Date: Fri, 14 Apr 2017 22:47:53 +0200 From: "Ronald Klop" <ronald-lists@klop.ws> To: "Alan Somers" <asomers@freebsd.org>, "Mark Johnston" <markj@freebsd.org> Cc: "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org>, "Ngie Cooper" <ngie@freebsd.org> Subject: Re: svn commit: r316938 - head/sbin/savecore Message-ID: <op.yypdd3pxkndu52@53556c9c.cm-6-6b.dynamic.ziggo.nl> In-Reply-To: <20170414202918.GD5039@wkstn-mjohnston.west.isilon.com> References: <201704141941.v3EJfmCW003347@repo.freebsd.org> <CAOtMX2gPHWRGiE9UA5AevZz=cTv_qksAWX0H-xRjDEHp0huCVg@mail.gmail.com> <20170414202918.GD5039@wkstn-mjohnston.west.isilon.com>
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On Fri, 14 Apr 2017 22:29:18 +0200, Mark Johnston <markj@freebsd.org> 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 <ngie@freebsd.org> 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 <rang@acm.com> (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.
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