From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B4A01C18E5A for ; Wed, 11 Mar 2020 14:41:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0807720650 for ; Wed, 11 Mar 2020 14:41:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="gDGVqloe" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729927AbgCKOlk (ORCPT ); Wed, 11 Mar 2020 10:41:40 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:33305 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729057AbgCKOlk (ORCPT ); Wed, 11 Mar 2020 10:41:40 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1583937699; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=oi39w6c8WmZF4VD2SAl+7GXpBzzUSxdZMb4is4/iUjc=; b=gDGVqloeKy0uQKg4vzmBANyzcKd2gl+QBhSRa2dtO3ej8UUI9ML5pEvl5XZytR6bjMeeB9 oyrUY7e6XvyHDWON1LqpKheKvFibS/G8y6V+nOjm2llZHehHfxxFILoficoqIctwXPQKW5 F/+s7PQ4DkGO4HSiMWdBsox21GRRXOE= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-369-oaGi-oZRO3uadCugnnOKxA-1; Wed, 11 Mar 2020 10:41:35 -0400 X-MC-Unique: oaGi-oZRO3uadCugnnOKxA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8B2B31088384; Wed, 11 Mar 2020 14:41:33 +0000 (UTC) Received: from horse.redhat.com (unknown [10.18.25.210]) by smtp.corp.redhat.com (Postfix) with ESMTP id F268960C18; Wed, 11 Mar 2020 14:41:24 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id 84EA122021D; Wed, 11 Mar 2020 10:41:24 -0400 (EDT) Date: Wed, 11 Mar 2020 10:41:24 -0400 From: Vivek Goyal To: Miklos Szeredi Cc: Amir Goldstein , linux-fsdevel , linux-kernel , linux-nvdimm , virtio-fs@redhat.com, Stefan Hajnoczi , "Dr. David Alan Gilbert" , "Michael S. Tsirkin" , Peng Tao Subject: Re: [PATCH 12/20] fuse: Introduce setupmapping/removemapping commands Message-ID: <20200311144124.GB83257@redhat.com> References: <20200304165845.3081-1-vgoyal@redhat.com> <20200304165845.3081-13-vgoyal@redhat.com> <20200310203321.GF38440@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, Mar 11, 2020 at 03:19:18PM +0100, Miklos Szeredi wrote: > On Wed, Mar 11, 2020 at 8:03 AM Amir Goldstein wrote: > > > > On Tue, Mar 10, 2020 at 10:34 PM Vivek Goyal wrote: > > > > > > On Tue, Mar 10, 2020 at 08:49:49PM +0100, Miklos Szeredi wrote: > > > > On Wed, Mar 4, 2020 at 5:59 PM Vivek Goyal wrote: > > > > > > > > > > Introduce two new fuse commands to setup/remove memory mappings. This > > > > > will be used to setup/tear down file mapping in dax window. > > > > > > > > > > Signed-off-by: Vivek Goyal > > > > > Signed-off-by: Peng Tao > > > > > --- > > > > > include/uapi/linux/fuse.h | 37 +++++++++++++++++++++++++++++++++++++ > > > > > 1 file changed, 37 insertions(+) > > > > > > > > > > diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h > > > > > index 5b85819e045f..62633555d547 100644 > > > > > --- a/include/uapi/linux/fuse.h > > > > > +++ b/include/uapi/linux/fuse.h > > > > > @@ -894,4 +894,41 @@ struct fuse_copy_file_range_in { > > > > > uint64_t flags; > > > > > }; > > > > > > > > > > +#define FUSE_SETUPMAPPING_ENTRIES 8 > > > > > +#define FUSE_SETUPMAPPING_FLAG_WRITE (1ull << 0) > > > > > +struct fuse_setupmapping_in { > > > > > + /* An already open handle */ > > > > > + uint64_t fh; > > > > > + /* Offset into the file to start the mapping */ > > > > > + uint64_t foffset; > > > > > + /* Length of mapping required */ > > > > > + uint64_t len; > > > > > + /* Flags, FUSE_SETUPMAPPING_FLAG_* */ > > > > > + uint64_t flags; > > > > > + /* Offset in Memory Window */ > > > > > + uint64_t moffset; > > > > > +}; > > > > > + > > > > > +struct fuse_setupmapping_out { > > > > > + /* Offsets into the cache of mappings */ > > > > > + uint64_t coffset[FUSE_SETUPMAPPING_ENTRIES]; > > > > > + /* Lengths of each mapping */ > > > > > + uint64_t len[FUSE_SETUPMAPPING_ENTRIES]; > > > > > +}; > > > > > > > > fuse_setupmapping_out together with FUSE_SETUPMAPPING_ENTRIES seem to be unused. > > > > > > This looks like leftover from the old code. I will get rid of it. Thanks. > > > > > > > Hmm. I wonder if we should keep some out args for future extensions. > > Maybe return the mapped size even though it is all or nothing at this > > point? > > > > I have interest in a similar FUSE mapping functionality that was prototyped > > by Miklos and published here: > > https://lore.kernel.org/linux-fsdevel/CAJfpegtjEoE7H8tayLaQHG9fRSBiVuaspnmPr2oQiOZXVB1+7g@mail.gmail.com/ > > > > In this prototype, a FUSE_MAP command is used by the server to map a > > range of file to the kernel for io. The command in args are quite similar to > > those in fuse_setupmapping_in, but since the server is on the same host, > > the mapping response is {mapfd, offset, size}. > > Right. So the difference is in which entity allocates the mapping. > IOW whether the {fd, offset, size} is input or output in the protocol. > > I don't remember the reasons for going with the mapping being > allocated by the client, not the other way round. Vivek? I think one of the main reasons is memory reclaim. Once all ranges in a cache range are allocated, we need to free a memory range which can be reused. And client has all the logic to free up that range so that it can be remapped and reused for a different file/offset. Server will not know any of this. So I will think that for virtiofs, server might not be able to decide where to map a section of file and it has to be told explicitly by the client. > > If the allocation were to be by the server, we could share the request > type and possibly some code between the two, although the I/O > mechanism would still be different. > So input parameters of both FUSE_SETUPMAPPING and FUSE_MAP seem similar (except the moffset field). Given output of FUSE_MAP reqeust is very different, I would think it will be easier to have it as a separate command. Or can it be some sort of optional output args which can differentiate between two types of requests. /me personally finds it simpler to have separate command instead of overloading FUSE_SETUPMAPPING. But its your call. :-) Vivek