Messages in this thread | | | Date | Wed, 7 Mar 2007 08:08:53 +0100 | From | Nick Piggin <> | Subject | Re: [patch 4/6] mm: merge populate and nopage into fault (fixes nonlinear) |
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On Tue, Mar 06, 2007 at 10:51:01PM -0800, Andrew Morton wrote: > On Wed, 21 Feb 2007 05:50:17 +0100 (CET) Nick Piggin <npiggin@suse.de> 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?
I cc'ed him when first posting it. He didn't disagree.
> > NOPAGE_REFAULT is removed. This should be implemented with ->fault, and > > no users have hit mainline yet. > > Did benh agree with that?
Yes.
> The patch unchangeloggedly adds a basic new structure to core mm > (fault_data). Would be nice to document its fields, especially `flags'.
OK. This is actually something that I would like more people to review. Do we need any different fields? Should it be passed as arguments instead of a structure?
> 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.
Yes we should. Not all those filesystem changes have been tested.
> Does anybody really pass a NULL `type' arg into filemap_nopage()?
Dunno, it's exported. I remove that completely in a subsequent patch anyway.
> This patch seems to churn things around an awful lot for minimal benefit.
Well it fixes the whole design of the nonlinear fault path. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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