From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ryusuke Konishi Subject: Re: Some nilfs comments Date: Wed, 24 Dec 2008 02:23:37 +0900 (JST) Message-ID: <20081224.022337.30445207.ryusuke@osrg.net> References: <1229568775.27170.134.camel@think.oraclecorp.com> <20081222.180719.88488712.ryusuke@osrg.net> <20081222130152.GA23725@aardappel.13thmonkey.org> Reply-To: NILFS Users mailing list Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20081222130152.GA23725-5cYspOl2ggRz6xQTk39kMVfVdRo2wo/d@public.gmane.org> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: users-bounces-JrjvKiOkagjYtjvyW6yDsg@public.gmane.org Errors-To: users-bounces-JrjvKiOkagjYtjvyW6yDsg@public.gmane.org To: users-JrjvKiOkagjYtjvyW6yDsg@public.gmane.org, reinoud-S783fYmB3Ccdnm+yROfE0A@public.gmane.org Cc: chris.mason-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org Hi Reinoud, On Mon, 22 Dec 2008 14:01:52 +0100, Reinoud Zandijk wrote: > On Mon, Dec 22, 2008 at 06:07:19PM +0900, Ryusuke Konishi wrote: > > Well, I feel that the following two matters are particularlly > > questionable and need to be checked: > > > > - struct the_nilfs: > > NILFS allows users to mount snapshots without making additional > > devices or volumes. This is achieved by sharing a block device > > among multiple mount instances (i.e. super_block structs). > > the_nilfs struct is used for this sharing. > > > > This approach seems to be peculiar to nilfs, and I feel it needs > > attention. > > I've dug into this too and decided to use the same mechanism for my > implementation. I think its nice to have all the fs's administration centered > at one place; i even have all the btree stuff there. One thing indeed is that > its not possible to do say `unmount /dev/wd0a' if there are multiple mounts on > it... but maybe thats better even ;) or its even a positive thing to just > unmount all the mounts in one go. I don't know the mount/umount interface of NetBSD, but perhaps unmount system call takes a directory argument instead of a device. If so, your kernel code would become similar to our nilfs. Though the linux umount command can take a device argument, only the latest mount is detached ;) > > Thanks, I've also started to read btrfs. > > I'll see it during the Christmas holidays ;) > > Whats your first impression? Want to take over things/ideas? Isn't that a > quite different FS structurally since it doesn't have segments? (AFAIK!) Yeah, btrfs has flexible and rich volume management layer, so very interesting. The snapshot code and c-tree also look like fun. Regards, Ryusuke