jbd2: refactor wait logic for transaction updates into a common function

No functionality change as such in this patch. This only refactors the
common piece of code which waits for t_updates to finish into a common
function named as jbd2_journal_wait_updates(journal_t *)

Signed-off-by: Ritesh Harjani <riteshh@linux.ibm.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/8c564f70f4b2591171677a2a74fccb22a7b6c3a4.1642416995.git.riteshh@linux.ibm.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/jbd2/commit.c

@@ -484,22 +484,9 @@ void jbd2_journal_commit_transaction(journal_t *journal)
 	stats.run.rs_running = jbd2_time_diff(commit_transaction->t_start,
 					      stats.run.rs_locked);
 
-	spin_lock(&commit_transaction->t_handle_lock);
-	while (atomic_read(&commit_transaction->t_updates)) {
-		DEFINE_WAIT(wait);
+	// waits for any t_updates to finish
+	jbd2_journal_wait_updates(journal);
 
-		prepare_to_wait(&journal->j_wait_updates, &wait,
-					TASK_UNINTERRUPTIBLE);
-		if (atomic_read(&commit_transaction->t_updates)) {
-			spin_unlock(&commit_transaction->t_handle_lock);
-			write_unlock(&journal->j_state_lock);
-			schedule();
-			write_lock(&journal->j_state_lock);
-			spin_lock(&commit_transaction->t_handle_lock);
-		}
-		finish_wait(&journal->j_wait_updates, &wait);
-	}
-	spin_unlock(&commit_transaction->t_handle_lock);
 	commit_transaction->t_state = T_SWITCH;
 	write_unlock(&journal->j_state_lock);
 
@@ -817,7 +804,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
 	commit_transaction->t_state = T_COMMIT_DFLUSH;
 	write_unlock(&journal->j_state_lock);
 
-	/* 
+	/*
 	 * If the journal is not located on the file system device,
 	 * then we must flush the file system device before we issue
 	 * the commit record

fs/jbd2/transaction.c

@@ -449,7 +449,7 @@ static int start_this_handle(journal_t *journal, handle_t *handle,
 	}
 
 	/* OK, account for the buffers that this operation expects to
-	 * use and add the handle to the running transaction. 
+	 * use and add the handle to the running transaction.
 	 */
 	update_t_max_wait(transaction, ts);
 	handle->h_transaction = transaction;
@@ -836,6 +836,35 @@ int jbd2_journal_restart(handle_t *handle, int nblocks)
 }
 EXPORT_SYMBOL(jbd2_journal_restart);
 
+/*
+ * Waits for any outstanding t_updates to finish.
+ * This is called with write j_state_lock held.
+ */
+void jbd2_journal_wait_updates(journal_t *journal)
+{
+	transaction_t *commit_transaction = journal->j_running_transaction;
+
+	if (!commit_transaction)
+		return;
+
+	spin_lock(&commit_transaction->t_handle_lock);
+	while (atomic_read(&commit_transaction->t_updates)) {
+		DEFINE_WAIT(wait);
+
+		prepare_to_wait(&journal->j_wait_updates, &wait,
+					TASK_UNINTERRUPTIBLE);
+		if (atomic_read(&commit_transaction->t_updates)) {
+			spin_unlock(&commit_transaction->t_handle_lock);
+			write_unlock(&journal->j_state_lock);
+			schedule();
+			write_lock(&journal->j_state_lock);
+			spin_lock(&commit_transaction->t_handle_lock);
+		}
+		finish_wait(&journal->j_wait_updates, &wait);
+	}
+	spin_unlock(&commit_transaction->t_handle_lock);
+}
+
 /**
  * jbd2_journal_lock_updates () - establish a transaction barrier.
  * @journal:  Journal to establish a barrier on.
@@ -863,27 +892,9 @@ void jbd2_journal_lock_updates(journal_t *journal)
 		write_lock(&journal->j_state_lock);
 	}
 
-	/* Wait until there are no running updates */
-	while (1) {
-		transaction_t *transaction = journal->j_running_transaction;
-
-		if (!transaction)
-			break;
+	/* Wait until there are no running t_updates */
+	jbd2_journal_wait_updates(journal);
 
-		spin_lock(&transaction->t_handle_lock);
-		prepare_to_wait(&journal->j_wait_updates, &wait,
-				TASK_UNINTERRUPTIBLE);
-		if (!atomic_read(&transaction->t_updates)) {
-			spin_unlock(&transaction->t_handle_lock);
-			finish_wait(&journal->j_wait_updates, &wait);
-			break;
-		}
-		spin_unlock(&transaction->t_handle_lock);
-		write_unlock(&journal->j_state_lock);
-		schedule();
-		finish_wait(&journal->j_wait_updates, &wait);
-		write_lock(&journal->j_state_lock);
-	}
 	write_unlock(&journal->j_state_lock);
 
 	/*

include/linux/jbd2.h

@@ -594,7 +594,7 @@ struct transaction_s
 	 */
 	unsigned long		t_log_start;
 
-	/* 
+	/*
 	 * Number of buffers on the t_buffers list [j_list_lock, no locks
 	 * needed for jbd2 thread]
 	 */
@@ -1538,6 +1538,8 @@ extern int	 jbd2_journal_flush(journal_t *journal, unsigned int flags);
 extern void	 jbd2_journal_lock_updates (journal_t *);
 extern void	 jbd2_journal_unlock_updates (journal_t *);
 
+void jbd2_journal_wait_updates(journal_t *);
+
 extern journal_t * jbd2_journal_init_dev(struct block_device *bdev,
 				struct block_device *fs_dev,
 				unsigned long long start, int len, int bsize);