From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailgw-02.dd24.net ([193.46.215.43]:40916 "EHLO mailgw-02.dd24.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751148AbcISTpw (ORCPT ); Mon, 19 Sep 2016 15:45:52 -0400 Message-ID: <1474314346.10189.19.camel@scientia.net> Subject: Re: stability matrix (was: Is stability a joke?) From: Christoph Anton Mitterer To: dave@jikos.cz Cc: linux-btrfs@vger.kernel.org Date: Mon, 19 Sep 2016 21:45:46 +0200 In-Reply-To: <20160919152753.GG933@twin.jikos.cz> References: <57D51BF9.2010907@online.no> <20160912142714.GE16983@twin.jikos.cz> <52304724-5bca-a1e6-527f-040085c7ab19@gmail.com> <20160912165107.GG16983@twin.jikos.cz> <58a954fc-bbd5-3fb5-9f23-008ed7f7121d@gmail.com> <20160915010759.GD32452@DigitalMercury.dynalias.net> <5dec6544a78a0301a8e0cd9086179f99@crc.id.au> <1473905644.8603.44.camel@scientia.net> <20160919152753.GG933@twin.jikos.cz> Content-Type: multipart/signed; micalg="sha-512"; protocol="application/x-pkcs7-signature"; boundary="=-Iv8mPfBZNhdBw6akD7ud" Mime-Version: 1.0 Sender: linux-btrfs-owner@vger.kernel.org List-ID: --=-Iv8mPfBZNhdBw6akD7ud Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable +1 for all your changes with the following comments in addition... On Mon, 2016-09-19 at 17:27 +0200, David Sterba wrote: > That's more like a usecase, thats out of the scope of the tabular > overview. But we have an existing page UseCases that I'd like to > transform to a more structured and complete overview of usceases of > various features, so the UUID collisions would build on top of that > with > "and this could hapen if ...". Well I don't agree here and see it basically like Austin. It's not that these UUID collisions can only happen in special circumstances but plain normal situations that always used to work with probably literally each and every fs. (So much for the accidental corruptions). And an attack is probably never "usecase dependant"... it always depends on the attacker. And since that seems to be a pretty real attack vector, I'd also say it's mandatory to quite clearly warn about that deficiency... TBH, I'm rather surprised that this situation seems to be kinda "accepted". I had a chat with CM recently and he implied things might be solved with encryption. While this is probably