btrfs: don't force commit if we are data

We used to unconditionally commit the transaction at least 2 times and
then on the 3rd try check against pinned space to make sure committing
the transaction was worth the effort.  This is overkill, we know nobody
is going to steal our reservation, and if we can't make our reservation
with the pinned amount simply bail out.

This also cleans up the passing of bytes_needed to
may_commit_transaction, as that was the thing we added into place in
order to accomplish this behavior.  We no longer need it so remove that
mess.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Tested-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/space-info.c

@@ -579,8 +579,7 @@ static void shrink_delalloc(struct btrfs_fs_info *fs_info,
  * will return -ENOSPC.
  */
 static int may_commit_transaction(struct btrfs_fs_info *fs_info,
-				  struct btrfs_space_info *space_info,
-				  u64 bytes_needed)
+				  struct btrfs_space_info *space_info)
 {
 	struct reserve_ticket *ticket = NULL;
 	struct btrfs_block_rsv *delayed_rsv = &fs_info->delayed_block_rsv;
@@ -588,24 +587,13 @@ static int may_commit_transaction(struct btrfs_fs_info *fs_info,
 	struct btrfs_block_rsv *trans_rsv = &fs_info->trans_block_rsv;
 	struct btrfs_trans_handle *trans;
 	u64 reclaim_bytes = 0;
+	u64 bytes_needed = 0;
 	u64 cur_free_bytes = 0;
-	bool do_commit = false;
 
 	trans = (struct btrfs_trans_handle *)current->journal_info;
 	if (trans)
 		return -EAGAIN;
 
-	/*
-	 * If we are data and have passed in U64_MAX we just want to
-	 * unconditionally commit the transaction to match the previous data
-	 * flushing behavior.
-	 */
-	if ((space_info->flags & BTRFS_BLOCK_GROUP_DATA) &&
-	    bytes_needed == U64_MAX) {
-		do_commit = true;
-		goto check_pinned;
-	}
-
 	spin_lock(&space_info->lock);
 	cur_free_bytes = btrfs_space_info_used(space_info, true);
 	if (cur_free_bytes < space_info->total_bytes)
@@ -631,7 +619,6 @@ static int may_commit_transaction(struct btrfs_fs_info *fs_info,
 	if (!bytes_needed)
 		return 0;
 
-check_pinned:
 	trans = btrfs_join_transaction(fs_info->extent_root);
 	if (IS_ERR(trans))
 		return PTR_ERR(trans);
@@ -641,8 +628,7 @@ static int may_commit_transaction(struct btrfs_fs_info *fs_info,
 	 * we have block groups that are going to be freed, allowing us to
 	 * possibly do a chunk allocation the next loop through.
 	 */
-	if (do_commit ||
-	    test_bit(BTRFS_TRANS_HAVE_FREE_BGS, &trans->transaction->flags) ||
+	if (test_bit(BTRFS_TRANS_HAVE_FREE_BGS, &trans->transaction->flags) ||
 	    __percpu_counter_compare(&space_info->total_bytes_pinned,
 				     bytes_needed,
 				     BTRFS_TOTAL_BYTES_PINNED_BATCH) >= 0)
@@ -759,7 +745,7 @@ static void flush_space(struct btrfs_fs_info *fs_info,
 		btrfs_wait_on_delayed_iputs(fs_info);
 		break;
 	case COMMIT_TRANS:
-		ret = may_commit_transaction(fs_info, space_info, num_bytes);
+		ret = may_commit_transaction(fs_info, space_info);
 		break;
 	default:
 		ret = -ENOSPC;