From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 97E171BBBE5; Tue, 25 Nov 2025 02:49:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764038977; cv=none; b=bdUFNAI906qKVt2Eo+0caZmt9PA12jlpPIXuehzvAZ3Snh/oHb2O+7R4h5jzjJtW4B+J+oWWloBpulK74wXFifIBnHNPxxNBPxQo9sMvA5zhuNETRvkyNb4tDoE96hFK6bo0gEiEL/1wSPXg+db12l+YIlCW9VBSZObp1utoxJU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764038977; c=relaxed/simple; bh=6gQjztsDDlh8n/eTljRDdlDWD5jAcdxxhM0F5+hbMUU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=i6gW9Zo5P6jF7CIrnW0jTvrmWn2eT72PZSuOzQpc4KJexos4pqHz7PyuS76V/cmjuFwvUOxYvmRZ81y5O+I8X/lWbQBBk9c6RJbFCNrpdaEBKVVHcpJr5lZDCtx29ze9z7a8RgypNj6DltA2BLidkBhyZ3/FUMWVUGtFFVRajFs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=O60DemiN; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="O60DemiN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DB22FC4CEFB; Tue, 25 Nov 2025 02:49:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764038977; bh=6gQjztsDDlh8n/eTljRDdlDWD5jAcdxxhM0F5+hbMUU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=O60DemiNA5KuF1BgeDQzAvVVBaj+pyx9Kg8vxWVP8gVszGkzdj6AnTEtIZSp7Q4r8 hCX9AB55IF6+0tkPPYq0Vkg5rAAweSqFyMHh7y/4n39Qf/AXahyQzhgpKqmN9qWlLB ocV8J0wcBiz3EuvCt1QW0uRMpVsuIzbjBGCTpB/xf5xeFVEvU0eVUzDmKRPnWS46MT P94e/PZGyr+s7po/ovXM4mwBanFJ6O64V6eHMrR2CeIK/VgjguAoXZUyqepu6y1x10 2iQ4QrH8G5790i2Lp8U/vRxpmSwQJEKGthtvnknz8VhuC/+ykgAaS9gU63uonAGtVT T2DfM34cA/0/g== Date: Mon, 24 Nov 2025 19:49:35 -0700 From: Keith Busch To: Christoph Hellwig Cc: Keith Busch , dm-devel@lists.linux.dev, linux-block@vger.kernel.org, snitzer@kernel.org, axboe@kernel.dk, ebiggers@kernel.org Subject: Re: [PATCHv2 1/3] block: remove stacking default dma_alignment Message-ID: References: <20251124170903.3931792-1-kbusch@meta.com> <20251124170903.3931792-2-kbusch@meta.com> <20251124171230.GA29490@lst.de> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251124171230.GA29490@lst.de> On Mon, Nov 24, 2025 at 06:12:30PM +0100, Christoph Hellwig wrote: > 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. That should have the same result, but it's totally fine with me if you prefer the caller overwrite the default instead.