From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 3C1CF30DD2A; Mon, 18 Aug 2025 09:08:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755508120; cv=none; b=a8NcxwmQXO/bRPu0MJiXjaP/Tg7s/0TFt0LzJDQC3pWaIXIqLflCKDY0Q06OyOUnZnLejWdD1a0GehfA3zU+pDSTckTc/HXcpR51+RL7nDE7T1NBrPkvmbezKLG+oI/ypvE8vJuuCoS0IZQYEVst5fyIcze6a0ErZeuvFBZfc64= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755508120; c=relaxed/simple; bh=xdH66jWgpzzTFfGTToB5qVH9hBTVfljWsEB7eaJd07o=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ui9xB6j4cMth2diTOiUfTiRNWuAbd+Bef0JNLBAVPgOSd9KHwdRBldgD+wSl37qiftOOvyzVKExmV0Md2bGhNqrzT1xB8d8aGzfDiINfm7Y7VtRsNQgLM7Cf7uYvdEDrQamyLqLmWC38I29iFNvZNYWOYAJckVd+wtFsX8eYN4Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=Su+5NzDC; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Su+5NzDC" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=yHL7eu5GUAZjY3FC7EVLvh5Bh6QegvU2AsH3mijGkys=; b=Su+5NzDCgNR88W1ifQhiFSAeCR 28/W8l8unnJvRjND+oy/ZBeiui7ZfrDP8KbU6jvgAaSxBVuqmBNrmPdBakVoKRw5aeAgxuKB9WsRV 2mwlzBQdpVDrUhKjVeAgM6pDp4tP4B356O48X58qxICg1YRSzFDxKlcT0N59JjCC77TXFWwX5vUR+ d59aqQDT9m5GhTYfeHqkowG8tt2Bqb+oTdRm8fKKdIKh1rYMdbF2LD8zrOUHXk65y13vZptw7upQT yAko7GXDFJI3CwVzu7l8QHLLzpJpGQK05tlDEENV0vmAckaz0Si9TguT6G5zJjiSrYZce+h1J73Yb Rsw4i5OQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1unvr1-0000000718x-16Cz; Mon, 18 Aug 2025 09:08:35 +0000 Date: Mon, 18 Aug 2025 02:08:35 -0700 From: Christoph Hellwig To: Yu Kuai Cc: Christoph Hellwig , Damien Le Moal , colyli@kernel.org, linux-raid@vger.kernel.org, linux-block@vger.kernel.org, "yukuai (C)" Subject: Re: [PATCH 1/2] block: ignore underlying non-stack devices io_opt Message-ID: References: <4aa48545-7398-c346-5968-5d08f29748c4@huaweicloud.com> <917dc054-8423-4e49-7101-1667e64aae10@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-raid@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: <917dc054-8423-4e49-7101-1667e64aae10@huaweicloud.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Mon, Aug 18, 2025 at 04:57:30PM +0800, Yu Kuai wrote: > Ok, let's ignore the case there are other drivers in the stack chains, > just in this case: mdraid on the top of another mdraid, which we already > have. And in order not to introduce regression, we can do this inside > mdraid. Whatever you want to do in that case you can do by looking at BLK_FEAT_RAID_PARTIAL_STRIPES_EXPENSIVE. But I'm not even sure what you want to do. Assume you have to raid5 stacked on top of each other, using the same chunk size, but a different non-multiple number of stripe units. The only thing you could do is to multiply the values, but I doubt anything above will take the resulting number serious. And depending on the stripe size of the lower raid5 the upper one might not even be capable of feeding it large enough I/O.