linux-kernel - Re: [patch 3/3] mm: fault handler to replace nopage and populate

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Date:	Sun, 08 Oct 2006 12:12:42 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Andrew Morton <akpm@...l.org>
CC:	Nick Piggin <npiggin@...e.de>,
	Linux Memory Management <linux-mm@...ck.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [patch 3/3] mm: fault handler to replace nopage and populate

Andrew Morton wrote:

>- You may find that gcc generates crap code for the initialisation of the
>  `struct fault_data'.  If so, filling the fields in by hand one-at-a-time
>  will improve things.
>

OK.

>- So is the plan here to migrate all code over to using
>  vm_operations.fault() and to finally remove vm_operations.nopage and
>  .nopfn?  If so, that'd be nice.
>

Definitely remove .nopage, .populate, and hopefully .page_mkwrite.

.nopfn is a little harder because it doesn't quite follow the same pattern
as the others (eg. has no struct page).

>- As you know, there is a case for constructing that `struct fault_data'
>  all the way up in do_no_page(): so we can pass data back, asking
>  do_no_page() to rerun the fault if we dropped mmap_sem.
>

That is what it is doing - do_no_page should go away (it is basically
duplicated in __do_fault -- I left it there because I don't know if people
are happy to have a flag day or slowly migrate over).

But I have converted regular pagecache (mm/filemap.c) to use .fault rather
than .nopage and .populate, so you should be able to do the mmap_sem thing
right now. That's something maybe you could look at if you get time? Ie.
whether this .fault handler thing will be sufficient for you.

>- No useful opinion on the substance of this patch, sorry.  It's Saturday ;)
>

No hurry. Thanks for the quick initial comments.

--

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