Hi Peter
On Fri, 10 Apr 2020 11:32:34 -0400 Peter Xu wrote:
>
> I'm not sure this is correct. As I mentioned, the commit wanted to
> apply the uffd-wp bit even for the swap entries so that even the swap
> entries got swapped in, the page will still be write protected. So
> IIUC think we can't remove that.
>
Thank you for explaining that we would flip-flop uffd-wp in f45ec5ff16.
The input to test robot now looks like the diff below after restoring
CONFIG_MIGRATION.
--- b/mm/mprotect.c
+++ c/mm/mprotect.c
@@ -139,9 +139,9 @@ static unsigned long change_pte_range(st
}
ptep_modify_prot_commit(vma, addr, pte, oldpte, ptent);
pages++;
- } else if (is_swap_pte(oldpte)) {
+ } else if (IS_ENABLED(CONFIG_MIGRATION)) {
swp_entry_t entry = pte_to_swp_entry(oldpte);
- pte_t newpte;
+ pte_t newpte = oldpte;
if (is_write_migration_entry(entry)) {
/*
@@ -154,7 +154,9 @@ static unsigned long change_pte_range(st
newpte = pte_swp_mksoft_dirty(newpte);
if (pte_swp_uffd_wp(oldpte))
newpte = pte_swp_mkuffd_wp(newpte);
- } else if (is_write_device_private_entry(entry)) {
+ }
+
+ if (is_write_device_private_entry(entry)) {
/*
* We do not preserve soft-dirtiness. See
* copy_one_pte() for explanation.
@@ -163,8 +165,6 @@ static unsigned long change_pte_range(st
newpte = swp_entry_to_pte(entry);
if (pte_swp_uffd_wp(oldpte))
newpte = pte_swp_mkuffd_wp(newpte);
- } else {
- newpte = oldpte;
}
if (uffd_wp)
