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 ECEBE1D5145 for ; Mon, 7 Jul 2025 15:56:55 +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=1751903816; cv=none; b=TWOXo39AhqZjY2UJKB8l2alryFa4+TR9JiNP+peMTHTztlHMqygQE+lZcW59P3C5Sn3W3WV997kQ8/zwlyxGa9Ps7FfptfRcuAkja0y5y8PyGKvpaHv3t/Vd4R4go7I1kipwhY35ez7ANyhzFO7GE7mUdUX+VtrNYQgjol/+A70= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751903816; c=relaxed/simple; bh=K4TsgEfbZBCaB5T+UtpxvoxOzf99yOdPJVsE+Cw+Y0k=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=I8ykAA3Q192Ok+YnrsqP7ufidqq0EV0z+rzxLS4S4dT2gZOqzlkkvSXbZDnDqUvtsxj15m9VDg4c8+GI3OfAOPdbadeb75IvtLNF7HQxo61EHiRZ3MT1zi1uV4RBnYmoM1ufS1TSlIsbUy8xJ7JTq0RxAK9ql3VDnMIfVMogDyw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Z5AcbnHd; 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="Z5AcbnHd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 014CCC4CEE3; Mon, 7 Jul 2025 15:56:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1751903815; bh=K4TsgEfbZBCaB5T+UtpxvoxOzf99yOdPJVsE+Cw+Y0k=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Z5AcbnHd8RRLiGwhKyQCEKRiHwDNnLOxKiGli9/0YhEm80kN3aq/ruts5qIlYk5A6 6LpG+1G1+nv05A1Wxr2wUxcViszbUUm6gRJ2PqKzMEPDftjSXMsLAnPx0t/HtgU+st aqb4rtSXW2NfYnQuUwDRBiTdswIlRVJchl73ewkVGZ+x5/szVxEYKqT3RhUV5sw1pF R6nLYOibtMPyw1r6GIReKmpLlJCUhkTQUuSks/bAkErPer/csYqicOpJusESYU0MBH v/28k6znhy+zdn7NhyN02dMIM1MVXWXuUzUAXgK81kQxg1bzeeefYX5fR8CSVJrZ7d 5OAt+Oi6Olaxw== Date: Mon, 7 Jul 2025 09:56:53 -0600 From: Keith Busch To: Hannes Reinecke Cc: Christoph Hellwig , Alan Adamson , John Garry , "Martin K. Petersen" , Jens Axboe , linux-nvme@lists.infradead.org, linux-block@vger.kernel.org Subject: Re: What should we do about the nvme atomics mess? Message-ID: References: <20250707141834.GA30198@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: On Mon, Jul 07, 2025 at 05:26:46PM +0200, Hannes Reinecke wrote: > On 7/7/25 16:24, Keith Busch wrote: > > On Mon, Jul 07, 2025 at 04:18:34PM +0200, Christoph Hellwig wrote: > > > We could: > > > > > > I. revert the check and the subsequent fixup. If you really want > > > to use the nvme atomics you already better pray a lot anyway > > > due to issue 1) > > > II. limit the check to multi-controller subsystems > > > III. don't allow atomics on controllers that only report AWUPF and > > > limit support to controllers that support that more sanely > > > defined NAWUPF > > > > > > I guess for 6.16 we are limited to I. to bring us back to the previous > > > state, but I have a really bad gut feeling about it given the really > > > bad spec language and a lot of low quality NVMe implementations we're > > > seeing these days. > > > > I like option III. The controler scoped atomic size is broken for all > > the reasons you mentioned, so I vote we not bother trying to make sense > > of it. > > > Agree. We might consider I. as a fixup for stable, but should continue > with III going forward. I think the NVMe TWG might want to consider an ECN to deprecate or at least recommend against AUWPF, too. Just to throw AWUPF a lifeline for legecy devices, we could potentially make sense of the value if Identify Controller says: 1. CMIC == 0; and 2. OACS.NMS == 0; and 3. a. FNA.FNS == 1; or b. NN == 1 And if those conditions are true, then the controller and namespace scopes resolve to a single namespace format, so the values should be one in the same. The only way it could change, then, is a format command, which means there couldn't be an in-use filesystem depending on it not changing.