Re: [PATCH 2/2] mm/hugetlb: add wrapper functions for interactions with page cache

[Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>]

On 6/9/23 12:49 PM, Sidhartha Kumar wrote:
> Signed-off-by: Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>

Sorry, I missed adding the commit message to this. It should be:

Add filemap_lock_hugetlb_folio() which is wraps __filemap_get_folio()
and passes in a linear page index. hugetlb_add_to_page_cache() is modified
to also compute a linear page index before calling into page cache code.

linear_page_index() is modified to perform the computation on hugetlb
so we can use it in the page cache wrappers.

> ---
>   fs/hugetlbfs/inode.c    | 14 +++++++-------
>   include/linux/hugetlb.h | 21 +++++++++++++++++++--
>   include/linux/pagemap.h |  2 --
>   mm/hugetlb.c            | 22 +++++++++++++---------
>   4 files changed, 39 insertions(+), 20 deletions(-)
>
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 90361a922cec7..90d27a8af4b6a 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -617,20 +617,19 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
>   	struct hstate *h = hstate_inode(inode);
>   	struct address_space *mapping = &inode->i_data;
>   	const pgoff_t start = lstart >> huge_page_shift(h);
> -	const pgoff_t end = lend >> huge_page_shift(h);
>   	struct folio_batch fbatch;
>   	pgoff_t next, index;
>   	int i, freed = 0;
>   	bool truncate_op = (lend == LLONG_MAX);
>   
>   	folio_batch_init(&fbatch);
> -	next = start;
> -	while (filemap_get_folios(mapping, &next, end - 1, &fbatch)) {
> +	next = lstart;
> +	while (filemap_get_folios(mapping, &next, lend - 1, &fbatch)) {
>   		for (i = 0; i < folio_batch_count(&fbatch); ++i) {
>   			struct folio *folio = fbatch.folios[i];
>   			u32 hash = 0;
>   
> -			index = folio->index;
> +			index = (folio->index) >> huge_page_shift(h);
>   			hash = hugetlb_fault_mutex_hash(mapping, index);
>   			mutex_lock(&hugetlb_fault_mutex_table[hash]);
>   
> @@ -693,10 +692,11 @@ static void hugetlbfs_zero_partial_page(struct hstate *h,
>   					loff_t start,
>   					loff_t end)
>   {
> -	pgoff_t idx = start >> huge_page_shift(h);
> +	struct mm_struct *mm = current->mm;
> +	struct vm_area_struct *vma = find_vma(mm, start);
>   	struct folio *folio;
>   
> -	folio = filemap_lock_folio(mapping, idx);
> +	folio = filemap_lock_hugetlb_folio(vma, start);
>   	if (IS_ERR(folio))
>   		return;
>   
> @@ -868,7 +868,7 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
>   		}
>   		clear_huge_page(&folio->page, addr, pages_per_huge_page(h));
>   		__folio_mark_uptodate(folio);
> -		error = hugetlb_add_to_page_cache(folio, mapping, index);
> +		error = hugetlb_add_to_page_cache(folio, &pseudo_vma, mapping, addr);
>   		if (unlikely(error)) {
>   			restore_reserve_on_error(h, &pseudo_vma, addr, folio);
>   			folio_put(folio);
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 21f942025fecd..55f90e051b7a2 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -727,8 +727,8 @@ struct folio *alloc_hugetlb_folio_nodemask(struct hstate *h, int preferred_nid,
>   				nodemask_t *nmask, gfp_t gfp_mask);
>   struct folio *alloc_hugetlb_folio_vma(struct hstate *h, struct vm_area_struct *vma,
>   				unsigned long address);
> -int hugetlb_add_to_page_cache(struct folio *folio, struct address_space *mapping,
> -			pgoff_t idx);
> +int hugetlb_add_to_page_cache(struct folio *folio, struct vm_area_struct *vma,
> +				struct address_space *mapping, unsigned long address);
>   void restore_reserve_on_error(struct hstate *h, struct vm_area_struct *vma,
>   				unsigned long address, struct folio *folio);
>   
> @@ -755,6 +755,16 @@ static inline struct hugepage_subpool *hugetlb_folio_subpool(struct folio *folio
>   	return folio->_hugetlb_subpool;
>   }
>   
> +/* Wrapper function for __filemap_get_folio*/
> +static inline struct folio *filemap_lock_hugetlb_folio(struct vm_area_struct *vma,
> +						unsigned long address)
