Re: [PATCH v2 3/3] hugetlb: Convert hugetlb_wp() to use struct vm_fault

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On 2024/4/2 04:26, Vishal Moola (Oracle) wrote:
hugetlb_wp() can use the struct vm_fault passed in from hugetlb_fault().
This alleviates the stack by consolidating 5 variables into a single
struct.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>
---
  mm/hugetlb.c | 61 ++++++++++++++++++++++++++--------------------------
  1 file changed, 30 insertions(+), 31 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index aca2f11b4138..d4f26947173e 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5918,18 +5918,16 @@ static void unmap_ref_private(struct mm_struct *mm, struct vm_area_struct *vma,
   * Keep the pte_same checks anyway to make transition from the mutex easier.
   */
  static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma,
-		       unsigned long address, pte_t *ptep, unsigned int flags,
-		       struct folio *pagecache_folio, spinlock_t *ptl,
+		       struct folio *pagecache_folio,

The same as comment in the previous thread.

Muchun,
Thanks.

  		       struct vm_fault *vmf)
  {
-	const bool unshare = flags & FAULT_FLAG_UNSHARE;
-	pte_t pte = huge_ptep_get(ptep);
+	const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;
+	pte_t pte = huge_ptep_get(vmf->pte);
  	struct hstate *h = hstate_vma(vma);
  	struct folio *old_folio;
  	struct folio *new_folio;
  	int outside_reserve = 0;
  	vm_fault_t ret = 0;
-	unsigned long haddr = address & huge_page_mask(h);
  	struct mmu_notifier_range range;
/*
@@ -5952,7 +5950,7 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma,
/* Let's take out MAP_SHARED mappings first. */
  	if (vma->vm_flags & VM_MAYSHARE) {
-		set_huge_ptep_writable(vma, haddr, ptep);
+		set_huge_ptep_writable(vma, vmf->address, vmf->pte);
  		return 0;
  	}
@@ -5971,7 +5969,7 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma,
  			SetPageAnonExclusive(&old_folio->page);
  		}
  		if (likely(!unshare))
-			set_huge_ptep_writable(vma, haddr, ptep);
+			set_huge_ptep_writable(vma, vmf->address, vmf->pte);
delayacct_wpcopy_end();
  		return 0;
@@ -5998,8 +5996,8 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma,
  	 * Drop page table lock as buddy allocator may be called. It will
  	 * be acquired again before returning to the caller, as expected.
  	 */
-	spin_unlock(ptl);
-	new_folio = alloc_hugetlb_folio(vma, haddr, outside_reserve);
+	spin_unlock(vmf->ptl);
+	new_folio = alloc_hugetlb_folio(vma, vmf->address, outside_reserve);
if (IS_ERR(new_folio)) {
  		/*
@@ -6024,19 +6022,21 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma,
  			 *
  			 * Reacquire both after unmap operation.
  			 */
-			idx = vma_hugecache_offset(h, vma, haddr);
+			idx = vma_hugecache_offset(h, vma, vmf->address);
  			hash = hugetlb_fault_mutex_hash(mapping, idx);
  			hugetlb_vma_unlock_read(vma);
  			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
- unmap_ref_private(mm, vma, &old_folio->page, haddr);
+			unmap_ref_private(mm, vma, &old_folio->page,
+					vmf->address);
mutex_lock(&hugetlb_fault_mutex_table[hash]);
  			hugetlb_vma_lock_read(vma);
-			spin_lock(ptl);
-			ptep = hugetlb_walk(vma, haddr, huge_page_size(h));
-			if (likely(ptep &&
-				   pte_same(huge_ptep_get(ptep), pte)))
+			spin_lock(vmf->ptl);
+			vmf->pte = hugetlb_walk(vma, vmf->address,
