From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 6 Mar 2007 22:51:01 -0800 From: Andrew Morton Subject: Re: [patch 4/6] mm: merge populate and nopage into fault (fixes nonlinear) Message-Id: <20070306225101.f393632c.akpm@linux-foundation.org> In-Reply-To: <20070221023735.6306.83373.sendpatchset@linux.site> References: <20070221023656.6306.246.sendpatchset@linux.site> <20070221023735.6306.83373.sendpatchset@linux.site> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Linux Memory Management , Linux Kernel , Benjamin Herrenschmidt , Ingo Molnar List-ID: On Wed, 21 Feb 2007 05:50:17 +0100 (CET) Nick Piggin wrote: > Nonlinear mappings are (AFAIKS) simply a virtual memory concept that > encodes the virtual address -> file offset differently from linear > mappings. > > I can't see why the filesystem/pagecache code should need to know anything > about it, except for the fact that the ->nopage handler didn't quite pass > down enough information (ie. pgoff). But it is more logical to pass pgoff > rather than have the ->nopage function calculate it itself anyway. And > having the nopage handler install the pte itself is sort of nasty. > > This patch introduces a new fault handler that replaces ->nopage and > ->populate and (later) ->nopfn. Most of the old mechanism is still in place > so there is a lot of duplication and nice cleanups that can be removed if > everyone switches over. > > The rationale for doing this in the first place is that nonlinear mappings > are subject to the pagefault vs invalidate/truncate race too, and it seemed > stupid to duplicate the synchronisation logic rather than just consolidate > the two. > It's awkward to layer a largely do-nothing patch like this on top of a significant functional change. Makes it harder to isolate the source of regressions, harder to revert the do-something patch. > After this patch, MAP_NONBLOCK no longer sets up ptes for pages present in > pagecache. Seems like a fringe functionality anyway. Does Ingo agree? > NOPAGE_REFAULT is removed. This should be implemented with ->fault, and > no users have hit mainline yet. Did benh agree with that? The patch unchangeloggedly adds a basic new structure to core mm (fault_data). Would be nice to document its fields, especially `flags'. Please add less pointless blank lines. How well has this been tested? The ocfs2 changes? gfs2? We should at least give those guys a heads-up. Does anybody really pass a NULL `type' arg into filemap_nopage()? This patch seems to churn things around an awful lot for minimal benefit. -- 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