[PATCH 4/4] btrfs: remove fs_info::transaction_blocked_wait

[David Sterba <dsterba@suse.com>]

Previous commit removed last use of transaction_blocked_wait. There were
still the waking call sites, that are now without use as there's nothing
populating the wait list.

As wake_up has a memory barrier semantics, it's directly replaced by
smp_mb. The transaction state TRANS_STATE_COMMIT_START is now perhaps
trivial, but there's more code relying on that, it's left in place to
keep the behaviour as close as possible to the original code.

Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/ctree.h       | 1 -
 fs/btrfs/disk-io.c     | 5 ++---
 fs/btrfs/super.c       | 1 -
 fs/btrfs/transaction.c | 3 ++-
 4 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index c601f6733576..384c00c982ab 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -683,7 +683,6 @@ struct btrfs_fs_info {
 	struct btrfs_transaction *running_transaction;
 	wait_queue_head_t transaction_throttle;
 	wait_queue_head_t transaction_wait;
-	wait_queue_head_t transaction_blocked_wait;
 	wait_queue_head_t async_submit_wait;
 
 	/*
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index d1d5091a8385..bad7df788458 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2986,7 +2986,6 @@ void btrfs_init_fs_info(struct btrfs_fs_info *fs_info)
 
 	init_waitqueue_head(&fs_info->transaction_throttle);
 	init_waitqueue_head(&fs_info->transaction_wait);
-	init_waitqueue_head(&fs_info->transaction_blocked_wait);
 	init_waitqueue_head(&fs_info->async_submit_wait);
 	init_waitqueue_head(&fs_info->delayed_iputs_wait);
 
@@ -4918,8 +4917,8 @@ void btrfs_cleanup_one_transaction(struct btrfs_transaction *cur_trans,
 	btrfs_destroy_delayed_refs(cur_trans, fs_info);
 
 	cur_trans->state = TRANS_STATE_COMMIT_START;
-	wake_up(&fs_info->transaction_blocked_wait);
-
+	/* Serialize state change, but there are no waiters */
+	smp_mb();
 	cur_trans->state = TRANS_STATE_UNBLOCKED;
 	wake_up(&fs_info->transaction_wait);
 
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index bc613218c8c5..8d87da2b2377 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -302,7 +302,6 @@ void __btrfs_abort_transaction(struct btrfs_trans_handle *trans,
 	WRITE_ONCE(trans->transaction->aborted, errno);
 	/* Wake up anybody who may be waiting on this transaction */
 	wake_up(&fs_info->transaction_wait);
-	wake_up(&fs_info->transaction_blocked_wait);
 	__btrfs_handle_fs_error(fs_info, function, line, errno, NULL);
 }
 /*
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 5f3c95c876c8..1fd04170b0bf 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -2057,7 +2057,8 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 	}
 
 	cur_trans->state = TRANS_STATE_COMMIT_START;
-	wake_up(&fs_info->transaction_blocked_wait);
+	/* Serialize state change, but there are no waiters */
+	smp_mb();
 
 	if (cur_trans->list.prev != &fs_info->trans_list) {
 		enum btrfs_trans_state want_state = TRANS_STATE_COMPLETED;
-- 
2.31.1