From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f182.google.com ([209.85.223.182]:33088 "EHLO mail-io0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932607AbbLHMQR (ORCPT ); Tue, 8 Dec 2015 07:16:17 -0500 Received: by iouu10 with SMTP id u10so22741246iou.0 for ; Tue, 08 Dec 2015 04:16:16 -0800 (PST) Subject: Re: [PATCH] btrfs: Introduce new mount option to disable tree log replay To: Eric Sandeen , Christoph Anton Mitterer , Chandan Rajendra References: <1449468402-27914-1-git-send-email-quwenruo@cn.fujitsu.com> <5665B359.2050906@redhat.com> <2856934.1tulUexfpA@localhost.localdomain> <5665C1F2.8020407@redhat.com> <1449521684.6881.13.camel@scientia.net> <566610FA.1080408@redhat.com> Cc: Qu Wenruo , linux-btrfs@vger.kernel.org From: Austin S Hemmelgarn Message-ID: <5666C9F7.2030509@gmail.com> Date: Tue, 8 Dec 2015 07:15:51 -0500 MIME-Version: 1.0 In-Reply-To: <566610FA.1080408@redhat.com> Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-512; boundary="------------ms030607070505000104080209" Sender: linux-btrfs-owner@vger.kernel.org List-ID: This is a cryptographically signed message in MIME format. --------------ms030607070505000104080209 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 2015-12-07 18:06, Eric Sandeen wrote: > On 12/7/15 2:54 PM, Christoph Anton Mitterer wrote: > > ... > >> 2) a section that describes "ro" in btrfs-mount(5) which describes tha= t >> normal "ro" alone may cause changes on the device and which then refer= s >> to hard-ro and/or the list of options (currently nologreplay) which ar= e >> required right now to make it truly ro. >> >> >> I think this is important as an end-user probably expects "ro" to be >> truly ro, > > Yeah, I don't know that this is true. It hasn't been true for over a > decade (2?), with the most widely-used filesystem in linux history, i.e= =2E > ext3. So if btrfs wants to go on this re-education crusade, more power= > to you, but I don't know that it's really a fight worth fighting. ;) > Actually, AFAICT, it's been at least 4.5 decades. Last I checked, this=20 dates back to the original UNIX filesystems, which still updated atimes=20 even when mounted RO. Despite this, it really isn't a widely known or well documented behavior = outside of developers, forensic specialists, and people who have had to=20 deal with the implications it has on data recovery. There really isn't=20 any way that the user would know about it without being explicitly told, = and it's something that can have a serious impact on being able to=20 recover a broken filesystem. TBH, I really feel that _every_=20 filesystem's documentation should have something about how to make it=20 mount truly read-only, even if it's just a reference to how to mark the=20 block device read-only. --------------ms030607070505000104080209 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgMFADCABgkqhkiG9w0BBwEAAKCC Brgwgga0MIIEnKADAgECAgMRLfgwDQYJKoZIhvcNAQENBQAweTEQMA4GA1UEChMHUm9vdCBD QTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNp Z25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2VydC5vcmcwHhcN MTUwOTIxMTEzNTEzWhcNMTYwMzE5MTEzNTEzWjBjMRgwFgYDVQQDEw9DQWNlcnQgV29UIFVz ZXIxIzAhBgkqhkiG9w0BCQEWFGFoZmVycm9pbjdAZ21haWwuY29tMSIwIAYJKoZIhvcNAQkB FhNhaGVtbWVsZ0BvaGlvZ3QuY29tMIICIjANBgkqhkiG9w0BAQEFAAOCAg8AMIICCgKCAgEA nQ/81tq0QBQi5w316VsVNfjg6kVVIMx760TuwA1MUaNQgQ3NyUl+UyFtjhpkNwwChjgAqfGd LIMTHAdObcwGfzO5uI2o1a8MHVQna8FRsU3QGouysIOGQlX8jFYXMKPEdnlt0GoQcd+BtESr