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, 12 insertions, 6 deletions

diff --git a/include/trace/events/afs.h b/include/trace/events/afs.h
index c612cabbc378..f9691f69b2d6 100644
--- a/include/trace/events/afs.h
+++ b/include/trace/events/afs.h
@@ -33,6 +33,7 @@ enum afs_server_trace {
 	afs_server_trace_destroy,
 	afs_server_trace_free,
 	afs_server_trace_gc,
+	afs_server_trace_get_by_addr,
 	afs_server_trace_get_by_uuid,
 	afs_server_trace_get_caps,
 	afs_server_trace_get_install,
@@ -241,6 +242,7 @@ enum afs_cb_break_reason {
 	EM(afs_server_trace_destroy,		"DESTROY  ") \
 	EM(afs_server_trace_free,		"FREE     ") \
 	EM(afs_server_trace_gc,			"GC       ") \
+	EM(afs_server_trace_get_by_addr,	"GET addr ") \
 	EM(afs_server_trace_get_by_uuid,	"GET uuid ") \
 	EM(afs_server_trace_get_caps,		"GET caps ") \
 	EM(afs_server_trace_get_install,	"GET inst ") \
@@ -1271,26 +1273,30 @@ TRACE_EVENT(afs_cb_miss,
 	    );
 
 TRACE_EVENT(afs_server,
-	    TP_PROTO(struct afs_server *server, int usage, enum afs_server_trace reason),
+	    TP_PROTO(struct afs_server *server, int ref, int active,
+		     enum afs_server_trace reason),
 
-	    TP_ARGS(server, usage, reason),
+	    TP_ARGS(server, ref, active, reason),
 
 	    TP_STRUCT__entry(
 		    __field(unsigned int,		server		)
-		    __field(int,			usage		)
+		    __field(int,			ref		)
+		    __field(int,			active		)
 		    __field(int,			reason		)
 			     ),
 
 	    TP_fast_assign(
 		    __entry->server = server->debug_id;
-		    __entry->usage = usage;
+		    __entry->ref = ref;
+		    __entry->active = active;
 		    __entry->reason = reason;
 			   ),
 
-	    TP_printk("s=%08x %s u=%d",
+	    TP_printk("s=%08x %s u=%d a=%d",
 		      __entry->server,
 		      __print_symbolic(__entry->reason, afs_server_traces),
-		      __entry->usage)
+		      __entry->ref,
+		      __entry->active)
 	    );
 
 #endif /* _TRACE_AFS_H */