On 16.06.25 13:58, Alistair Popple wrote:
Currently dax is the only user of pmd and pud mapped ZONE_DEVICE
pages. Therefore page walkers that want to exclude DAX pages can check
pmd_devmap or pud_devmap. However soon dax will no longer set PFN_DEV,
meaning dax pages are mapped as normal pages.
Ensure page walkers that currently use pXd_devmap to skip DAX pages
continue to do so by adding explicit checks of the VMA instead.
> > Signed-off-by: Alistair Popple <apop...@nvidia.com>
Reviewed-by: Jason Gunthorpe <j...@nvidia.com>
Reviewed-by: Dan Williams <dan.j.willi...@intel.com>
---
Changes from v1:
- Remove vma_is_dax() check from mm/userfaultfd.c as
validate_move_areas() will already skip DAX VMA's on account of them
not being anonymous.
This should be documented in the patch description above.
---
fs/userfaultfd.c | 2 +-
mm/hmm.c | 2 +-
mm/userfaultfd.c | 6 ------
3 files changed, 2 insertions(+), 8 deletions(-)
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index ef054b3..a886750 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -304,7 +304,7 @@ static inline bool userfaultfd_must_wait(struct
userfaultfd_ctx *ctx,
goto out;
ret = false;
- if (!pmd_present(_pmd) || pmd_devmap(_pmd))
+ if (!pmd_present(_pmd) || vma_is_dax(vmf->vma))
goto out;
VMA checks should be done before doing any page table walk.
if (pmd_trans_huge(_pmd)) {
diff --git a/mm/hmm.c b/mm/hmm.c
index feac861..5311753 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -441,7 +441,7 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long
start, unsigned long end,
return hmm_vma_walk_hole(start, end, -1, walk);
}
- if (pud_leaf(pud) && pud_devmap(pud)) {
+ if (pud_leaf(pud) && vma_is_dax(walk->vma)) {
unsigned long i, npages, pfn;
unsigned int required_fault;
unsigned long *hmm_pfns;
Dito.
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 58b3ad6..8395db2 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -1818,12 +1818,6 @@ ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned
long dst_start,
ptl = pmd_trans_huge_lock(src_pmd, src_vma);
if (ptl) {
- if (pmd_devmap(*src_pmd)) {
- spin_unlock(ptl);
- err = -ENOENT;
- break;
- }
-
/* Check if we can move the pmd without splitting it. */
if (move_splits_huge_pmd(dst_addr, src_addr, src_start
+ len) ||
!pmd_none(dst_pmdval)) {
--
Cheers,
David / dhildenb
