From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailgw-01.dd24.net ([193.46.215.41]:42925 "EHLO mailgw-01.dd24.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751374AbbLLT6b (ORCPT ); Sat, 12 Dec 2015 14:58:31 -0500 Message-ID: <1449950306.6742.4.camel@scientia.net> Subject: Re: subvols and parents - how? From: Christoph Anton Mitterer To: Duncan <1i5t5.duncan@cox.net>, linux-btrfs@vger.kernel.org Date: Sat, 12 Dec 2015 20:58:26 +0100 In-Reply-To: References: <1448340960.14125.51.camel@scientia.net> <1448400350.21291.88.camel@scientia.net> <1449635797.20578.0.camel@scientia.net> Content-Type: multipart/signed; micalg="sha-512"; protocol="application/x-pkcs7-signature"; boundary="=-hLv0UYFqxZTsJqSgsAja" Mime-Version: 1.0 Sender: linux-btrfs-owner@vger.kernel.org List-ID: --=-hLv0UYFqxZTsJqSgsAja Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, 2015-12-09 at 10:53 +0000, Duncan wrote: > If you use the recipe (subvol create, cp with reflink) it suggests > there,=20 > you'll end up with the reflinked copy in a subvol. >=20 > You can then mount that subvol over top of the existing dir, and > *new*=20 > file opens will access the new subvol, tho existing open files will > of=20 > course continue to access the files/reflinks to which they have a=20 > reference, "underneath" the new mount. Sure, which would mean however that a downtime is still necessary. > For some services it's possible to signal them to reload their > files.=C2=A0=C2=A0 > Where this is possible, you can do the overmount trick and then > signal=20 > them to reload, and they should keep running, otherwise undisturbed > (altho=20 > any changes between the reflink and processing the signal will still > go=20 > to the existing open files, I don't believe there's a way around > that). Yep,.. but as you say,... it doesn't really help to avoid the downtime,... rather lead to data corruption (not on the filesystem level, of course, but within the application). > But AFAIK that's the closest it gets, and nothing more along that > line is=20 > planned. I've been so free to add that idea to the project ideas: https://btrfs.wiki.kernel.org/index.php/Project_ideas#.28Atomically.29_conv= ert_directories_into_subvolumes_and_vice_versa any developer or more experienced user than me is of course free to remove that again, if it seems not so important or isn't possible to be implemented. > In general, keep in mind that subvolumes work in most respects very > much=20 > like normal directories do, except where they don't. =3D:^) :-P :-P=C2=A0 Cheers, Chris. --=-hLv0UYFqxZTsJqSgsAja Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgMFADCABgkqhkiG9w0BBwEAAKCCEZIw ggW/MIIDp6ADAgECAgMCOakwDQYJKoZIhvcNAQENBQAwVDEUMBIGA1UEChMLQ0FjZXJ0IEluYy4x HjAcBgNVBAsTFWh0dHA6Ly93d3cuQ0FjZXJ0Lm9yZzEcMBoGA1UEAxMTQ0FjZXJ0IENsYXNzIDMg Um9vdDAeFw0xNDA2MTIxNjM2MThaFw0xNjA2MTExNjM2MThaMHwxITAfBgNVBAMTGENocmlzdG9w 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