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From: "Vishal Moola (Oracle)" <vishal.moola@gmail.com>
To: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org,
	akpm@linux-foundation.org,
	muchun.song@linux.dev,
	"Vishal Moola (Oracle)" <vishal.moola@gmail.com>
Subject: [PATCH 3/5] hugetlb: Convert hugetlb_wp() to use struct vm_fault
Date: Mon, 25 Mar 2024 15:33:37 -0700
Message-ID: <20240325223339.169350-4-vishal.moola@gmail.com>
In-Reply-To: <20240325223339.169350-1-vishal.moola@gmail.com>
References: <20240325223339.169350-1-vishal.moola@gmail.com>
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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@gmail.com>
---
 mm/hugetlb.c | 61 ++++++++++++++++++++++++++--------------------------
 1 file changed, 30 insertions(+), 31 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 819a6d067985..107b47329b9f 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5825,18 +5825,16 @@ 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,
 		       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;
 
 	/*
@@ -5859,7 +5857,7 @@ 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;
 	}
 
@@ -5878,7 +5876,7 @@ 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;
@@ -5905,8 +5903,8 @@ 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)) {
 		/*
@@ -5931,19 +5929,21 @@ 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
@@ -5965,37 +5965,38 @@ 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:
 	/*
@@ -6003,12 +6004,12 @@ 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;
@@ -6272,8 +6273,7 @@ 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);
@@ -6486,8 +6486,7 @@ 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);
-- 
2.43.0