From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f182.google.com ([209.85.223.182]:36370 "EHLO mail-io0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751825AbbK3QAq (ORCPT ); Mon, 30 Nov 2015 11:00:46 -0500 Received: by iofh3 with SMTP id h3so178842880iof.3 for ; Mon, 30 Nov 2015 08:00:45 -0800 (PST) Subject: Re: Bug/regression: Read-only mount not read-only To: Hugo Mills , Btrfs mailing list References: <20151128134634.GF24333@carfax.org.uk> <565C645C.5030608@gmail.com> <20151130152837.GB8775@carfax.org.uk> From: Austin S Hemmelgarn Message-ID: <565C72A0.4030002@gmail.com> Date: Mon, 30 Nov 2015 11:00:32 -0500 MIME-Version: 1.0 In-Reply-To: <20151130152837.GB8775@carfax.org.uk> Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-512; boundary="------------ms000009060405010009060700" Sender: linux-btrfs-owner@vger.kernel.org List-ID: This is a cryptographically signed message in MIME format. --------------ms000009060405010009060700 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: quoted-printable On 2015-11-30 10:28, Hugo Mills wrote: > On Mon, Nov 30, 2015 at 09:59:40AM -0500, Austin S Hemmelgarn wrote: >> On 2015-11-28 08:46, Hugo Mills wrote: >>> We've just had someone on IRC with a problem mounting their FS. T= he >>> main problem is that they've got a corrupt log tree. That isn't the >>> subject of this email, though. >>> >>> The issue I'd like to raise is that even with -oro as a point >>> option, the FS is trying to replay the log tree. The dmesg output fro= m >>> mount -oro is at the end of the email. >>> >>> Now, my memory, experience and understanding is that the FS >>> doesn't, and shouldn't replay the log tree on a RO mount, because the= >>> FS should still be consistent even without the reply, and >>> RO-means-actually-RO is possible and desirable. (Compared to a >>> journalling FS, where journal replay is required for a consistent, >>> usable FS). >> This is exactly how it should behave (being able to say that a RO >> mount is really RO (if atimes aren't enabled) is a huge selling >> point). On a side note, a properly designed journaling filesystem >> _can_ be made to behave like this, but it makes the filesystem >> _really_ slow if you don't have enough RAM to cache all the blocks >> modified by the journal (because each block access has to check the >> journal for modifications). >>> >>> So, this looks to me like a regression that's come in somewhere. >> I'm not sure that this ever worked the way it should. It should be >> fixed regardless of what state things were however. > > I'm pretty sure it was like that at some point, because I've used > it as a diagnostic tool: If you can mount OK with -oro, but not > without, then the log tree is broken, and btrfs-zero-log can be used > to good effect. (In fact, that's what I was trying to do with the OP > when I spotted the issue). Hmm, in that case, it looks like a bisection is in order, but that may=20 be tough without a known broken filesystem image. I would offer to try=20 and bisect it myself, but I seem to have misplaced the scripts I had=20 been using to automate testing, and I won't be able to take the time to=20 look for them properly (and possibly re-write them) until this weekend. --------------ms000009060405010009060700 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 hvcNAQkDMQsGCSqGSIb3DQEHATAcBgkqhkiG9w0BCQUxDxcNMTUxMTMwMTYwMDMyWjBPBgkq hkiG9w0BCQQxQgRAyex1QUrQibtspz78TeBIROdTCsLGw3jykp+/fyvc6OO+43nV8QIXLRMy rARzQowj88h8LMkfGh6fa1r6G4T3gzBsBgkqhkiG9w0BCQ8xXzBdMAsGCWCGSAFlAwQBKjAL BglghkgBZQMEAQIwCgYIKoZIhvcNAwcwDgYIKoZIhvcNAwICAgCAMA0GCCqGSIb3DQMCAgFA MAcGBSsOAwIHMA0GCCqGSIb3DQMCAgEoMIGRBgkrBgEEAYI3EAQxgYMwgYAweTEQMA4GA1UE ChMHUm9vdCBDQTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlD QSBDZXJ0IFNpZ25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2Vy dC5vcmcCAxEt+DCBkwYLKoZIhvcNAQkQAgsxgYOggYAweTEQMA4GA1UEChMHUm9vdCBDQTEe MBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNpZ25p bmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2VydC5vcmcCAxEt+DAN BgkqhkiG9w0BAQEFAASCAgBWIgoXeqnLJ4WP79cKa3SzXg/W/TWrbm5o8/PBxx3BP5QvXRaF jYFPkvqVeDSbjKyYUYykmnK0nHSnx9lMaqE6Erw4sqe1qesPQJy798xftBN/pATyl3Sb0GMg Vxz/q4I4KE4YGBDy6BuXpv9oooaBuYBheo2KqLTugDYwl0kr3lAeQQcPyP2Lvgmk/fiFxvUS J4kqHEklckghCNAm3bleLI3Nhg5Xr3U++H+QO5Bh2URpAJ7RO50g+d2juP3Mq5wj05HR21zN 2+lEbdtZg4qw08tkbMvnFzyG7bXpRwAObnYbFAARlu/fhOzC2P3hKMtmszWZWbRllQEMMPr4 4vI2AQGPc/k7nsoIvODYQ1MxZl618mhcXBL348Rvj7FEhOg77JNxg1afcOg9SxEc+7YO4J5G 4vkdJbeZUaPlcnRQLLtTKwpoHXbZBF2Ra7izvtJU22xdohpCmuSe/5dH+90KZw1B5xztzQlw 9m2bdJq3fsuNH//3QnFckJXrZQsaHOuwpG1zjJGZrF9DDPlYuyJsvvqxIVbFCnqq+p5wVMiI 1kvNQalY/xfrK97gRRFNvwuShwmsfZqP+qX4yifXq6m/31QSZf7qdbrInX9eRndi5Xuz6dCH iDtmvrWeVBsUDpTkqsm2B3fzPgSJ35Nvov5Ts0SYFEsHk30EDNQh1amUyQAAAAAAAA== --------------ms000009060405010009060700--