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Date: Sun, 12 Oct 2003 19:17:06 -0700
From: Andrew Morton <akpm@osdl.org>
To: Linus Torvalds <torvalds@osdl.org>
Cc: roland@redhat.com, mingo@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] report user-readable fixmap area in /proc/PID/maps
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Linus Torvalds <torvalds@osdl.org> wrote:
>
> If you really want /proc/PID/maps to look right, add a new vm_area_struct,
>  see if you can allocate it as part of the "struct mm_struct" so that we
>  don't get yet another (unnecessary) allocation on fork time.

It could be done "on demand".  So get_user_pages() and the /proc code will
call the new add_fixmap_vma() on entry.  Hence the additional overhead is
only incurred when /proc/pid/maps is accessed, or get_user_pages() is
called.

It'll need a new flag in mm_struct.  mm_struct.swap_address can be
salvaged: it is no longer used.