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charset="utf-8" This is a preparation patch for folio_split(). In the upcoming patch folio_split() will share folio unmapping and remapping code with split_huge_page_to_list_to_order(), so move the code to a common function __folio_split() first. Signed-off-by: Zi Yan --- mm/huge_memory.c | 107 +++++++++++++++++++++++++---------------------- 1 file changed, 57 insertions(+), 50 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 0cde13286bb0..e928082be3b2 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3730,57 +3730,9 @@ static int __split_unmapped_folio(struct folio *foli= o, int new_order, return ret; } =20 -/* - * This function splits a large folio into smaller folios of order @new_or= der. - * @page can point to any page of the large folio to split. The split oper= ation - * does not change the position of @page. - * - * Prerequisites: - * - * 1) The caller must hold a reference on the @page's owning folio, also k= nown - * as the large folio. - * - * 2) The large folio must be locked. - * - * 3) The folio must not be pinned. Any unexpected folio references, inclu= ding - * GUP pins, will result in the folio not getting split; instead, the c= aller - * 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 o= rder-1 - * folio only has subpages 0 and 1. File-backed order-1 folios are supp= orted, - * since they do not use _deferred_list. - * - * After splitting, the caller's folio reference will be transferred to @p= age, - * resulting in a raised refcount of @page after this call. The other page= s 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 disappear= ed, - * 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 =3D page_folio(page); struct deferred_split *ds_queue =3D 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); @@ -3996,6 +3948,61 @@ int split_huge_page_to_list_to_order(struct page *pa= ge, struct list_head *list, return ret; } =20 +/* + * This function splits a large folio into smaller folios of order @new_or= der. + * @page can point to any page of the large folio to split. The split oper= ation + * does not change the position of @page. + * + * Prerequisites: + * + * 1) The caller must hold a reference on the @page's owning folio, also k= nown + * as the large folio. + * + * 2) The large folio must be locked. + * + * 3) The folio must not be pinned. Any unexpected folio references, inclu= ding + * GUP pins, will result in the folio not getting split; instead, the c= aller + * 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 o= rder-1 + * folio only has subpages 0 and 1. File-backed order-1 folios are supp= orted, + * since they do not use _deferred_list. + * + * After splitting, the caller's folio reference will be transferred to @p= age, + * resulting in a raised refcount of @page after this call. The other page= s 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 disappear= ed, + * 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 =3D page_folio(page); + + return __folio_split(folio, new_order, page, list); +} + int min_order_for_split(struct folio *folio) { if (folio_test_anon(folio)) --=20 2.45.2