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
* 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)
/**
* 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)
{
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
* 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,
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
* 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,
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().
* [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)
projects / thirdparty / kernel / linux.git / commitdiff
