[PATCH 1/6] hugetlb: open-code hugetlb folio lookup index conversion

[Jane Chu <jane.chu@oracle.com>]

This patch removes `filemap_lock_hugetlb_folio()` and open-codes
the index conversion at each call site, making it explicit when
hugetlb code is translating a hugepage index into the base-page index
expected by `filemap_lock_folio()`.  As part of that cleanup,
it also uses a base-page index directly in `hugetlbfs_zero_partial_page()`,
where the byte offset is already page-granular. Overall, the change
makes the indexing model more obvious at the call sites and avoids
hiding the huge-index to base-index conversion inside a helper.

Suggested-by: David Hildenbrand <david@kernel.org>
Signed-off-by: Jane Chu <jane.chu@oracle.com>
---
 fs/hugetlbfs/inode.c    | 20 ++++++++++----------
 include/linux/hugetlb.h | 12 ------------
 mm/hugetlb.c            |  4 ++--
 3 files changed, 12 insertions(+), 24 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index cd6b22f6e2b1..cf79fb830377 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -242,9 +242,9 @@ static ssize_t hugetlbfs_read_iter(struct kiocb *iocb, struct iov_iter *to)
 	struct hstate *h = hstate_file(file);
 	struct address_space *mapping = file->f_mapping;
 	struct inode *inode = mapping->host;
-	unsigned long index = iocb->ki_pos >> huge_page_shift(h);
+	unsigned long idx = iocb->ki_pos >> huge_page_shift(h);
 	unsigned long offset = iocb->ki_pos & ~huge_page_mask(h);
-	unsigned long end_index;
+	unsigned long end_idx;
 	loff_t isize;
 	ssize_t retval = 0;
 
@@ -257,10 +257,10 @@ static ssize_t hugetlbfs_read_iter(struct kiocb *iocb, struct iov_iter *to)
 		isize = i_size_read(inode);
 		if (!isize)
 			break;
-		end_index = (isize - 1) >> huge_page_shift(h);
-		if (index > end_index)
+		end_idx = (isize - 1) >> huge_page_shift(h);
+		if (idx > end_idx)
 			break;
-		if (index == end_index) {
+		if (idx == end_idx) {
 			nr = ((isize - 1) & ~huge_page_mask(h)) + 1;
 			if (nr <= offset)
 				break;
@@ -268,7 +268,7 @@ static ssize_t hugetlbfs_read_iter(struct kiocb *iocb, struct iov_iter *to)
 		nr = nr - offset;
 
 		/* Find the folio */
-		folio = filemap_lock_hugetlb_folio(h, mapping, index);
+		folio = filemap_lock_folio(mapping, idx << huge_page_order(h));
 		if (IS_ERR(folio)) {
 			/*
 			 * We have a HOLE, zero out the user-buffer for the
@@ -307,10 +307,10 @@ static ssize_t hugetlbfs_read_iter(struct kiocb *iocb, struct iov_iter *to)
 				retval = -EFAULT;
 			break;
 		}
-		index += offset >> huge_page_shift(h);
+		idx += offset >> huge_page_shift(h);
 		offset &= ~huge_page_mask(h);
 	}
-	iocb->ki_pos = ((loff_t)index << huge_page_shift(h)) + offset;
+	iocb->ki_pos = ((loff_t)idx << huge_page_shift(h)) + offset;
 	return retval;
 }
 
@@ -652,10 +652,10 @@ static void hugetlbfs_zero_partial_page(struct hstate *h,
 					loff_t start,
 					loff_t end)
 {
-	pgoff_t idx = start >> huge_page_shift(h);
+	pgoff_t index = start >> PAGE_SHIFT; 
 	struct folio *folio;
 
-	folio = filemap_lock_hugetlb_folio(h, mapping, idx);
+	folio = filemap_lock_folio(mapping, index);
 	if (IS_ERR(folio))
 		return;
 
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 9c098a02a09e..c64c6e5e50f5 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -829,12 +829,6 @@ static inline unsigned int blocks_per_huge_page(struct hstate *h)
 	return huge_page_size(h) / 512;
 }
 
-static inline struct folio *filemap_lock_hugetlb_folio(struct hstate *h,
-				struct address_space *mapping, pgoff_t idx)
-{
-	return filemap_lock_folio(mapping, idx << huge_page_order(h));
-}
-
 #include <asm/hugetlb.h>
 
 #ifndef is_hugepage_only_range
@@ -1106,12 +1100,6 @@ static inline struct hugepage_subpool *hugetlb_folio_subpool(struct folio *folio
 	return NULL;
 }
 
-static inline struct folio *filemap_lock_hugetlb_folio(struct hstate *h,
-				struct address_space *mapping, pgoff_t idx)
-{
-	return NULL;
-}
-
 static inline int isolate_or_dissolve_huge_folio(struct folio *folio,
 						struct list_head *list)
 {
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index a786034ac95c..38b39eaf46cc 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5724,7 +5724,7 @@ static vm_fault_t hugetlb_no_page(struct address_space *mapping,
 	 * before we get page_table_lock.
 	 */
 	new_folio = false;
-	folio = filemap_lock_hugetlb_folio(h, mapping, vmf->pgoff);
+	folio = filemap_lock_folio(mapping, vmf->pgoff << huge_page_order(h));
 	if (IS_ERR(folio)) {
 		size = i_size_read(mapping->host) >> huge_page_shift(h);
 		if (vmf->pgoff >= size)
@@ -6208,7 +6208,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
 
 	if (is_continue) {
 		ret = -EFAULT;
-		folio = filemap_lock_hugetlb_folio(h, mapping, idx);
+		folio = filemap_lock_folio(mapping, idx << huge_page_order(h));
 		if (IS_ERR(folio))
 			goto out;
 		folio_in_pagecache = true;
-- 
2.43.5