From owner-freebsd-hackers@freebsd.org Tue Dec 8 20:20:30 2015 Return-Path: Delivered-To: freebsd-hackers@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 5D41E9D4006 for ; Tue, 8 Dec 2015 20:20:30 +0000 (UTC) (envelope-from wlosh@bsdimp.com) Received: from mail-qg0-x234.google.com (mail-qg0-x234.google.com [IPv6:2607:f8b0:400d:c04::234]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 0C9AF1159 for ; Tue, 8 Dec 2015 20:20:30 +0000 (UTC) (envelope-from wlosh@bsdimp.com) Received: by qgea14 with SMTP id a14so35142954qge.0 for ; Tue, 08 Dec 2015 12:20:29 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bsdimp-com.20150623.gappssmtp.com; s=20150623; h=mime-version:sender:in-reply-to:references:date:message-id:subject :from:to:cc:content-type; bh=GJ2jNatMBS0ZJqS2GAinDf2YJJxuJC47TKhH/rAmFH8=; b=JzhvexfJV+yCWvTlqESz0pkwUJuax9ExhPubY+tLgLsGXJlYZdQvAtGMD/RpOStIhA cMyT7CNgUZUC5TzGxusWUqUQQZ24VdRrJZAz9a241EWE0dV25vOiTCGA8CPYVjJRIZJ+ KmvdIwA+q4car1aeaUzfYU1gLZPR3zkMRr04ilsO77tA96G/Z7xut4CmtBxGj13FQwpr j7tfsEvRmV7zoOgxcAL/R9h8f7dD9xVirqrJUTNJR/jXpkK1dsrF+8J1c7hFa1viIQfV Kzp9/9cnznPOq0+N2ci1UwyuucLniKYfaDs1Fde4JtW5qs18PxiyffS8z8xnT60Qxn0X 7vAg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:sender:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=GJ2jNatMBS0ZJqS2GAinDf2YJJxuJC47TKhH/rAmFH8=; b=J3t6uNh+ZTZ4nbpWZb9YgOnEYoTfXevnrp7CkKurhJhOkpHT3n5HKHWM4nJNbqRCmx Ep+XhCt0ewY60ikHCHIfQJLyKSPKviei4oufyB+0axF4pS7CLYUmlJagCttOeu7mGa86 A9CDiTrD0kFZ8nPwli8T4VfD1IeraQFgD6/8j3NRXsLHsBoJjuFsbbo5AIAxgQnCWxLt BDgCAwLw8WmPtUHin1awiPliG0vEUAjEoVSaa5/yEd0aUNAFTqb6ebgMi4OwB3ftZt97 +Y5gMktNHcYgPyRoY7JUMGALYr3S2QOpMRQP/2khhQSSd6xSQm7dfAzFHkV4ibNx/gAO booQ== X-Gm-Message-State: ALoCoQmOioCdmDkOux9sJdq/+apMFW2mP8mRsyPn1JY5bhSgLzXW3lkQBfflmqOkjCltNE5GKWdmuqMzZclUUFgTc/Ld7yQC+Q== MIME-Version: 1.0 X-Received: by 10.55.40.153 with SMTP id o25mr2123871qko.93.1449606028482; Tue, 08 Dec 2015 12:20:28 -0800 (PST) Sender: wlosh@bsdimp.com Received: by 10.140.27.181 with HTTP; Tue, 8 Dec 2015 12:20:28 -0800 (PST) X-Originating-IP: [2601:280:4900:3700:4d3f:8eba:ea86:7700] In-Reply-To: <86wpsopulm.fsf@desk.des.no> References: <201512052002.tB5K2ZEA026540@chez.mckusick.com> <86poyhqsdh.fsf@desk.des.no> <86fuzdqjwn.fsf@desk.des.no> <864mfssxgt.fsf@desk.des.no> <86wpsord9l.fsf@desk.des.no> <566726ED.2010709@multiplay.co.uk> <0DB97CBA-4DC3-4D52-AE9D-54546292D66F@bsdimp.com> <86d1ugrb7j.fsf@desk.des.no> <868u54radx.fsf@desk.des.no> <86wpsopulm.fsf@desk.des.no> Date: Tue, 8 Dec 2015 13:20:28 -0700 X-Google-Sender-Auth: gW0hxhKspDt0jkTB2EYQs93Gh-U Message-ID: Subject: Re: DELETE support in the VOP_STRATEGY(9)? From: Warner Losh To: =?UTF-8?Q?Dag=2DErling_Sm=C3=B8rgrav?= Cc: "freebsd-hackers@freebsd.org" , Steven Hartland Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Content-Filtered-By: Mailman/MimeDel 2.1.20 X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 08 Dec 2015 20:20:30 -0000 On Tue, Dec 8, 2015 at 1:13 PM, Dag-Erling Sm=C3=B8rgrav wrote= : > Warner Losh writes: > > And to be fair, having an additional property of =E2=80=98seeks are nea= rly > > free=E2=80=99 would also be a good way to tell. I=E2=80=99m not convinc= ed it is worth > > the effort to add it to all the storage devices in the tree when > > GEOM::candelete is a good proxy. > > I just provided you with an (admittedly fictional, but not unreasonable) > example of a layer which implements BIO_DELETE on top of storage that > may or may not have free seeks. The two are completely orthogonal; they > just happen to be strongly correlated on currently available hardware. > > Note that my fictional example would guarantee that BIO_DELETEd space > reads back as zeroes, even if the request doesn't align with physical > block boundaries. Sounds pretty useful to me, even if it doesn't > guarantee that the deleted data cannot be recovered from the physical > media by a sufficiently determined attacker with access to liquid > nitrogen and an electron microscope. And when there's an actual example, I'm happy to re-examine the use of GEOM::candelete. Warner