mm/huge_memory: move folio split common code to __folio_split() (6384dd1d) · Commits · git / linux-net

mm/huge_memory.c

+62 −50

Original line number	Diff line number	Diff line
		@@ -3869,57 +3869,9 @@ static int __split_unmapped_folio(struct folio *folio, int new_order,
		return ret;
		}

		/*
		* This function splits a large folio into smaller folios of order @new_order.
		* @page can point to any page of the large folio to split. The split operation
		* does not change the position of @page.
		*
		* Prerequisites:
		*
		* 1) The caller must hold a reference on the @page's owning folio, also known
		* as the large folio.
		*
		* 2) The large folio must be locked.
		*
		* 3) The folio must not be pinned. Any unexpected folio references, including
		* GUP pins, will result in the folio not getting split; instead, the caller
		* will receive an -EAGAIN.
		*
		* 4) @new_order > 1, usually. Splitting to order-1 anonymous folios is not
		* supported for non-file-backed folios, because folio->_deferred_list, which
		* is used by partially mapped folios, is stored in subpage 2, but an order-1
		* folio only has subpages 0 and 1. File-backed order-1 folios are supported,
		* since they do not use _deferred_list.
		*
		* After splitting, the caller's folio reference will be transferred to @page,
		* resulting in a raised refcount of @page after this call. The other pages may
		* be freed if they are not mapped.
		*
		* If @list is null, tail pages will be added to LRU list, otherwise, to @list.
		*
		* Pages in @new_order will inherit the mapping, flags, and so on from the
		* huge page.
		*
		* Returns 0 if the huge page was split successfully.
		*
		* Returns -EAGAIN if the folio has unexpected reference (e.g., GUP) or if
		* the folio was concurrently removed from the page cache.
		*
		* Returns -EBUSY when trying to split the huge zeropage, if the folio is
		* under writeback, if fs-specific folio metadata cannot currently be
		* released, or if some unexpected race happened (e.g., anon VMA disappeared,
		* truncation).
		*
		* Callers should ensure that the order respects the address space mapping
		* min-order if one is set for non-anonymous folios.
		*
		* Returns -EINVAL when trying to split to an order that is incompatible
		* with the folio. Splitting to order 0 is compatible with all folios.
		*/
		int split_huge_page_to_list_to_order(struct page page, struct list_head list,
		unsigned int new_order)
		static int __folio_split(struct folio *folio, unsigned int new_order,
		struct page page, struct list_head list)
		{
		struct folio *folio = page_folio(page);
		struct deferred_split *ds_queue = get_deferred_split_queue(folio);
		/* reset xarray order to new order after split */
		XA_STATE_ORDER(xas, &folio->mapping->i_pages, folio->index, new_order);
		@@ -3995,6 +3947,11 @@ int split_huge_page_to_list_to_order(struct page page, struct list_head list,
		mapping = folio->mapping;

		/* Truncated ? */
		/*
		* TODO: add support for large shmem folio in swap cache.
		* When shmem is in swap cache, mapping is NULL and
		* folio_test_swapcache() is true.
		*/
		if (!mapping) {
		ret = -EBUSY;
		goto out;
		@@ -4129,6 +4086,61 @@ int split_huge_page_to_list_to_order(struct page page, struct list_head list,
		return ret;
		}

		/*
		* This function splits a large folio into smaller folios of order @new_order.
		* @page can point to any page of the large folio to split. The split operation
		* does not change the position of @page.
		*
		* Prerequisites:
		*
		* 1) The caller must hold a reference on the @page's owning folio, also known
		* as the large folio.
		*
		* 2) The large folio must be locked.
		*
		* 3) The folio must not be pinned. Any unexpected folio references, including
		* GUP pins, will result in the folio not getting split; instead, the caller
		* will receive an -EAGAIN.
		*
		* 4) @new_order > 1, usually. Splitting to order-1 anonymous folios is not
		* supported for non-file-backed folios, because folio->_deferred_list, which
		* is used by partially mapped folios, is stored in subpage 2, but an order-1
		* folio only has subpages 0 and 1. File-backed order-1 folios are supported,
		* since they do not use _deferred_list.
		*
		* After splitting, the caller's folio reference will be transferred to @page,
		* resulting in a raised refcount of @page after this call. The other pages may
		* be freed if they are not mapped.
		*
		* If @list is null, tail pages will be added to LRU list, otherwise, to @list.
		*
		* Pages in @new_order will inherit the mapping, flags, and so on from the
		* huge page.
		*
		* Returns 0 if the huge page was split successfully.
		*
		* Returns -EAGAIN if the folio has unexpected reference (e.g., GUP) or if
		* the folio was concurrently removed from the page cache.
		*
		* Returns -EBUSY when trying to split the huge zeropage, if the folio is
		* under writeback, if fs-specific folio metadata cannot currently be
		* released, or if some unexpected race happened (e.g., anon VMA disappeared,
		* truncation).
		*
		* Callers should ensure that the order respects the address space mapping
		* min-order if one is set for non-anonymous folios.
		*
		* Returns -EINVAL when trying to split to an order that is incompatible
		* with the folio. Splitting to order 0 is compatible with all folios.
		*/
		int split_huge_page_to_list_to_order(struct page page, struct list_head list,
		unsigned int new_order)
		{
		struct folio *folio = page_folio(page);

		return __folio_split(folio, new_order, page, list);
		}

		int min_order_for_split(struct folio *folio)
		{
		if (folio_test_anon(folio))