Btrfs: remove no longer used stuff for tracking pending ordered extents

Tracking pending ordered extents per transaction was introduced in commit
50d9aa99bd35 ("Btrfs: make sure logged extents complete in the current
transaction V3") and later updated in commit 161c3549b45a ("Btrfs: change
how we wait for pending ordered extents").

However now that on fsync we always wait for ordered extents to complete
before logging, done in commit 5636cf7d6dc8 ("btrfs: remove the logged
extents infrastructure"), we no longer need the stuff to track for pending
ordered extents, which was not completely removed in the mentioned commit.
So remove the remaining of the pending ordered extents infrastructure.

Reviewed-by: Liu Bo <[e-mail]>
Signed-off-by: Filipe Manana <[e-mail]>
Signed-off-by: David Sterba <[e-mail]>

fs/btrfs/ordered-data.c

···
 	struct btrfs_inode *btrfs_inode = BTRFS_I(inode);
 	struct btrfs_root *root = btrfs_inode->root;
 	struct rb_node *node;
-	bool dec_pending_ordered = false;
 
 	/* This is paired with btrfs_add_ordered_extent. */
 	spin_lock(&btrfs_inode->lock);
···
 	if (tree->last == node)
 		tree->last = NULL;
 	set_bit(BTRFS_ORDERED_COMPLETE, &entry->flags);
-	if (test_and_clear_bit(BTRFS_ORDERED_PENDING, &entry->flags))
-		dec_pending_ordered = true;
 	spin_unlock_irq(&tree->lock);
-
-	/*
-	 * The current running transaction is waiting on us, we need to let it
-	 * know that we're complete and wake it up.
-	 */
-	if (dec_pending_ordered) {
-		struct btrfs_transaction *trans;
-
-		/*
-		 * The checks for trans are just a formality, it should be set,
-		 * but if it isn't we don't want to deref/assert under the spin
-		 * lock, so be nice and check if trans is set, but ASSERT() so
-		 * if it isn't set a developer will notice.
-		 */
-		spin_lock(&fs_info->trans_lock);
-		trans = fs_info->running_transaction;
-		if (trans)
-			refcount_inc(&trans->use_count);
-		spin_unlock(&fs_info->trans_lock);
-
-		ASSERT(trans);
-		if (trans) {
-			if (atomic_dec_and_test(&trans->pending_ordered))
-				wake_up(&trans->pending_wait);
-			btrfs_put_transaction(trans);
-		}
-	}
 
 	spin_lock(&root->ordered_extent_lock);
 	list_del_init(&entry->root_extent_list);

fs/btrfs/ordered-data.h

···
 				       * the isize. */
 #define BTRFS_ORDERED_TRUNCATED 8 /* Set when we have to truncate an extent */
 
-#define BTRFS_ORDERED_PENDING 9 /* We are waiting for this ordered extent to
-				  * complete in the current transaction. */
 #define BTRFS_ORDERED_REGULAR 10 /* Regular IO for COW */
 
 struct btrfs_ordered_extent {

fs/btrfs/transaction.c

···
 	extwriter_counter_init(cur_trans, type);
 	init_waitqueue_head(&cur_trans->writer_wait);
 	init_waitqueue_head(&cur_trans->commit_wait);
-	init_waitqueue_head(&cur_trans->pending_wait);
 	cur_trans->state = TRANS_STATE_RUNNING;
 	/*
 	 * One for this trans handle, one so it will live on until we
 	 * commit the transaction.
 	 */
 	refcount_set(&cur_trans->use_count, 2);
-	atomic_set(&cur_trans->pending_ordered, 0);
 	cur_trans->flags = 0;
 	cur_trans->start_time = ktime_get_seconds();
 
···
 		btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
 }
 
-static inline void
-btrfs_wait_pending_ordered(struct btrfs_transaction *cur_trans)
-{
-	wait_event(cur_trans->pending_wait,
-		   atomic_read(&cur_trans->pending_ordered) == 0);
-}
-
 int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 {
 	struct btrfs_fs_info *fs_info = trans->fs_info;
···
 		goto cleanup_transaction;
 
 	btrfs_wait_delalloc_flush(fs_info);
-
-	btrfs_wait_pending_ordered(cur_trans);
 
 	btrfs_scrub_pause(fs_info);
 	/*

fs/btrfs/transaction.h

···
 	 */
 	atomic_t num_writers;
 	refcount_t use_count;
-	atomic_t pending_ordered;
 
 	unsigned long flags;
 
···
 	time64_t start_time;
 	wait_queue_head_t writer_wait;
 	wait_queue_head_t commit_wait;
-	wait_queue_head_t pending_wait;
 	struct list_head pending_snapshots;
 	struct list_head pending_chunks;
 	struct list_head switch_commits;