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Date:   Tue, 2 May 2023 21:18:01 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Christoph =?iso-8859-1?Q?B=F6hmwalder?= 
        <christoph.boehmwalder@linbit.com>
Cc:     Jens Axboe <axboe@kernel.dk>, drbd-dev@lists.linbit.com,
        linux-kernel@vger.kernel.org,
        Lars Ellenberg <lars.ellenberg@linbit.com>,
        Philipp Reisner <philipp.reisner@linbit.com>,
        linux-block@vger.kernel.org, Thomas Voegtle <tv@lio96.de>
Subject: Re: [PATCH] drbd: do not set REQ_PREFLUSH when submitting barrier
Message-ID: <ZFHgefWofVt24tRl@infradead.org>
References: <20230502092922.175857-1-christoph.boehmwalder@linbit.com>
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On Tue, May 02, 2023 at 11:29:22AM +0200, Christoph B?hmwalder 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.