btrfs: add a flush step for delayed iputs

Delayed iputs could very well free up enough space without needing to
commit the transaction, so make this step it's own step.  This will
allow us to skip the step for evictions in a later patch.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.h

@@ -2548,7 +2548,8 @@ enum btrfs_flush_state {
 	FLUSH_DELALLOC_WAIT	=	6,
 	ALLOC_CHUNK		=	7,
 	ALLOC_CHUNK_FORCE	=	8,
-	COMMIT_TRANS		=	9,
+	RUN_DELAYED_IPUTS	=	9,
+	COMMIT_TRANS		=	10,
 };
 
 int btrfs_subvolume_reserve_metadata(struct btrfs_root *root,

fs/btrfs/space-info.c

@@ -664,7 +664,7 @@ static void flush_space(struct btrfs_fs_info *fs_info,
 		if (ret > 0 || ret == -ENOSPC)
 			ret = 0;
 		break;
-	case COMMIT_TRANS:
+	case RUN_DELAYED_IPUTS:
 		/*
 		 * If we have pending delayed iputs then we could free up a
 		 * bunch of pinned space, so make sure we run the iputs before
@@ -672,7 +672,8 @@ static void flush_space(struct btrfs_fs_info *fs_info,
 		 */
 		btrfs_run_delayed_iputs(fs_info);
 		btrfs_wait_on_delayed_iputs(fs_info);
-
+		break;
+	case COMMIT_TRANS:
 		ret = may_commit_transaction(fs_info, space_info);
 		break;
 	default:

include/trace/events/btrfs.h

@@ -1088,6 +1088,7 @@ TRACE_EVENT(btrfs_trigger_flush,
 		{ FLUSH_DELAYED_REFS,		"FLUSH_ELAYED_REFS"},		\
 		{ ALLOC_CHUNK,			"ALLOC_CHUNK"},			\
 		{ ALLOC_CHUNK_FORCE,		"ALLOC_CHUNK_FORCE"},		\
+		{ RUN_DELAYED_IPUTS,		"RUN_DELAYED_IPUTS"},		\
 		{ COMMIT_TRANS,			"COMMIT_TRANS"})
 
 TRACE_EVENT(btrfs_flush_space,