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 3390D1552F6; Tue, 5 Nov 2024 16:00:57 +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=1730822459; cv=none; b=mTO2J1fb0eteNY5iVQXrchzldrPq99dbW1A/a+x+MkLHhvVI/QWXenvKO4GK1uc1sUZXFH4qsq83TpSqNyZr4Sidxw2p7xGfC6E+ZaUTRqz44lOnKJxT8XCuK2de42FGapGTZIc5V1Dz7PQIq8P51gp/l6I+FLVgdBexDXussUQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730822459; c=relaxed/simple; bh=0hFYpv05gf9VcHrx0UUx/n/00VxqWSThLGDwJAV0lm0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KDqHusfOyI5CrJClASLa0PTZGePFTuFyV2+KhaUGFPwvixJFbJiVJEw8Gse4HFTpHhxvjcJAy8KRvoPXHFzf7wpTg1+hszIQ4SAT/kVQL2ZJDZyS3hCH/sxpjm5Jhv1etDK4kzb1/LLPWP3m+mvUDfCUBjLM8U/n32fMFi3ndwY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (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=none (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 DD1D5227AAC; Tue, 5 Nov 2024 17:00:51 +0100 (CET) Date: Tue, 5 Nov 2024 17:00:51 +0100 From: Christoph Hellwig To: Kanchan Joshi Cc: Christoph Hellwig , Anuj gupta , Anuj Gupta , axboe@kernel.dk, kbusch@kernel.org, martin.petersen@oracle.com, asml.silence@gmail.com, brauner@kernel.org, jack@suse.cz, viro@zeniv.linux.org.uk, io-uring@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, gost.dev@samsung.com, linux-scsi@vger.kernel.org, vishak.g@samsung.com, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v7 06/10] io_uring/rw: add support to send metadata along with read/write Message-ID: <20241105160051.GA7599@lst.de> References: <20241104140601.12239-1-anuj20.g@samsung.com> <20241104140601.12239-7-anuj20.g@samsung.com> <20241105095621.GB597@lst.de> <20241105135657.GA4775@lst.de> Precedence: bulk X-Mailing-List: io-uring@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: User-Agent: Mutt/1.5.17 (2007-11-01) On Tue, Nov 05, 2024 at 09:21:27PM +0530, Kanchan Joshi wrote: > Can add the documentation (if this version is palatable for Jens/Pavel), > but this was discussed in previous iteration: > > 1. Each meta type may have different space requirement in SQE. > > Only for PI, we need so much space that we can't fit that in first SQE. > The SQE128 requirement is only for PI type. > Another different meta type may just fit into the first SQE. For that we > don't have to mandate SQE128. Ok, I'm really confused now. The way I understood Anuj was that this is NOT about block level metadata, but about other uses of the big SQE. Which version is right? Or did I just completely misunderstand Anuj? > 2. If two meta types are known not to co-exist, they can be kept in the > same place within SQE. Since each meta-type is a flag, we can check what > combinations are valid within io_uring and throw the error in case of > incompatibility. And this sounds like what you refer to is not actually block metadata as in this patchset or nvme, (or weirdly enough integrity in the block layer code). > 3. Previous version was relying on SQE128 flag. If user set the ring > that way, it is assumed that PI information was sent. > This is more explicitly conveyed now - if user passed META_TYPE_PI flag, > it has sent the PI. This comment in the code: > > + /* if sqe->meta_type is META_TYPE_PI, last 32 bytes are for PI */ > + union { > > If this flag is not passed, parsing of second SQE is skipped, which is > the current behavior as now also one can send regular (non pi) > read/write on SQE128 ring. And while I don't understand how this threads in with the previous statements, this makes sense. If you only want to send a pointer (+len) to metadata you can use the normal 64-byte SQE. If you want to send a PI tuple you need SEQ128. Is that what the various above statements try to express? If so the right API to me would be to have two flags: - a flag that a pointer to metadata is passed. This can work with a 64-bit SQE. - another flag that a PI tuple is passed. This requires a 128-byte and also the previous flag. > > > > > ---end quoted text---