From owner-svn-src-head@freebsd.org Fri Apr 14 20:47:59 2017 Return-Path: Delivered-To: svn-src-head@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 33613D3AF71; Fri, 14 Apr 2017 20:47:59 +0000 (UTC) (envelope-from ronald-lists@klop.ws) Received: from smarthost1.greenhost.nl (smarthost1.greenhost.nl [195.190.28.81]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id EFFF4AD; Fri, 14 Apr 2017 20:47:57 +0000 (UTC) (envelope-from ronald-lists@klop.ws) Received: from smtp.greenhost.nl ([213.108.104.138]) by smarthost1.greenhost.nl with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.84_2) (envelope-from ) id 1cz88I-0005S3-Li; Fri, 14 Apr 2017 22:47:55 +0200 Content-Type: text/plain; charset=utf-8; format=flowed; delsp=yes To: "Alan Somers" , "Mark Johnston" Cc: "svn-src-head@freebsd.org" , "svn-src-all@freebsd.org" , "src-committers@freebsd.org" , "Ngie Cooper" Subject: Re: svn commit: r316938 - head/sbin/savecore References: <201704141941.v3EJfmCW003347@repo.freebsd.org> <20170414202918.GD5039@wkstn-mjohnston.west.isilon.com> Date: Fri, 14 Apr 2017 22:47:53 +0200 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit From: "Ronald Klop" Message-ID: In-Reply-To: <20170414202918.GD5039@wkstn-mjohnston.west.isilon.com> User-Agent: Opera Mail/12.16 (FreeBSD) X-Authenticated-As-Hash: 398f5522cb258ce43cb679602f8cfe8b62a256d1 X-Virus-Scanned: by clamav at smarthost1.samage.net X-Spam-Level: / X-Spam-Score: -0.2 X-Spam-Status: No, score=-0.2 required=5.0 tests=ALL_TRUSTED, BAYES_50 autolearn=disabled version=3.4.0 X-Scan-Signature: 4868b52b90b9144be14ceb212c82ef23 X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 14 Apr 2017 20:47:59 -0000 On Fri, 14 Apr 2017 22:29:18 +0200, Mark Johnston wrote: > On Fri, Apr 14, 2017 at 01:49:51PM -0600, Alan Somers wrote: >> On Fri, Apr 14, 2017 at 1:41 PM, Ngie Cooper wrote: >> > Author: ngie >> > Date: Fri Apr 14 19:41:48 2017 >> > New Revision: 316938 >> > URL: https://svnweb.freebsd.org/changeset/base/316938 >> > >> > Log: >> > savecore: fix space calculation with respect to `minfree` in >> check_space(..) >> > >> > - Use strtoll(3) instead of atoi(3), because atoi(3) limits the >> > representable data to INT_MAX. Check the values received from >> > strtoll(3), trimming trailing whitespace off the end to maintain >> > POLA. >> > - Use `KiB` instead of `kB` when describing free space, total space, >> > etc. I am now fully aware of `KiB` being the IEC standard for 1024 >> > bytes and `kB` being the IEC standard for 1000 bytes. >> > - Store available number of KiB in `available` so it can be more >> > easily queried and compared to ensure that there are enough KiB to >> > store the dump image on disk. >> > - Print out the reserved space on disk, per `minfree`, so end-users >> > can troubleshoot why check_space(..) is reporting that there isn't >> > enough free space. >> > >> > MFC after: 7 weeks >> > Reviewed by: Anton Rang (earlier diff), cem >> (earlier diff) >> > Tested with: positive/negative cases (see review); make tinderbox >> > Sponsored by: Dell EMC Isilon >> > Differential Revision: D10379 >> >> The free space calculation is still uselessly conservative, because it >> doesn't account for the fact that core dumps will always be either >> spare or compressed. The result is that savecore will frequently >> refuse to save corefiles even when there's plenty of space. I >> proposed removing the space check altogether in >> https://reviews.freebsd.org/D2587. However, I agreed to wait until >> after the compressed core dump feature was merged, because then mostly >> accurate space checks will be possible. AFAIK the compressed core >> dump feature still hasn't been finished. > > I had held off on it for a while because it was going to conflict with > the work to add encrypted dump support, which of course has finished. > > The patch to add compression support is here and should largely still > work: > https://people.freebsd.org/~markj/patches/core-compression/20141110-kern_dump.diff > > I've been hesitant about pushing it forward: > - The dump_write* APIs need some simplification after the addition of > encrypted dump support and support for dumping to 4Kn drives. > - I'm not sure how encryption should compose with compression. It seems > intuitively obvious that we should compress before encrypting if the > compression is to be of any use, but I don't know enough to know > whether the compression might somehow compromise the effectiveness of > the encryption. > > If anyone has some insight on the second of these two points, I'd > appreciate hearing it. About compression before encryption there is some information. For example: https://en.wikipedia.org/wiki/CRIME Openssh removed compression in pre-authentication in http://www.openssh.com/txt/release-7.4 Regards, Ronald.