--- Jim Bauer <jfbauer@nfr.com> wrote:
> > You don't really need zap_page_range() to remove the old
> > mapping. Since you know the virtual address at which the
> > page is mapped, you can also find out where the corresponding
> > PTE (page table entry) is. Then you can clear the entry
> > with ptep_get_and_clear(). This lets you save the old PTE,
> > from which you can get to the page using pte_page(). You
> > can then free the page or do whatever else you want with it.
>
> Know of a good example of this?
I couldn't find an example in any 2.5.x driver. But here is
what is needed:
{
struct mm_struct *mm;
pgd_t *pgd;
pmd_t *pmd;
pte_t *ptep, pte;
struct page *old_page;
struct page *new_page = ...; /* new page to be mapped in */
pgprot_t prot = ...; /* PTE flags. _PAGE_RW, PAGE_SHARED, etc.
* Set appropriately. */
mm = current->mm;
spin_lock(&mm->page_table_lock);
pgd = pgd_offset(mm, address);
pmd = pmd_offset(pgd, address);
ptep = pte_offset_map(pmd, address);
pte = ptep_get_and_clear(ptep);
set_pte(ptep, mk_pte(new_page, prot));
spin_unlock(&mm->page_table_lock);
old_page = pte_page(pte);
...
}
Not many error checks are needed in this case since we
know that the required address definitely has a mapping
in the process page table.
-Ravi.
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