On Mon, 17 Apr 2006, KAMEZAWA Hiroyuki wrote:
> > Note that there is an issue with your approach. If a migration entry is
> > copied during fork then SWP_MIGRATION_WRITE must become SWP_MIGRATION_READ
> > for some cases. Would you look into fixing this?
> Thank you for pointing out the issue.
>
> In my understanding, copy_page_range() is used at fork().
> This finally calls copy_one_pte() and copies ptes one by one.
Right this is one spot but the ptes in the original mm must also be marked
read. Are there any additional races?
> Maybe, I'll do like this.
> ==
> 438 if (unlikely(!pte_present(pte)) {
> 439 if (!pte_file(pte)) {
> 440 swap_duplicate(pte_to_swp_entry(pte));
> entry = pte_to_swp_entry(pte);
> #ifdef CONFIG_MIGRATION
> if (is_migration_entry(entry)) {
> ......always copy as MIGRATION_READ.
> }
> #endif
> 441 /* make sure dst_mm is on swapoff's mmlist. */
Looks okay for this one location.
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