Re: [PATCH 2.6.21] cramfs: add cramfs Linear XIP
From: Carsten Otte
Date: Sat Jun 09 2007 - 04:10:05 EST
Justin Treon wrote:
--- Carsten Otte <cotte@xxxxxxxxxx> wrote:
We use vmem_map on 390:
The nice thing about this approach is: we use page->count and rmap,
both already exist and are perfectly suited for our purpose.Can you give an example of the proper way to use sparsemem in this case?
The downside: We need mem_map struct page entries behind all memory
segments. Nowerdays we can easily create those via vmem_map/sparsemem.
- __segment_load[arch/s390/mm/extmem.c] calls add_shared_memory() to
create struct page entries behind a segment
- segment_unload (same file) calls remove_shared_memory() to remove
parts of the mem_map array again
- arch/s390/mm/vmem.c implements both callbacks
As far as I know, this can also be archived with sparsemem.
Unfortunately I don't have an example for sparsemem at hand, I would
try to use sparse_add_one_section()[mm/sparse.c].
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