Btrfs: simpler and more efficient cleanup of a log tree's extent io tree

We currently are in a loop finding each range (corresponding to a btree
node/leaf) in a log root's extent io tree and then clean it up. This is a
waste of time since we are traversing the extent io tree's rb_tree more
times then needed (one for a range lookup and another for cleaning it up)
without any good reason.

We free the log trees when we are in the critical section of a transaction
commit (the transaction state is set to TRANS_STATE_COMMIT_DOING), so it's
of great convenience to do everything as fast as possible in order to
reduce the time we block other tasks from starting a new transaction.

So fix this by traversing the extent io tree once and cleaning up all its
records in one go while traversing it.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 2 insertions, 14 deletions

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index aa4bc4845ef0..013d0abcd46b 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -3201,8 +3201,6 @@ static void free_log_tree(struct btrfs_trans_handle *trans,
                           struct btrfs_root *log)
 {
         int ret;
-        u64 start;
-        u64 end;
         struct walk_control wc = {
                 .free = 1,
                 .process_func = process_one_buffer
@@ -3216,18 +3214,8 @@ static void free_log_tree(struct btrfs_trans_handle *trans,
                         btrfs_handle_fs_error(log->fs_info, ret, NULL);
         }
 
-        while (1) {
-                ret = find_first_extent_bit(&log->dirty_log_pages,
-                                0, &start, &end,
-                                EXTENT_DIRTY | EXTENT_NEW | EXTENT_NEED_WAIT,
-                                NULL);
-                if (ret)
-                        break;
-
-                clear_extent_bits(&log->dirty_log_pages, start, end,
-                                  EXTENT_DIRTY | EXTENT_NEW | EXTENT_NEED_WAIT);
-        }
-
+        clear_extent_bits(&log->dirty_log_pages, 0, (u64)-1,
+                          EXTENT_DIRTY | EXTENT_NEW | EXTENT_NEED_WAIT);
         free_extent_buffer(log->node);
         kfree(log);
 }