From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx2-b.sourceforge.net ([10.3.1.92] helo=mail.sourceforge.net) by sc8-sf-list1.sourceforge.net with esmtp (Exim 4.30) id 1EIC8w-0007Jb-EB for user-mode-linux-devel@lists.sourceforge.net; Wed, 21 Sep 2005 14:28:42 -0700 Received: from lakshmi.addtoit.com ([198.99.130.6] helo=lakshmi.solana.com) by mail.sourceforge.net with esmtp (Exim 4.44) id 1EIC8v-0001IP-Hr for user-mode-linux-devel@lists.sourceforge.net; Wed, 21 Sep 2005 14:28:42 -0700 From: Jeff Dike Subject: Re: [uml-devel] Review needed for ubd fixes Message-ID: <20050921204507.GA9918@ccure.user-mode-linux.org> References: <200509172245.j8HMjqJD009056@ccure.user-mode-linux.org> <200509211749.46125.blaisorblade@yahoo.it> <20050921180436.GA7712@ccure.user-mode-linux.org> <200509212106.39169.blaisorblade@yahoo.it> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <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 16:45:07 -0400 To: Blaisorblade Cc: user-mode-linux-devel@lists.sourceforge.net, Bodo Stroesser On Wed, Sep 21, 2005 at 09:06:38PM +0200, Blaisorblade wrote: > 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. Yeah, I'm concerned about O_DIRECT. Also, what happens when we write a page to disk, and immediately afterwards, it gets dirty again and written again? Is there a barrier between the two? > No, I was thinking to you enforcing ordering to comply to what journaled > filesystems expect. Yeah, but there's more ordering than that. > 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). We get requests from the block layer, not the fs. And physical disks are allowed to reorder requests, so I think there is some flexibility there. Jeff ------------------------------------------------------- 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