From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751844Ab3HAAy7 (ORCPT ); Wed, 31 Jul 2013 20:54:59 -0400 Received: from ipmail05.adl6.internode.on.net ([150.101.137.143]:34679 "EHLO ipmail05.adl6.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750845Ab3HAAy5 (ORCPT ); Wed, 31 Jul 2013 20:54:57 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AjgFAE2x+VF5LPxHgWdsb2JhbABbDr0DhS6BHBcOAQEWJiiCJAEBBAE6HCgLCAMYCSUPBSUDIQESiAoFuRkWj3iECwOXXooiigJQKg Date: Thu, 1 Aug 2013 10:54:47 +1000 From: Dave Chinner To: "Theodore Ts'o" , Namjae Jeon , adilger.kernel@dilger.ca, bpm@sgi.com, elder@kernel.org, hch@infradead.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org, xfs@oss.sgi.com, a.sangwan@samsung.com, Namjae Jeon Subject: Re: [PATCH 1/3] fs: Introduce new flag FALLOC_FL_COLLAPSE_RANGE Message-ID: <20130801005447.GS13468@dastard> References: <1375281721-15840-1-git-send-email-linkinjeon@gmail.com> <20130731220154.GA11378@thunk.org> <20130801002341.GI7118@dastard> <20130801004645.GC11378@thunk.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130801004645.GC11378@thunk.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 31, 2013 at 08:46:45PM -0400, Theodore Ts'o wrote: > On Thu, Aug 01, 2013 at 10:23:41AM +1000, Dave Chinner wrote: > > On Wed, Jul 31, 2013 at 06:01:54PM -0400, Theodore Ts'o wrote: > > > Have you considered what happens if you have a 10 megabyte file, of > > > which the first 5 megs are mmap'ed into a userspace process. > > > > > > Now suppose you call COLLAPASE_RANGE on a one megabyte range starting > > > at offset 1024k from the beginning of the file. > > > > > > Does the right thing happen to the mmap'ed region in memory? > > > > Implementation detail. like a hole punch, it needs to invalidate the > > range that it is operating over so mmap()d regions are refaulted > > after the operation is done. > > It's not just the range that it's operating on, but also the region > beyond the range that's been collapsed out. Yes, that's part of "the range that it is operating over". > A quick eyeball of the patch didn't seem to show any code that handled > this, which is why I asked the question. Right, but really it's the least of the problems I've noticed - the XFS code is fundamentally broken in many ways - once I've finished commenting on it, I'll have a quick look to see if the ext4 code has the same fundamental flaws.... Cheers, Dave. -- Dave Chinner david@fromorbit.com