the case for at least some of the described problems, it rather seems like a workaround: - why making btrfs-encryption mandatory for devices who have partially =C2=A0 secured access (e.g. where a systemdisk with btrfs is not physically =C2=A0 accessible but a USB port is) - what about users that rather want to use block device encryption =C2=A0 instead of fs-level-encryption? > > - in-band dedupe > > =C2=A0 deduped are IIRC not bitwise compared by the kernel before de- > > duping, > > =C2=A0 as it's the case with offline dedupe. > > =C2=A0 Even if this is considered safe by the community... I think user= s > > =C2=A0 should be told. > Only features merged are reflected. And the out-of-band dedupe does > full > memcpy. See btrfs_cmp_data() called from btrfs_extent_same(). Ah,... I kinda thought it was already merged ... possibly got confused by the countless patch iterations of it ;) > > - btrfs check --repair (and others?) > > =C2=A0 Telling people that this may often cause more harm than good. > I think userspace tools do not belong to the overview. Well... I wouldn't mind if there was a btrfs-progs status page... (and both link each other). OTOH,... the user probably wants one central point where all relevant info can be found... and not again having to dig through n websites. > > - even mounting a fs ro, may cause it to be changed >=20 > This would go to the UseCases Fine for me. >=20 > >=20 > > - DB/VM-image like IO patterns + nodatacow + (!)checksumming > > =C2=A0 + (auto)defrag + snapshots > > =C2=A0 a) > > =C2=A0 People typically may have the impression: > > =C2=A0 btrfs =3D checksummed =3D> als is guaranteed to be "valid" (or a= t > > least > > =C2=A0 noticed) > > =C2=A0 However this isn't the case for nodatacow'ed files, which in tur= n > > is > > =C2=A0 kinda "mandatory" for DB/VM-image like IO patterns, cause > > otherwise > > =C2=A0 these would fragment to heavily (see (b). > > =C2=A0 Unless claimed by some people, none of the major DBs or VM-image > > =C2=A0 formats do general checksumming on their own, most even don't > > support > > =C2=A0 it, some that do wouldn't do it without app-support and few > > "just" > > =C2=A0 don't do it per default. > > =C2=A0 Thus one should bump people to this situation and that they may > > not > > =C2=A0 