JBD commit callback capability

@@ -250,6 +250,13 @@ static inline struct journal_head *bh2jh
 	return bh->b_private;
 }
 
+#define HAVE_JOURNAL_CALLBACK_STATUS
+struct journal_callback {
+	struct list_head jcb_list;
+	void (*jcb_func)(struct journal_callback *jcb, int error);
+	/* user data goes here */
+};
+
 struct jbd_revoke_table_s;
 
 /* The handle_t type represents a single atomic update being performed

@@ -280,6 +287,12 @@ struct handle_s 
 	   operations */
 	int			h_err;
 
+	/* List of application registered callbacks for this handle.
+	 * The function(s) will be called after the transaction that
+	 * this handle is part of has been committed to disk.
+	 */
+	struct list_head	h_jcb;
+
 	/* Flags */
 	unsigned int	h_sync:		1;	/* sync-on-close */
 	unsigned int	h_jdata:	1;	/* force data journaling */

@@ -399,6 +412,10 @@ struct transaction_s 
 
 	/* How many handles used this transaction? */
 	int t_handle_count;
+
+	/* List of registered callback functions for this transaction.
+	 * Called when the transaction is committed. */
+	struct list_head	t_jcb;
 };
 
 

@@ -647,6 +664,9 @@ extern int	 journal_invalidatepage(journ
 extern int	 journal_try_to_free_buffers(journal_t *, struct page *, int);
 extern int	 journal_stop(handle_t *);
 extern int	 journal_flush (journal_t *);
+extern void	 journal_callback_set(handle_t *handle,
+				      void (*fn)(struct journal_callback *,int),
+				      struct journal_callback *jcb);
 
 extern void	 journal_lock_updates (journal_t *);
 extern void	 journal_unlock_updates (journal_t *);

@@ -592,7 +592,8 @@ void __journal_drop_transaction(journal_
 	J_ASSERT (transaction->t_log_list == NULL);
 	J_ASSERT (transaction->t_checkpoint_list == NULL);
 	J_ASSERT (transaction->t_updates == 0);
-	
+	J_ASSERT (list_empty(&transaction->t_jcb));
+
 	J_ASSERT (transaction->t_journal->j_committing_transaction !=
 					transaction);
 	

@@ -471,7 +471,7 @@ start_journal_io:
            transaction's t_log_list queue, and metadata buffers are on
            the t_iobuf_list queue.
 
-	   Wait for the transactions in reverse order.  That way we are
+	   Wait for the buffers in reverse order.  That way we are
 	   less likely to be woken up until all IOs have completed, and
 	   so we incur less scheduling load.
 	*/

@@ -563,8 +563,10 @@ start_journal_io:
 
 	jbd_debug(3, "JBD: commit phase 6\n");
 
-	if (is_journal_aborted(journal))
+	if (is_journal_aborted(journal)) {
+		unlock_journal(journal);
 		goto skip_commit;
+	}
 
 	/* Done it all: now write the commit record.  We should have
 	 * cleaned up our previous buffers by now, so if we are in abort

@@ -574,9 +576,10 @@ start_journal_io:
 	descriptor = journal_get_descriptor_buffer(journal);
 	if (!descriptor) {
 		__journal_abort_hard(journal);
+		unlock_journal(journal);
 		goto skip_commit;
 	}
-	
+
 	/* AKPM: buglet - add `i' to tmp! */
 	for (i = 0; i < jh2bh(descriptor)->b_size; i += 512) {
 		journal_header_t *tmp =

@@ -596,14 +599,32 @@ start_journal_io:
 		__brelse(bh);		/* One for getblk() */
 		journal_unlock_journal_head(descriptor);
 	}
-	lock_journal(journal);
 
 	/* End of a transaction!  Finally, we can do checkpoint
            processing: any buffers committed as a result of this
            transaction can be removed from any checkpoint list it was on
            before. */
 
-skip_commit:
+skip_commit: /* The journal should be unlocked by now. */
+
+	/* Call any callbacks that had been registered for handles in this
+	 * transaction.  It is up to the callback to free any allocated
+	 * memory.
+	 */
+	if (!list_empty(&commit_transaction->t_jcb)) {
+		struct list_head *p, *n;
+		int error = is_journal_aborted(journal);
+
+		list_for_each_safe(p, n, &commit_transaction->t_jcb) {
+			struct journal_callback *jcb;
+
+			jcb = list_entry(p, struct journal_callback, jcb_list);
+			list_del(p);
+			jcb->jcb_func(jcb, error);
+		}
+	}
+
+	lock_journal(journal);
 
 	jbd_debug(3, "JBD: commit phase 7\n");
 

@@ -58,6 +58,7 @@ EXPORT_SYMBOL(journal_sync_buffer);
 #endif
 EXPORT_SYMBOL(journal_flush);
 EXPORT_SYMBOL(journal_revoke);
+EXPORT_SYMBOL(journal_callback_set);
 
 EXPORT_SYMBOL(journal_init_dev);
 EXPORT_SYMBOL(journal_init_inode);

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