From owner-freebsd-hackers@freebsd.org Wed Sep 23 22:43:23 2020 Return-Path: Delivered-To: freebsd-hackers@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id C32A43E09F0 for ; Wed, 23 Sep 2020 22:43:23 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4BxY9k3vJmz4SvX for ; Wed, 23 Sep 2020 22:43:22 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from tom.home (kib@localhost [127.0.0.1]) by kib.kiev.ua (8.16.1/8.16.1) with ESMTPS id 08NMh8fU068290 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Thu, 24 Sep 2020 01:43:11 +0300 (EEST) (envelope-from kostikbel@gmail.com) DKIM-Filter: OpenDKIM Filter v2.10.3 kib.kiev.ua 08NMh8fU068290 Received: (from kostik@localhost) by tom.home (8.16.1/8.16.1/Submit) id 08NMh8gK068289; Thu, 24 Sep 2020 01:43:08 +0300 (EEST) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com using -f Date: Thu, 24 Sep 2020 01:43:08 +0300 From: Konstantin Belousov To: Alexander Leidinger Cc: freebsd-hackers@freebsd.org Subject: Re: RFC: copy_file_range(3) Message-ID: <20200923224308.GK2570@kib.kiev.ua> References: <20200923122401.Horde.uXmEqpCzVbCyXTuyukZeRwU@webmail.leidinger.net> <20200923145615.GH2570@kib.kiev.ua> <20200923212135.Horde.KVi_zSxPaGuNqcGzm_Qxani@webmail.leidinger.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200923212135.Horde.KVi_zSxPaGuNqcGzm_Qxani@webmail.leidinger.net> X-Spam-Status: No, score=-1.0 required=5.0 tests=ALL_TRUSTED,BAYES_00, DKIM_ADSP_CUSTOM_MED,FORGED_GMAIL_RCVD,FREEMAIL_FROM, NML_ADSP_CUSTOM_MED autolearn=no autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on tom.home X-Rspamd-Queue-Id: 4BxY9k3vJmz4SvX X-Spamd-Bar: / Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=fail reason="No valid SPF, No valid DKIM" header.from=gmail.com (policy=none); spf=softfail (mx1.freebsd.org: 2001:470:d5e7:1::1 is neither permitted nor denied by domain of kostikbel@gmail.com) smtp.mailfrom=kostikbel@gmail.com X-Spamd-Result: default: False [0.10 / 15.00]; RCVD_TLS_ALL(0.00)[]; ARC_NA(0.00)[]; DMARC_POLICY_SOFTFAIL(0.10)[gmail.com : No valid SPF, No valid DKIM,none]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FREEMAIL_FROM(0.00)[gmail.com]; MIME_GOOD(-0.10)[text/plain]; HAS_XAW(0.00)[]; R_SPF_SOFTFAIL(0.00)[~all]; NEURAL_SPAM_MEDIUM(0.13)[0.126]; TO_MATCH_ENVRCPT_SOME(0.00)[]; NEURAL_HAM_SHORT(-0.08)[-0.079]; RCPT_COUNT_TWO(0.00)[2]; NEURAL_SPAM_LONG(0.06)[0.056]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; FREEMAIL_ENVFROM(0.00)[gmail.com]; ASN(0.00)[asn:6939, ipnet:2001:470::/32, country:US]; MIME_TRACE(0.00)[0:+]; MAILMAN_DEST(0.00)[freebsd-hackers]; RCVD_COUNT_TWO(0.00)[2] X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.33 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 23 Sep 2020 22:43:23 -0000 On Wed, Sep 23, 2020 at 09:21:35PM +0200, Alexander Leidinger wrote: > Quoting Konstantin Belousov (from Wed, 23 Sep 2020 > 17:56:15 +0300): > > > On Wed, Sep 23, 2020 at 12:24:01PM +0200, Alexander Leidinger via > > freebsd-hackers wrote: > > > Quoting Rick Macklem (from Wed, 23 Sep 2020 01:18:18 > > > +0000): > > > > > > > Well, I ran some quick benchmarks using the attached programs, > > > plus "cp" both > > > > before and with your copy_file_range() patch. > > > > copya - Does what I think your plan is above, with a limit of 2Mbytes > > > > for "len". > > > > copyb -Just uses copy_file_range() with 128Mbytes for "len". > > > > > > > > I first created the sparse file with createsparse.c. It is admittedly a > > > > worst case, > > > > creating alternating holes and data blocks of the minimum size > > > supported by > > > > the file system. (I ran it on a UFS file system created with defaults, > > > > so the minimum > > > > hole size is 32Kbytes.) > > > > > > Not related to the topic of changing cp, but related to the topic of > > > copy_file_range: does nullfs support (as in pass-through to the underlying > > > FS) copy_file_range? > > > > Nullfs bypasses VOP_COPY_FILE_RANGE() same as any other multi-vp arg > > VOP. What makes you think it is different ? > > I understand "bypass" as "does not handle copy_file_range". And from what I > was understanding in this discussion, each FS-driver needs to be modified to > support copy_file_range. I've never looked into the nullfs code (and VFS is > for me some kind of object oriented interface into which FSes can plug into, > with a generic "I can't do that" for parts of the interface which needs a FS > specific implementation in case the FS doesn't provide this part), so I do > not know how it handles the "place A is a portal into place B". Naivly > speaking I would assume it translates a request for a specific path by > modifying the path internally, but for that it needs to provide an. I do not > know how much meta-data needs to be handled / kept in memory / generated for > this. I had the options "maybe to much for a pass-through", and "maybe not > too much for a pass-through". To me it makes sense, that nullfs is able to > handle this (I have a samba server in a jail which has some datasets mounted > via nullfs, and the same datasets are also mounted into other jails and > served read-only via a webserver or other kinds of servers, and would be > usefule if samba could use copy_file_range on nullfs). You could argue that > my question was more "is nullfs modified to handle copy_file_range", than > "does it technically pass-through". Bypass mean that nullfs forwards the call to corresponding VOP of the lower vnode. This should be described in D&I book, also see the comment at the start of null_vnops.c (I did not rechecked it for accuracy). We have fallback VOP vector that is invoked when filesystem does not implement some VOP. In case of copy_file_range VOP, the slot is filled by vop_stdcopy_file_range() that is a wrapper around vn_generic_copy_file_range(). AFAIR, only NFS client implements non-default implementation for copy_file_range() VOP. So UFS/ZFS/msdosfs use vn_generic_copy_file_range(). All this assumes that invp and outvp belongs to the same filesystem. If they do not, as was in case of cp /dev/null something, vn_copy_file_range() directly invokes vn_generic_copy_file_range(). The later is a loop around VOP_READ() passing buffer to VOP_WRITE(), as somebody could reasonably expect. invokes