[PATCH v3 10/14] linux/mm.h: move page_zone_id() and more to mm/folio_zone.h

[Max Kellermann <max.kellermann@ionos.com>]

This is needed to eliminate linux/skbuff.h's dependency on linux/mm.h.

Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
---
 include/linux/mm.h            | 28 +--------------------------
 include/linux/mm/folio_zone.h | 36 +++++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 27 deletions(-)
 create mode 100644 include/linux/mm/folio_zone.h

diff --git a/include/linux/mm.h b/include/linux/mm.h
index e8a914e7bebd..b3f83fb26aca 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -5,6 +5,7 @@
 #include <linux/mm/folio_next.h>
 #include <linux/mm/folio_size.h>
 #include <linux/mm/folio_usage.h>
+#include <linux/mm/folio_zone.h>
 #include <linux/mm/page_address.h>
 #include <linux/mm/page_section.h>
 #include <linux/errno.h>
@@ -1370,33 +1371,6 @@ static inline bool is_nommu_shared_mapping(vm_flags_t flags)
 }
 #endif
 
-/*
- * The identification function is mainly used by the buddy allocator for
- * determining if two pages could be buddies. We are not really identifying
- * the zone since we could be using the section number id if we do not have
- * node id available in page flags.
- * We only guarantee that it will return the same value for two combinable
- * pages in a zone.
- */
-static inline int page_zone_id(struct page *page)
-{
-	return (page->flags >> ZONEID_PGSHIFT) & ZONEID_MASK;
-}
-
-#ifdef NODE_NOT_IN_PAGE_FLAGS
-int page_to_nid(const struct page *page);
-#else
-static inline int page_to_nid(const struct page *page)
-{
-	return (PF_POISONED_CHECK(page)->flags >> NODES_PGSHIFT) & NODES_MASK;
-}
-#endif
-
-static inline int folio_nid(const struct folio *folio)
-{
-	return page_to_nid(&folio->page);
-}
-
 #ifdef CONFIG_NUMA_BALANCING
 /* page access time bits needs to hold at least 4 seconds */
 #define PAGE_ACCESS_TIME_MIN_BITS	12
diff --git a/include/linux/mm/folio_zone.h b/include/linux/mm/folio_zone.h
new file mode 100644
index 000000000000..572fe37068f1
--- /dev/null
+++ b/include/linux/mm/folio_zone.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_MM_FOLIO_ZONE_H
+#define _LINUX_MM_FOLIO_ZONE_H
+
+#include <linux/mm_types.h> // for struct page, struct folio
+#include <linux/mmzone.h> // for ZONEID_*, NODES_*
+#include <linux/page-flags.h> // for PF_POISONED_CHECK()
+
+/*
+ * The identification function is mainly used by the buddy allocator for
+ * determining if two pages could be buddies. We are not really identifying
+ * the zone since we could be using the section number id if we do not have
+ * node id available in page flags.
+ * We only guarantee that it will return the same value for two combinable
+ * pages in a zone.
+ */
+static inline int page_zone_id(struct page *page)
+{
+	return (page->flags >> ZONEID_PGSHIFT) & ZONEID_MASK;
+}
+
+#ifdef NODE_NOT_IN_PAGE_FLAGS
+int page_to_nid(const struct page *page);
+#else
+static inline int page_to_nid(const struct page *page)
+{
+	return (PF_POISONED_CHECK(page)->flags >> NODES_PGSHIFT) & NODES_MASK;
+}
+#endif
+
+static inline int folio_nid(const struct folio *folio)
+{
+	return page_to_nid(&folio->page);
+}
+
+#endif /* _LINUX_MM_FOLIO_ZONE_H */
-- 
2.39.2