get this "correctness" guarantee here. > > =C2=A0 b) > > =C2=A0 IIRC, it doesn't even help to simply not use nodatacow on such > > files > > =C2=A0 and using auto-defrag instead to countermeasure the fragmenting, > > as > > =C2=A0 that one doesn't perform too well on large files. >=20 > Same. Fine for me either... you already said above you would mention the nodatacow=3D>no-checksumming=3D>no-verification-and-no-raid-repair in the general section... this is enough for that place. > > For specific features: > > - Autodefrag > > =C2=A0 - didn't that also cause reflinks to be broken up? >=20 > No and never had. Absolutely sure? One year ago, I was told that at first too so I started using it, but later on some (IIRC) developer said auto-defrag would also suffer from it. > > - RAID* > > =C2=A0 No userland tools for monitoring/etc. >=20 > That's a usability bug. Well it is and it will probably go away sooner or later... but the unaware user may not really realise that he actually has to take care on this by himself for now. So I though it would be helpful to have it added. Best wishes, Chris. --=-Iv8mPfBZNhdBw6akD7ud Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgMFADCABgkqhkiG9w0BBwEAAKCCEmow ggXiMIIDyqADAgECAhBctkhuRwyYxn/2gNtkSuKNMA0GCSqGSIb3DQEBCwUAMH0xCzAJBgNVBAYT AklMMRYwFAYDVQQKEw1TdGFydENvbSBMdGQuMSswKQYDVQQLEyJTZWN1cmUgRGlnaXRhbCBDZXJ0 aWZpY2F0ZSBTaWduaW5nMSkwJwYDVQQDEyBTdGFydENvbSBDZXJ0aWZpY2F0aW9uIEF1dGhvcml0 eTAeFw0xNTEyMTYwMTAwMDVaFw0zMDEyMTYwMTAwMDVaMHUxCzAJBgNVBAYTAklMMRYwFAYDVQQK Ew1TdGFydENvbSBMdGQuMSkwJwYDVQQLEyBTdGFydENvbSBDZXJ0aWZpY2F0aW9uIEF1dGhvcml0 eTEjMCEGA1UEAxMaU3RhcnRDb20gQ2xhc3MgMiBDbGllbnQgQ0EwggEiMA0GCSqGSIb3DQEBAQUA A4IBDwAwggEKAoIBAQDuD1CMlQkjhKz1UGqP1jeiTiH9MgllRz6vOPrVG/eE0H/J4QQLV/PeL8RT 4xc44bEzsoJu0IhwnEchb+TxE/qw88w7hxODuw3N8Faxix6a1jp83+RWvZHZf78+O+3GYBpekZfT Oe9A/FoTXbcgwZfLTMQodn+ckNnX31M/1M2f2/7VA7QBlvihontyHQOlIlryQXnGI0UMCD21oopK tW48ckv0wUVg8irBKGMeD65gTON/Fsw/ZBbBqadoD1jt85FIM1ql24WUBEBwO1d0ykCKOIbgcqes 3fbcjQpruUNMBbIu1MMIRMqwjx/M7IvSKcS7VYRWl0/K2byzWvBAHh/1AgMBAAGjggFkMIIBYDAO BgNVHQ8BAf8EBAMCAQYwHQYDVR0lBBYwFAYIKwYBBQUHAwIGCCsGAQUFBwMEMBIGA1UdEwEB/wQI MAYBAf8CAQAwMgYDVR0fBCswKTAnoCWgI4YhaHR0cDovL2NybC5zdGFydHNzbC5jb20vc2ZzY2Eu Y3JsMGYGCCsGAQUFBwEBBFowWDAkBggrBgEFBQcwAYYYaHR0cDovL29jc3Auc3RhcnRzc2wuY29t