From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by mail19.linbit.com (LINBIT Mail Daemon) with ESMTP id 4F8191608F3 for ; Fri, 6 Feb 2026 08:18:25 +0100 (CET) Date: Thu, 5 Feb 2026 22:43:18 -0800 From: Christoph Hellwig To: Christoph =?iso-8859-1?Q?B=F6hmwalder?= Subject: Re: [PATCH] drbd: always set BLK_FEAT_STABLE_WRITES Message-ID: References: <20260205173928.3166880-2-christoph.boehmwalder@linbit.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260205173928.3166880-2-christoph.boehmwalder@linbit.com> Cc: Jens Axboe , Philipp Reisner , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, Lars Ellenberg , drbd-dev@lists.linbit.com List-Id: "*Coordination* of development, patches, contributions -- *Questions* \(even to developers\) go to drbd-user, please." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, Feb 05, 2026 at 06:39:29PM +0100, Christoph Böhmwalder wrote: > DRBD requires stable pages because it may read the same bio data > multiple times for local disk I/O and network transmission, and in > some cases for calculating checksums. > > The BLK_FEAT_STABLE_WRITES flag is set when the device is first > created, but blk_set_stacking_limits() clears it whenever a > backing device is attached. In some cases the flag may be > inherited from the backing device, but we want it to be enabled > at all times. This looks like a bug. If an underlying device requires BLK_FEAT_STABLE_WRITES, the upper device needs to inherit it. > Note: this commit is based on the for-6.19/block tree in case it is > still possible to take it into the 6.19 release as this *could* lead > to silent data corruption. However, due to other protection > mechanisms in DRBD, this is relatively unlikely to happen in the > real world and we have not seen any corresponding reports from users. > So if this only lands in 6.20/7.0, it is also fine. I'm fine with this as a hot fix for 6.19 and -stable: Reviewed-by: Christoph Hellwig But can you please also do the proper block layer fix and then revert the drbd one?