From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933044AbWF2WOo (ORCPT ); Thu, 29 Jun 2006 18:14:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933045AbWF2WOn (ORCPT ); Thu, 29 Jun 2006 18:14:43 -0400 Received: from smtp-out.google.com ([216.239.45.12]:64583 "EHLO smtp-out.google.com") by vger.kernel.org with ESMTP id S933044AbWF2WOm (ORCPT ); Thu, 29 Jun 2006 18:14:42 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=received:message-id:date:from:user-agent: x-accept-language:mime-version:to:cc:subject:references:in-reply-to: content-type:content-transfer-encoding; b=kwn/ljuO5hzG/3JVejxPmlajI8qP6iLynwx2JqPFKF1PKcQeMDpm9V/d2U+wES2n0 32cx0dfzC67/LgDxHb38A== Message-ID: <44A450BB.60105@google.com> Date: Thu, 29 Jun 2006 15:14:19 -0700 From: Daniel Phillips User-Agent: Mozilla Thunderbird 1.0.8 (X11/20060502) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Andreas Dilger CC: Johann Lombardi , sho@tnes.nec.co.jp, cmm@us.ibm.com, ext2-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [RFC 1/2] ext3: enlarge blocksize and fix rec_len overflow References: <20060628205238sho@rifu.tnes.nec.co.jp> <20060628155048.GG2893@chiva> <20060628202421.GL5318@schatzie.adilger.int> <44A417A3.80001@google.com> <20060629202700.GD5318@schatzie.adilger.int> In-Reply-To: <20060629202700.GD5318@schatzie.adilger.int> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Andreas Dilger wrote: > On Jun 29, 2006 11:10 -0700, Daniel Phillips wrote: >>Andreas Dilger wrote: >>>On Jun 28, 2006 17:50 +0200, Johann Lombardi wrote: >>> >>>>ext2/ext3_dir_entry_2 has a 16-bit entry(rec_len) and it would overflow >>>>with 64KB blocksize. This patch prevent from overflow by limiting >>>>rec_len to 65532. >>> >>>Having a max rec_len of 65532 is rather unfortunate, since the dir >>>blocks always need to filled with dir entries. 65536 - 65532 = 4, and >>>the minimum ext3_dir_entry size is 8 bytes. I would instead make this >>>maybe 64 bytes less so that there is room for a filename in the "tail" >>>dir_entry. >> >>Then why not introduce a little symmetry by making max rec_len 2**15 and >>treat big directory blocks as an array of smaller ones? I dimly recall >>the page-cache oriented Ext2 dir code already does this. > > I have no objection to this at all, but I think it will lead to a slightly > more complex implementation. We even discussed in the distant past to > make large directories a series of 4kB "chunks", for fs blocksize >= 4kB. > This has negative implications for large filenames because the internal > free space fragmentation is high, but has the advantage that it might > eventually still be usable if we can get blocksize > PAGE_SIZE. > > The difficulty is that when freeing dir entires you would have to be > concerned with a merging a dir_entry that is spanning the middle > of a 2^16 block. That is easy, just don't let an entry span subblocks by not letting delete merge past the end of a subblock, just a minor tweak. New block initialization needs an outer loop on subblocks and that's it, I think. Regards, Daniel