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

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Message-Id: <1160351174.14601.3.camel@localhost.localdomain>
Date:	Mon, 09 Oct 2006 09:46:13 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
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

> - 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.

Agreed. That would also allow to pass down knowledge of wether we can be
interruptible or not (coming from userland or not). Useful in a few case
when dealing with strange hw mappings.

Now, fault() still returns a struct page and thus doesn't quite fix the
problem I'm exposing in my "User switchable HW mappings & cie" mail I
posted today in which case we need to either duplicate the truncate
logic in no_pfn() or get rid of no_pfn() and set the PTE from the fault
handler . I tend to prefer the later provided that it's strictly limited
for mappings that do not have a struct page though.

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