From owner-freebsd-hackers@freebsd.org Mon Mar 4 15:42:24 2019 Return-Path: Delivered-To: freebsd-hackers@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id BA68D15167E5 for ; Mon, 4 Mar 2019 15:42:24 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id E40246FCC3; Mon, 4 Mar 2019 15:42:23 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from tom.home (kib@localhost [127.0.0.1]) by kib.kiev.ua (8.15.2/8.15.2) with ESMTPS id x24FgCt2067452 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Mon, 4 Mar 2019 17:42:15 +0200 (EET) (envelope-from kostikbel@gmail.com) DKIM-Filter: OpenDKIM Filter v2.10.3 kib.kiev.ua x24FgCt2067452 Received: (from kostik@localhost) by tom.home (8.15.2/8.15.2/Submit) id x24FgC70067451; Mon, 4 Mar 2019 17:42:12 +0200 (EET) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com using -f Date: Mon, 4 Mar 2019 17:42:12 +0200 From: Konstantin Belousov To: Alan Somers Cc: FreeBSD Hackers Subject: Re: Adding namecache entries outside of vfs_lookup and vn_open ? Message-ID: <20190304154212.GP68879@kib.kiev.ua> References: <20190303110346.GH68879@kib.kiev.ua> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.3 (2019-02-01) 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=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on tom.home X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 04 Mar 2019 15:42:24 -0000 On Mon, Mar 04, 2019 at 08:24:27AM -0700, Alan Somers wrote: > On Sun, Mar 3, 2019 at 4:03 AM Konstantin Belousov wrote: > > Similar discussion occured some time ago. I think that the current > > selection of the cases where namecache entry is created, is optimized > > for the scenario where extracting large tarball does not largely affect > > the non-directory elements of the cache. If you do such extraction, > > it is unlikely that you will access most of the files shortly. > > I don't understand this objection. When you extract a tarball full of > non-empty files, don't you still need to open every file to write its > contents, creating a namecache entry for each one? No, you don't. Typically, when archiver parsed the stream and noted that there is a file to create with a content, it - opens the file, and gets the file descriptor returned to usermode. Internally, kernel does (vn_open_cred()) namei() <- this call returns no vnode because the file is non-existent, and does not create negative cache entry, see NOCACHE argument for cn_flags. VOP_CREATE() <- creating the file, again not caching assign the vnode returned, to the file - now the process has the descriptor for writes, but namecache entry is still not installed. - content is written, file is closed.