Re: [PATCH] drbd: do not set REQ_PREFLUSH when submitting barrier

[Christoph Hellwig]

On Tue, May 02, 2023 at 11:29:22AM +0200, Christoph Böhmwalder wrote:
>  	struct bio *bio = bio_alloc(device->ldev->backing_bdev, 0,
> -				    REQ_OP_FLUSH | REQ_PREFLUSH, GFP_NOIO);
> +				    REQ_OP_FLUSH, GFP_NOIO);

This isn't going to work.  flush bios are (somewhat confusingly)
implemented as writes with no data and the preflush flag.  So this
should be:

	REQ_OP_WRITE | REQ_PREFLUSH.

and it looks like whatever flushing this does hasn't wroked for a long
time.