From mboxrd@z Thu Jan 1 00:00:00 1970 From: Austin S Hemmelgarn Subject: Re: Tux3 Report: How fast can we fail? Date: Wed, 27 May 2015 11:37:51 -0400 Message-ID: <5565E4CF.3070205@gmail.com> References: <8f886f13-6550-4322-95be-93244ae61045@phunq.net> <55523C88.9080809@phunq.net> <20150526100326.GA8854@amd> <55657446.40805@gmail.com> <5565CF03.9010202@gmail.com> <5565E0F4.1050403@gmail.com> Mime-Version: 1.0 Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha1; boundary="------------ms050903030909010205070702" To: Mosis Tembo , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Return-path: In-Reply-To: <5565E0F4.1050403@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org This is a cryptographically signed message in MIME format. --------------ms050903030909010205070702 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: quoted-printable On 2015-05-27 11:21, Mosis Tembo wrote: > > On 05/27/2015 04:04 PM, Austin S Hemmelgarn wrote: >> On 2015-05-27 03:37, Mosis Tembo wrote: >>> >>> On 05/26/2015 12:03 PM, Pavel Machek wrote: >>>>> We identified the following quality metrics for this algorithm: >>>>> >>>>> 1) Never fails to detect out of space in the front end. >>>>> 2) Always fills a volume to 100% before reporting out of space. >>>>> 3) Allows rm, rmdir and truncate even when a volume is full. >>> >>> This is definitely nonsense. You can not rm, rmdir and truncate >>> when the volume is full. You will need a free space on disk to perfor= m >>> such operations. Do you know why? >>> >> I assume you are referring either to Tux3 specifically or COW >> filesystems in general, > > > I am referring to modern file systems with transaction models and > delayed actions. > Tux3 is not the case? > In a sensibly designed non-COW filesystem, unlink, truncate, and=20 FALLOCATE_FL_{PUNCH_HOLE,COLLAPSE_RANGE} should never need to allocate=20 anything. On well designed COW filesystems, you keep a reserve of space = that is only available for temporary internal use so that these will=20 work even when you report the volume as 100% full so you can free space. = This is what BTRFS does (although it doesn't always work because of=20 segregating data and metadata), and I believe that tux3 does this also,=20 although I don't remember for certain. > >> because you very much _can_ do any of those on any of the non-COW >> filesystems in the Linux kernel > > > It is simply incorrect. ReiserFS is a counterexample. > Apologies, I didn't