btrfs: don't run delayed refs in the end transaction logic

Over the years we have built up a lot of infrastructure to keep delayed
refs in check, mostly by running them at btrfs_end_transaction() time.
We have a lot of different maths we do to figure out how much, if we
should do it inline or async, etc.  This existed because we had no
feedback mechanism to force the flushing of delayed refs when they
became a problem.  However with the enospc flushing infrastructure in
place for flushing delayed refs when they put too much pressure on the
enospc system we have this problem solved.  Rip out all of this code as
it is no longer needed.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/transaction.c

@@ -798,22 +798,12 @@ static int should_end_transaction(struct btrfs_trans_handle *trans)
 int btrfs_should_end_transaction(struct btrfs_trans_handle *trans)
 {
 	struct btrfs_transaction *cur_trans = trans->transaction;
-	int updates;
-	int err;
 
 	smp_mb();
 	if (cur_trans->state >= TRANS_STATE_BLOCKED ||
 	    cur_trans->delayed_refs.flushing)
 		return 1;
 
-	updates = trans->delayed_ref_updates;
-	trans->delayed_ref_updates = 0;
-	if (updates) {
-		err = btrfs_run_delayed_refs(trans, updates * 2);
-		if (err) /* Error code will also eval true */
-			return err;
-	}
-
 	return should_end_transaction(trans);
 }
 
@@ -843,11 +833,8 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
 {
 	struct btrfs_fs_info *info = trans->fs_info;
 	struct btrfs_transaction *cur_trans = trans->transaction;
-	u64 transid = trans->transid;
-	unsigned long cur = trans->delayed_ref_updates;
 	int lock = (trans->type != TRANS_JOIN_NOLOCK);
 	int err = 0;
-	int must_run_delayed_refs = 0;
 
 	if (refcount_read(&trans->use_count) > 1) {
 		refcount_dec(&trans->use_count);
@@ -858,27 +845,6 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
 	btrfs_trans_release_metadata(trans);
 	trans->block_rsv = NULL;
 
-	if (!list_empty(&trans->new_bgs))
-		btrfs_create_pending_block_groups(trans);
-
-	trans->delayed_ref_updates = 0;
-	if (!trans->sync) {
-		must_run_delayed_refs =
-			btrfs_should_throttle_delayed_refs(trans);
-		cur = max_t(unsigned long, cur, 32);
-
-		/*
-		 * don't make the caller wait if they are from a NOLOCK
-		 * or ATTACH transaction, it will deadlock with commit
-		 */
-		if (must_run_delayed_refs == 1 &&
-		    (trans->type & (__TRANS_JOIN_NOLOCK | __TRANS_ATTACH)))
-			must_run_delayed_refs = 2;
-	}
-
-	btrfs_trans_release_metadata(trans);
-	trans->block_rsv = NULL;
-
 	if (!list_empty(&trans->new_bgs))
 		btrfs_create_pending_block_groups(trans);
 
@@ -923,10 +889,6 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
 	}
 
 	kmem_cache_free(btrfs_trans_handle_cachep, trans);
-	if (must_run_delayed_refs) {
-		btrfs_async_run_delayed_refs(info, cur, transid,
-					     must_run_delayed_refs == 1);
-	}
 	return err;
 }