afs: Fix whole-volume callback handling

It's possible for an AFS file server to issue a whole-volume notification
that callbacks on all the vnodes in the file have been broken.  This is
done for R/O and backup volumes (which don't have per-file callbacks) and
for things like a volume being taken offline.

Fix callback handling to detect whole-volume notifications, to track it
across operations and to check it during inode validation.

Fixes: c435ee3455 ("afs: Overhaul the callback handling")
Signed-off-by: David Howells <dhowells@redhat.com>

fs/afs/internal.h

@@ -461,6 +461,9 @@ struct afs_volume {
 	rwlock_t		servers_lock;	/* Lock for ->servers */
 	unsigned int		servers_seq;	/* Incremented each time ->servers changes */
 
+	unsigned		cb_v_break;	/* Break-everything counter. */
+	rwlock_t		cb_break_lock;
+
 	afs_voltype_t		type;		/* type of volume */
 	short			error;
 	char			type_force;	/* force volume type (suppress R/O -> R/W) */
@@ -521,6 +524,7 @@ struct afs_vnode {
 	/* outstanding callback notification on this file */
 	struct afs_cb_interest	*cb_interest;	/* Server on which this resides */
 	unsigned int		cb_s_break;	/* Mass break counter on ->server */
+	unsigned int		cb_v_break;	/* Mass break counter on ->volume */
 	unsigned int		cb_break;	/* Break counter on vnode */
 	seqlock_t		cb_lock;	/* Lock for ->cb_interest, ->status, ->cb_*break */
 
@@ -662,6 +666,17 @@ static inline struct afs_cb_interest *afs_get_cb_interest(struct afs_cb_interest
 	return cbi;
 }
 
+static inline unsigned int afs_calc_vnode_cb_break(struct afs_vnode *vnode)
+{
+	return vnode->cb_break + vnode->cb_s_break + vnode->cb_v_break;
+}
+
+static inline unsigned int afs_cb_break_sum(struct afs_vnode *vnode,
+					    struct afs_cb_interest *cbi)
+{
+	return vnode->cb_break + cbi->server->cb_s_break + vnode->volume->cb_v_break;
+}
+
 /*
  * cell.c
  */