From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx1-b.sourceforge.net ([10.3.1.91] helo=mail.sourceforge.net) by sc8-sf-list1.sourceforge.net with esmtp (Exim 4.30) id 1EI9wq-000819-Hc for user-mode-linux-devel@lists.sourceforge.net; Wed, 21 Sep 2005 12:08:04 -0700 Received: from smtp005.mail.ukl.yahoo.com ([217.12.11.36]) by mail.sourceforge.net with smtp (Exim 4.44) id 1EI9wl-0000Zi-I6 for user-mode-linux-devel@lists.sourceforge.net; Wed, 21 Sep 2005 12:08:04 -0700 From: Blaisorblade Subject: Re: [uml-devel] Review needed for ubd fixes References: <200509172245.j8HMjqJD009056@ccure.user-mode-linux.org> <200509211749.46125.blaisorblade@yahoo.it> <20050921180436.GA7712@ccure.user-mode-linux.org> In-Reply-To: <20050921180436.GA7712@ccure.user-mode-linux.org> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200509212106.39169.blaisorblade@yahoo.it> Sender: user-mode-linux-devel-admin@lists.sourceforge.net Errors-To: user-mode-linux-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: The user-mode Linux development list List-Post: List-Help: List-Subscribe: , List-Archive: Date: Wed, 21 Sep 2005 21:06:38 +0200 To: Jeff Dike Cc: user-mode-linux-devel@lists.sourceforge.net, Bodo Stroesser On Wednesday 21 September 2005 20:04, Jeff Dike wrote: > On Wed, Sep 21, 2005 at 05:49:43PM +0200, Blaisorblade wrote: [...] > > Don't think it's reasonable to expect this. I think that filesystems like > > ext2 will never produce write barriers - they are needed for journaled > > FS's. > I thought your point was to rely on the block layer to order overlapping > writes for us. The block layer is supposed to merge as far as possible overlapping writes, that's reasonable, but not dependable. Say it gets the overlapping request *after* it sent the first one - we'll see both. Also, this is trivially true for output done through page cache, but for the rest I don't know if explicit merging is implemented. For the buffer cache (i.e. fs metadata) it may still hold, but I'm not sure at all. Not that it matters for us - we can't depend on it anyway. No, I was thinking to you enforcing ordering to comply to what journaled filesystems expect. Btw: even when we aren't using COW, we're supposed to do writes in the order the fs passed them to us - at least when write barriers are explicitly sent (don't know if there's something to care normally - I know this as a LWN.net reader, not as an hacker in this area). > It sounded reasonable to me :-) > Jeff -- Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!". Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894) http://www.user-mode-linux.org/~blaisorblade ___________________________________ Yahoo! Mail: gratis 1GB per i messaggi e allegati da 10MB http://mail.yahoo.it ------------------------------------------------------- SF.Net email is sponsored by: Tame your development challenges with Apache's Geronimo App Server. Download it for free - -and be entered to win a 42" plasma tv or your very own Sony(tm)PSP. Click here to play: http://sourceforge.net/geronimo.php _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel