Messages in this thread Patch in this message | | | Date | Thu, 23 Jun 2005 17:07:52 +1000 | From | Nick Piggin <> | Subject | Re: [patch][rfc] 4/5: remap ZERO_PAGE mappings |
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4/5 Remap ZERO_PAGE ptes when remapping memory. This is currently just an optimisation for MIPS, which is the only architecture with multiple zero pages - it now retains the mapping it needs for good cache performance, and as well do_wp_page is now able to always correctly detect and optimise zero page COW faults.
In future, this becomes required in order to always be able to detect whether a pte points to a ZERO_PAGE using only the pte, vaddr pair.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Index: linux-2.6/mm/mremap.c =================================================================== --- linux-2.6.orig/mm/mremap.c +++ linux-2.6/mm/mremap.c @@ -141,6 +141,10 @@ move_one_page(struct vm_area_struct *vma if (dst) { pte_t pte; pte = ptep_clear_flush(vma, old_addr, src); + /* ZERO_PAGE can be dependant on virtual addr */ + if (pfn_valid(pte_pfn(pte)) && + pte_page(pte) == ZERO_PAGE(old_addr)) + pte = pte_wrprotect(mk_pte(ZERO_PAGE(new_addr), new_vma->vm_page_prot)); set_pte_at(mm, new_addr, dst, pte); } else error = -ENOMEM; | |