From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (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 328F53043D0 for ; Mon, 24 Nov 2025 17:12:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.95.11.211 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764004355; cv=none; b=qXZT6IKdJTHO+iRiNVDiUDl2WpRKyYvLxeDXfWKXC+yL6JJhd6dRI5nYtDvkhEFcoGcdI3nPtesjiXMN3cRp4uErOos+t8cZdwKv87gofn7DjjC0TUB1LEkJUQtmD/03asjypVVplJeTZCDPrdxZSme5MhW8o+z5DYGry5Mqs+c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764004355; c=relaxed/simple; bh=IElTkPtUepoxZWCCFUry0ZzlqgirtvL9ZRknXY7xvzI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=TEjyxRoAtN2aRBh/Sr+wJXfRRO3Z3idwA9aiHVxTEVJtFmfWIiq35yTWKpH//sQGB31nBddhN5Md3rgEI7mukn+CGqZGvVGQGkfQoDiNL7Z3cmk8mgGhxjO8aaYzzlhoITZwxHXVf1Eh9xxPQ6zuhYTANWdFl9BdbDHbetqTo/o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lst.de; spf=pass smtp.mailfrom=lst.de; arc=none smtp.client-ip=213.95.11.211 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lst.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=lst.de Received: by verein.lst.de (Postfix, from userid 2407) id B455A68B05; Mon, 24 Nov 2025 18:12:30 +0100 (CET) Date: Mon, 24 Nov 2025 18:12:30 +0100 From: Christoph Hellwig To: Keith Busch Cc: dm-devel@lists.linux.dev, linux-block@vger.kernel.org, snitzer@kernel.org, hch@lst.de, axboe@kernel.dk, ebiggers@kernel.org, Keith Busch Subject: Re: [PATCHv2 1/3] block: remove stacking default dma_alignment Message-ID: <20251124171230.GA29490@lst.de> References: <20251124170903.3931792-1-kbusch@meta.com> <20251124170903.3931792-2-kbusch@meta.com> Precedence: bulk X-Mailing-List: dm-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251124170903.3931792-2-kbusch@meta.com> User-Agent: Mutt/1.5.17 (2007-11-01) On Mon, Nov 24, 2025 at 09:09:01AM -0800, Keith Busch wrote: > From: Keith Busch > > The dma_alignment becomes 511 anyway if the caller doesn't explicitly > set it. But setting this default prevents the stacked device from > requesting a lower value even if it can handle lower alignments. Given how much trouble we had with drivers doing software processing and unaligned buffers I'd feel more comfortable keeping this default limitation. Drivers that want to relax it can still trivially do that right after calling blk_set_stacking_limits.