pivbGWUEkPs1CwM6WOrs+09bAJP3qzKIr0VxervFrzrC5Dg9Rf18r9WXHElBuWHg4GYHNJ2V Ab8iKc10h44FnqxZK8RDN8ts/xX93i9bIBmHnFfyNRfiOUtNVeynJbf6kVtdHP+CRBkXCNRZ qyQT7gbTGD24P92PS2UTmDfplSBcWcTn65o3xWfesbf02jF6PL3BCrVnDRI4RgYxG3zFBJuG qvMoEODLhHKSXPAyQhwZINigZNdw5G1NqjXqUw+lIqdQvoPijK9J3eijiakh9u2bjWOMaleI SMRR6XsdM2O5qun1dqOrCgRkM0XSNtBQ2JjY7CycIx+qifJWsRaYWZz0aQU4ZrtAI7gVhO9h pyNaAGjvm7PdjEBiXq57e4QcgpwzvNlv8pG1c/hnt0msfDWNJtl3b6elhQ2Pz4w/QnWifZ8E BrFEmjeeJa2dqjE3giPVWrsH+lOvQQONsYJOuVb8b0zao4vrWeGmW2q2e3pdv0Axzm/60cJQ haZUv8+JdX9ZzqxOm5w5eUQSclt84u+D+hsCAwEAAaOCAVkwggFVMAwGA1UdEwEB/wQCMAAw VgYJYIZIAYb4QgENBEkWR1RvIGdldCB5b3VyIG93biBjZXJ0aWZpY2F0ZSBmb3IgRlJFRSBo ZWFkIG92ZXIgdG8gaHR0cDovL3d3dy5DQWNlcnQub3JnMA4GA1UdDwEB/wQEAwIDqDBABgNV HSUEOTA3BggrBgEFBQcDBAYIKwYBBQUHAwIGCisGAQQBgjcKAwQGCisGAQQBgjcKAwMGCWCG SAGG+EIEATAyBggrBgEFBQcBAQQmMCQwIgYIKwYBBQUHMAGGFmh0dHA6Ly9vY3NwLmNhY2Vy dC5vcmcwMQYDVR0fBCowKDAmoCSgIoYgaHR0cDovL2NybC5jYWNlcnQub3JnL3Jldm9rZS5j cmwwNAYDVR0RBC0wK4EUYWhmZXJyb2luN0BnbWFpbC5jb22BE2FoZW1tZWxnQG9oaW9ndC5j b20wDQYJKoZIhvcNAQENBQADggIBADMnxtSLiIunh/TQcjnRdf63yf2D8jMtYUm4yDoCF++J jCXbPQBGrpCEHztlNSGIkF3PH7ohKZvlqF4XePWxpY9dkr/pNyCF1PRkwxUURqvuHXbu8Lwn 8D3U2HeOEU3KmrfEo65DcbanJCMTTW7+mU9lZICPP7ZA9/zB+L0Gm1UNFZ6AU50N/86vjQfY WgkCd6dZD4rQ5y8L+d/lRbJW7ZGEQw1bSFVTRpkxxDTOwXH4/GpQfnfqTAtQuJ1CsKT12e+H NSD/RUWGTr289dA3P4nunBlz7qfvKamxPymHeBEUcuICKkL9/OZrnuYnGROFwcdvfjGE5iLB kjp/ttrY4aaVW5EsLASNgiRmA6mbgEAMlw3RwVx0sVelbiIAJg9Twzk4Ct6U9uBKiJ8S0sS2 8RCSyTmCRhJs0vvva5W9QUFGmp5kyFQEoSfBRJlbZfGX2ehI2Hi3U2/PMUm2ONuQG1E+a0AP u7I0NJc/Xil7rqR0gdbfkbWp0a+8dAvaM6J00aIcNo+HkcQkUgtfrw+C2Oyl3q8IjivGXZqT 5UdGUb2KujLjqjG91Dun3/RJ/qgQlotH7WkVBs7YJVTCxfkdN36rToPcnMYOI30FWa0Q06gn F6gUv9/mo6riv3A5bem/BdbgaJoPnWQD9D8wSyci9G4LKC+HQAMdLmGoeZfpJzKHMYIE0TCC BM0CAQEwgYAweTEQMA4GA1UEChMHUm9vdCBDQTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNl cnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNpZ25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcN AQkBFhJzdXBwb3J0QGNhY2VydC5vcmcCAxEt+DANBglghkgBZQMEAgMFAKCCAiEwGAYJKoZI hvcNAQkDMQsGCSqGSIb3DQEHATAcBgkqhkiG9w0BCQUxDxcNMTUxMjA4MTIxNTUxWjBPBgkq hkiG9w0BCQQxQgRAwWE/BxgNP/+2FHAfM+O48jDT9TrBsWbcyKXYW+M3Vlk1sbtvJ8HTeUOX zknL3R57E+Vm62aomSjM2xwbejrDOjBsBgkqhkiG9w0BCQ8xXzBdMAsGCWCGSAFlAwQBKjAL BglghkgBZQMEAQIwCgYIKoZIhvcNAwcwDgYIKoZIhvcNAwICAgCAMA0GCCqGSIb3DQMCAgFA MAcGBSsOAwIHMA0GCCqGSIb3DQMCAgEoMIGRBgkrBgEEAYI3EAQxgYMwgYAweTEQMA4GA1UE ChMHUm9vdCBDQTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlD QSBDZXJ0IFNpZ25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2Vy dC5vcmcCAxEt+DCBkwYLKoZIhvcNAQkQAgsxgYOggYAweTEQMA4GA1UEChMHUm9vdCBDQTEe MBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNpZ25p bmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2VydC5vcmcCAxEt+DAN BgkqhkiG9w0BAQEFAASCAgAXh5HQczsk6BoKjnV+wmj9h/G5EcQ8MEWc7xj61E+cEc1mFFwu RLjVuwGW5O4NkF3w+xQjhfM1N8a5hvTqCNa/2B7XrycaCvSn4KNQ7o1u/re6WdaHPcKZxvo5 bIxuec5Y1l1+CxdKjDcFRntRnwKF1DTMb6Ag6xvyD0eCKfGIn4sguKOFu4Pv2EwcZVAvVBnQ XvzONBzjxjXW2Y3JVRK08MMj9Z0fXhFKzsftKkaU8ZEpNAY92ApTFuv6f2kvuzEyUdRjUq50 Bt48sa2tZG7vC+zRKCpUjSYD3fXFMjWCERsFjPFW2BV0vc8ETVGped0GRLHpwkLDiOG2pf7A DPSxhBGJgcOQfx3FNb45es/F0xbOOB+HyBJVESgQ9CBBCrb0ndVWio/3d0UgD7n1w7+b44lF oO8UeDVRlaQfVk9QMU1NPHQYUFgek5kvnWLVMFQ/xBjKXqzOEg/qx73kpjOILcgfFJB2xNMO kihsLuQ8Bjf/Iha6tF1ttcjazkwqpumBWoLnOzkwRDmbXsqlOSTbAjZlQYsyioW1KZVzSH/2 E4VkhukUyd6vkxXQ7fxl6GUvnRqnY84r+BUxPZ31cHT32VJvzCyV9DBhZHSnKWavAsMdxf89 XNtGk0aRP5XiD2Oxn/iC8RzFyYQYj2COv23Ak/lVJswzYF+pbStLyse/fwAAAAAAAA== --------------ms030607070505000104080209--