know about ReiserFS having issues with that (it's=20 the only one that I haven't used, and this is yet another reason I=20 probably never will), but I know for a fact that it does work on ext*,=20 XFS, and JFS (I'm not entirely certain about OCFS2 and GFS2, and NILFS2=20 is technically COW because it's log structured). > >> (I know from experience). Also, IIRC, it was mentioned somewhere that= >> Tux3 keeps a small reserve of space on the volume for internal >> operations; and, I would assume that if that is the case, it reports >> the volume full when everything *except* that reserve of space is >> used, in which case rm, rmdir, and truncate should work fine when the >> volume is full. > > > Sorry, I prefer to not manipulate with rumors and assumptions when it c= omes > to the review for kernel inclusion. > Entirely understandable. --------------ms050903030909010205070702 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIIGuDCC BrQwggScoAMCAQICAxBuVTANBgkqhkiG9w0BAQ0FADB5MRAwDgYDVQQKEwdSb290IENBMR4w HAYDVQQLExVodHRwOi8vd3d3LmNhY2VydC5vcmcxIjAgBgNVBAMTGUNBIENlcnQgU2lnbmlu ZyBBdXRob3JpdHkxITAfBgkqhkiG9w0BCQEWEnN1cHBvcnRAY2FjZXJ0Lm9yZzAeFw0xNTAz MjUxOTM0MzhaFw0xNTA5MjExOTM0MzhaMGMxGDAWBgNVBAMTD0NBY2VydCBXb1QgVXNlcjEj MCEGCSqGSIb3DQEJARYUYWhmZXJyb2luN0BnbWFpbC5jb20xIjAgBgkqhkiG9w0BCQEWE2Fo ZW1tZWxnQG9oaW9ndC5jb20wggIiMA0GCSqGSIb3DQEBAQUAA4ICDwAwggIKAoICAQCdD/zW 2rRAFCLnDfXpWxU1+ODqRVUgzHvrRO7ADUxRo1CBDc3JSX5TIW2OGmQ3DAKGOACp8Z0sgxMc B05tzAZ/M7m4jajVrwwdVCdrwVGxTdAai7Kwg4ZCVfyMVhcwo8R2eW3QahBx34G0RKumK9sZ ZQSQ+zULAzpY6uz7T1sAk/erMoivRXF6u8WvOsLkOD1F/Xyv1ZccSUG5YeDgZgc0nZUBvyIp zXSHjgWerFkrxEM3y2z/Ff3eL1sgGYecV/I1F+I5S01V7Kclt/qRW10c/4JEGRcI1FmrJBPu BtMYPbg/3Y9LZROYN+mVIFxZxOfrmjfFZ96xt/TaMXo8vcEKtWcNEjhGBjEbfMUEm4aq8ygQ 4MuEcpJc8DJCHBkg2KBk13DkbU2qNepTD6Uip1C+g+KMr0nd6KOJqSH27ZuNY4xqV4hIxFHp ex0zY7mq6fV2o6sKBGQzRdI20FDYmNjsLJwjH6qJ8laxFphZnPRpBThmu0AjuBWE72GnI1oA aO+bs92MQGJernt7hByCnDO82W/ykbVz+Ge3Sax8NY0m2Xdvp6WFDY/PjD9CdaJ9nwQGsUSa N54lrZ2qMTeCI9Vauwf6U69BA42xgk65VvxvTNqji+tZ4aZbarZ7el2/QDHOb/rRwlCFplS/ z4l1f1nOrE6bnDl5RBJyW3zi74P6GwIDAQABo4IBWTCCAVUwDAYDVR0TAQH/BAIwADBWBglg hkgBhvhCAQ0ESRZHVG8gZ2V0IHlvdXIgb3duIGNlcnRpZmljYXRlIGZvciBGUkVFIGhlYWQg b3ZlciB0byBodHRwOi8vd3d3LkNBY2VydC5vcmcwDgYDVR0PAQH/BAQDAgOoMEAGA1UdJQQ5 MDcGCCsGAQUFBwMEBggrBgEFBQcDAgYKKwYBBAGCNwoDBAYKKwYBBAGCNwoDAwYJYIZIAYb4 QgQBMDIGCCsGAQUFBwEBBCYwJDAiBggrBgEFBQcwAYYWaHR0cDovL29jc3AuY2FjZXJ0Lm9y ZzAxBgNVHR8EKjAoMCagJKAihiBodHRwOi8vY3JsLmNhY2VydC5vcmcvcmV2b2tlLmNybDA0 