ext4: Replace hackish ext4_mb_poll_new_transaction with commit callback

The multiblock allocator needs to be able to release blocks (and issue
a blkdev discard request) when the transaction which freed those
blocks is committed.  Previously this was done via a polling mechanism
when blocks are allocated or freed.  A much better way of doing things
is to create a jbd2 callback function and attaching the list of blocks
to be freed directly to the transaction structure.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 9 insertions, 0 deletions

diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 463d6f10b64f..c7d106ef22e2 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -641,6 +641,11 @@ struct transaction_s
          */
         int t_handle_count;
 
+        /*
+         * For use by the filesystem to store fs-specific data
+         * structures associated with the transaction
+         */
+        struct list_head        t_private_list;
 };
 
 struct transaction_run_stats_s {
@@ -935,6 +940,10 @@ struct journal_s
 
         pid_t                   j_last_sync_writer;
 
+        /* This function is called when a transaction is closed */
+        void                    (*j_commit_callback)(journal_t *,
+                                                     transaction_t *);
+
         /*
          * Journal statistics
          */