On Mon, 17 Apr 2006 17:27:48 -0700 (PDT)
Christoph Lameter <[email protected]> wrote:
> On Tue, 18 Apr 2006, KAMEZAWA Hiroyuki wrote:
>
> > Then,
> >
> > if (is_migration_entry(entry)) {
> > change_to_read_migration_entry(entry);
> > copy_entry(entry);
> > }
> >
> > is sane.
>
> Hmmm... Looks like I need to do the patch. Is the following okay? This
> will also only work on cow mappings.
>
I think okay.
BTW, when copying mm, mm->mmap_sem is held. Is mm->mmap_sem is not held while
page migraion now ? I'm sorry I can't catch up all changes.
or Is this needed for lazy migration (migration-on-fault) ?
-Kame
>
>
> Read/Write migration entries: Implement correct behavior in copy_one_pte
>
> Migration entries with write permission must become SWP_MIGRATION_READ
> entries if a COW mapping is processed. The migration entries from which
> the copy is being made must also become SWP_MIGRATION_READ. This mimicks
> the copying of pte for an anonymous page.
>
> Signed-off-by: KAMEZAWA Hiroyuki <[email protected]>
> Signed-off-by: Christoph Lameter <[email protected]>
>
> Index: linux-2.6.17-rc1-mm2/mm/memory.c
> ===================================================================
> --- linux-2.6.17-rc1-mm2.orig/mm/memory.c 2006-04-17 16:23:50.000000000 -0700
> +++ linux-2.6.17-rc1-mm2/mm/memory.c 2006-04-17 17:25:50.000000000 -0700
> @@ -434,7 +434,9 @@ copy_one_pte(struct mm_struct *dst_mm, s
> /* pte contains position in swap or file, so copy. */
> if (unlikely(!pte_present(pte))) {
> if (!pte_file(pte)) {
> - swap_duplicate(pte_to_swp_entry(pte));
> + swp_entry_t entry = pte_to_swp_entry(pte);
> +
> + swap_duplicate(entry);
> /* make sure dst_mm is on swapoff's mmlist. */
> if (unlikely(list_empty(&dst_mm->mmlist))) {
> spin_lock(&mmlist_lock);
> @@ -443,6 +445,19 @@ copy_one_pte(struct mm_struct *dst_mm, s
> &src_mm->mmlist);
> spin_unlock(&mmlist_lock);
> }
> + if (is_migration_entry(entry) &&
> + is_cow_mapping(vm_flags)) {
> + page = migration_entry_to_page(entry);
> +
> + /*
> + * COW mappings require pages in both parent
> + * and child to be set to read.
> + */
> + entry = make_migration_entry(page,
> + ` SWP_MIGRATION_READ);
> + pte = swp_entry_to_pte(entry);
> + set_pte_at(src_mm, addr, src_pte, pte);
> + }
> }
> goto out_set_pte;
> }
>
-
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