[PATCH] JBD: implement t_jcb locking

Provide the designed locking around the transaction's t_jcb callback list.

It turns out that this is wholly redundant at present.

fs/jbd/commit.c

@@ -607,10 +607,14 @@ void journal_commit_transaction(journal_t *journal)
 		unlock_journal(journal);
 	}
 	
-	/* Call any callbacks that had been registered for handles in this
+	/*
+	 * Call any callbacks that had been registered for handles in this
 	 * transaction.  It is up to the callback to free any allocated
 	 * memory.
+	 *
+	 * The spinlocking (t_jcb_lock) here is surely unnecessary...
 	 */
+	spin_lock(&commit_transaction->t_jcb_lock);
 	if (!list_empty(&commit_transaction->t_jcb)) {
 		struct list_head *p, *n;
 		int error = is_journal_aborted(journal);
@@ -620,9 +624,12 @@ void journal_commit_transaction(journal_t *journal)
 
 			jcb = list_entry(p, struct journal_callback, jcb_list);
 			list_del(p);
+			spin_unlock(&commit_transaction->t_jcb_lock);
 			jcb->jcb_func(jcb, error);
+			spin_lock(&commit_transaction->t_jcb_lock);
 		}
 	}
+	spin_unlock(&commit_transaction->t_jcb_lock);
 
 	lock_journal(journal);
 

fs/jbd/transaction.c

@@ -41,15 +41,15 @@
  *	processes trying to touch the journal while it is in transition.
  */
 
-static transaction_t * get_transaction (journal_t * journal, int is_try)
+static transaction_t *get_transaction(journal_t *journal)
 {
 	transaction_t * transaction;
 
-	transaction = jbd_kmalloc (sizeof (transaction_t), GFP_NOFS);
+	transaction = jbd_kmalloc(sizeof(*transaction), GFP_NOFS);
 	if (!transaction)
 		return NULL;
 	
-	memset (transaction, 0, sizeof (transaction_t));
+	memset(transaction, 0, sizeof(*transaction));
 	
 	transaction->t_journal = journal;
 	transaction->t_state = T_RUNNING;
@@ -120,7 +120,7 @@ static int start_this_handle(journal_t *journal, handle_t *handle)
 	
 repeat_locked:
 	if (!journal->j_running_transaction)
-		get_transaction(journal, 0);
+		get_transaction(journal);
 	/* @@@ Error? */
 	J_ASSERT(journal->j_running_transaction);
 	
@@ -1277,16 +1277,15 @@ void journal_forget (handle_t *handle, struct buffer_head *bh)
  * and has the caller-specific data afterwards.
  */
 void journal_callback_set(handle_t *handle,
-			  void (*func)(struct journal_callback *jcb, int error),
-			  struct journal_callback *jcb)
+			void (*func)(struct journal_callback *jcb, int error),
+			struct journal_callback *jcb)
 {
-	lock_kernel();
+	spin_lock(&handle->h_transaction->t_jcb_lock);
 	list_add_tail(&jcb->jcb_list, &handle->h_jcb);
+	spin_unlock(&handle->h_transaction->t_jcb_lock);
 	jcb->jcb_func = func;
-	unlock_kernel();
 }
 
-
 /**
  * int journal_stop() - complete a transaction
  * @handle: tranaction to complete.
@@ -1357,7 +1356,9 @@ int journal_stop(handle_t *handle)
 	}
 
 	/* Move callbacks from the handle to the transaction. */
+	spin_lock(&transaction->t_jcb_lock);
 	list_splice(&handle->h_jcb, &transaction->t_jcb);
+	spin_unlock(&transaction->t_jcb_lock);
 
 	/*
 	 * If the handle is marked SYNC, we need to set another commit