linux-kernel - [RFC PATCH v2 09/47] hugetlb: make huge_pte_lockptr take an explicit shift argument.

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Date:   Fri, 21 Oct 2022 16:36:25 +0000
From:   James Houghton <jthoughton@...gle.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>,
        Muchun Song <songmuchun@...edance.com>,
        Peter Xu <peterx@...hat.com>
Cc:     David Hildenbrand <david@...hat.com>,
        David Rientjes <rientjes@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Mina Almasry <almasrymina@...gle.com>,
        "Zach O'Keefe" <zokeefe@...gle.com>,
        Manish Mishra <manish.mishra@...anix.com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Yang Shi <shy828301@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        James Houghton <jthoughton@...gle.com>
Subject: [RFC PATCH v2 09/47] hugetlb: make huge_pte_lockptr take an explicit
 shift argument.

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@...gle.com>
---
 arch/powerpc/mm/pgtable.c | 3 ++-
 include/linux/hugetlb.h   | 9 ++++-----
 mm/hugetlb.c              | 7 ++++---
 mm/migrate.c              | 3 ++-
 4 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
index cb2dcdb18f8e..035a0df47af0 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 6e0c36b08a0c..db3ed6095b1c 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -934,12 +934,11 @@ 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;
 }
 
@@ -1144,7 +1143,7 @@ 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;
@@ -1206,7 +1205,7 @@ 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;
 }
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index a18143add956..ef7662bd0068 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4847,7 +4847,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
 		}
 
 		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);
 again:
@@ -4925,7 +4925,8 @@ 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)) {
@@ -4979,7 +4980,7 @@ 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
diff --git a/mm/migrate.c b/mm/migrate.c
index 1457cdbb7828..a0105fa6e3b2 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -334,7 +334,8 @@ void __migration_entry_wait_huge(pte_t *ptep, spinlock_t *ptl)
 
 void migration_entry_wait_huge(struct vm_area_struct *vma, pte_t *pte)
 {
-	spinlock_t *ptl = huge_pte_lockptr(hstate_vma(vma), vma->vm_mm, pte);
+	spinlock_t *ptl = huge_pte_lockptr(huge_page_shift(hstate_vma(vma)),
+					   vma->vm_mm, pte);
 
 	__migration_entry_wait_huge(pte, ptl);
 }
-- 
2.38.0.135.g90850a2211-goog