On 11.02.21 10:30, Jan Kara wrote:

quoted

  	 */
  	unsigned long		t_log_start;
  
-	/* Number of buffers on the t_buffers list [j_list_lock] */
+	/* Number of buffers on the t_buffers list [j_list_lock, no lock for quick racy checks] */
  	int			t_nr_buffers;

So this case is actually somewhat different now that I audited the uses.
There are two types of users - commit code (fs/jbd2/commit.c) and others.
Other users properly use j_list_lock to access t_nr_buffers. Commit code
does not use any locks because committing transaction is fully in
ownership of the jbd2 thread and all other users need to check & wait for
commit to be finished before doing anything with the transaction's buffers.

Mhm I see.
What about '[..., no locks needed for jbd2 thread]'?

How do the others wait for the commit to be finished?

- Alex

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