afs: Add some callback management tracepoints

Add a couple of tracepoints to track callback management:

 (1) afs_cb_miss - Logs when we were unable to apply a callback, either due
     to the inode being discarded or due to a competing thread applying a
     callback first.

 (2) afs_cb_break - Logs when we attempted to clear the noted callback
     promise, either due to the server explicitly breaking the callback,
     the callback promise lapsing or a local event obsoleting it.

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

1 files changed, 12 insertions, 4 deletions

diff --git a/fs/afs/callback.c b/fs/afs/callback.c
index 915010464572..d66cd0364243 100644
--- a/fs/afs/callback.c
+++ b/fs/afs/callback.c
@@ -212,7 +212,7 @@ void afs_init_callback_state(struct afs_server *server)
 /*
  * actually break a callback
  */
-void __afs_break_callback(struct afs_vnode *vnode)
+void __afs_break_callback(struct afs_vnode *vnode, enum afs_cb_break_reason reason)
 {
         _enter("");
 
@@ -223,13 +223,17 @@ void __afs_break_callback(struct afs_vnode *vnode)
 
                 if (vnode->lock_state == AFS_VNODE_LOCK_WAITING_FOR_CB)
                         afs_lock_may_be_available(vnode);
+
+                trace_afs_cb_break(&vnode->fid, vnode->cb_break, reason, true);
+        } else {
+                trace_afs_cb_break(&vnode->fid, vnode->cb_break, reason, false);
         }
 }
 
-void afs_break_callback(struct afs_vnode *vnode)
+void afs_break_callback(struct afs_vnode *vnode, enum afs_cb_break_reason reason)
 {
         write_seqlock(&vnode->cb_lock);
-        __afs_break_callback(vnode);
+        __afs_break_callback(vnode, reason);
         write_sequnlock(&vnode->cb_lock);
 }
 
@@ -277,6 +281,8 @@ static void afs_break_one_callback(struct afs_server *server,
 
                         write_lock(&volume->cb_v_break_lock);
                         volume->cb_v_break++;
+                        trace_afs_cb_break(fid, volume->cb_v_break,
+                                           afs_cb_break_for_volume_callback, false);
                         write_unlock(&volume->cb_v_break_lock);
                 } else {
                         data.volume = NULL;
@@ -285,8 +291,10 @@ static void afs_break_one_callback(struct afs_server *server,
                                                 afs_iget5_test, &data);
                         if (inode) {
                                 vnode = AFS_FS_I(inode);
-                                afs_break_callback(vnode);
+                                afs_break_callback(vnode, afs_cb_break_for_callback);
                                 iput(inode);
+                        } else {
+                                trace_afs_cb_miss(fid, afs_cb_break_for_callback);
                         }
                 }
         }