From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Wilcox Subject: COW pages and FL_PUNCH_HOLE Date: Tue, 5 Dec 2017 07:34:01 -0800 Message-ID: <20171205153401.GC28760@bombadil.infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Linux API List-Id: linux-api@vger.kernel.org I don't see a discussion of this anywhere ... and I thought linux-api was the right place to ask. I see holepunch as being "like ftruncate() but for the middle of the file". So it feels weird to me that MAP_PRIVATE behaves differently; truncate will rip out COWed pages, but holepunch won't. Is there a good reason for this behaviour, and is it too late to change?