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, 6 insertions, 2 deletions

diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index ee17c868ad2c..cb70e1c234cc 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -498,7 +498,7 @@ struct afs_server {
 	struct hlist_node	addr6_link;	/* Link in net->fs_addresses6 */
 	struct hlist_node	proc_link;	/* Link in net->fs_proc */
 	struct afs_server	*gc_next;	/* Next server in manager's list */
-	time64_t		put_time;	/* Time at which last put */
+	time64_t		unuse_time;	/* Time at which last unused */
 	unsigned long		flags;
 #define AFS_SERVER_FL_NOT_READY	1		/* The record is not ready for use */
 #define AFS_SERVER_FL_NOT_FOUND	2		/* VL server says no such server */
@@ -512,7 +512,8 @@ struct afs_server {
 #define AFS_SERVER_FL_NO_RM2	10		/* Fileserver doesn't support YFS.RemoveFile2 */
 #define AFS_SERVER_FL_HAVE_EPOCH 11		/* ->epoch is valid */
 #define AFS_SERVER_FL_NEEDS_UPDATE 12		/* Fileserver address list is out of date */
-	atomic_t		usage;
+	atomic_t		ref;		/* Object refcount */
+	atomic_t		active;		/* Active user count */
 	u32			addr_version;	/* Address list version */
 	u32			cm_epoch;	/* Server RxRPC epoch */
 	unsigned int		debug_id;	/* Debugging ID for traces */
@@ -1244,6 +1245,9 @@ extern struct afs_server *afs_find_server(struct afs_net *,
 extern struct afs_server *afs_find_server_by_uuid(struct afs_net *, const uuid_t *);
 extern struct afs_server *afs_lookup_server(struct afs_cell *, struct key *, const uuid_t *, u32);
 extern struct afs_server *afs_get_server(struct afs_server *, enum afs_server_trace);
+extern struct afs_server *afs_use_server(struct afs_server *, enum afs_server_trace);
+extern void afs_unuse_server(struct afs_net *, struct afs_server *, enum afs_server_trace);
+extern void afs_unuse_server_notime(struct afs_net *, struct afs_server *, enum afs_server_trace);
 extern void afs_put_server(struct afs_net *, struct afs_server *, enum afs_server_trace);
 extern void afs_manage_servers(struct work_struct *);
 extern void afs_servers_timer(struct timer_list *);