Introduce do_huge_zero_wp_pmd() to handle wp-fault on a hugezeropage and
replace it with a PMD-mapped THP. Change the helpers introduced in the
previous patch to flush TLB entry corresponding to the hugezeropage,
and preserve PMD uffd-wp marker. In case of failure, fallback to
splitting the PMD.
Signed-off-by: Dev Jain <dev.jain@xxxxxxx>
---
include/linux/huge_mm.h | 6 ++++
mm/huge_memory.c | 79 +++++++++++++++++++++++++++++++++++------
mm/memory.c | 5 +--
3 files changed, 78 insertions(+), 12 deletions(-)
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index e25d9ebfdf89..fdd2cf473a3c 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -9,6 +9,12 @@
#include <linux/kobject.h>
vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf);
+vm_fault_t thp_fault_alloc(gfp_t gfp, int order, struct vm_area_struct *vma,
+ unsigned long haddr, struct folio **foliop,
+ unsigned long addr);
+void map_pmd_thp(struct folio *folio, struct vm_fault *vmf,
+ struct vm_area_struct *vma, unsigned long haddr,
+ pgtable_t pgtable);
int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma);
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 58125fbcc532..150163ad77d3 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -943,9 +943,9 @@ unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
}
EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
-static vm_fault_t thp_fault_alloc(gfp_t gfp, int order, struct vm_area_struct *vma,
- unsigned long haddr, struct folio **foliop,
- unsigned long addr)
+vm_fault_t thp_fault_alloc(gfp_t gfp, int order, struct vm_area_struct *vma,
+ unsigned long haddr, struct folio **foliop,
+ unsigned long addr)
{
struct folio *folio = vma_alloc_folio(gfp, order, vma, haddr, true);
@@ -984,21 +984,29 @@ static void __thp_fault_success_stats(struct vm_area_struct *vma, int order)
count_memcg_event_mm(vma->vm_mm, THP_FAULT_ALLOC);
}
-static void map_pmd_thp(struct folio *folio, struct vm_fault *vmf,
- struct vm_area_struct *vma, unsigned long haddr,
- pgtable_t pgtable)
+void map_pmd_thp(struct folio *folio, struct vm_fault *vmf,
+ struct vm_area_struct *vma, unsigned long haddr,
+ pgtable_t pgtable)
{
- pmd_t entry;
+ pmd_t entry, old_pmd;
+ bool is_pmd_none = pmd_none(*vmf->pmd);
entry = mk_huge_pmd(&folio->page, vma->vm_page_prot);
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
folio_add_new_anon_rmap(folio, vma, haddr, RMAP_EXCLUSIVE);
folio_add_lru_vma(folio, vma);
- pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
+ if (!is_pmd_none) {
+ old_pmd = pmdp_huge_clear_flush(vma, haddr, vmf->pmd);
+ if (pmd_uffd_wp(old_pmd))
+ entry = pmd_mkuffd_wp(entry);
+ }
+ if (pgtable)
+ pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
- mm_inc_nr_ptes(vma->vm_mm);
+ if (is_pmd_none)
+ mm_inc_nr_ptes(vma->vm_mm);
}
static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf)
@@ -1576,6 +1584,50 @@ void huge_pmd_set_accessed(struct vm_fault *vmf)
spin_unlock(vmf->ptl);
}
+static vm_fault_t do_huge_zero_wp_pmd_locked(struct vm_fault *vmf,
+ unsigned long haddr,
+ struct folio *folio)
+{
+ struct vm_area_struct *vma = vmf->vma;
+ vm_fault_t ret = 0;
+
+ ret = check_stable_address_space(vma->vm_mm);
+ if (ret)
+ goto out;
+ map_pmd_thp(folio, vmf, vma, haddr, NULL);
+out:
+ return ret;
+}
+
+static vm_fault_t do_huge_zero_wp_pmd(struct vm_fault *vmf, unsigned long haddr)
+{
+ struct vm_area_struct *vma = vmf->vma;
+ gfp_t gfp = vma_thp_gfp_mask(vma);
+ struct mmu_notifier_range range;
+ struct folio *folio = NULL;
+ vm_fault_t ret = 0;
+
+ ret = thp_fault_alloc(gfp, HPAGE_PMD_ORDER, vma, haddr, &folio,
+ vmf->address);
+ if (ret)
+ goto out;
+
+ mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm, haddr,
+ haddr + HPAGE_PMD_SIZE);
+ mmu_notifier_invalidate_range_start(&range);
+ vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
+ if (unlikely(!pmd_same(pmdp_get(vmf->pmd), vmf->orig_pmd)))
+ goto unlock;
+ ret = do_huge_zero_wp_pmd_locked(vmf, haddr, folio);
+ if (!ret)
+ __thp_fault_success_stats(vma, HPAGE_PMD_ORDER);
+unlock:
+ spin_unlock(vmf->ptl);
+ mmu_notifier_invalidate_range_end(&range);
+out:
+ return ret;
+}
+
vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf)
{
const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;
@@ -1588,8 +1640,15 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf)
vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
VM_BUG_ON_VMA(!vma->anon_vma, vma);
- if (is_huge_zero_pmd(orig_pmd))
+ if (is_huge_zero_pmd(orig_pmd)) {
+ vm_fault_t ret = do_huge_zero_wp_pmd(vmf, haddr);
+
+ if (!(ret & VM_FAULT_FALLBACK))
+ return ret;
+
+ /* Fallback to splitting PMD if THP cannot be allocated */
goto fallback;
+ }
spin_lock(vmf->ptl);
diff --git a/mm/memory.c b/mm/memory.c
index 3c01d68065be..c081a25f5173 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5409,9 +5409,10 @@ static inline vm_fault_t wp_huge_pmd(struct vm_fault *vmf)
if (vma_is_anonymous(vma)) {
if (likely(!unshare) &&
userfaultfd_huge_pmd_wp(vma, vmf->orig_pmd)) {
- if (userfaultfd_wp_async(vmf->vma))
+ if (!userfaultfd_wp_async(vmf->vma))
+ return handle_userfault(vmf, VM_UFFD_WP);
+ if (!is_huge_zero_pmd(vmf->orig_pmd))
goto split;
- return handle_userfault(vmf, VM_UFFD_WP);
}
return do_huge_pmd_wp_page(vmf);
}
--
2.30.2