BgNVHREELTArgRRhaGZlcnJvaW43QGdtYWlsLmNvbYETYWhlbW1lbGdAb2hpb2d0LmNvbTAN BgkqhkiG9w0BAQ0FAAOCAgEAGvl7xb42JMRH5D/vCIDYvFY3dR2FPd5kmOqpKU/fvQ8ovmJa p5N/FDrsCL+YdslxPY+AAn78PYmL5pFHTdRadT++07DPIMtQyy2qd+XRmz6zP8Il7vGcEDmO WmMLYMq4xV9s/N7t7JJp6ftdIYUcoTVChUgilDaRWMLidtslCdRsBVfUjPb1bF5Ua31diKDP e0M9/e2CU36rbcTtiNCXhptMigzuL3zJXUf2B9jyUV8pnqNEQH36fqJ7YTBLcpq3aYa2XbAH Hgx9GehJBIqwspDmhPCFZ/QmqUXCkt+XfvinQ2NzKR6P3+OdYbwqzVX8BdMeojh7Ig8x/nIx mQ+/ufstL1ZYp0bg13fyK/hPYSIBpayaC76vzWovkIm70DIDRIFLi20p/qTd7rfDYy831Hjm +lDdCECF9bIXEWFk33kA97dgQIMbf5chEmlFg8S0e4iw7LMjvRqMX3eCD8GJ2+oqyZUwzZxy S0Mx+rBld5rrN7LsXwZ671HsGqNeYbYeU25e7t7/Gcc6Bd/kPfA+adEuUGFcvUKH3trDYqNq 6mOkAd8WO/mQadlc3ztS++XDMhmIpfBre9MPAr6usqf+wc+R8Nk9KLK39kEgrqVfzc/fgf8L MaD4rHnusdg4gca6Yi+kNrm99anw7SwaBrBvULYBp7ixNRUhaYiNW4YjTrYxggShMIIEnQIB ATCBgDB5MRAwDgYDVQQKEwdSb290IENBMR4wHAYDVQQLExVodHRwOi8vd3d3LmNhY2VydC5v cmcxIjAgBgNVBAMTGUNBIENlcnQgU2lnbmluZyBBdXRob3JpdHkxITAfBgkqhkiG9w0BCQEW EnN1cHBvcnRAY2FjZXJ0Lm9yZwIDEG5VMAkGBSsOAwIaBQCgggH1MBgGCSqGSIb3DQEJAzEL BgkqhkiG9w0BBwEwHAYJKoZIhvcNAQkFMQ8XDTE1MDUyNzE1Mzc1MVowIwYJKoZIhvcNAQkE MRYEFIdcjcAacyQ2zZX2i9A8iJnXLPqlMGwGCSqGSIb3DQEJDzFfMF0wCwYJYIZIAWUDBAEq MAsGCWCGSAFlAwQBAjAKBggqhkiG9w0DBzAOBggqhkiG9w0DAgICAIAwDQYIKoZIhvcNAwIC AUAwBwYFKw4DAgcwDQYIKoZIhvcNAwICASgwgZEGCSsGAQQBgjcQBDGBgzCBgDB5MRAwDgYD VQQKEwdSb290IENBMR4wHAYDVQQLExVodHRwOi8vd3d3LmNhY2VydC5vcmcxIjAgBgNVBAMT GUNBIENlcnQgU2lnbmluZyBBdXRob3JpdHkxITAfBgkqhkiG9w0BCQEWEnN1cHBvcnRAY2Fj ZXJ0Lm9yZwIDEG5VMIGTBgsqhkiG9w0BCRACCzGBg6CBgDB5MRAwDgYDVQQKEwdSb290IENB MR4wHAYDVQQLExVodHRwOi8vd3d3LmNhY2VydC5vcmcxIjAgBgNVBAMTGUNBIENlcnQgU2ln bmluZyBBdXRob3JpdHkxITAfBgkqhkiG9w0BCQEWEnN1cHBvcnRAY2FjZXJ0Lm9yZwIDEG5V MA0GCSqGSIb3DQEBAQUABIICAHh5uGmeAmeJKv2ulIWjfjQX5PVjtZ7ZYAa3wgLNerUNLfjT ARwl5PbUTuBPzMC3rCcEBdBT4nXlorlSb1QNvRQm21sdZUYngFOzxesZSIhRDry9Xu9cSQON g8/7C/ourRdZtfV0l8Q/EnGpWSQ1TfE+F1iruvcvO8lcma+GMeMXQ+UvSfhV5oIriyEDbxHh b2kt3AEDUzwvgr5TNcTyH59PgZBsLxzHhKnqgNP+y/DessaY2BlVNDjiCN8ct/jZtZbsICHx 2dy4B8/OylApPX4kWEBLHlmgssPg+ojIBw39wRK/BJ48oUZ8pdYGGHLXn09xg9jn6YABHENB 3zohbMYmK5yha3ZPe75VNtDFJOQarRt9j/SQ8BAj2U+MvWk/BqxaaRS/WPJZAjrFLMClLoLv xQi1vebtlWlMU2Xng79/weZ+1cDO/Es0jwOs+JbvFrvMmPKnmbmCWnggwwlDpbjxVQXOdqph tgeZY/2RTIMORKfJI7fsDUf+ujBEOJk0rsINGMbv1FNnFZ4CPXP911cHJu8Te6YsCmJ4goJ+ 4rq1RCfARdzs/s6HiMotmPmypYKY2jZJPWwxrfAd9eHAprStu/RNdvu3N3quE7APq0OXWG3N ABsgEl56bYQmlssyalVDjD6cSC5FKkDCQMdZm5GEiTlJxcHIXtDXw1wHuhlGAAAAAAAA --------------ms050903030909010205070702--