mm: move page->deferred_list to folio->_deferred_list

Remove the entire block of definitions for the second tail page, and add
the deferred list to the struct folio.  This actually moves _deferred_list
to a different offset in struct folio because I don't see a need to
include the padding.

This lets us use list_for_each_entry_safe() in deferred_split_scan()
and avoid a number of calls to compound_head().

Link: https://lkml.kernel.org/r/20230111142915.1001531-25-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 15 insertions, 17 deletions

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index bfa960f012fa..a4138daaa0b8 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2756,9 +2756,9 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
 	/* Prevent deferred_split_scan() touching ->_refcount */
 	spin_lock(&ds_queue->split_queue_lock);
 	if (folio_ref_freeze(folio, 1 + extra_pins)) {
-		if (!list_empty(page_deferred_list(&folio->page))) {
+		if (!list_empty(&folio->_deferred_list)) {
 			ds_queue->split_queue_len--;
-			list_del(page_deferred_list(&folio->page));
+			list_del(&folio->_deferred_list);
 		}
 		spin_unlock(&ds_queue->split_queue_lock);
 		if (mapping) {
@@ -2873,8 +2873,8 @@ static unsigned long deferred_split_scan(struct shrinker *shrink,
 	struct pglist_data *pgdata = NODE_DATA(sc->nid);
 	struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
 	unsigned long flags;
-	LIST_HEAD(list), *pos, *next;
-	struct page *page;
+	LIST_HEAD(list);
+	struct folio *folio, *next;
 	int split = 0;
 
 #ifdef CONFIG_MEMCG
@@ -2884,14 +2884,13 @@ static unsigned long deferred_split_scan(struct shrinker *shrink,
 
 	spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
 	/* Take pin on all head pages to avoid freeing them under us */
-	list_for_each_safe(pos, next, &ds_queue->split_queue) {
-		page = list_entry((void *)pos, struct page, deferred_list);
-		page = compound_head(page);
-		if (get_page_unless_zero(page)) {
-			list_move(page_deferred_list(page), &list);
+	list_for_each_entry_safe(folio, next, &ds_queue->split_queue,
+							_deferred_list) {
+		if (folio_try_get(folio)) {
+			list_move(&folio->_deferred_list, &list);
 		} else {
-			/* We lost race with put_compound_page() */
-			list_del_init(page_deferred_list(page));
+			/* We lost race with folio_put() */
+			list_del_init(&folio->_deferred_list);
 			ds_queue->split_queue_len--;
 		}
 		if (!--sc->nr_to_scan)
@@ -2899,16 +2898,15 @@ static unsigned long deferred_split_scan(struct shrinker *shrink,
 	}
 	spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
 
-	list_for_each_safe(pos, next, &list) {
-		page = list_entry((void *)pos, struct page, deferred_list);
-		if (!trylock_page(page))
+	list_for_each_entry_safe(folio, next, &list, _deferred_list) {
+		if (!folio_trylock(folio))
 			goto next;
 		/* split_huge_page() removes page from list on success */
-		if (!split_huge_page(page))
+		if (!split_folio(folio))
 			split++;
-		unlock_page(page);
+		folio_unlock(folio);
 next:
-		put_page(page);
+		folio_put(folio);
 	}
 
 	spin_lock_irqsave(&ds_queue->split_queue_lock, flags);