diff options
| -rw-r--r-- | include/linux/huge_mm.h | 10 | ||||
| -rw-r--r-- | mm/huge_memory.c | 52 |
2 files changed, 34 insertions, 28 deletions
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index a06924cf4065..9f7f7d772fe5 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -386,9 +386,9 @@ static inline int split_huge_page_to_order(struct page *page, unsigned int new_o return split_huge_page_to_list_to_order(page, NULL, new_order); } -/* - * try_folio_split_to_order - try to split a @folio at @page to @new_order using - * non uniform split. +/** + * try_folio_split_to_order() - try to split a @folio at @page to @new_order + * using non uniform split. * @folio: folio to be split * @page: split to @new_order at the given page * @new_order: the target split order @@ -398,7 +398,7 @@ static inline int split_huge_page_to_order(struct page *page, unsigned int new_o * folios are put back to LRU list. Use min_order_for_split() to get the lower * bound of @new_order. * - * Return: 0: split is successful, otherwise split failed. + * Return: 0 - split is successful, otherwise split failed. */ static inline int try_folio_split_to_order(struct folio *folio, struct page *page, unsigned int new_order) @@ -483,6 +483,8 @@ static inline spinlock_t *pud_trans_huge_lock(pud_t *pud, /** * folio_test_pmd_mappable - Can we map this folio with a PMD? * @folio: The folio to test + * + * Return: true - @folio can be mapped, false - @folio cannot be mapped. */ static inline bool folio_test_pmd_mappable(struct folio *folio) { diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 30d6afc79016..3d87127c02cf 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3493,8 +3493,9 @@ static void __split_folio_to_order(struct folio *folio, int old_order, ClearPageCompound(&folio->page); } -/* - * It splits an unmapped @folio to lower order smaller folios in two ways. +/** + * __split_unmapped_folio() - splits an unmapped @folio to lower order folios in + * two ways: uniform split or non-uniform split. * @folio: the to-be-split folio * @new_order: the smallest order of the after split folios (since buddy * allocator like split generates folios with orders from @folio's @@ -3511,26 +3512,27 @@ static void __split_folio_to_order(struct folio *folio, int old_order, * uniform_split is true. * 2. buddy allocator like (non-uniform) split: the given @folio is split into * half and one of the half (containing the given page) is split into half - * until the given @page's order becomes @new_order. This is done when + * until the given @folio's order becomes @new_order. This is done when * uniform_split is false. * * The high level flow for these two methods are: - * 1. uniform split: a single __split_folio_to_order() is called to split the - * @folio into @new_order, then we traverse all the resulting folios one by - * one in PFN ascending order and perform stats, unfreeze, adding to list, - * and file mapping index operations. - * 2. non-uniform split: in general, folio_order - @new_order calls to - * __split_folio_to_order() are made in a for loop to split the @folio - * to one lower order at a time. The resulting small folios are processed - * like what is done during the traversal in 1, except the one containing - * @page, which is split in next for loop. + * + * 1. uniform split: @xas is split with no expectation of failure and a single + * __split_folio_to_order() is called to split the @folio into @new_order + * along with stats update. + * 2. non-uniform split: folio_order - @new_order calls to + * __split_folio_to_order() are expected to be made in a for loop to split + * the @folio to one lower order at a time. The folio containing @split_at + * is split in each iteration. @xas is split into half in each iteration and + * can fail. A failed @xas split leaves split folios as is without merging + * them back. * * After splitting, the caller's folio reference will be transferred to the - * folio containing @page. The caller needs to unlock and/or free after-split - * folios if necessary. + * folio containing @split_at. The caller needs to unlock and/or free + * after-split folios if necessary. * - * For !uniform_split, when -ENOMEM is returned, the original folio might be - * split. The caller needs to check the input folio. + * Return: 0 - successful, <0 - failed (if -ENOMEM is returned, @folio might be + * split but not to @new_order, the caller needs to check) */ static int __split_unmapped_folio(struct folio *folio, int new_order, struct page *split_at, struct xa_state *xas, @@ -3650,8 +3652,8 @@ bool uniform_split_supported(struct folio *folio, unsigned int new_order, return true; } -/* - * __folio_split: split a folio at @split_at to a @new_order folio +/** + * __folio_split() - split a folio at @split_at to a @new_order folio * @folio: folio to split * @new_order: the order of the new folio * @split_at: a page within the new folio @@ -3669,7 +3671,7 @@ bool uniform_split_supported(struct folio *folio, unsigned int new_order, * 1. for uniform split, @lock_at points to one of @folio's subpages; * 2. for buddy allocator like (non-uniform) split, @lock_at points to @folio. * - * return: 0: successful, <0 failed (if -ENOMEM is returned, @folio might be + * Return: 0 - successful, <0 - failed (if -ENOMEM is returned, @folio might be * split but not to @new_order, the caller needs to check) */ static int __folio_split(struct folio *folio, unsigned int new_order, @@ -4047,14 +4049,13 @@ int __split_huge_page_to_list_to_order(struct page *page, struct list_head *list unmapped); } -/* - * folio_split: split a folio at @split_at to a @new_order folio +/** + * folio_split() - split a folio at @split_at to a @new_order folio * @folio: folio to split * @new_order: the order of the new folio * @split_at: a page within the new folio - * - * return: 0: successful, <0 failed (if -ENOMEM is returned, @folio might be - * split but not to @new_order, the caller needs to check) + * @list: after-split folios are added to @list if not null, otherwise to LRU + * list * * It has the same prerequisites and returns as * split_huge_page_to_list_to_order(). @@ -4068,6 +4069,9 @@ int __split_huge_page_to_list_to_order(struct page *page, struct list_head *list * [order-4, {order-3}, order-3, order-5, order-6, order-7, order-8]. * * After split, folio is left locked for caller. + * + * Return: 0 - successful, <0 - failed (if -ENOMEM is returned, @folio might be + * split but not to @new_order, the caller needs to check) */ int folio_split(struct folio *folio, unsigned int new_order, struct page *split_at, struct list_head *list) |