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 9B08E14A8E; Mon, 16 Jun 2025 05:25:31 +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=1750051533; cv=none; b=SsVe8kzeIPSELCOWhWeEp32DiA5r1Hoas3PaOeaTV6mPYyk1uvdTJjSQfKxLUfOsvLTeKWBdf4XRIrvOdFvhYiyeWoil31FDZ+2kx4tfQenbaESOQD7q4npDXKXf/r3MLUbkQnhq+XYF6GrqWS6O9YSqIMXnaf/kScKklvMC/Uo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750051533; c=relaxed/simple; bh=dU9R8MC6xbPrHNM/OSqF0vDUwVpni+pZRmmj2opuiWM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=UE9MZJpHk3XUJ4whbKUTT76I42DKmKuI9N472ON8b4mQiDGfXZY8VAIP8mZl46JUjtCSG7JW89Y3r5eOWdWSk381/rw0ppoQFaS/AT0sRn9b0eeuUp1ce5jGCZcmSEGXD9tIu+VVVSLOkgDI+QqoJL71lVdSEp+2Vt4GumKT51Y= 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=b/nuvRU2; 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="b/nuvRU2" 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=0ilKtUDLU3xGxduLonN3eGibnQvh68iPK6xSKyYUOoU=; b=b/nuvRU2/IoozMkhu3mIHfAyEl RKkQiEF+lhJUc10muHa6qXv1EXRebIM1fQTmhK2lF+fL0DqGhiHbG4ZWjR5LIgs9CFo8Z3Y2ZV1kY j/70R4chy02UprCaSQIywOcRQF1wRLUZKZsIERdMGYzlFNFhpaHyFO+2cigQZViw4farcxUf6TbYB UABDK7RtyPFSpYwhJesGSSkdH17qkYOL8VWFgqJ3baziBIGFJ3vfi1CeVThA9FDkTm2kE0stGx7kH ei0r1f5w7M9vLrL8bhmfvoCd9UFQTdw0WpoBSeeI+Q+VPjNp9p02KiaKHDf8EHdNKmmbHC63UWqS4 NnPSoXnA==; Received: from hch by bombadil.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1uR2LU-00000003QVL-1zRf; Mon, 16 Jun 2025 05:25:24 +0000 Date: Sun, 15 Jun 2025 22:25:24 -0700 From: Christoph Hellwig To: wangtao Cc: Christoph Hellwig , Christian =?iso-8859-1?Q?K=F6nig?= , "sumit.semwal@linaro.org" , "kraxel@redhat.com" , "vivek.kasireddy@intel.com" , "viro@zeniv.linux.org.uk" , "brauner@kernel.org" , "hughd@google.com" , "akpm@linux-foundation.org" , "amir73il@gmail.com" , "benjamin.gaignard@collabora.com" , "Brian.Starkey@arm.com" , "jstultz@google.com" , "tjmercier@google.com" , "jack@suse.cz" , "baolin.wang@linux.alibaba.com" , "linux-media@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , "linaro-mm-sig@lists.linaro.org" , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "wangbintian(BintianWang)" , yipengxiang , liulu 00013167 , hanfeng 00012985 Subject: Re: [PATCH v4 0/4] Implement dmabuf direct I/O via copy_file_range Message-ID: References: <20250603095245.17478-1-tao.wangtao@honor.com> <09c8fb7c-a337-4813-9f44-3a538c4ee8b1@amd.com> <5d36abace6bf492aadd847f0fabc38be@honor.com> <761986ec0f404856b6f21c3feca67012@honor.com> <34c2dbc06d074ffbb8f920418636bafc@honor.com> Precedence: bulk X-Mailing-List: linux-fsdevel@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: <34c2dbc06d074ffbb8f920418636bafc@honor.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Fri, Jun 13, 2025 at 09:33:55AM +0000, wangtao wrote: > > > > > On Mon, Jun 09, 2025 at 09:32:20AM +0000, wangtao wrote: > > > Are you suggesting adding an ITER_DMABUF type to iov_iter, > > > > Yes. > > May I clarify: Do all disk operations require data to pass through > memory (reading into memory or writing from memory)? In the block layer, > the bio structure uses bio_iov_iter_get_pages to convert iter_type > objects into memory-backed bio_vec representations. > However, some dmabufs are not memory-based, making page-to-bio_vec > conversion impossible. This suggests adding a callback function in > dma_buf_ops to handle dmabuf- to-bio_vec conversion. bios do support PCI P2P tranfers. This could be fairly easily extended to other peer to peer transfers if we manage to come up with a coherent model for them. No need for a callback.