From owner-freebsd-current@freebsd.org Mon Jul 13 01:09:56 2020 Return-Path: Delivered-To: freebsd-current@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 C3A3935472D for ; Mon, 13 Jul 2020 01:09:56 +0000 (UTC) (envelope-from jmg@gold.funkthat.com) Received: from gold.funkthat.com (gate2.funkthat.com [208.87.223.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "gate2.funkthat.com", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4B4ltX14SBz4FJ0 for ; Mon, 13 Jul 2020 01:09:55 +0000 (UTC) (envelope-from jmg@gold.funkthat.com) Received: from gold.funkthat.com (localhost [127.0.0.1]) by gold.funkthat.com (8.15.2/8.15.2) with ESMTPS id 06D19fDr070744 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Sun, 12 Jul 2020 18:09:41 -0700 (PDT) (envelope-from jmg@gold.funkthat.com) Received: (from jmg@localhost) by gold.funkthat.com (8.15.2/8.15.2/Submit) id 06D19fIC070743; Sun, 12 Jul 2020 18:09:41 -0700 (PDT) (envelope-from jmg) Date: Sun, 12 Jul 2020 18:09:41 -0700 From: John-Mark Gurney To: d@delphij.net Cc: freebsd-current@freebsd.org Subject: Re: Is there any error checking on swap? Message-ID: <20200713010941.GK4213@funkthat.com> Mail-Followup-To: d@delphij.net, freebsd-current@freebsd.org References: <20200712033332.GA63411@www.zefox.net> <20200712072911.GG4213@funkthat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="e9ndEBTQFD7P4kUb" Content-Disposition: inline In-Reply-To: X-Operating-System: FreeBSD 11.3-STABLE amd64 X-PGP-Fingerprint: D87A 235F FB71 1F3F 55B7 ED9B D5FF 5A51 C0AC 3D65 X-Files: The truth is out there X-URL: https://www.funkthat.com/ X-Resume: https://www.funkthat.com/~jmg/resume.html X-TipJar: bitcoin:13Qmb6AeTgQecazTWph4XasEsP7nGRbAPE X-to-the-FBI-CIA-and-NSA: HI! HOW YA DOIN? can i haz chizburger? User-Agent: Mutt/1.6.1 (2016-04-27) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.4.3 (gold.funkthat.com [127.0.0.1]); Sun, 12 Jul 2020 18:09:41 -0700 (PDT) X-Rspamd-Queue-Id: 4B4ltX14SBz4FJ0 X-Spamd-Bar: / Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=none; spf=none (mx1.freebsd.org: domain of jmg@gold.funkthat.com has no SPF policy when checking 208.87.223.18) smtp.mailfrom=jmg@gold.funkthat.com X-Spamd-Result: default: False [0.77 / 15.00]; RCVD_TLS_ALL(0.00)[]; ARC_NA(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; FROM_HAS_DN(0.00)[]; NEURAL_SPAM_SHORT(0.22)[0.218]; MIME_GOOD(-0.20)[multipart/signed,text/plain]; TO_DN_NONE(0.00)[]; DMARC_NA(0.00)[funkthat.com]; AUTH_NA(1.00)[]; NEURAL_SPAM_MEDIUM(0.34)[0.345]; TO_MATCH_ENVRCPT_SOME(0.00)[]; RCPT_COUNT_TWO(0.00)[2]; NEURAL_SPAM_LONG(0.11)[0.112]; SIGNED_PGP(-2.00)[]; FORGED_SENDER(0.30)[jmg@funkthat.com,jmg@gold.funkthat.com]; R_SPF_NA(0.00)[no SPF