From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Young Subject: COW page cache for file hole? Date: Wed, 4 May 2011 10:45:42 +0800 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 To: Linux Kernel Mailing List , linux-mm , linux-fsdevel@vger.kernel.org, Wu Fengguang Return-path: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Hi, During test fengguang's readahead alloc-noretry patch, I have some thoughts In the 1000 dd case, page cache of sparse file hole are all zero indeed. So what about make a global zero page for that purpose, fs level know it is a hole, when write occurs on that page we can alloc a new page for that. I have no enough knowledge to implement it so just give out the question without patch, sorry. BTW, was there any attempt for this before? -- Regards dave