From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hans Reiser Subject: Re: File as a directory - VFS Changes Date: Tue, 31 May 2005 08:04:42 -0700 Message-ID: <429C7D0A.6040200@namesys.com> References: <17050.62052.318426.711322@gargle.gargle.HOWL> <75229416615-BeMail@cr593174-a> <17052.12223.708707.757538@gargle.gargle.HOWL> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: list-help: list-unsubscribe: list-post: Errors-To: flx@namesys.com In-Reply-To: <17052.12223.708707.757538@gargle.gargle.HOWL> List-Id: Content-Type: text/plain; charset="us-ascii" To: Nikita Danilov Cc: "Alexander G. M. Smith" , leocomerford@gmail.com, reiserfs-list@namesys.com, ninja@slaphack.com Nikita Danilov wrote: >Alexander G. M. Smith writes: > > Nikita Danilov wrote on Mon, 30 May 2005 15:00:52 +0400: > > > Nothing in VFS prevents files from supporting both read(2) and > > > readdir(3). The problem is with link(2): VFS assumes that directories > > > form _tree_, that is, every directory has well-defined parent. > > > > At least that's one problem that's solveable. Just define one of > > the parents as the master parent directory, with a guaranteed path > > up to the root, and have the others as auxiliary parents. That > > also gives you a good path name to each and every file-thing. > > > > The VFS or the file system (depending on where the designers want > > to split the work) will still have to handle cycles in the graph > > to recompute the new master parents, when an old one gets deleted > > or moved. > >Cycle may consists of more graph nodes than fits into memory. > There are pathname length restrictions already in the kernel that should prevent that, yes? >Cycle >detection is crucial for rename semantics, and if >cycle-just-about-to-be-formed doesn't fit into memory it's not clear how >to detect it, because tree has to be locked while checked for cycles, and >one definitely doesn't want to keep such a lock over IO. > > > > > - Alex > >Nikita. > > > >