Re: [PATCH 1 of 13] Add apply_to_page_range() which applies a function to a pte range

From: Eric W. Biederman
Date: Tue Aug 01 2006 - 08:08:12 EST

Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx> writes:

> 2 files changed, 99 insertions(+)
> include/linux/mm.h | 5 ++
> mm/memory.c | 94 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> Add a new mm function apply_to_page_range() which applies a given
> function to every pte in a given virtual address range in a given mm
> structure. This is a generic alternative to cut-and-pasting the Linux
> idiomatic pagetable walking code in every place that a sequence of
> PTEs must be accessed.
> Although this interface is intended to be useful in a wide range of
> situations, it is currently used specifically by several Xen
> subsystems, for example: to ensure that pagetables have been allocated
> for a virtual address range, and to construct batched special
> pagetable update requests to map I/O memory (in ioremap()).

- You don't handle huge pages. For a generic function
that sounds like a problem.
- I believe there is a reason the kernel doesn't already have
a function like this. I seem to recall there being efficiency
and fast path arguments.
- Placing this code in mm/memory.c without a common consumer is
pure kernel bloat for everyone who doesn't use this function,
which is just about everyone.

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