MDAGCCsGAQUFBzAChiRodHRwOi8vYWlhLnN0YXJ0c3NsLmNvbS9jZXJ0cy9jYS5jcnQwHQYDVR0O BBYEFJmXqxg1OotZRUOYsnJxyPT7Cc8WMB8GA1UdIwQYMBaAFE4L7xqkQFulF2mHMMo0aEPQQa7y MD8GA1UdIAQ4MDYwNAYEVR0gADAsMCoGCCsGAQUFBwIBFh5odHRwOi8vd3d3LnN0YXJ0c3NsLmNv bS9wb2xpY3kwDQYJKoZIhvcNAQELBQADggIBAJlBQQTO9iT1TjA0eEO7V/1AbBvMAfibjAgofxmJ 01jBmHKg0pbTjWInTTYoxb3LBgz3mfjvvS1PjnIfb29MyVm0G/PSHjgq7Ews1dEJMPC9XTuxPf2c +MWLkynBlotW542JprW+iTWfZafyUtzIKW1hk0YASJ8zSSj8D++9yR+0UhkbvlECJkdi1+et0EaI 7HIX6ccj1rfcFFflWX/fPT64dn9jpg9s0nuJug4WsVkEK236WndZoMHrZmgF7CIyZ3T0muqYwkAS DDcRt9A21o/Mc+D8Q6GVmKRGB3gEKvOtsioHZEqJv6CdAm3a6gloo5pX3RL1eCzc8Lzfs4T0ISZj r8xNMbTGlsuHaFH+stDewKsfnpo4N64OtAGrzmVfFFsMIRENRHsVlSEe/6LVpBpjn00+7bqEN3qe qSxIOraYJ12mJ08G4YnP2U1fadHIaS50O5ZXqAivoBl9pi/6CBNc5wIMlkXMyFZ0sLsI+9ErFDu9 OJhX7iWCo69X0ydlzXj08+2K1PKyr+g6/vTPHur63JotNrhyoWEJyWEjBLA4QmJXfGpB5u+bCwNf sFpcYAlkiFt1Rs2vemgSBy3q4DHDbPKvr1YImZNRSHP+TX9NP94JRkmqcyD/qaN7u2JV1pRAlwG0 npyrn6ZQM1QHV+iFbwQ4VqLMWk//QVo/rZy1MIIGPjCCBSagAwIBAgIQPZ6tDP/RHLwcz1F+2kRA DzANBgkqhkiG9w0BAQsFADB1MQswCQYDVQQGEwJJTDEWMBQGA1UEChMNU3RhcnRDb20gTHRkLjEp MCcGA1UECxMgU3RhcnRDb20gQ2VydGlmaWNhdGlvbiBBdXRob3JpdHkxIzAhBgNVBAMTGlN0YXJ0 Q29tIENsYXNzIDIgQ2xpZW50IENBMB4XDTE2MDEwMjAyMDIzNloXDTE4MDEwMjAyMDIzNlowejEL MAkGA1UEBhMCREUxDzANBgNVBAgMBkJheWVybjERMA8GA1UEBwwITcO8bmNoZW4xITAfBgNVBAMM GENocmlzdG9waCBBbnRvbiBNaXR0ZXJlcjEkMCIGCSqGSIb3DQEJARYVY2FsZXN0eW9Ac2NpZW50 aWEubmV0MIICIjANBgkqhkiG9w0BAQEFAAOCAg8AMIICCgKCAgEAsoxs789VtR81tlqeP2vwE3Cp YosZYRfrovj+Wb91paoV5OQcFuXA7yONnLsWxOnJ3AGgy1/wG79Ko+yHSmF2K88pEWjrFe0zmZWZ 0b2OtMoKLEjxz7Nz2N7/lmgss8XinJ083LwLKSe4f+JLjnF5hX/g6wG4NkFXVOIf2YFZ0+c1NYFQ T6Vy42EWdk+JLDoXjyd2hEperLCz9rQr2k3wh0cn8R1FDUGerBGpMnvyKV6JXj5vZsqJnmiiId9e 0IdBj4Wcs3hT2usk6dJYwHrZ8b7Fkv6BRq90DUI7i8+ukTdp5hnAb8TPSbe1JS4h3Jc7r2NVLkpo Gbuw98er9s2PEAvpECD3toO3ojBevL56vEDbGa5tXpvvcWCz6t3QyEKJ2E54hWw1fbUA0BtydQC0 mhKBtrENVnnCDrSgiyBMnd8y+kw6iPKeJEjNObGubc4BZp47zPn/ZiDBaHue6S0MXsoS7XEGOuCU 09S/8kD8wTecBg+KdlLSNkLm+xqx6Cy7zwcj3IuQv0PeWi4kfEkAJfl8IeAP/4049iA6a1rkhJl7 1rDjpEGBCG+i9BAgBeNdHLtQ7bugdvU+GfHjFXEU1emUk91E2liML8kpCvhUAXcLhhL8bxPJiX2/ VQ2esrpQVO56OzpivNauonLaWmHEKOSfPC3s5AKMytMTiUiszEUCAwEAAaOCAcMwggG/MAsGA1Ud DwQEAwIEsDAdBgNVHSUEFjAUBggrBgEFBQcDAgYIKwYBBQUHAwQwCQYDVR0TBAIwADAdBgNVHQ4E FgQUwRklxF1ZV2ooSMkFwLiK13apkK0wHwYDVR0jBBgwFoAUmZerGDU6i1lFQ5iycnHI9PsJzxYw