Re: [PATCH 2/2] mm/migrate: preserve soft dirty in remove_migration_pte()

[Christoph Hellwig]

On Mon, Aug 31, 2020 at 02:22:22PM -0700, Ralph Campbell wrote:
> The code to remove a migration PTE and replace it with a device private
> PTE was not copying the soft dirty bit from the migration entry.
> This could lead to page contents not being marked dirty when faulting
> the page back from device private memory.
> 
> Signed-off-by: Ralph Campbell 

Looks good,

Reviewed-by: Christoph Hellwig 

[PATCH 2/2] mm/migrate: preserve soft dirty in remove_migration_pte()

[Ralph Campbell]

The code to remove a migration PTE and replace it with a device private
PTE was not copying the soft dirty bit from the migration entry.
This could lead to page contents not being marked dirty when faulting
the page back from device private memory.

Signed-off-by: Ralph Campbell 
---
 mm/migrate.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/migrate.c b/mm/migrate.c
index fe339a847328..4f89360d9e77 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -249,6 +249,8 @@ static bool remove_migration_pte(struct page *page, struct 
vm_area_struct *vma,
if (unlikely(is_device_private_page(new))) {
entry = make_device_private_entry(new, pte_write(pte));
pte = swp_entry_to_pte(entry);
+   if (pte_swp_soft_dirty(*pvmw.pte))
+   pte = pte_swp_mksoft_dirty(pte);
if (pte_swp_uffd_wp(*pvmw.pte))
pte = pte_swp_mkuffd_wp(pte);
}
-- 
2.20.1