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-rw-r--r--mm/huge_memory.c107
1 files changed, 83 insertions, 24 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index b2df788c11faf..006b192ea6ab9 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2770,7 +2770,6 @@ static void lru_add_page_tail(struct page *head, struct page *tail,
struct lruvec *lruvec, struct list_head *list)
{
VM_BUG_ON_PAGE(!PageHead(head), head);
- VM_BUG_ON_PAGE(PageCompound(tail), head);
VM_BUG_ON_PAGE(PageLRU(tail), head);
lockdep_assert_held(&lruvec->lru_lock);
@@ -2791,7 +2790,8 @@ static void lru_add_page_tail(struct page *head, struct page *tail,
}
static void __split_huge_page_tail(struct folio *folio, int tail,
- struct lruvec *lruvec, struct list_head *list)
+ struct lruvec *lruvec, struct list_head *list,
+ unsigned int new_order)
{
struct page *head = &folio->page;
struct page *page_tail = head + tail;
@@ -2861,10 +2861,15 @@ static void __split_huge_page_tail(struct folio *folio, int tail,
* which needs correct compound_head().
*/
clear_compound_head(page_tail);
+ if (new_order) {
+ prep_compound_page(page_tail, new_order);
+ folio_prep_large_rmappable(new_folio);
+ }
/* Finally unfreeze refcount. Additional reference from page cache. */
- page_ref_unfreeze(page_tail, 1 + (!folio_test_anon(folio) ||
- folio_test_swapcache(folio)));
+ page_ref_unfreeze(page_tail,
+ 1 + ((!folio_test_anon(folio) || folio_test_swapcache(folio)) ?
+ folio_nr_pages(new_folio) : 0));
if (folio_test_young(folio))
folio_set_young(new_folio);
@@ -2882,7 +2887,7 @@ static void __split_huge_page_tail(struct folio *folio, int tail,
}
static void __split_huge_page(struct page *page, struct list_head *list,
- pgoff_t end)
+ pgoff_t end, unsigned int new_order)
{
struct folio *folio = page_folio(page);
struct page *head = &folio->page;
@@ -2890,11 +2895,12 @@ static void __split_huge_page(struct page *page, struct list_head *list,
struct address_space *swap_cache = NULL;
unsigned long offset = 0;
int i, nr_dropped = 0;
+ unsigned int new_nr = 1 << new_order;
int order = folio_order(folio);
unsigned int nr = 1 << order;
/* complete memcg works before add pages to LRU */
- split_page_memcg(head, order, 0);
+ split_page_memcg(head, order, new_order);
if (folio_test_anon(folio) && folio_test_swapcache(folio)) {
offset = swp_offset(folio->swap);
@@ -2907,8 +2913,8 @@ static void __split_huge_page(struct page *page, struct list_head *list,
ClearPageHasHWPoisoned(head);
- for (i = nr - 1; i >= 1; i--) {
- __split_huge_page_tail(folio, i, lruvec, list);
+ for (i = nr - new_nr; i >= new_nr; i -= new_nr) {
+ __split_huge_page_tail(folio, i, lruvec, list, new_order);
/* Some pages can be beyond EOF: drop them from page cache */
if (head[i].index >= end) {
struct folio *tail = page_folio(head + i);
@@ -2929,24 +2935,30 @@ static void __split_huge_page(struct page *page, struct list_head *list,
}
}
- ClearPageCompound(head);
+ if (!new_order)
+ ClearPageCompound(head);
+ else {
+ struct folio *new_folio = (struct folio *)head;
+
+ folio_set_order(new_folio, new_order);
+ }
unlock_page_lruvec(lruvec);
/* Caller disabled irqs, so they are still disabled here */
- split_page_owner(head, order, 0);
+ split_page_owner(head, order, new_order);
/* See comment in __split_huge_page_tail() */
if (PageAnon(head)) {
/* Additional pin to swap cache */
if (PageSwapCache(head)) {
- page_ref_add(head, 2);
+ page_ref_add(head, 1 + new_nr);
xa_unlock(&swap_cache->i_pages);
} else {
page_ref_inc(head);
}
} else {
/* Additional pin to page cache */
- page_ref_add(head, 2);
+ page_ref_add(head, 1 + new_nr);
xa_unlock(&head->mapping->i_pages);
}
local_irq_enable();
@@ -2958,7 +2970,15 @@ static void __split_huge_page(struct page *page, struct list_head *list,
if (folio_test_swapcache(folio))
split_swap_cluster(folio->swap);
- for (i = 0; i < nr; i++) {
+ /*
+ * set page to its compound_head when split to non order-0 pages, so
+ * we can skip unlocking it below, since PG_locked is transferred to
+ * the compound_head of the page and the caller will unlock it.
