When we receive a flush command (or "barrier" in DRBD), we currently use
a REQ_OP_FLUSH with the REQ_PREFLUSH flag set.

The correct way to submit a flush bio is by using a REQ_OP_WRITE without
any data, and set the REQ_PREFLUSH flag.

Since commit b4a6bb3a67aa ("block: add a sanity check for non-write
flush/fua bios"), this triggers a warning in the block layer, but this
has been broken for quite some time before that.

So use the correct set of flags to actually make the flush happen.

Cc: Christoph Hellwig <hch@infradead.org>
Cc: stable@vger.kernel.org
Fixes: f9ff0da56437 ("drbd: allow parallel flushes for multi-volume resources")
Reported-by: Thomas Voegtle <tv@lio96.de>
Signed-off-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
---
Previous, incorrect version of this patch:
https://lore.kernel.org/all/20230502092922.175857-1-christoph.boehmwalder@linbit.com/

 drivers/block/drbd/drbd_receiver.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index e54404c632e7..34b112752ab1 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -1283,7 +1283,7 @@ static void one_flush_endio(struct bio *bio)
 static void submit_one_flush(struct drbd_device *device, struct issue_flush_context *ctx)
 {
 	struct bio *bio = bio_alloc(device->ldev->backing_bdev, 0,
-				    REQ_OP_FLUSH | REQ_PREFLUSH, GFP_NOIO);
+				    REQ_OP_WRITE | REQ_PREFLUSH, GFP_NOIO);
 	struct one_flush_context *octx = kmalloc(sizeof(*octx), GFP_NOIO);
 
 	if (!octx) {
-- 
2.39.2

On Wed, 03 May 2023 14:19:37 +0200, Christoph Böhmwalder wrote:
> When we receive a flush command (or "barrier" in DRBD), we currently use
> a REQ_OP_FLUSH with the REQ_PREFLUSH flag set.
> 
> The correct way to submit a flush bio is by using a REQ_OP_WRITE without
> any data, and set the REQ_PREFLUSH flag.
> 
> Since commit b4a6bb3a67aa ("block: add a sanity check for non-write
> flush/fua bios"), this triggers a warning in the block layer, but this
> has been broken for quite some time before that.
> 
> [...]

Applied, thanks!

[1/1] drbd: correctly submit flush bio on barrier
      commit: 3899d94e3831ee07ea6821c032dc297aec80586a

Best regards,
-- 
Jens Axboe

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>