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 ED09237A3DB
	for <linux-block@vger.kernel.org>; Wed, 29 Oct 2025 13:51:21 +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=1761745884; cv=none; b=P98Bny9LhvAhubCirwl1Vhu+XzMAzjkzB7muBYlRiRxlqSaLag7ToJtg/cEDDdcmtxxYKPkBwRPRYs28OM8axGdEx6T3bx+Y16kKvbYJKi9LnTW5REOPRTloBC3IZ5WHcZAZTPrTfwsQnVoJFCsELXiSvo9ZZii/ybj63+ICpM8=
ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org;
	s=arc-20240116; t=1761745884; c=relaxed/simple;
	bh=M8O6EYhvoHtk1oX3mzMTNrM7EWuKSzGh8vwQp0ckoq0=;
	h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version:
	 Content-Type:Content-Disposition:In-Reply-To; b=e+UOhXu78/TVSwydEQqFN4zTo/+9eT/dslon0WZTy6gE6rrEKgmxjbKwpaZ/dXBv6S4f0T4C0MBigz97/lfKFUjaayzMLea0Z+X27K1hI/MoerE3u8DZxquzhbKj4L/6qnpFZP3BcOomGf/RIJyxCvqGWW++aehUrwPSJIM+Lf0=
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 38F2A227A88; Wed, 29 Oct 2025 14:51:18 +0100 (CET)
Date: Wed, 29 Oct 2025 14:51:17 +0100
From: Christoph Hellwig <hch@lst.de>
To: Hans Holmberg <hans.holmberg@wdc.com>
Cc: Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
	Keith Busch <kbusch@kernel.org>,
	Damien Le Moal <dlemoal@kernel.org>,
	Johannes Thumshirn <johannes.thumshirn@wdc.com>,
	Christoph Hellwig <hch@lst.de>,
	Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>,
	Andreas Hindborg <a.hindborg@kernel.org>
Subject: Re: [PATCH] null_blk: set dma alignment to logical block size
Message-ID: <20251029135117.GB15688@lst.de>
References: <20251029133956.19554-1-hans.holmberg@wdc.com> <20251029135103.GA15688@lst.de>
Precedence: bulk
X-Mailing-List: linux-block@vger.kernel.org
List-Id: <linux-block.vger.kernel.org>
List-Subscribe: <mailto:linux-block+subscribe@vger.kernel.org>
List-Unsubscribe: <mailto:linux-block+unsubscribe@vger.kernel.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20251029135103.GA15688@lst.de>
User-Agent: Mutt/1.5.17 (2007-11-01)

On Wed, Oct 29, 2025 at 02:51:03PM +0100, Christoph Hellwig wrote:
> On Wed, Oct 29, 2025 at 02:39:56PM +0100, Hans Holmberg wrote:
> > This driver assumes that bio vectors are memory aligned to the logical
> > block size, so set the queue limit to reflect that.
> > 
> > Unless we set up the limit based on the logical block size, we will go
> > out of page bounds in copy_to_nullb / copy_from_nullb.
> > 
> > Signed-off-by: Hans Holmberg <hans.holmberg@wdc.com>
> > ---
> > 
> > A fixes tag would be in order, but I have not figured out exactly when
> > this became a problem.
> 
> In theory probably since day 1, and in practice since direct I/O allowed
> less than lba size memory alignment:
> 
> Fixes: bf8d08532bc1 ("iomap: add support for dma aligned direct-io")
> Fixes: b1a000d3b8ec ("block: relax direct io memory alignment")

Oh, and the patch itself of course looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>