> +{
> +	struct address_space *mapping = vma->vm_file->f_mapping;
> +
> +	pgoff_t idx = linear_page_index(vma, address);
> +	return __filemap_get_folio(mapping, idx, FGP_LOCK, 0);
> +}
> +
>   static inline void hugetlb_set_folio_subpool(struct folio *folio,
>   					struct hugepage_subpool *subpool)
>   {
> @@ -1021,6 +1031,13 @@ static inline struct hugepage_subpool *hugetlb_folio_subpool(struct folio *folio
>   	return NULL;
>   }
>   
> +/* Wrapper function for __filemap_get_folio*/
> +static inline struct folio *filemap_lock_hugetlb_folio(struct vm_area_struct *vma,
> +						unsigned long address)
> +{
> +	return NULL;
> +}
> +
>   static inline int isolate_or_dissolve_huge_page(struct page *page,
>   						struct list_head *list)
>   {
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index 17c414fc2136e..ae8f36966d7b3 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -860,8 +860,6 @@ 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 dfa412d8cb300..824d6d215a161 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -951,7 +951,7 @@ static long region_count(struct resv_map *resv, long f, long t)
>   
>   /*
>    * Convert the address within this vma to the page offset within
> - * the mapping, in pagecache page units; huge pages here.
> + * the mapping, in huge page units here.
>    */
>   static pgoff_t vma_hugecache_offset(struct hstate *h,
>   			struct vm_area_struct *vma, unsigned long address)
> @@ -5730,7 +5730,7 @@ 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();
> @@ -5740,13 +5740,16 @@ static bool hugetlbfs_pagecache_present(struct hstate *h,
>   	return present;
>   }
>   
> -int hugetlb_add_to_page_cache(struct folio *folio, struct address_space *mapping,
> -			   pgoff_t idx)
> +int hugetlb_add_to_page_cache(struct folio *folio,
> +			struct vm_area_struct *vma,
> +			struct address_space *mapping,
> +			unsigned long address)
>   {
>   	struct inode *inode = mapping->host;
>   	struct hstate *h = hstate_inode(inode);
>   	int err;
>   
> +	pgoff_t idx = linear_page_index(vma, address);
>   	__folio_set_locked(folio);
>   	err = __filemap_add_folio(mapping, folio, idx, GFP_KERNEL, NULL);
>   
> @@ -5854,7 +5857,8 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
>   	 * before we get page_table_lock.
>   	 */
>   	new_folio = false;
> -	folio = filemap_lock_folio(mapping, idx);
> +
> +	folio = filemap_lock_hugetlb_folio(vma, address);
>   	if (IS_ERR(folio)) {
>   		size = i_size_read(mapping->host) >> huge_page_shift(h);
>   		if (idx >= size)
> @@ -5913,7 +5917,7 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
>   		new_folio = true;
>   
>   		if (vma->vm_flags & VM_MAYSHARE) {
> -			int err = hugetlb_add_to_page_cache(folio, mapping, idx);
> +			int err = hugetlb_add_to_page_cache(folio, vma, mapping, address);
>   			if (err) {
>   				/*
>   				 * err can't be -EEXIST which implies someone
> @@ -6145,7 +6149,7 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
>   		/* Just decrements count, does not deallocate */
>   		vma_end_reservation(h, vma, haddr);
>   
> -		pagecache_folio = filemap_lock_folio(mapping, idx);
> +		pagecache_folio = filemap_lock_hugetlb_folio(vma, address);
>   		if (IS_ERR(pagecache_folio))
>   			pagecache_folio = NULL;
>   	}
> @@ -6258,7 +6262,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
>   
>   	if (is_continue) {
>   		ret = -EFAULT;
> -		folio = filemap_lock_folio(mapping, idx);
> +		folio = filemap_lock_hugetlb_folio(dst_vma, dst_addr);
>   		if (IS_ERR(folio))
>   			goto out;
>   		folio_in_pagecache = true;
> @@ -6350,7 +6354,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
>   		 * hugetlb_fault_mutex_table that here must be hold by
>   		 * the caller.
>   		 */
> -		ret = hugetlb_add_to_page_cache(folio, mapping, idx);
> +		ret = hugetlb_add_to_page_cache(folio, dst_vma, mapping, dst_addr);
>   		if (ret)
>   			goto out_release_nounlock;
>   		folio_in_pagecache = true;