Re: general protection fault: from release_blocks_on_commit

[Eric Sandeen <sandeen@redhat.com>]

Theodore Tso wrote:

> I looked at this some more, and at least in theory it could happen
> that we could not have any buffers that need to be checkpointed (so
> t_checkpoint_list and t_checkpoint_io_list are NULL), but there are
> still blocks to be released (or some other users of the jbd2 layer
> still wants to have the callback be called).  So I'm currently testing
> this patch (see below).
> 
> 							- Ted

Looks reasonable to me from a correctness perspective, anyway, as long
as holding the j_list_lock over that callback is ok.

It does fix the oops-on-reboot that I could reproduce.

-Eric


> diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
> index 8b119e1..ebc667b 100644
> --- a/fs/jbd2/commit.c
> +++ b/fs/jbd2/commit.c
> @@ -974,6 +974,9 @@ restart_loop:
>  	journal->j_committing_transaction = NULL;
>  	spin_unlock(&journal->j_state_lock);
>  
> +	if (journal->j_commit_callback)
> +		journal->j_commit_callback(journal, commit_transaction);
> +
>  	if (commit_transaction->t_checkpoint_list == NULL &&
>  	    commit_transaction->t_checkpoint_io_list == NULL) {
>  		__jbd2_journal_drop_transaction(journal, commit_transaction);
> @@ -995,11 +998,8 @@ restart_loop:
>  	}
>  	spin_unlock(&journal->j_list_lock);
>  
> -	if (journal->j_commit_callback)
> -		journal->j_commit_callback(journal, commit_transaction);
> -
>  	trace_mark(jbd2_end_commit, "dev %s transaction %d head %d",
> -		   journal->j_devname, commit_transaction->t_tid,
> +		   journal->j_devname, journal->j_commit_sequence,
>  		   journal->j_tail_sequence);
>  	jbd_debug(1, "JBD: commit %d complete, head %d\n",
>  		  journal->j_commit_sequence, journal->j_tail_sequence);