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From:   Sidhartha Kumar <sidhartha.kumar@oracle.com>
To:     linux-kernel@vger.kernel.org, linux-mm@kvack.org
Cc:     akpm@linux-foundation.org, songmuchun@bytedance.com,
        mike.kravetz@oracle.com, willy@infradead.org,
        Sidhartha Kumar <sidhartha.kumar@oracle.com>
Subject: [RFC PATCH 2/4] mm/hugetlb: remove hugetlb_basepage_index()
Date:   Thu, 13 Apr 2023 16:14:50 -0700
Message-Id: <20230413231452.84529-3-sidhartha.kumar@oracle.com>
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hugetlb_basepage_index() can now be removed as hugetlb pages have ->index
in PAGE_SIZE. This also allows removals of vma_hugecache_offset() and
linear_hugepage_index() which are replaced by calls to
linear_page_index().

Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
---
 include/linux/pagemap.h |  7 ------
 mm/hugetlb.c            | 50 ++++++++---------------------------------
 2 files changed, 9 insertions(+), 48 deletions(-)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 330b1db913f5a..bb60282317875 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -792,16 +792,11 @@ static inline pgoff_t page_to_index(struct page *page)
 	return head->index + page - head;
 }
 
-extern pgoff_t hugetlb_basepage_index(struct page *page);
-
 /*
  * Get the offset in PAGE_SIZE (even for hugetlb pages).
- * (TODO: hugetlb pages should have ->index in PAGE_SIZE)
  */
 static inline pgoff_t page_to_pgoff(struct page *page)
 {
-	if (unlikely(PageHuge(page)))
-		return hugetlb_basepage_index(page);
 	return page_to_index(page);
 }
 
@@ -854,8 +849,6 @@ static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
 					unsigned long address)
 {
 	pgoff_t pgoff;
-	if (unlikely(is_vm_hugetlb_page(vma)))
-		return linear_hugepage_index(vma, address);
 	pgoff = (address - vma->vm_start) >> PAGE_SHIFT;
 	pgoff += vma->vm_pgoff;
 	return pgoff;
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index f16b25b1a6b93..011020a30f4ac 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -949,24 +949,6 @@ static long region_count(struct resv_map *resv, long f, long t)
 	return chg;
 }
 
-/*
- * Convert the address within this vma to the page offset within
- * the mapping, in pagecache page units; huge pages here.
- */
-static pgoff_t vma_hugecache_offset(struct hstate *h,
-			struct vm_area_struct *vma, unsigned long address)
-{
-	return ((address - vma->vm_start) >> huge_page_shift(h)) +
-			(vma->vm_pgoff >> huge_page_order(h));
-}
-
-pgoff_t linear_hugepage_index(struct vm_area_struct *vma,
-				     unsigned long address)
-{
-	return vma_hugecache_offset(hstate_vma(vma), vma, address);
-}
-EXPORT_SYMBOL_GPL(linear_hugepage_index);
-
 /*
  * Return the size of the pages allocated when backing a VMA. In the majority
  * cases this will be same size as used by the page table entries.
@@ -2087,21 +2069,6 @@ struct address_space *hugetlb_page_mapping_lock_write(struct page *hpage)
 
 	return NULL;
 }
-
-pgoff_t hugetlb_basepage_index(struct page *page)
-{
-	struct page *page_head = compound_head(page);
-	pgoff_t index = page_index(page_head);
-	unsigned long compound_idx;
-
-	if (compound_order(page_head) > MAX_ORDER)
-		compound_idx = page_to_pfn(page) - page_to_pfn(page_head);
-	else
-		compound_idx = page - page_head;
-
-	return (index << compound_order(page_head)) + compound_idx;
-}
-
 static struct folio *alloc_buddy_hugetlb_folio(struct hstate *h,
 		gfp_t gfp_mask, int nid, nodemask_t *nmask,
 		nodemask_t *node_alloc_noretry)
@@ -2703,7 +2670,7 @@ static long __vma_reservation_common(struct hstate *h,
 	if (!resv)
 		return 1;
 
-	idx = vma_hugecache_offset(h, vma, addr);
+	idx = linear_page_index(vma, addr);
 	switch (mode) {
 	case VMA_NEEDS_RESV:
 		ret = region_chg(resv, idx, idx + 1, &dummy_out_regions_needed);
@@ -4810,6 +4777,7 @@ static void hugetlb_vm_op_open(struct vm_area_struct *vma)
 static void hugetlb_vm_op_close(struct vm_area_struct *vma)
 {
 	struct hstate *h = hstate_vma(vma);
+	unsigned int order = huge_page_order(h);
 	struct resv_map *resv;
 	struct hugepage_subpool *spool = subpool_vma(vma);
 	unsigned long reserve, start, end;
@@ -4821,11 +4789,11 @@ static void hugetlb_vm_op_close(struct vm_area_struct *vma)
 	if (!resv || !is_vma_resv_set(vma, HPAGE_RESV_OWNER))
 		return;
 
-	start = vma_hugecache_offset(h, vma, vma->vm_start);
-	end = vma_hugecache_offset(h, vma, vma->vm_end);
+	start = linear_page_index(vma, vma->vm_start);
+	end = linear_page_index(vma, vma->vm_end);
 
 	reserve = (end - start) - region_count(resv, start, end);
-	hugetlb_cgroup_uncharge_counter(resv, start, end);
+	hugetlb_cgroup_uncharge_counter(resv, start >> order, end >> order);
 	if (reserve) {
 		/*
 		 * Decrement reserve counts.  The global reserve count may be
@@ -5582,7 +5550,7 @@ 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 = linear_page_index(vma, address);
 			hash = hugetlb_fault_mutex_hash(mapping, idx);
 			hugetlb_vma_unlock_read(vma);
 			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
@@ -5669,7 +5637,7 @@ static bool hugetlbfs_pagecache_present(struct hstate *h,
 			struct vm_area_struct *vma, unsigned long address)
 {
 	struct address_space *mapping = vma->vm_file->f_mapping;
-	pgoff_t idx = vma_hugecache_offset(h, vma, address);
+	pgoff_t idx = linear_page_index(vma, address);
 	bool present;
 
 	rcu_read_lock();
@@ -6014,7 +5982,7 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 	 * the same page in the page cache.
 	 */
 	mapping = vma->vm_file->f_mapping;
-	idx = vma_hugecache_offset(h, vma, haddr);
+	idx = linear_page_index(vma, address);
 	hash = hugetlb_fault_mutex_hash(mapping, idx);
 	mutex_lock(&hugetlb_fault_mutex_table[hash]);
 
@@ -6185,7 +6153,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
 	bool wp_enabled = (flags & MFILL_ATOMIC_WP);
 	struct hstate *h = hstate_vma(dst_vma);
 	struct address_space *mapping = dst_vma->vm_file->f_mapping;
-	pgoff_t idx = vma_hugecache_offset(h, dst_vma, dst_addr);
+	pgoff_t idx = linear_page_index(dst_vma, dst_addr);
 	unsigned long size;
 	int vm_shared = dst_vma->vm_flags & VM_SHARED;
 	pte_t _dst_pte;
-- 
2.39.2