linux-kernel - Confusion about __do_fault and MM

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Date:	Mon, 10 Nov 2014 16:23:57 -0800
From:	Joel Fernandes <agnel.joel@...il.com>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"kernelnewbies@...nelnewbies.org" <kernelnewbies@...nelnewbies.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>
Subject: Confusion about __do_fault and MM_ANONPAGES

Hi,

I have some confusion about when is anon=1 when __do_fault is called.

__do_fault seems to be called only when the page fault is of a linear
or a non-linear mapping. My understanding is neither of these can be
anonymous, so I am confused about the below code fragment:

In which case is anon=1 when memory.c::__do_fault is called?
In __do_fault, you'll see something like...
        if (anon) {
            inc_mm_counter_fast(mm, MM_ANONPAGES);
            page_add_new_anon_rmap(page, vma, address);
        } else {


Thanks!
Joel
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