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

jane.chu
2026-04-13T16:31:14Z

On 4/13/2026 9:22 AM, Oscar Salvador wrote:
> 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.

Indeed the situation that both idx/index can represent both huge page
index and base page index had led me intentionally memorize which is
representing what in a given local context. I thought that to denote
'index' to base page granularity and 'idx' to huge page granularity
could relax the readers.

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

thanks,
-jane

>
>
>> ---
>> 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
>>
>