From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 5 May 2001 23:01:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 5 May 2001 23:01:06 -0400 Received: from f00f.stub.clear.net.nz ([203.167.224.51]:51984 "HELO metastasis.f00f.org") by vger.kernel.org with SMTP id ; Sat, 5 May 2001 23:01:02 -0400 Date: Sun, 6 May 2001 15:00:58 +1200 From: Chris Wedgwood To: Andrea Arcangeli Cc: Jens Axboe , Rogier Wolff , Linus Torvalds , Alan Cox , volodya@mindspring.com, Alexander Viro , linux-kernel@vger.kernel.org Subject: Re: [PATCH] SMP race in ext2 - metadata corruption. Message-ID: <20010506150058.A31393@metastasis.f00f.org> In-Reply-To: <200105041140.NAA03391@cave.bitwizard.nl> <20010504135614.S16507@suse.de> <20010504172940.U3762@athlon.random> <20010505151808.A29451@metastasis.f00f.org> <20010506023723.A22850@athlon.random> <20010506141437.A31269@metastasis.f00f.org> <20010506045001.C22850@athlon.random> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <20010506045001.C22850@athlon.random>; from andrea@suse.de on Sun, May 06, 2001 at 04:50:01AM +0200 X-No-Archive: Yes Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, May 06, 2001 at 04:50:01AM +0200, Andrea Arcangeli wrote: Moving e2fsck into the kernel is a completly different matter than caching the blockdevice accesses with pagecache instead of buffercache. No, I was takling about user space fsck using character devices. Solaris is one example. I have no idea why/if other got rid of it completly, but the fact block_dev is useful has nothing to do if it's in pagecache or in buffercache, really. I'm not claiming it is... what I'm asking is _why_ do we need block devices once 'everything' lives in the page cache? It's just that by doing it in pagecache you can mmap it as well and it will provide overall better performance and it's probably cleaner design. The only visible change is that you will be able to mmap a blockdevice as well. Why? What needs to mmap a block device? Since these are typically larger than that you can mmap into a 32-bit address space (yes, I'm ignoring the 5% or so of cases where this isn't true) I'm not aware on many applications that do it. Databases typically _want_ raw/character device access and do their own buffering, I assume related applications also do. About a kernel based fsck Alexander told me he likes it, I personally don't care about it that much because I believe... As I said, I'm not takling about kernel based fsck, although for _VERY_ large filesystems even with journalling I suspect it will be required one day (so it can run in the background and do consistency checking when the machine is idle). --cw