2023-05-03 12:24:16

by Christoph Böhmwalder

Subject: [PATCH] drbd: correctly submit flush bio on barrier

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 <[email protected]>
Cc: [email protected]
Fixes: f9ff0da56437 ("drbd: allow parallel flushes for multi-volume resources")
Reported-by: Thomas Voegtle <[email protected]>
Signed-off-by: Christoph Böhmwalder <[email protected]>
---
Previous, incorrect version of this patch:
https://lore.kernel.org/all/[email protected]/

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

2023-05-03 15:23:57

by Christoph Hellwig

Subject: Re: [PATCH] drbd: correctly submit flush bio on barrier

Looks good:

Reviewed-by: Christoph Hellwig <[email protected]>

2023-05-03 15:50:13

by Jens Axboe

Subject: Re: [PATCH] drbd: correctly submit flush bio on barrier

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