+					huge_page_size(h));
+			if (likely(vmf->pte &&
+				   pte_same(huge_ptep_get(vmf->pte), pte)))
  				goto retry_avoidcopy;
  			/*
  			 * race occurs while re-acquiring page table
@@ -6058,37 +6058,38 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma,
  	if (unlikely(ret))
  		goto out_release_all;
- if (copy_user_large_folio(new_folio, old_folio, address, vma)) {
+	if (copy_user_large_folio(new_folio, old_folio, vmf->real_address, vma)) {
  		ret = VM_FAULT_HWPOISON_LARGE;
  		goto out_release_all;
  	}
  	__folio_mark_uptodate(new_folio);
- mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, haddr,
-				haddr + huge_page_size(h));
+	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, vmf->address,
+				vmf->address + huge_page_size(h));
  	mmu_notifier_invalidate_range_start(&range);
/*
  	 * Retake the page table lock to check for racing updates
  	 * before the page tables are altered
  	 */
-	spin_lock(ptl);
-	ptep = hugetlb_walk(vma, haddr, huge_page_size(h));
-	if (likely(ptep && pte_same(huge_ptep_get(ptep), pte))) {
+	spin_lock(vmf->ptl);
+	vmf->pte = hugetlb_walk(vma, vmf->address, huge_page_size(h));
+	if (likely(vmf->pte && pte_same(huge_ptep_get(vmf->pte), pte))) {
  		pte_t newpte = make_huge_pte(vma, &new_folio->page, !unshare);
/* Break COW or unshare */
-		huge_ptep_clear_flush(vma, haddr, ptep);
+		huge_ptep_clear_flush(vma, vmf->address, vmf->pte);
  		hugetlb_remove_rmap(old_folio);
-		hugetlb_add_new_anon_rmap(new_folio, vma, haddr);
+		hugetlb_add_new_anon_rmap(new_folio, vma, vmf->address);
  		if (huge_pte_uffd_wp(pte))
  			newpte = huge_pte_mkuffd_wp(newpte);
-		set_huge_pte_at(mm, haddr, ptep, newpte, huge_page_size(h));
+		set_huge_pte_at(mm, vmf->address, vmf->pte, newpte,
+				huge_page_size(h));
  		folio_set_hugetlb_migratable(new_folio);
  		/* Make the old page be freed below */
  		new_folio = old_folio;
  	}
-	spin_unlock(ptl);
+	spin_unlock(vmf->ptl);
  	mmu_notifier_invalidate_range_end(&range);
  out_release_all:
  	/*
@@ -6096,12 +6097,12 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma,
  	 * unshare)
  	 */
  	if (new_folio != old_folio)
-		restore_reserve_on_error(h, vma, haddr, new_folio);
+		restore_reserve_on_error(h, vma, vmf->address, new_folio);
  	folio_put(new_folio);
  out_release_old:
  	folio_put(old_folio);
- spin_lock(ptl); /* Caller expects lock to be held */
+	spin_lock(vmf->ptl); /* Caller expects lock to be held */
delayacct_wpcopy_end();
  	return ret;
@@ -6365,8 +6366,7 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
  	hugetlb_count_add(pages_per_huge_page(h), mm);
  	if ((vmf->flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED)) {
  		/* Optimization, do the COW without a second fault */
-		ret = hugetlb_wp(mm, vma, vmf->real_address, vmf->pte,
-				vmf->flags, folio, vmf->ptl, vmf);
+		ret = hugetlb_wp(mm, vma, folio, vmf);
  	}
spin_unlock(vmf->ptl);
@@ -6579,8 +6579,7 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
if (flags & (FAULT_FLAG_WRITE|FAULT_FLAG_UNSHARE)) {
  		if (!huge_pte_write(vmf.orig_pte)) {
-			ret = hugetlb_wp(mm, vma, address, vmf.pte, flags,
-					 pagecache_folio, vmf.ptl, &vmf);
+			ret = hugetlb_wp(mm, vma, pagecache_folio, &vmf);
  			goto out_put_page;
  		} else if (likely(flags & FAULT_FLAG_WRITE)) {
  			vmf.orig_pte = huge_pte_mkdirty(vmf.orig_pte);





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