netfs: Remove global reference count lock.

* libnetfs/drop-node.c: Remove use of netfs_node_refcnt_lock.
* libnetfs/init-init.c: Remove netfs_node_refcnt_lock.
* libnetfs/make-node.c: Initialize refcounts in refcounts_init.
* libnetfs/netfs.h: Use refcounts_t for tracking node references. Remove
netfs_node_refcnt_lock. Add netfs_nref_light, netfs_nrele_light and
handler netfs_try_dropping_softrefs. Adjust comments.
* libnetfs/nput.c: Use refcounts_t. Call netfs_try_dropping_softrefs to
remove any soft reference that the translator might have acquired
during the lifetime of the node. Implement empty
netfs_try_dropping_softrefs.
* libnetfs/nref.c: Implement netfs_nref_light.
* libnetfs/nrele.c: Use refcounts_t and netfs_try_dropping_softrefs.
Implement netfs_nrele_light.
* ftpfs/dir.c: Use netfs_nref without locking the old
netfs_node_refcnt_lock.
* ftpfs/node.c: Likewise.
* usermux/mux.c: Use netfs_nref to increase hard references of the node.
* hostmux/mux.c: Use netfs_nref to increase hard references of the node.
* trans/fakeroot.c (new_node): Use a light reference when storing a node in the
hash table.
* trans/fakeroot.c (netfs_try_dropping_softrefs): Implement
netfs_try_dropping_softrefs to remove the node from the hash table.
* trans/fakeroot.c (netfs_node_norefs): Remove code to remove the node
from the hash table.
* trans/fakeroot.c (netfs_S_dir_lookup): Simplify lookup code since we
don't need to lock netfs_node_refcnt_lock anymore.
* procfs/netfs.c: Remove use of netfs_node_refcnt_lock.
* nfs/cache.c: Add mutex to handle exclusive access to nodehash. This
replaces the use of netfs_node_refcnt_lock.
* nfs/cache.c (lookup_handle): Use nodehash_ihash_lock when accessing
nodehash. Use netfs_nref_light to add one soft reference to the node
just added to nodehash.
* nfs/cache.c (netfs_node_norefs): Use netfs_nref. Don't use
netfs_node_refcnt_lock and don't remove the node from nodehash here.
* nfs/cache.c (netfs_try_dropping_softrefs): Drop the light reference
when the node has no more hard references.
* nfs/cache.c (recache_handle): Use nodehash_ihash_lock instead.
* nfs/ops.c (netds_attempt_unlink): Use refcounts_references.
* console/console.c (netfs_node_norefs): Use a soft reference to store
a node in dir_node, cons_node, disp_node, inp_node.
* console/console.c (netfs_try_dropping_softrefs): When dropping all
soft references remove node pointer from the fields above.

1 files changed, 18 insertions, 9 deletions

diff --git a/libnetfs/nput.c b/libnetfs/nput.c
index 522c714a..b04fc4b0 100644
--- a/libnetfs/nput.c
+++ b/libnetfs/nput.c
@@ -23,15 +23,24 @@
 void
 netfs_nput (struct node *np)
 {
-  pthread_spin_lock (&netfs_node_refcnt_lock);
-  assert (np->references);
-  np->references--;
-  if (np->references == 0)
+  struct references result;
+
+  refcounts_demote (&np->refcounts, &result);
+
+  if (result.hard == 0)
+    netfs_try_dropping_softrefs (np);
+
+  refcounts_deref_weak (&np->refcounts, &result);
+
+  if (result.hard == 0 && result.weak == 0)
     netfs_drop_node (np);
-    /* netfs_drop_node drops netfs_node_refcnt_lock for us.  */
   else
-    {
-      pthread_spin_unlock (&netfs_node_refcnt_lock);
-      pthread_mutex_unlock (&np->lock);
-    }
+    pthread_mutex_unlock (&np->lock);
+}
+
+/* The last hard reference to NP has gone away; the user must define
+   this function in order to drop all the soft references.  */
+void __attribute__ ((weak))
+netfs_try_dropping_softrefs (struct node *np)
+{
 }