[PATCH 09/12] mm: Update vm_normal_page() callers to accept FS DAX pages

Alistair Popple
2024-09-10T04:15:44Z

Currently if a PTE points to a FS DAX page vm_normal_page() will
return NULL as these have their own special refcounting scheme. A
future change will allow FS DAX pages to be refcounted the same as any
other normal page.

Therefore vm_normal_page() will start returning FS DAX pages. To avoid
any change in behaviour callers that don't expect FS DAX pages will
need to explicitly check for this. As vm_normal_page() can already
return ZONE_DEVICE pages most callers already include a check for any
ZONE_DEVICE page.

However some callers don't, so add explicit checks where required.

Signed-off-by: Alistair Popple <apopple@nvidia.com>
---
arch/x86/mm/pat/memtype.c | 4 +++-
fs/proc/task_mmu.c | 16 ++++++++++++----
mm/memcontrol-v1.c | 2 +-
3 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/arch/x86/mm/pat/memtype.c b/arch/x86/mm/pat/memtype.c
index 1fa0bf6..eb84593 100644
--- a/arch/x86/mm/pat/memtype.c
+++ b/arch/x86/mm/pat/memtype.c
@@ -951,6 +951,7 @@ static void free_pfn_range(u64 paddr, unsigned long size)
static int follow_phys(struct vm_area_struct *vma, unsigned long *prot,
resource_size_t *phys)
{
+ struct folio *folio;
pte_t *ptep, pte;
spinlock_t *ptl;

@@ -960,7 +961,8 @@ static int follow_phys(struct vm_area_struct *vma, unsigned long *prot,
pte = ptep_get(ptep);

/* Never return PFNs of anon folios in COW mappings. */
- if (vm_normal_folio(vma, vma->vm_start, pte)) {
+ folio = vm_normal_folio(vma, vma->vm_start, pte);
+ if (folio || (folio && !folio_is_device_dax(folio))) {
pte_unmap_unlock(ptep, ptl);
return -EINVAL;
}
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 5f171ad..456b010 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -816,6 +816,8 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,

if (pte_present(ptent)) {
page = vm_normal_page(vma, addr, ptent);
+ if (page && is_device_dax_page(page))
+ page = NULL;
young = pte_young(ptent);
dirty = pte_dirty(ptent);
present = true;
@@ -864,6 +866,8 @@ static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,

if (pmd_present(*pmd)) {
page = vm_normal_page_pmd(vma, addr, *pmd);
+ if (page && is_device_dax_page(page))
+ page = NULL;
present = true;
} else if (unlikely(thp_migration_supported() && is_swap_pmd(*pmd))) {
swp_entry_t entry = pmd_to_swp_entry(*pmd);
@@ -1385,7 +1389,7 @@ static inline bool pte_is_pinned(struct vm_area_struct *vma, unsigned long addr,
if (likely(!test_bit(MMF_HAS_PINNED, &vma->vm_mm->flags)))
return false;
folio = vm_normal_folio(vma, addr, pte);
- if (!folio)
+ if (!folio || folio_is_device_dax(folio))
return false;
return folio_maybe_dma_pinned(folio);
}
@@ -1710,6 +1714,8 @@ static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm,
frame = pte_pfn(pte);
flags |= PM_PRESENT;
page = vm_normal_page(vma, addr, pte);
+ if (page && is_device_dax_page(page))
+ page = NULL;
if (pte_soft_dirty(pte))
flags |= PM_SOFT_DIRTY;
if (pte_uffd_wp(pte))
@@ -2096,7 +2102,8 @@ static unsigned long pagemap_page_category(struct pagemap_scan_private *p,

if (p->masks_of_interest & PAGE_IS_FILE) {
page = vm_normal_page(vma, addr, pte);
- if (page && !PageAnon(page))
+ if (page && !PageAnon(page) &&
+ !is_device_dax_page(page))
categories |= PAGE_IS_FILE;
}

@@ -2158,7 +2165,8 @@ static unsigned long pagemap_thp_category(struct pagemap_scan_private *p,

if (p->masks_of_interest & PAGE_IS_FILE) {
page = vm_normal_page_pmd(vma, addr, pmd);
- if (page && !PageAnon(page))
+ if (page && !PageAnon(page) &&
+ !is_device_dax_page(page))
categories |= PAGE_IS_FILE;
}

@@ -2919,7 +2927,7 @@ static struct page *can_gather_numa_stats_pmd(pmd_t pmd,
return NULL;

page = vm_normal_page_pmd(vma, addr, pmd);
- if (!page)
+ if (!page || is_device_dax_page(page))
return NULL;

if (PageReserved(page))
diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c
index b37c0d8..e16053c 100644
--- a/mm/memcontrol-v1.c
+++ b/mm/memcontrol-v1.c
@@ -667,7 +667,7 @@ static struct page *mc_handle_present_pte(struct vm_area_struct *vma,
{
struct page *page = vm_normal_page(vma, addr, ptent);

- if (!page)
+ if (!page || is_device_dax_page(page))
return NULL;
if (PageAnon(page)) {
if (!(mc.flags & MOVE_ANON))
--
git-series 0.9.1