record]; SUBJECT_ENDS_QUESTION(1.00)[]; R_DKIM_NA(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; MIME_TRACE(0.00)[0:+,1:+,2:~]; FROM_NEQ_ENVFROM(0.00)[jmg@funkthat.com,jmg@gold.funkthat.com]; ASN(0.00)[asn:32354, ipnet:208.87.216.0/21, country:US] X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.33 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 13 Jul 2020 01:09:56 -0000 --e9ndEBTQFD7P4kUb Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Xin Li wrote this message on Sun, Jul 12, 2020 at 15:06 -0700: >=20 >=20 > On 7/12/20 12:29 AM, John-Mark Gurney wrote: > > bob prohaska wrote this message on Sat, Jul 11, 2020 at 20:33 -0700: > >> Is there any error checking on swap traffic, along the lines of > >> a checksum or parity test?=20 > >> > >> Just curious what happens if a page written out is corrupted when > >> it comes back. > >=20 > > Looks like it doesn't: > > https://svnweb.freebsd.org/base/head/sys/vm/swap_pager.c?annotate=3D361= 965#l1389 >=20 > Technically one can enable checks with e.g. geli(8), but note that the > geli(8) provider will not "prime" the HMAC data so attaching the device > will immediately spam the system log with some authentication errors due > to GEOM tasting (because the kernel would try to read locations that > potentially contain metadata for other GEOM providers). Yeah, and enabling auth w/ geli(8) is problematic, as it creates a disconnect between layers, as it expands 4096 byte writes to 9 512 byte sector writes, if you're using a 4k drive (which is pretty much the only thing sold these days), the performance is likely to be pretty terrible... see: https://svnweb.freebsd.org/base/head/sys/geom/eli/g_eli_integrity.c?annotat= e=3D361481#l56 So, it'd be doable, but less than ideal... > For the case of swap, since the write is always page sized, it's > probably optimal to implement something in the swap layer itself and > store the expected checksums in memory. +1 --=20 John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not." --e9ndEBTQFD7P4kUb Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQJ8BAEBCgBmBQJfC7RUXxSAAAAAAC4AKGlzc3Vlci1mcHJAbm90YXRpb25zLm9w ZW5wZ3AuZmlmdGhob3JzZW1hbi5uZXQ2MEI1RTRGMTNDNzYyMDZDNjEyMDBCNjAy MDVGMEIzM0REMDA2QURBAAoJECBfCzPdAGrakmUQAKcZeuy8dCLIfJfwcCS/+mrd ThVb+JYaVUDv1vavVU4iXH66/Nqw7+WC29ZrMOJCtQ8ttSRahzn5xpOt3xSXt+Ks Hk8qfdpPOgK35QVmwJFncpqAzhY020JKHk79+xssBs0ukxF+KRk0RIrR26av2iTF 5Prz3eIQv16OedQWYJXxXLW3umNbt2OPzI3pl1Kd8FpEE2/xRuvH1NmVxuHadDtB FK2VNdiumSEHhXbya6O/nCNljzlmLZ3X7OEa9YHsCJ6+gM/s/LAq0kvizigfNX5Q o0UCTmvURvtmOYuzhJd0ZwwDWM4+X0DkdKGJhGmw7pOizFqKtH1mnbSBKRjPcz5q MRG1tHYZ+EffB3aGKPfsuEZNXQtsuJz5B9atkoju8v0ELLa6Xt0x+F6NFY19jg5F vYEOdhC7PdX4GT1z+7S5UrWfZBISd0zAssZcXKKJLXQtVtT2kriFr35jhWXndF/l VDs+W7Uy4Er9tqxCxKVfbJIwmvFTShBu2/Zk7qanIGTncnBw1+GIJOmN+nuAkRf5 mJZvlHZH3D9wrqpqMZhtO7n4C4BCZi3wrUW7g6DSLq8DJD9cddvM0xz8vNieJ2Sa qwed+ZLb3L9pT/v3gOYj2UYaKcxG9HskqTxYf6c2jJRsbLihNkG608aL6xnDHB/5 sXD0vlegZSLxeQZPR51o =nyzJ -----END PGP SIGNATURE----- --e9ndEBTQFD7P4kUb--