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

Oscar Salvador
2026-04-13T16:23:00Z

On Thu, Apr 09, 2026 at 05:41:52PM -0600, Jane Chu wrote:
> 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>

It kind of funny that most of the patch is s/index/idx noise.
Checking mm/hugetlb* and fs/hugetlb/* we do have a mix of index/idx but
I would say that idx predominates, so I am ok with going with that one.

Acked-by: Oscar Salvador <osalvador@suse.de>

> ---
> 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
>

--
Oscar Salvador
SUSE Labs