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 916A0155342 for ; Fri, 3 May 2024 16:22:57 +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=1714753380; cv=none; b=gbrBpmDQWHJS/uIpDDgoZQSYlfictNKCSl1y7tQhB3jbVHqV4Q+Xxa/mndqGWFOXGSqT0freOGD/lRsef6NvcfWq7hCIkYBsWTOyCDDUIoeWi1G5cQaGT4RPxkvBY3P0wjXSQs6FxZb4M/+EjBzVx9V1dQDvtBxFN8/f80y9Qiw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714753380; c=relaxed/simple; bh=SRtJ8KBHw8d4CKKy8rTTzwTvgnBLctc9QV0NRPlj8qM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=W61U3MYY0WoXT6QZxoIWclT0Ua2tByVsdhZVlJ7wbWNyaV7gZotohG6YVjO4WjEmQ3KtmP63rYnpJHZL2Uf7Ei11r8knfZQeXQuqHJwrZTa7jbS7T4HsvY54oC5KwD6fPbTJ9ZS231Ym7PG2prqfRCHMj2jnvIl4I96PlWPR8FU= 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 4605768AFE; Fri, 3 May 2024 18:22:52 +0200 (CEST) Date: Fri, 3 May 2024 18:22:52 +0200 From: Christoph Hellwig To: Matthew Wilcox Cc: Christoph Hellwig , Hannes Reinecke , Kundan Kumar , axboe@kernel.dk, linux-block@vger.kernel.org, joshi.k@samsung.com, mcgrof@kernel.org, anuj20.g@samsung.com, nj.shetty@samsung.com, c.gameti@samsung.com, gost.dev@samsung.com Subject: Re: [PATCH v2] block : add larger order folio size instead of pages Message-ID: <20240503162252.GA25087@lst.de> References: <20240430175014.8276-1-kundan.kumar@samsung.com> <317ce09b-5fec-4ed2-b32c-d098767956d0@suse.de> <20240502125340.GB20610@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: User-Agent: Mutt/1.5.17 (2007-11-01) On Fri, May 03, 2024 at 04:26:55PM +0100, Matthew Wilcox wrote: > I think this is wandering into a minefield. I'm pretty sure > it's considered valid to split the bio, and complete the two halves > independently. Each one will put the refcounts for the pages it touches, > and if we do this early putting of references, that's going to fail. That's now how bios work. The submitter always operates on the entire bio using the _all iterators. bios do get split and advances, but that only affects the bi_iter state. In a perfect world we'd split the memory containers aspect of the bio from the iterator, but that would be a lot of churn and we've got bigger fish to fry.