Re: new barrier warnings in 2.6.29-rc1

[Tejun Heo <tj@kernel.org>]

Hello, Jens.

Jens Axboe wrote:
> On Tue, Jan 13 2009, Tejun Heo wrote:
>> I think the right thing to do is setting REQ_QUIET on the trial
>> barrier request.
> 
> It would surely work, but XFS doesn't really have a way to do that. Then
> we would have to add a bio quiet flag and inherit that.
> 
> I kind of liked the old behaviour. What about something like the below?
> 
> diff --git a/block/blk-core.c b/block/blk-core.c
> index a824e49..eddba4a 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -1448,6 +1448,11 @@ static inline void __generic_make_request(struct bio *bio)
>  			err = -EOPNOTSUPP;
>  			goto end_io;
>  		}
> +		if (bio_barrier(bio) && bio_has_data(bio) &&
> +		    (q->next_ordered == QUEUE_ORDERED_NONE)) {
> +			err = -EOPNOTSUPP;
> +			goto end_io;
> +		}
>  
>  		ret = q->make_request_fn(q, bio);
>  	} while (ret);

I have no objection against it.  I kind of like having single test
point but it's a corner case anyway so no biggie.

Thanks.

-- 
tejun