On 9/13/21 9:15 AM, Alex Sierra wrote:
From: Ralph Campbell <rcampbell@xxxxxxxxxx>
ZONE_DEVICE struct pages have an extra reference count that complicates the
code for put_page() and several places in the kernel that need to check the
reference count to see that a page is not being used (gup, compaction,
migration, etc.). Clean up the code so the reference count doesn't need to
be treated specially for ZONE_DEVICE.
Signed-off-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
Signed-off-by: Alex Sierra <alex.sierra@xxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
---
v2:
AS: merged this patch in linux 5.11 version
v5:
AS: add condition at try_grab_page to check for the zone device type, while
page ref counter is checked less/equal to zero. In case of device zone, pages
ref counter are initialized to zero.
v7:
AS: fix condition at try_grab_page added at v5, is invalid. It supposed
to fix xfstests/generic/413 test, however, there's a known issue on
this test where DAX mapped area DIO to non-DAX expect to fail.
https://patchwork.kernel.org/project/fstests/patch/1489463960-3579-1-git-send-email-xzhou@xxxxxxxxxx
This condition was removed after rebase over patch series
https://lore.kernel.org/r/20210813044133.1536842-4-jhubbard@xxxxxxxxxx
---
arch/powerpc/kvm/book3s_hv_uvmem.c | 2 +-
drivers/gpu/drm/nouveau/nouveau_dmem.c | 2 +-
fs/dax.c | 4 +-
include/linux/dax.h | 2 +-
include/linux/memremap.h | 7 +--
include/linux/mm.h | 11 ----
lib/test_hmm.c | 2 +-
mm/internal.h | 8 +++
mm/memremap.c | 69 +++++++-------------------
mm/migrate.c | 5 --
mm/page_alloc.c | 3 ++
mm/swap.c | 45 ++---------------
12 files changed, 45 insertions(+), 115 deletions(-)
I don't see mm/memcontrol.c listed here so I think you will need this fragment too:
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 389b5766e74f..0cc9c7c71e79 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5541,11 +5541,7 @@ static struct page *mc_handle_swap_pte(struct vm_area_struct *vma,
*/
if (is_device_private_entry(ent)) {
page = pfn_swap_entry_to_page(ent);
- /*
- * MEMORY_DEVICE_PRIVATE means ZONE_DEVICE page and which have
- * a refcount of 1 when free (unlike normal page)
- */
- if (!page_ref_add_unless(page, 1, 1))
+ if (!get_page_unless_zero(page))
return NULL;
return page;
}
