Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262810AbUDEIXT (ORCPT ); Mon, 5 Apr 2004 04:23:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263171AbUDEIXT (ORCPT ); Mon, 5 Apr 2004 04:23:19 -0400 Received: from gprs214-14.eurotel.cz ([160.218.214.14]:57218 "EHLO amd.ucw.cz") by vger.kernel.org with ESMTP id S262810AbUDEIXR (ORCPT ); Mon, 5 Apr 2004 04:23:17 -0400 Date: Mon, 5 Apr 2004 10:22:58 +0200 From: Pavel Machek To: =?iso-8859-1?Q?J=F6rn?= Engel Cc: Jamie Lokier , Chris Friesen , mj@ucw.cz, jack@ucw.cz, "Patrick J. LoPresti" , linux-kernel@vger.kernel.org Subject: Re: [PATCH] cowlinks v2 Message-ID: <20040405082258.GC29705@elf.ucw.cz> References: <20040402180128.GA363@elf.ucw.cz> <20040402181707.GA28112@wohnheim.fh-wedel.de> <20040402182357.GB410@elf.ucw.cz> <20040402200921.GC653@mail.shareable.org> <20040402213933.GB246@elf.ucw.cz> <406DE280.6050109@nortelnetworks.com> <20040403004947.GI653@mail.shareable.org> <20040403082303.GA1316@elf.ucw.cz> <20040403131539.GA4706@mail.shareable.org> <20040405081925.GC28924@wohnheim.fh-wedel.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040405081925.GC28924@wohnheim.fh-wedel.de> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1542 Lines: 37 Hi! > > > > > Could you not change it back to a normal inode when refcount becomes 1? > > > > > > > > You can only do that if the cowid object has a pointer to the last > > > > remaining reference to it. That's possible, but more complicated and > > > > would incur a little more I/O per cow operation. > > > > > > You'd have to have pointers to all references to it... because you > > > can't tell in advance which one will be the last to go away. > > > > Exactly. Each of the cow pointers would need to be linked in a doubly > > linked list containing them all. > > I don't like the list idea. Having the extra cowid (I prefer inode) > indirection costs a few bytes and one lookup, not much. The list is > way too much overhead to get rid of so little in a few cases. Nobody likes the "list idea". > If you really want to, create a new syscall foldfile() that will > remove the indirection for one file, if possible. Then userspace can > do the ugly work of scanning for single-linked cowids (or just leave > it). We could automaticaly remove them when we see them, or on first open( O_RDWR) or something, or just leave them alone. Definitely leave them alone for first version. Pavel -- When do you have a heart between your knees? [Johanka's followup: and *two* hearts?] - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/