bwYIKwYBBQUHAQEEYzBhMCQGCCsGAQUFBzABhhhodHRwOi8vb2NzcC5zdGFydHNzbC5jb20wOQYI KwYBBQUHMAKGLWh0dHA6Ly9haWEuc3RhcnRzc2wuY29tL2NlcnRzL3NjYS5jbGllbnQyLmNydDA4 BgNVHR8EMTAvMC2gK6AphidodHRwOi8vY3JsLnN0YXJ0c3NsLmNvbS9zY2EtY2xpZW50Mi5jcmww IAYDVR0RBBkwF4EVY2FsZXN0eW9Ac2NpZW50aWEubmV0MCMGA1UdEgQcMBqGGGh0dHA6Ly93d3cu c3RhcnRzc2wuY29tLzBUBgNVHSAETTBLMAwGCisGAQQBgbU3BgEwOwYLKwYBBAGBtTcBAgQwLDAq BggrBgEFBQcCARYeaHR0cDovL3d3dy5zdGFydHNzbC5jb20vcG9saWN5MA0GCSqGSIb3DQEBCwUA A4IBAQBb8EIsoUN/tgUgQqrNXNtlksPep84kx5yRBgr71uf3ITLddGtzfDBj6KdZUoy7SG3MQkyO kvYmXBClj23rv8Iol48/3oi9XWZw5EV3uHrRse1TzQgMPZE0hZsDgkqXVoxMQfk55ndjZIHMfSkn hdnqSP5zZ4TCmDEKLppPMDcQSSrjilnbthpxlIJzeGeEFtrh6ssh/oF6mUaEGFcd8kx9RS51K1gt H4J36y4E6pKB7EdxG2+0yVzAIta8dkD/BiMCKRWhp1EmzQ2uIh2nX5y8t4e2xHHuiy11Yeq6UTW/ JmfxF4xcbkNK/rv9ISBg9K+mZtg2QXr+P/CJBtej2RLUMIIGPjCCBSagAwIBAgIQPZ6tDP/RHLwc z1F+2kRADzANBgkqhkiG9w0BAQsFADB1MQswCQYDVQQGEwJJTDEWMBQGA1UEChMNU3RhcnRDb20g THRkLjEpMCcGA1UECxMgU3RhcnRDb20gQ2VydGlmaWNhdGlvbiBBdXRob3JpdHkxIzAhBgNVBAMT GlN0YXJ0Q29tIENsYXNzIDIgQ2xpZW50IENBMB4XDTE2MDEwMjAyMDIzNloXDTE4MDEwMjAyMDIz NlowejELMAkGA1UEBhMCREUxDzANBgNVBAgMBkJheWVybjERMA8GA1UEBwwITcO8bmNoZW4xITAf BgNVBAMMGENocmlzdG9waCBBbnRvbiBNaXR0ZXJlcjEkMCIGCSqGSIb3DQEJARYVY2FsZXN0eW9A c2NpZW50aWEubmV0MIICIjANBgkqhkiG9w0BAQEFAAOCAg8AMIICCgKCAgEAsoxs789VtR81tlqe P2vwE3CpYosZYRfrovj+Wb91paoV5OQcFuXA7yONnLsWxOnJ3AGgy1/wG79Ko+yHSmF2K88pEWjr Fe0zmZWZ0b2OtMoKLEjxz7Nz2N7/lmgss8XinJ083LwLKSe4f+JLjnF5hX/g6wG4NkFXVOIf2YFZ 0+c1NYFQT6Vy42EWdk+JLDoXjyd2hEperLCz9rQr2k3wh0cn8R1FDUGerBGpMnvyKV6JXj5vZsqJ nmiiId9e0IdBj4Wcs3hT2usk6dJYwHrZ8b7Fkv6BRq90DUI7i8+ukTdp5hnAb8TPSbe1JS4h3Jc7 r2NVLkpoGbuw98er9s2PEAvpECD3toO3ojBevL56vEDbGa5tXpvvcWCz6t3QyEKJ2E54hWw1fbUA 0BtydQC0mhKBtrENVnnCDrSgiyBMnd8y+kw6iPKeJEjNObGubc4BZp47zPn/ZiDBaHue6S0MXsoS 7XEGOuCU09S/8kD8wTecBg+KdlLSNkLm+xqx6Cy7zwcj3IuQv0PeWi4kfEkAJfl8IeAP/4049iA6 a1rkhJl71rDjpEGBCG+i9BAgBeNdHLtQ7bugdvU+GfHjFXEU1emUk91E2liML8kpCvhUAXcLhhL8 bxPJiX2/VQ2esrpQVO56OzpivNauonLaWmHEKOSfPC3s5AKMytMTiUiszEUCAwEAAaOCAcMwggG/ MAsGA1UdDwQEAwIEsDAdBgNVHSUEFjAUBggrBgEFBQcDAgYIKwYBBQUHAwQwCQYDVR0TBAIwADAd BgNVHQ4EFgQUwRklxF1ZV2ooSMkFwLiK13apkK0wHwYDVR0jBBgwFoAUmZerGDU6i1lFQ5iycnHI 9PsJzxYwbwYIKwYBBQUHAQEEYzBhMCQGCCsGAQUFBzABhhhodHRwOi8vb2NzcC5zdGFydHNzbC5j b20wOQYIKwYBBQUHMAKGLWh0dHA6Ly9haWEuc3RhcnRzc2wuY29tL2NlcnRzL3NjYS5jbGllbnQy