afs: Split the usage count on struct afs_server

Split the usage count on the afs_server struct to have an active count that
registers who's actually using it separately from the reference count on
the object.

This allows a future patch to dispatch polling probes without advancing the
"unuse" time into the future each time we emit a probe, which would
otherwise prevent unused server records from expiring.

Included in this:

 (1) The latter part of afs_destroy_server() in which the RCU destruction
     of afs_server objects is invoked and the outstanding server count is
     decremented is split out into __afs_put_server().

 (2) afs_put_server() now calls __afs_put_server() rather then setting the
     management timer.

 (3) The calls begun by afs_fs_give_up_all_callbacks() and
     afs_fs_get_capabilities() can now take a ref on the server record, so
     afs_destroy_server() can just drop its ref and needn't wait for the
     completion of these calls.  They'll put the ref when they're done.

 (4) Because of (3), afs_fs_probe_done() no longer needs to wake up
     afs_destroy_server() with server->probe_outstanding.

 (5) afs_gc_servers can be simplified.  It only needs to check if
     server->active is 0 rather than playing games with the refcount.

 (6) afs_manage_servers() can propose a server for gc if usage == 0 rather
     than if ref == 1.  The gc is effected by (5).

Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 5 insertions, 4 deletions

diff --git a/fs/afs/proc.c b/fs/afs/proc.c
index 468e1713bce1..9bce7898cd7d 100644
--- a/fs/afs/proc.c
+++ b/fs/afs/proc.c
@@ -378,19 +378,20 @@ static int afs_proc_servers_show(struct seq_file *m, void *v)
 	int i;
 
 	if (v == SEQ_START_TOKEN) {
-		seq_puts(m, "UUID                                 USE ADDR\n");
+		seq_puts(m, "UUID                                 REF ACT ADDR\n");
 		return 0;
 	}
 
 	server = list_entry(v, struct afs_server, proc_link);
 	alist = rcu_dereference(server->addresses);
-	seq_printf(m, "%pU %3d %pISpc%s\n",
+	seq_printf(m, "%pU %3d %3d %pISpc%s\n",
 		   &server->uuid,
-		   atomic_read(&server->usage),
+		   atomic_read(&server->ref),
+		   atomic_read(&server->active),
 		   &alist->addrs[0].transport,
 		   alist->preferred == 0 ? "*" : "");
 	for (i = 1; i < alist->nr_addrs; i++)
-		seq_printf(m, "                                         %pISpc%s\n",
+		seq_printf(m, "                                             %pISpc%s\n",
 			   &alist->addrs[i].transport,
 			   alist->preferred == i ? "*" : "");
 	return 0;