Message-ID: <20250730092139.3890844-2-balbirs@nvidia.com>
Date: Wed, 30 Jul 2025 19:21:29 +1000
From: Balbir Singh <balbirs@...dia.com>
To: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org,
	Balbir Singh <balbirs@...dia.com>,
	Karol Herbst <kherbst@...hat.com>,
	Lyude Paul <lyude@...hat.com>,
	Danilo Krummrich <dakr@...nel.org>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>,
	Jérôme Glisse <jglisse@...hat.com>,
	Shuah Khan <shuah@...nel.org>,
	David Hildenbrand <david@...hat.com>,
	Barry Song <baohua@...nel.org>,
	Baolin Wang <baolin.wang@...ux.alibaba.com>,
	Ryan Roberts <ryan.roberts@....com>,
	Matthew Wilcox <willy@...radead.org>,
	Peter Xu <peterx@...hat.com>,
	Zi Yan <ziy@...dia.com>,
	Kefeng Wang <wangkefeng.wang@...wei.com>,
	Jane Chu <jane.chu@...cle.com>,
	Alistair Popple <apopple@...dia.com>,
	Donet Tom <donettom@...ux.ibm.com>,
	Ralph Campbell <rcampbell@...dia.com>,
	Mika Penttilä <mpenttil@...hat.com>,
	Matthew Brost <matthew.brost@...el.com>,
	Francois Dugast <francois.dugast@...el.com>
Subject: [v2 01/11] mm/zone_device: support large zone device private folios

Add routines to support allocation of large order zone device folios
and helper functions for zone device folios, to check if a folio is
device private and helpers for setting zone device data.

When large folios are used, the existing page_free() callback in
pgmap is called when the folio is freed, this is true for both
PAGE_SIZE and higher order pages.

Cc: Karol Herbst <kherbst@...hat.com>
Cc: Lyude Paul <lyude@...hat.com>
Cc: Danilo Krummrich <dakr@...nel.org>
Cc: David Airlie <airlied@...il.com>
Cc: Simona Vetter <simona@...ll.ch>
Cc: "Jérôme Glisse" <jglisse@...hat.com>
Cc: Shuah Khan <shuah@...nel.org>
Cc: David Hildenbrand <david@...hat.com>
Cc: Barry Song <baohua@...nel.org>
Cc: Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc: Ryan Roberts <ryan.roberts@....com>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: Peter Xu <peterx@...hat.com>
Cc: Zi Yan <ziy@...dia.com>
Cc: Kefeng Wang <wangkefeng.wang@...wei.com>
Cc: Jane Chu <jane.chu@...cle.com>
Cc: Alistair Popple <apopple@...dia.com>
Cc: Donet Tom <donettom@...ux.ibm.com>
Cc: Ralph Campbell <rcampbell@...dia.com>
Cc: Mika Penttilä <mpenttil@...hat.com>
Cc: Matthew Brost <matthew.brost@...el.com>
Cc: Francois Dugast <francois.dugast@...el.com>

Signed-off-by: Balbir Singh <balbirs@...dia.com>
---
 include/linux/memremap.h | 10 ++++++++-
 mm/memremap.c            | 48 +++++++++++++++++++++++++++++-----------
 2 files changed, 44 insertions(+), 14 deletions(-)

diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index 4aa151914eab..a0723b35eeaa 100644
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -199,7 +199,7 @@ static inline bool folio_is_fsdax(const struct folio *folio)
 }
 