+ */
+ if (new_order)
+ page = compound_head(page);
+
+ for (i = 0; i < nr; i += new_nr) {
struct page *subpage = head + i;
if (subpage == page)
continue;
@@ -2992,29 +3012,36 @@ bool can_split_folio(struct folio *folio, int *pextra_pins)
}
/*
- * This function splits huge page into normal pages. @page can point to any
- * subpage of huge page to split. Split doesn't change the position of @page.
+ * This function splits huge page into pages in @new_order. @page can point to
+ * any subpage of huge page to split. Split doesn't change the position of
+ * @page.
+ *
+ * NOTE: order-1 anonymous folio is not supported because _deferred_list,
+ * which is used by partially mapped folios, is stored in subpage 2 and an
+ * order-1 folio only has subpage 0 and 1. File-backed order-1 folios are OK,
+ * since they do not use _deferred_list.
*
* Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
* The huge page must be locked.
*
* If @list is null, tail pages will be added to LRU list, otherwise, to @list.
*
- * Both head page and tail pages will inherit mapping, flags, and so on from
- * the hugepage.
+ * Pages in new_order will inherit mapping, flags, and so on from the hugepage.
*
- * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
- * they are not mapped.
+ * GUP pin and PG_locked transferred to @page or the compound page @page belongs
+ * to. Rest subpages can be freed if they are not mapped.
*
* Returns 0 if the hugepage is split successfully.
* Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
* us.
*/
-int split_huge_page_to_list(struct page *page, struct list_head *list)
+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);
struct deferred_split *ds_queue = get_deferred_split_queue(folio);
- XA_STATE(xas, &folio->mapping->i_pages, folio->index);
+ /* reset xarray order to new order after split */
+ XA_STATE_ORDER(xas, &folio->mapping->i_pages, folio->index, new_order);
struct anon_vma *anon_vma = NULL;
struct address_space *mapping = NULL;
int extra_pins, ret;
@@ -3024,6 +3051,31 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
+ /* Cannot split anonymous THP to order-1 */
+ if (new_order == 1 && folio_test_anon(folio)) {
+ VM_WARN_ONCE(1, "Cannot split to order-1 folio");
+ return -EINVAL;
+ }
+
+ if (new_order) {
+ /* Only swapping a whole PMD-mapped folio is supported */
+ if (folio_test_swapcache(folio))
+ return -EINVAL;
+ /* Split shmem folio to non-zero order not supported */
+ if (shmem_mapping(folio->mapping)) {
+ VM_WARN_ONCE(1,
+ "Cannot split shmem folio to non-0 order");
+ return -EINVAL;
+ }
+ /* No split if the file system does not support large folio */
+ if (!mapping_large_folio_support(folio->mapping)) {
+ VM_WARN_ONCE(1,
+ "Cannot split file folio to non-0 order");
+ return -EINVAL;
+ }
+ }
+
+
is_hzp = is_huge_zero_page(&folio->page);
if (is_hzp) {
pr_warn_ratelimited("Called split_huge_page for huge zero page\n");
@@ -3120,14 +3172,21 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
if (folio_order(folio) > 1 &&
!list_empty(&folio->_deferred_list)) {
ds_queue->split_queue_len--;
- list_del(&folio->_deferred_list);
+ /*
+ * Reinitialize page_deferred_list after removing the
+ * page from the split_queue, otherwise a subsequent
+ * split will see list corruption when checking the
+ * page_deferred_list.
+ */
+ list_del_init(&folio->_deferred_list);
}
spin_unlock(&ds_queue->split_queue_lock);
if (mapping) {
int nr = folio_nr_pages(folio);
xas_split(&xas, folio, folio_order(folio));
- if (folio_test_pmd_mappable(folio)) {
+ if (folio_test_pmd_mappable(folio) &&
+ new_order < HPAGE_PMD_ORDER) {
if (folio_test_swapbacked(folio)) {
__lruvec_stat_mod_folio(folio,
NR_SHMEM_THPS, -nr);
@@ -3139,7 +3198,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
}
}
- __split_huge_page(page, list, end);
+ __split_huge_page(page, list, end, new_order);
ret = 0;
} else {
spin_unlock(&ds_queue->split_queue_lock);
generated by cgit 1.2.3-korg (git 2.39.0) at 2024-05-20 03:11:05 +0000