
 	while (!hlist_empty(&tmp)) {
 		d = hlist_entry(tmp.first, struct nfs4_deviceid_node, tmpnode);
 		hlist_del(&d->tmpnode);