LmNydDA4BgNVHR8EMTAvMC2gK6AphidodHRwOi8vY3JsLnN0YXJ0c3NsLmNvbS9zY2EtY2xpZW50 Mi5jcmwwIAYDVR0RBBkwF4EVY2FsZXN0eW9Ac2NpZW50aWEubmV0MCMGA1UdEgQcMBqGGGh0dHA6 Ly93d3cuc3RhcnRzc2wuY29tLzBUBgNVHSAETTBLMAwGCisGAQQBgbU3BgEwOwYLKwYBBAGBtTcB AgQwLDAqBggrBgEFBQcCARYeaHR0cDovL3d3dy5zdGFydHNzbC5jb20vcG9saWN5MA0GCSqGSIb3 DQEBCwUAA4IBAQBb8EIsoUN/tgUgQqrNXNtlksPep84kx5yRBgr71uf3ITLddGtzfDBj6KdZUoy7 SG3MQkyOkvYmXBClj23rv8Iol48/3oi9XWZw5EV3uHrRse1TzQgMPZE0hZsDgkqXVoxMQfk55ndj ZIHMfSknhdnqSP5zZ4TCmDEKLppPMDcQSSrjilnbthpxlIJzeGeEFtrh6ssh/oF6mUaEGFcd8kx9 RS51K1gtH4J36y4E6pKB7EdxG2+0yVzAIta8dkD/BiMCKRWhp1EmzQ2uIh2nX5y8t4e2xHHuiy11 Yeq6UTW/JmfxF4xcbkNK/rv9ISBg9K+mZtg2QXr+P/CJBtej2RLUMYIEfjCCBHoCAQEwgYkwdTEL MAkGA1UEBhMCSUwxFjAUBgNVBAoTDVN0YXJ0Q29tIEx0ZC4xKTAnBgNVBAsTIFN0YXJ0Q29tIENl cnRpZmljYXRpb24gQXV0aG9yaXR5MSMwIQYDVQQDExpTdGFydENvbSBDbGFzcyAyIENsaWVudCBD QQIQPZ6tDP/RHLwcz1F+2kRADzANBglghkgBZQMEAgMFAKCCAcUwGAYJKoZIhvcNAQkDMQsGCSqG SIb3DQEHATAcBgkqhkiG9w0BCQUxDxcNMTYwOTE5MTk0NTQ2WjBPBgkqhkiG9w0BCQQxQgRASZFY mE8zFLOSA9t4hr6Hwhxbo7yDLtnYjLSmloY6HPMxua1i8avUxJP0if365+t4VltmEceZE4AHKzOq nuFq/TCBmgYJKwYBBAGCNxAEMYGMMIGJMHUxCzAJBgNVBAYTAklMMRYwFAYDVQQKEw1TdGFydENv bSBMdGQuMSkwJwYDVQQLEyBTdGFydENvbSBDZXJ0aWZpY2F0aW9uIEF1dGhvcml0eTEjMCEGA1UE AxMaU3RhcnRDb20gQ2xhc3MgMiBDbGllbnQgQ0ECED2erQz/0Ry8HM9RftpEQA8wgZwGCyqGSIb3 DQEJEAILMYGMoIGJMHUxCzAJBgNVBAYTAklMMRYwFAYDVQQKEw1TdGFydENvbSBMdGQuMSkwJwYD VQQLEyBTdGFydENvbSBDZXJ0aWZpY2F0aW9uIEF1dGhvcml0eTEjMCEGA1UEAxMaU3RhcnRDb20g Q2xhc3MgMiBDbGllbnQgQ0ECED2erQz/0Ry8HM9RftpEQA8wDQYJKoZIhvcNAQEBBQAEggIAcHtY t1Tp31vk8ZFA5AWaqJGULAM4GyojzMX3ftKEmG1ms4zTkaQRx4q99CUt+0iqnKZmBIvFtV66vRRU rr9VifF8cTo6lspAyqPxzhULAxMxddbqomPtiSJBmuFn9092HcYD0wA/ksNbQEotUzvHN6SUV77C VFwYyPMX8ZdDZWDnqyUvrHob2gHko6rY+QNj9DH7SSBDgqZPbVpi30d5xYhbHmKdU8Xn0KfciGjs AWy27r62t3/6LPxA5b3s/UAsJmkBFyOXQ0h9x2VsqPEVSpaVxTUqWS4iDDIPQrLMnqJW2Rzjn2X1 FCACYy7057PMDdvzIiMg8RjYonTm2yDodlqMpl1o6v6HjX9Lx2Ebjutqrq++4tzzRGU2xDgu5gET U5j0adRExTKevZcn5co3ahtmwIm6T14RyUaP100Zl+IqURw27x3rkheLEWJx5OHbfgtznOr6uPwp ptTVcFnBfVF+Y+YIrlaBLcwvPVbRi3JTYixDuzqne7o5Rg5K+yMjMzG3GTrRkctNSABgAdTzgURh UlIpOVUM/iNUf7+4pwrpBGzwcfL0BHj9VQF++iI/ifgS4Et8h48RsLnUKiaq+mvljdL7QdWQn5rM 6oNc4dDs6r3BgIbVj9hzIECQHxQcHTz/fw4qOh+RHnto50rsXciUCsxDZZksHsQuUJsUZu8AAAAA AAA= --=-Iv8mPfBZNhdBw6akD7ud--