linux-kernel - [PATCH] drbd: correctly submit flush bio on barrier

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Date:   Wed,  3 May 2023 14:19:37 +0200
From:   Christoph Böhmwalder 
        <christoph.boehmwalder@...bit.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     drbd-dev@...ts.linbit.com, linux-kernel@...r.kernel.org,
        Lars Ellenberg <lars.ellenberg@...bit.com>,
        Philipp Reisner <philipp.reisner@...bit.com>,
        linux-block@...r.kernel.org,
        Christoph Böhmwalder 
        <christoph.boehmwalder@...bit.com>,
        Christoph Hellwig <hch@...radead.org>, stable@...r.kernel.org,
        Thomas Voegtle <tv@...96.de>
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 <hch@...radead.org>
Cc: stable@...r.kernel.org
Fixes: f9ff0da56437 ("drbd: allow parallel flushes for multi-volume resources")
Reported-by: Thomas Voegtle <tv@...96.de>
Signed-off-by: Christoph Böhmwalder <christoph.boehmwalder@...bit.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