From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 17EC9264638; Fri, 13 Feb 2026 06:05:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770962759; cv=none; b=CZrF51q3v0O0kuA8ce0Ujfz2CToj9kBDSUB2wPAi8gi0MoN3veP5KKia2XQQrosky6Uf2bDNgV5blxSnZp8jqfji63sVbtUwWiDgtyq+QINbLjC9u8wip7C0ISceTgGTfNMZY3PoZj06YEEckt9obqvhnxn6IyCEoFGxnIjY0lo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770962759; c=relaxed/simple; bh=t0ATrk0joZXMp/XpctJ5VdxjPgIC1hcX+JPHGmC4VvA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=XJ3VyS1ccPHK3S1cfrmjwduV8CKYSgFDI8UEmPrTunU8ntFsA+lz80AA2d8bdmf8/KNODeWZNnUWyYJfPKR86q0i6GC/sjqbetUI28j8B94Jv5uGdOauih6MRi1Ae5UfzopNyPHdFw1VX+iUUDr4bjr525rOJf8NmG1TuGYehOw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=jK6FbZ40; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="jK6FbZ40" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Transfer-Encoding :Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=PZUSXqE0G9A6YIVtMGcb/ILxAy5ED9bTFTJF56eUpSA=; b=jK6FbZ40StO4DgcPKg6ynS9q3d gxfdkgbRWWgKKKlxzlqfhngzUJkYgfuG6ojrcIlwYr9AgnaOOmSbay+WaOnMciYC8ZqeVOoHRIC9z L5LbQH7VlR1wnBoL+wCYSI+NrcSRYdGNGnWMG1JMu9Ydgqez8nittbDXwWdgb6c0hObDbWdI0YdYI N0BuCV3Sma3qP7RNbu4z80chU/IG1ItwLjFSEQN+kvBN25mfBBRsakr2mwN0JTOt+TdPDgKyq+4IO W0pt4iaDXKXBvT/e2GPgqpwKPNEJdPU7zCc33paWIeojVaeukIRy+rMT+gBxS2U60gA88VLAHhmAN RnjZvLGQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1vqmJO-000000033Fm-2AIN; Fri, 13 Feb 2026 06:05:54 +0000 Date: Thu, 12 Feb 2026 22:05:54 -0800 From: Christoph Hellwig To: Christoph =?iso-8859-1?Q?B=F6hmwalder?= Cc: Christoph Hellwig , Jens Axboe , drbd-dev@lists.linbit.com, linux-kernel@vger.kernel.org, Lars Ellenberg , Philipp Reisner , linux-block@vger.kernel.org Subject: Re: [PATCH] drbd: always set BLK_FEAT_STABLE_WRITES Message-ID: References: <20260205173928.3166880-2-christoph.boehmwalder@linbit.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Thu, Feb 12, 2026 at 04:01:43PM +0100, Christoph Böhmwalder wrote: > The current block layer logic actually seems correct to me. The > underlying device may or may not require stable writes, but regardless > of that, DRBD itself definitely does need it. In blk_stack_limits, DRBD > is the top device, and DRBD's backing disk is the bottom device. If the > backing disk happens to require stable writes, this would indeed be > correctly inherited. > > So the only missing logic is that DRBD still wants to enable stable > writes for itself even if the backing disk does *not* request it. > So it seems to me that this patch is the correct fix for DRBD's special > case. > > Is it not supposed to work like that? No, I guess I just misunderstood your report.