From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 4CA1411CBA; Wed, 10 Jun 2026 18:45:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781117148; cv=none; b=BW+lr5MJ2mefpApzAc6jhaGaunkiqImVAy1Olw7CzB8XVOlE1iU2hmyj9iRrXllRnHFxpqH9LqTVAmFzmVC7cYUk6QRtBzYouBzybLzdzYot3L9PHQXeizQRvnDqSyukY2zkmI1yXQgO5TLag/QvmthdF0/Ozdf51ONmM4hb+fI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781117148; c=relaxed/simple; bh=LE5C4qBWe7pizBvMhax7Oh1me7f4eIedM/LvdugVUVk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=KU1oDEWnPqxFI1qnf2o6ymA2LLJLO7rhwHZQVrcaAZ/iBO9PxNthPm7oVUQC9m9LTNv67D9JpK15LAb7SsuhxakCwVN/xvJRXTuERbafST6Wo87o1G1xw9Rw93sEqO5kEsTXdJbe574d397nzgdLxcUu5nmEOj8UDnfx1cTj3Vg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ffxOLSon; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ffxOLSon" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2BDA51F00893; Wed, 10 Jun 2026 18:45:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781117147; bh=CdwshvM9ZlryXVSDDelKO7PEGUTQ/phxdGshSPOhRig=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=ffxOLSonZmlgW6xII3PiZD7CERx2Ps3q2e1v0oG69HTGO4OiPSe51WjWmsPgzu8Th Kqh3oxBhjyUEl2P5TlDNGkIQAE9ddoGRhd5fnx+1wyJKmH1H9o0f5t325L9wEF+Bde NxLaJdI8IYFU3NUzKHRIPoTgpENSo0ntah0QwnDPjvG5vRIL29rzUCHFPji7ld4U5C Y9tvZau3HfQJj3Nq3TdvKtowQSyS3IIsccQZ90bUwTCMFm967oidD5+DsLJdEJK65G 5LJTZWv9kFEzdHNeJbt4uM530l7EE+UrZzic7klpYSDrGHPfVv9zgIcSi9rhd0MR4t FEp3oANNNH7Bw== Message-ID: <8c47b58d-9ff0-499e-a629-b9cf76186db6@kernel.org> Date: Wed, 10 Jun 2026 20:45:40 +0200 Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC v1] io_uring/rsrc: add fast path huge page handling in buffer registration To: Matthew Wilcox Cc: Christoph Hellwig , sw.prabhu6@gmail.com, axboe@kernel.dk, io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, dave@stgolabs.net, dongjoo.seo1@samsung.com, Swarna Prabhu , "linux-mm@kvack.org" , Zi Yan References: <20260608062937.804758-1-sw.prabhu6@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/10/26 20:10, Matthew Wilcox wrote: > On Wed, Jun 10, 2026 at 03:18:52PM +0200, David Hildenbrand (Arm) wrote: >> On 6/10/26 13:34, Christoph Hellwig wrote: >>> >>> I think whatever we're going to use for direct I/O has to also support >>> non-folio pages, especially PCI P2P memory. So coming up with an >>> interface that support this ASAP would be helpful. >> >> Yes. >> >> I think we can keep returning pages as long a the unpin interface knows the >> right thing to do to unpin them. > > This would be the get_user_phyrs() interface I've talked about before. > > https://lore.kernel.org/all/ZbVO2RKhw-dLUMvf@casper.infradead.org/ > and the long thread: > https://lore.kernel.org/all/YdyKWeU0HTv8m7wD@casper.infradead.org/ > >> Would there be users for a new interface that returns page ranges as described >> above, that would want to still unpin stuff partially? E.g., we give them a page >> range that belongs to the same folio with only a single pin/reference, but they >> would want to logically split that range and unpin pages individually? > > Urgh, no, we shouldn't do that. ranges should be pinned / unpinned > as a whole. I'm sympathetic to "for this special operation we need to > create a new range from this existing range and adjust the refcount(s) > appropriately so each of the two rangees can be put separately", but > I'm not sympathetic to "we need to allow each page to be individually > refcounted". Yes, me too. I wanted to understand if that a common thing to happen for users, such that we would have to worry about it right from the start. -- Cheers, David