[RFC PATCH 18/18] mm: Add pfn_range_put()

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

This function will be used imminently.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/mm.h |  7 ++++++
 mm/swap.c          | 56 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 63 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index a517ef8d2386..4f9e2cfb372e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1515,6 +1515,13 @@ typedef union {
 void release_pages(release_pages_arg, int nr);
 void folios_put(struct folio_batch *folios);
 
+struct pfn_range {
+	unsigned long start;
+	unsigned long end;
+};
+
+void pfn_range_put(struct pfn_range *range, unsigned int nr);
+
 static inline void put_page(struct page *page)
 {
 	struct folio *folio = page_folio(page);
diff --git a/mm/swap.c b/mm/swap.c
index 8bd15402cd8f..218d2cc4c6f4 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -1027,6 +1027,62 @@ void folios_put(struct folio_batch *folios)
 }
 EXPORT_SYMBOL(folios_put);
 
+void pfn_range_put(struct pfn_range *range, unsigned int nr)
+{
+	struct folio_batch folios;
+	unsigned int i;
+	struct lruvec *lruvec = NULL;
+	unsigned long flags = 0;
+
+	folio_batch_init(&folios);
+	for (i = 0; i < nr; i++) {
+		struct folio *folio = pfn_folio(range[i].start);
+		unsigned int refs = range[i].end - range[i].start;
+
+		if (folio_is_zone_device(folio)) {
+			if (lruvec) {
+				unlock_page_lruvec_irqrestore(lruvec, flags);
+				lruvec = NULL;
+			}
+			if (put_devmap_managed_page_refs(&folio->page, refs))
+				continue;
+			if (folio_ref_sub_and_test(folio, refs))
+				free_zone_device_page(&folio->page);
+			continue;
+		}
+
+		if (!folio_ref_sub_and_test(folio, refs))
+			continue;
+
+		/* hugetlb has its own memcg */
+		if (folio_test_hugetlb(folio)) {
+			if (lruvec) {
+				unlock_page_lruvec_irqrestore(lruvec, flags);
+				lruvec = NULL;
+			}
+			free_huge_folio(folio);
+			continue;
+		}
+
+		__page_cache_release(folio, &lruvec, &flags);
+		if (folio_batch_add(&folios, folio) == 0) {
+			if (lruvec) {
+				unlock_page_lruvec_irqrestore(lruvec, flags);
+				lruvec = NULL;
+			}
+			mem_cgroup_uncharge_folios(&folios);
+			free_unref_folios(&folios);
+		}
+	}
+	if (lruvec)
+		unlock_page_lruvec_irqrestore(lruvec, flags);
+
+	if (folios.nr) {
+		mem_cgroup_uncharge_folios(&folios);
+		free_unref_folios(&folios);
+	}
+}
+
 /**
  * release_pages - batched put_page()
  * @arg: array of pages to release
-- 
2.40.1