fscache: Add tracepoints

Add some tracepoints to fscache:

 (*) fscache_cookie - Tracks a cookie's usage count.

 (*) fscache_netfs - Logs registration of a network filesystem, including
     the pointer to the cookie allocated.

 (*) fscache_acquire - Logs cookie acquisition.

 (*) fscache_relinquish - Logs cookie relinquishment.

 (*) fscache_enable - Logs enablement of a cookie.

 (*) fscache_disable - Logs disablement of a cookie.

 (*) fscache_osm - Tracks execution of states in the object state machine.

and cachefiles:

 (*) cachefiles_ref - Tracks a cachefiles object's usage count.

 (*) cachefiles_lookup - Logs result of lookup_one_len().

 (*) cachefiles_mkdir - Logs result of vfs_mkdir().

 (*) cachefiles_create - Logs result of vfs_create().

 (*) cachefiles_unlink - Logs calls to vfs_unlink().

 (*) cachefiles_rename - Logs calls to vfs_rename().

 (*) cachefiles_mark_active - Logs an object becoming active.

 (*) cachefiles_wait_active - Logs a wait for an old object to be
     destroyed.

 (*) cachefiles_mark_inactive - Logs an object becoming inactive.

 (*) cachefiles_mark_buried - Logs the burial of an object.

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

1 files changed, 14 insertions, 4 deletions

diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c
index e7f16a77a22a..405ebc3932c2 100644
--- a/fs/cachefiles/interface.c
+++ b/fs/cachefiles/interface.c
@@ -177,10 +177,12 @@ static void cachefiles_lookup_complete(struct fscache_object *_object)
  * increment the usage count on an inode object (may fail if unmounting)
  */
 static
-struct fscache_object *cachefiles_grab_object(struct fscache_object *_object)
+struct fscache_object *cachefiles_grab_object(struct fscache_object *_object,
+                                              enum fscache_obj_ref_trace why)
 {
         struct cachefiles_object *object =
                 container_of(_object, struct cachefiles_object, fscache);
+        int u;
 
         _enter("{OBJ%x,%d}", _object->debug_id, atomic_read(&object->usage));
 
@@ -188,7 +190,9 @@ struct fscache_object *cachefiles_grab_object(struct fscache_object *_object)
         ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
 #endif
 
-        atomic_inc(&object->usage);
+        u = atomic_inc_return(&object->usage);
+        trace_cachefiles_ref(object, _object->cookie,
+                             (enum cachefiles_obj_ref_trace)why, u);
         return &object->fscache;
 }
 
@@ -309,10 +313,12 @@ static void cachefiles_drop_object(struct fscache_object *_object)
 /*
  * dispose of a reference to an object
  */
-static void cachefiles_put_object(struct fscache_object *_object)
+static void cachefiles_put_object(struct fscache_object *_object,
+                                  enum fscache_obj_ref_trace why)
 {
         struct cachefiles_object *object;
         struct fscache_cache *cache;
+        int u;
 
         ASSERT(_object);
 
@@ -328,7 +334,11 @@ static void cachefiles_put_object(struct fscache_object *_object)
         ASSERTIFCMP(object->fscache.parent,
                     object->fscache.parent->n_children, >, 0);
 
-        if (atomic_dec_and_test(&object->usage)) {
+        u = atomic_dec_return(&object->usage);
+        trace_cachefiles_ref(object, _object->cookie,
+                             (enum cachefiles_obj_ref_trace)why, u);
+        ASSERTCMP(u, !=, -1);
+        if (u == 0) {
                 _debug("- kill object OBJ%x", object->fscache.debug_id);
 
                 ASSERT(!test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));