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From b28098f0eb0637d1c06aa38ce6041c8e0916199d Mon Sep 17 00:00:00 2001
From: Justus Winter <4winter@informatik.uni-hamburg.de>
Date: Sun, 18 May 2014 13:34:12 +0200
Subject: [PATCH 02/27] libnetfs: add netfs_make_node_alloc to allocate fat
nodes
libnetfs has two kind of nodes, struct node and struct netnode.
struct node is used to store libnetfs specific data, while struct
netnode contains user supplied data. Previously, both objects were
allocated separatly, and a pointer from the node to the netnode
provided a mapping from the former to the latter.
Provide a function netfs_make_node_alloc that allocates both nodes in
a contiguous region.
This reduces the memory allocation overhead when creating nodes. It
also makes the relation between node and netnode a simple offset
calculation. Provide two functions to compute the netnode address
from the node address and vice-versa.
Most notably, this makes implementing a cache on top of libnetfs
easier. Auxiliary data for the cache can be stored in the
user-defined netnode, and the fat node can be used as the value.
* libnetfs/make-node.c (init_node): Move initialization here.
(netfs_make_node): Use init_node.
(netfs_make_node_alloc): New function to allocate fat nodes.
* libnetfs/netfs.h (netfs_make_node_alloc): New declaration.
(netfs_node_netnode): Compute netnode address from node address.
(netfs_netnode_node): And vice-versa.
---
libnetfs/make-node.c | 29 +++++++++++++++++++++++------
libnetfs/netfs.h | 22 ++++++++++++++++++++++
2 files changed, 45 insertions(+), 6 deletions(-)
diff --git a/libnetfs/make-node.c b/libnetfs/make-node.c
index f20ada1..6bd8109 100644
--- a/libnetfs/make-node.c
+++ b/libnetfs/make-node.c
@@ -21,13 +21,9 @@
#include "netfs.h"
#include <hurd/fshelp.h>
-struct node *
-netfs_make_node (struct netnode *nn)
+static struct node *
+init_node (struct node *np, struct netnode *nn)
{
- struct node *np = malloc (sizeof (struct node));
- if (! np)
- return NULL;
-
np->nn = nn;
pthread_mutex_init (&np->lock, NULL);
@@ -40,3 +36,24 @@ netfs_make_node (struct netnode *nn)
return np;
}
+
+struct node *
+netfs_make_node (struct netnode *nn)
+{
+ struct node *np = malloc (sizeof (struct node));
+ if (! np)
+ return NULL;
+
+ return init_node (np, nn);
+}
+
+struct node *
+netfs_make_node_alloc (size_t size)
+{
+ struct node *np = malloc (sizeof (struct node) + size);
+
+ if (np == NULL)
+ return NULL;
+
+ return init_node (np, netfs_node_netnode (np));
+}
diff --git a/libnetfs/netfs.h b/libnetfs/netfs.h
index aef4a3d..e3c3b3e 100644
--- a/libnetfs/netfs.h
+++ b/libnetfs/netfs.h
@@ -372,6 +372,28 @@ extern int netfs_maxsymlinks;
If an error occurs, NULL is returned. */
struct node *netfs_make_node (struct netnode *);
+/* Create a new node structure. Also allocate SIZE bytes for the
+ netnode. The address of the netnode can be obtained using
+ netfs_node_netnode. The new node will have one hard reference and
+ no light references. If an error occurs, NULL is returned. */
+struct node *netfs_make_node_alloc (size_t size);
+
+/* Return the address of the netnode for NODE. NODE must have been
+ allocated using netfs_make_node_alloc. */
+static inline struct netnode *
+netfs_node_netnode (struct node *node)
+{
+ return (struct netnode *) ((char *) node + sizeof (struct node));
+}
+
+/* Return the address of the node for NETNODE. NETNODE must have been
+ allocated using netfs_make_node_alloc. */
+static inline struct node *
+netfs_netnode_node (struct netnode *netnode)
+{
+ return (struct node *) ((char *) netnode - sizeof (struct node));
+}
+
/* Whenever node->references is to be touched, this lock must be
held. Cf. netfs_nrele, netfs_nput, netfs_nref and netfs_drop_node. */
extern pthread_spinlock_t netfs_node_refcnt_lock;
--
2.0.0.rc2
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