From owner-freebsd-hackers@FreeBSD.ORG Sat Jan 2 03:32:57 2010 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 3C9AA106568B for ; Sat, 2 Jan 2010 03:32:57 +0000 (UTC) (envelope-from giffunip@tutopia.com) Received: from web113517.mail.gq1.yahoo.com (web113517.mail.gq1.yahoo.com [98.136.167.57]) by mx1.freebsd.org (Postfix) with SMTP id 0DAB78FC0A for ; Sat, 2 Jan 2010 03:32:56 +0000 (UTC) Received: (qmail 84549 invoked by uid 60001); 2 Jan 2010 03:06:13 -0000 Message-ID: <454084.84334.qm@web113517.mail.gq1.yahoo.com> X-YMail-OSG: CgPAmHEVM1nmOIr3MhFs.SuXGzGCD1LHbvqpbPH8_t5RMa6Gh0bY3b4hnaho_OHgnLXLdAzUnAnReXmqXltmLzXxiGs_x1qy2pzKVYTHcLOFDUmoR9C.uEKEjCg1uMeGrF7m72CQ7bsD5rTFGvZzbpauPBBtQ4ihg5YN.o0gDVJJ4OXgtrnYcQ8cazXA721WGmn08WWEmEobFmUWvlk6TbrKBrFDQ4z9.D2xFcFSHnTKphzKFhA8jIbKVrlF3hstUJ.1E72C2PYWDoNOH08HpI61jKnocmOF79gRgFNAhPpqlbH2A11y3KhtcrcL6YiCzgT1tT4XrQW7qf3nW.6auEA4nLu3yNxEeVulK7VE2uzoqp1uyVZgAMjMF0nzR.Jrv8eH1hn9tWWFthc3pCbVOF2tghX7AydEkJmzXmHXHalWMbtLR.ghPgjy2xy7vKxGoulTTDo0aj3cB3iDDA3Ug_9EG9jLsZTrA2Bxb6EOW3c1y1l6d2x9JhTKf0eSNwJFtHRfjd8uTzG46NHUSSLA2LSVFdrYUS7lECtiWRVEjyxutEnYDLHCUWngWq4gzw.6_lMsGqRe0Z9CK1XtkA_oSBl97k9a63fhD7h2WvQMr2OuJkGQjgyH.GvDV1xHjNUcEpXyenVnXO80nDyZ.iRVuQyePV9ONNd1N3.3vaMVyzUhxUKRDsixvXo_d6Zv_SAkosBxvZBbt3F2IjzsbN2f1Q6zTJ1cqlD_GjFYwl9nd48zcA-- Received: from [190.157.123.47] by web113517.mail.gq1.yahoo.com via HTTP; Fri, 01 Jan 2010 19:06:13 PST X-RocketYMMF: giffunip X-Mailer: YahooMailClassic/9.0.20 YahooMailWebService/0.8.100.260964 Date: Fri, 1 Jan 2010 19:06:13 -0800 (PST) From: "Pedro F. Giffuni" To: freebsd-hackers@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailman-Approved-At: Sat, 02 Jan 2010 04:54:19 +0000 Cc: sarawgi.aditya@gmail.com, Ulf Lilleengen Subject: Re: [HEADSUP] Google SoC work on ext2fs to be committed X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: giffunip@tutopia.com List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 02 Jan 2010 03:32:57 -0000 Hello; I've been following closely this port and have been sending comments and patches to Aditya so I would like to comment on some points: - The code in it's current state is very similar to UFS1 without softupdates and EA/ACLs. - preallocation pretends to provide a similar effect as BSD's reallocblk (which is partially ported but may be difficult to finish). Preallocation has changed on different ext?fs versions but there are a couple of documents on the net on how this is done in linux. (1) - For the linux guys the Orlov allocator is their interpretation of what UFS knows to be the "dirpref changes". The code was ripped from FFS1 with some adaptations for ext2fs. The linux specific directory hacks don't apply. - While the benchmarking results are very similar, they achieve the results through different means: apparently making the code MPSafe (which was also heavily borrowed from UFS) has somewhat compensated for the removal of the preallocation code. Things TODO The fact that it so simple and similar to our beloved FFS1 and that the linux guys have published documents about it makes this filesystem an excellent target to play with. Some possibilities: - Implement preallocation. (1) - Htree is some similar to ufs dirhash. (2) - Ext3 Journaling (3) or maybe just gjournal support. (3) - Make it understand the basic ext4 layout. - NetBSD has some basic mkfs_ext2fs and fsck_ext2fs. I have to say Aditya did an excellent job, and was even careful to keep everything as similar as possible to UFS and NetBSD's ext2fs so we can adopt future enhancements they make. References (sorry for broken links) (1) http://ols.fedoraproject.org/OLS/Reprints-2008/kumar-reprint.pdf (2) http://www.kernel.org/doc/ols/2002/ols2002-pages-425-438.pdf (3) http://jamesthornton.com/hotlist/linux-filesystems/ext3-journal-design.pdf regards, Pedro.