Re: Short question about the mmap method

From: Douglas Gilbert (
Date: Sat Jan 05 2002 - 12:52:12 EST

Steffen Persvold <> wrote:

> I have a question regarding drivers implementing the
> mmap and nopage methods. In some references
> I've read that pages in kernel allocated memory (either
> allocated with kmalloc, vmalloc or __get_free_pages)
> should be set to reserved (mem_map_reserve or
> set_bit(PG_reserved, page->flags) before they can be
> mmap'ed to guarantee that they can't be swapped out.
> Is this true ?

I recently implemented the mmap() call in the SCSI generic
(sg) driver. See that driver in lk 2.4.17 or go to
and download version 3.1.22 of the sg driver from the table.
It will run on any kernel in the 2.4 series. It should
answer most of your questions (at least about mmap-ing
memory obtained from __get_free_pages() which is a bit

Doug Gilbert
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