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Date:   Fri, 24 Jun 2022 17:36:34 +0000
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Subject: [RFC PATCH 04/26] hugetlb: make huge_pte_lockptr take an explicit
 shift argument.
From:   James Houghton <jthoughton@google.com>
To:     Mike Kravetz <mike.kravetz@oracle.com>,
        Muchun Song <songmuchun@bytedance.com>,
        Peter Xu <peterx@redhat.com>
Cc:     David Hildenbrand <david@redhat.com>,
        David Rientjes <rientjes@google.com>,
        Axel Rasmussen <axelrasmussen@google.com>,
        Mina Almasry <almasrymina@google.com>,
        Jue Wang <juew@google.com>,
        Manish Mishra <manish.mishra@nutanix.com>,
        "Dr . David Alan Gilbert" <dgilbert@redhat.com>,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        James Houghton <jthoughton@google.com>
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Precedence: bulk

This is needed to handle PTL locking with high-granularity mapping. We
won't always be using the PMD-level PTL even if we're using the 2M
hugepage hstate. It's possible that we're dealing with 4K PTEs, in which
case, we need to lock the PTL for the 4K PTE.

Signed-off-by: James Houghton <jthoughton@google.com>
---
 arch/powerpc/mm/pgtable.c |  3 ++-
 include/linux/hugetlb.h   | 19 ++++++++++++++-----
 mm/hugetlb.c              |  9 +++++----
 mm/migrate.c              |  3 ++-
 mm/page_vma_mapped.c      |  3 ++-
 5 files changed, 25 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
index e6166b71d36d..663d591a8f08 100644
--- a/arch/powerpc/mm/pgtable.c
+++ b/arch/powerpc/mm/pgtable.c
@@ -261,7 +261,8 @@ int huge_ptep_set_access_flags(struct vm_area_struct *vma,
 
 		psize = hstate_get_psize(h);
 #ifdef CONFIG_DEBUG_VM
-		assert_spin_locked(huge_pte_lockptr(h, vma->vm_mm, ptep));
+		assert_spin_locked(huge_pte_lockptr(huge_page_shift(h),
+						    vma->vm_mm, ptep));
 #endif
 
 #else
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 498a4ae3d462..5fe1db46d8c9 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -868,12 +868,11 @@ static inline gfp_t htlb_modify_alloc_mask(struct hstate *h, gfp_t gfp_mask)
 	return modified_mask;
 }
 
-static inline spinlock_t *huge_pte_lockptr(struct hstate *h,
+static inline spinlock_t *huge_pte_lockptr(unsigned int shift,
 					   struct mm_struct *mm, pte_t *pte)
 {
-	if (huge_page_size(h) == PMD_SIZE)
+	if (shift == PMD_SHIFT)
 		return pmd_lockptr(mm, (pmd_t *) pte);
-	VM_BUG_ON(huge_page_size(h) == PAGE_SIZE);
 	return &mm->page_table_lock;
 }
 
@@ -1076,7 +1075,7 @@ static inline gfp_t htlb_modify_alloc_mask(struct hstate *h, gfp_t gfp_mask)
 	return 0;
 }
 
-static inline spinlock_t *huge_pte_lockptr(struct hstate *h,
+static inline spinlock_t *huge_pte_lockptr(unsigned int shift,
 					   struct mm_struct *mm, pte_t *pte)
 {
 	return &mm->page_table_lock;
@@ -1116,7 +1115,17 @@ static inline spinlock_t *huge_pte_lock(struct hstate *h,
 {
 	spinlock_t *ptl;
 
-	ptl = huge_pte_lockptr(h, mm, pte);
+	ptl = huge_pte_lockptr(huge_page_shift(h), mm, pte);
+	spin_lock(ptl);
+	return ptl;
+}
+
+static inline spinlock_t *huge_pte_lock_shift(unsigned int shift,
+					      struct mm_struct *mm, pte_t *pte)
+{
+	spinlock_t *ptl;
+
+	ptl = huge_pte_lockptr(shift, mm, pte);
 	spin_lock(ptl);
 	return ptl;
 }
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 0eec34edf3b2..d6d0d4c03def 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4817,7 +4817,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 			continue;
 
 		dst_ptl = huge_pte_lock(h, dst, dst_pte);
-		src_ptl = huge_pte_lockptr(h, src, src_pte);
+		src_ptl = huge_pte_lockptr(huge_page_shift(h), src, src_pte);
 		spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
 		entry = huge_ptep_get(src_pte);
 		dst_entry = huge_ptep_get(dst_pte);
@@ -4894,7 +4894,8 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 
 				/* Install the new huge page if src pte stable */
 				dst_ptl = huge_pte_lock(h, dst, dst_pte);
-				src_ptl = huge_pte_lockptr(h, src, src_pte);
+				src_ptl = huge_pte_lockptr(huge_page_shift(h),
+							   src, src_pte);
 				spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
 				entry = huge_ptep_get(src_pte);
 				if (!pte_same(src_pte_old, entry)) {
@@ -4948,7 +4949,7 @@ static void move_huge_pte(struct vm_area_struct *vma, unsigned long old_addr,
 	pte_t pte;
 
 	dst_ptl = huge_pte_lock(h, mm, dst_pte);
-	src_ptl = huge_pte_lockptr(h, mm, src_pte);
+	src_ptl = huge_pte_lockptr(huge_page_shift(h), mm, src_pte);
 
 	/*
 	 * We don't have to worry about the ordering of src and dst ptlocks
@@ -6024,7 +6025,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
 		page_in_pagecache = true;
 	}
 
-	ptl = huge_pte_lockptr(h, dst_mm, dst_pte);
+	ptl = huge_pte_lockptr(huge_page_shift(h), dst_mm, dst_pte);
 	spin_lock(ptl);
 
 	/*
diff --git a/mm/migrate.c b/mm/migrate.c
index e51588e95f57..a8a960992373 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -318,7 +318,8 @@ void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
 void migration_entry_wait_huge(struct vm_area_struct *vma,
 		struct mm_struct *mm, pte_t *pte)
 {
-	spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), mm, pte);
+	spinlock_t *ptl = huge_pte_lockptr(huge_page_shift(hstate_vma(vma)),
+					   mm, pte);
 	__migration_entry_wait(mm, pte, ptl);
 }
 
diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index c10f839fc410..8921dd4e41b1 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -174,7 +174,8 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
 		if (!pvmw->pte)
 			return false;
 
-		pvmw->ptl = huge_pte_lockptr(hstate, mm, pvmw->pte);
+		pvmw->ptl = huge_pte_lockptr(huge_page_shift(hstate),
+					     mm, pvmw->pte);
 		spin_lock(pvmw->ptl);
 		if (!check_pte(pvmw))
 			return not_found(pvmw);
-- 
2.37.0.rc0.161.g10f37bed90-goog