 #ifdef CONFIG_ZONE_DEVICE
-void zone_device_page_init(struct page *page);
+void zone_device_folio_init(struct folio *folio, unsigned int order);
 void *memremap_pages(struct dev_pagemap *pgmap, int nid);
 void memunmap_pages(struct dev_pagemap *pgmap);
 void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap);
@@ -209,6 +209,14 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
 bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn);
 
 unsigned long memremap_compat_align(void);
+
+static inline void zone_device_page_init(struct page *page)
+{
+	struct folio *folio = page_folio(page);
+
+	zone_device_folio_init(folio, 0);
+}
+
 #else
 static inline void *devm_memremap_pages(struct device *dev,
 		struct dev_pagemap *pgmap)
diff --git a/mm/memremap.c b/mm/memremap.c
index b0ce0d8254bd..3ca136e7455e 100644
--- a/mm/memremap.c
+++ b/mm/memremap.c
@@ -427,20 +427,19 @@ EXPORT_SYMBOL_GPL(get_dev_pagemap);
 void free_zone_device_folio(struct folio *folio)
 {
 	struct dev_pagemap *pgmap = folio->pgmap;
+	unsigned int nr = folio_nr_pages(folio);
+	int i;
 
 	if (WARN_ON_ONCE(!pgmap))
 		return;
 
 	mem_cgroup_uncharge(folio);
 
-	/*
-	 * Note: we don't expect anonymous compound pages yet. Once supported
-	 * and we could PTE-map them similar to THP, we'd have to clear
-	 * PG_anon_exclusive on all tail pages.
-	 */
 	if (folio_test_anon(folio)) {
-		VM_BUG_ON_FOLIO(folio_test_large(folio), folio);
-		__ClearPageAnonExclusive(folio_page(folio, 0));
+		for (i = 0; i < nr; i++)
+			__ClearPageAnonExclusive(folio_page(folio, i));
+	} else {
+		VM_WARN_ON_ONCE(folio_test_large(folio));
 	}
 
 	/*
@@ -464,11 +463,20 @@ void free_zone_device_folio(struct folio *folio)
 
 	switch (pgmap->type) {
 	case MEMORY_DEVICE_PRIVATE:
+		if (folio_test_large(folio)) {
+			folio_unqueue_deferred_split(folio);
+
+			percpu_ref_put_many(&folio->pgmap->ref, nr - 1);
+		}
+		pgmap->ops->page_free(&folio->page);
+		percpu_ref_put(&folio->pgmap->ref);
+		folio->page.mapping = NULL;
+		break;
 	case MEMORY_DEVICE_COHERENT:
 		if (WARN_ON_ONCE(!pgmap->ops || !pgmap->ops->page_free))
 			break;
-		pgmap->ops->page_free(folio_page(folio, 0));
-		put_dev_pagemap(pgmap);
+		pgmap->ops->page_free(&folio->page);
+		percpu_ref_put(&folio->pgmap->ref);
 		break;
 
 	case MEMORY_DEVICE_GENERIC:
@@ -491,14 +499,28 @@ void free_zone_device_folio(struct folio *folio)
 	}
 }
 
-void zone_device_page_init(struct page *page)
+void zone_device_folio_init(struct folio *folio, unsigned int order)
 {
+	struct page *page = folio_page(folio, 0);
+
+	VM_WARN_ON_ONCE(order > MAX_ORDER_NR_PAGES);
+
+	/*
+	 * Only PMD level migration is supported for THP migration
+	 */
+	WARN_ON_ONCE(order && order != HPAGE_PMD_ORDER);
+
 	/*
 	 * Drivers shouldn't be allocating pages after calling
 	 * memunmap_pages().
 	 */
-	WARN_ON_ONCE(!percpu_ref_tryget_live(&page_pgmap(page)->ref));
-	set_page_count(page, 1);
+	WARN_ON_ONCE(!percpu_ref_tryget_many(&page_pgmap(page)->ref, 1 << order));
+	folio_set_count(folio, 1);
 	lock_page(page);
+
+	if (order > 1) {
+		prep_compound_page(page, order);
+		folio_set_large_rmappable(folio);
+	}
 }
-EXPORT_SYMBOL_GPL(zone_device_page_init);
+EXPORT_SYMBOL_GPL(zone_device_folio_init);
-- 
2.50.1

Powered by blists - more mailing lists