From: Ralph Campbell <rcampbell@xxxxxxxxxx> Subject: mm/migrate: preserve soft dirty in remove_migration_pte() 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. Link: https://lkml.kernel.org/r/20200831212222.22409-3-rcampbell@xxxxxxxxxx Signed-off-by: Ralph Campbell <rcampbell@xxxxxxxxxx> Reviewed-by: Christoph Hellwig <hch@xxxxxx> Cc: Jerome Glisse <jglisse@xxxxxxxxxx> Cc: Alistair Popple <apopple@xxxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Cc: Jason Gunthorpe <jgg@xxxxxxxxxx> Cc: Bharata B Rao <bharata@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/migrate.c | 2 ++ 1 file changed, 2 insertions(+) --- a/mm/migrate.c~mm-migrate-preserve-soft-dirty-in-remove_migration_pte +++ a/mm/migrate.c @@ -249,6 +249,8 @@ static bool remove_migration_pte(struct 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); } _
