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 87DCC1BF3D; Mon, 19 Feb 2024 19:21:18 +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=1708370478; cv=none; b=SBF0I3XXx/ucgvyIoBHQXPkIz+aL/h2rpfRYye/znGquht+KP7tOJP+n9sIfIZdCv5ge82naMRc8nK4O4SHoLQUfkYkP2axvbzGG08tBZ9QyLNbtRYK3GHdRzCDsljVKU3BaY3KpOOHWIl/Zek084+fXTmmOw3m/xPyyQBMY5tw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708370478; c=relaxed/simple; bh=BU7vmtS91LW14umqdRks1US1wmoCN7BfyNRskJ+lpzg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=mc6sb+9HBgxmwuyl+D3F8kK0kW7JHCuVYq9kP6piFBor4padm1iphrSgCmg9epJn39UJRg4riEp68mo56byjdRtjz7C43fUxZoRFP9r7I/dME9A3YrQ6vlIiNLaXZTf/joYaCOhu6V7XTg7fqkX+b912k9VEK11b86JJOPXxmYE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=rDI2Tw7l; 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="rDI2Tw7l" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C5BB4C433F1; Mon, 19 Feb 2024 19:21:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1708370478; bh=BU7vmtS91LW14umqdRks1US1wmoCN7BfyNRskJ+lpzg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=rDI2Tw7lYr17vYfRVT31/CFWOTvQvw8vu8Kd10WZDkZAfAUrzH8Df4KP6kxyUwmrK rGFpMcWC60IsJ/xONKcoIBQHrAldlZdG91Eo5stQQ7g0kxVAFfd9FHlI499h6X/V9X uV3aNuG/f+xnORzGFBi12Jq9+lalxrUM0mCfg2eSqcmNxdvWWWj0HLY4KndwAixZ5R QrIt0Synm8G4YerLcrr4Ta1M2jUeYFvwJyqYGsqzjANrsTGlgG6z54InG3nSN7NzBy lWYK1LwZxKgM45/cm2HfebVej40pz17i5AFt4n/v5CPx9+emInzhElr3yhPEDIr6p7 ynArQJ8jnkTMw== Date: Mon, 19 Feb 2024 12:21:14 -0700 From: Keith Busch <kbusch@kernel.org> To: John Garry <john.g.garry@oracle.com> Cc: axboe@kernel.dk, hch@lst.de, sagi@grimberg.me, jejb@linux.ibm.com, martin.petersen@oracle.com, djwong@kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org, dchinner@redhat.com, jack@suse.cz, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-fsdevel@vger.kernel.org, tytso@mit.edu, jbongio@google.com, linux-scsi@vger.kernel.org, ojaswin@linux.ibm.com, linux-aio@kvack.org, linux-btrfs@vger.kernel.org, io-uring@vger.kernel.org, nilay@linux.ibm.com, ritesh.list@gmail.com, Alan Adamson <alan.adamson@oracle.com> Subject: Re: [PATCH v4 10/11] nvme: Atomic write support Message-ID: <ZdOqKr6Js_nlobh5@kbusch-mbp> References: <20240219130109.341523-1-john.g.garry@oracle.com> <20240219130109.341523-11-john.g.garry@oracle.com> Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: <io-uring.vger.kernel.org> List-Subscribe: <mailto:io-uring+subscribe@vger.kernel.org> List-Unsubscribe: <mailto:io-uring+unsubscribe@vger.kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20240219130109.341523-11-john.g.garry@oracle.com> On Mon, Feb 19, 2024 at 01:01:08PM +0000, John Garry wrote: > From: Alan Adamson <alan.adamson@oracle.com> > > Add support to set block layer request_queue atomic write limits. The > limits will be derived from either the namespace or controller atomic > parameters. > > NVMe atomic-related parameters are grouped into "normal" and "power-fail" > (or PF) class of parameter. For atomic write support, only PF parameters > are of interest. The "normal" parameters are concerned with racing reads > and writes (which also applies to PF). See NVM Command Set Specification > Revision 1.0d section 2.1.4 for reference. > > Whether to use per namespace or controller atomic parameters is decided by > NSFEAT bit 1 - see Figure 97: Identify - Identify Namespace Data Structure, > #NVM Command Set. > > NVMe namespaces may define an atomic boundary, whereby no atomic guarantees > are provided for a write which straddles this per-lba space boundary. The > block layer merging policy is such that no merges may occur in which the > resultant request would straddle such a boundary. > > Unlike SCSI, NVMe specifies no granularity or alignment rules. In addition, > again unlike SCSI, there is no dedicated atomic write command - a write > which adheres to the atomic size limit and boundary is implicitly atomic. > > If NSFEAT bit 1 is set, the following parameters are of interest: > - NAWUPF (Namespace Atomic Write Unit Power Fail) > - NABSPF (Namespace Atomic Boundary Size Power Fail) > - NABO (Namespace Atomic Boundary Offset) > > and we set request_queue limits as follows: > - atomic_write_unit_max = rounddown_pow_of_two(NAWUPF) > - atomic_write_max_bytes = NAWUPF > - atomic_write_boundary = NABSPF > > If in the unlikely scenario that NABO is non-zero, then atomic writes will > not be supported at all as dealing with this adds extra complexity. This > policy may change in future. > > In all cases, atomic_write_unit_min is set to the logical block size. > > If NSFEAT bit 1 is unset, the following parameter is of interest: > - AWUPF (Atomic Write Unit Power Fail) > > and we set request_queue limits as follows: > - atomic_write_unit_max = rounddown_pow_of_two(AWUPF) > - atomic_write_max_bytes = AWUPF > - atomic_write_boundary = 0 > > The block layer requires that the atomic_write_boundary value is a > power-of-2. However, it is really only required that atomic_write_boundary > be a multiple of atomic_write_unit_max. As such, if NABSPF were not a > power-of-2, atomic_write_unit_max could be reduced such that it was > divisible into NABSPF. However, this complexity will not be yet supported. > > A helper function, nvme_valid_atomic_write(), is also added for the > submission path to verify that a request has been submitted to the driver > will actually be executed atomically. Maybe patch 11 should be folded into this one. No bigged, the series as a whole looks good. Reviewed-by: Keith Busch <kbusch@kernel.org>