From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: VM_PFNMAP and do_no_pfn handler References: From: Jes Sorensen Date: 20 Feb 2006 10:55:26 -0500 In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org Return-Path: To: Hugh Dickins Cc: linux-mm@kvack.org, Linus Torvalds , Carsten Otte , roe@sgi.com, Robin Holt , Jack Steiner List-ID: >>>>> "Hugh" == Hugh Dickins writes: Hugh> On Mon, 20 Feb 2006, Jes Sorensen wrote: >> Any suggestions? (or rather, what obvious thing did I miss? ;-) Hugh> I believe you'll be safe for as long as your driver prohibits Hugh> COW mappings. You're not the only one to have VM_PFNMAP areas Hugh> which don't follow Linus' vm_pgoff rule: which is why he added Hugh> the !is_cow_mapping letout late in 2.6.15-rc. We cannot change Hugh> that lightly. Hugh> I think you're worrying too much, unless you anticipate wanting Hugh> to extend to COW mappings later. That would indeed need Hugh> vm_normal_page to be changed (and I know what change to make, Hugh> but Linus hated it!). Hi Hugh, Thanks for the explanation. It just seemed to me that is_cow_mapping() seemed a bit of a strange name for a 'this_mapping_really_has_no_struct_page_behind_it_honest()' function. Is there some reason why we try to look up the struct page for anything mapped VM_PFNMAP? I can live with the current situation, but maybe it would be worth adding some extra explanation to vm_normal_page() then? I hope to post the changes I have in mind for do_no_pfn() and the driver within a couple of days for those who are interested. Cheers, Jes -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org