On 11.09.24 08:56, Dev Jain wrote:
Introduce do_huge_zero_wp_pmd() to handle wp-fault on a hugezeropage and
replace it with a PMD-mapped THP. Change the helper introduced in the
previous patch to flush TLB entry corresponding to the hugezeropage.
In case of failure, fallback to splitting the PMD.
Signed-off-by: Dev Jain <dev.jain@xxxxxxx>
---
mm/huge_memory.c | 52 +++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 49 insertions(+), 3 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index b96a1ff2bf40..3e28946a805f 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -987,16 +987,20 @@ static void __pmd_thp_fault_success_stats(struct vm_area_struct *vma)
static void map_pmd_thp(struct folio *folio, struct vm_fault *vmf,
struct vm_area_struct *vma, unsigned long haddr)
{
- 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);
+ if (!is_pmd_none)
+ old_pmd = pmdp_huge_clear_flush(vma, haddr, vmf->pmd);
This should likely be done in the caller.
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);
And this as well.
No need to make this function deal with this if the callers exactly know
what they are doing.
}
static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf)
@@ -1576,6 +1580,41 @@ void huge_pmd_set_accessed(struct vm_fault *vmf)
spin_unlock(vmf->ptl);
}
+static vm_fault_t do_huge_zero_wp_pmd(struct vm_fault *vmf, unsigned long haddr)
Is there a need to pass in "haddr" if we have the vmf?
+{
+ struct vm_area_struct *vma = vmf->vma;
+ gfp_t gfp = vma_thp_gfp_mask(vma);
+ struct mmu_notifier_range range;
+ struct folio *folio;
+ vm_fault_t ret = 0;
+
+ folio = pmd_thp_fault_alloc(gfp, vma, haddr, vmf->address);
+ if (unlikely(!folio)) {
+ ret = VM_FAULT_FALLBACK;
+ 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 release;
+ ret = check_stable_address_space(vma->vm_mm);
+ if (ret)
+ goto release;
The clear+flush really belongs here.
+ map_pmd_thp(folio, vmf, vma, haddr);
+ __pmd_thp_fault_success_stats(vma);
+ goto unlock;
+release:
+ folio_put(folio);
+unlock:
+ spin_unlock(vmf->ptl);
+ mmu_notifier_invalidate_range_end(&range);
+out:
+ return ret;
+}
+
--
Cheers,
David / dhildenb
