mm: page_alloc: add __split_page()

Factor out the splitting of non-compound page from make_alloc_exact() and
split_page() into a new helper function __split_page().

While at it, convert the VM_BUG_ON_PAGE() into a VM_WARN_ON_PAGE().

Link: https://lkml.kernel.org/r/20260109093136.1491549-3-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Muchun Song <muchun.song@linux.dev>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

2 files changed, 23 insertions, 8 deletions

diff --git a/include/linux/mmdebug.h b/include/linux/mmdebug.h
index 14a45979cccc..ab60ffba08f5 100644
--- a/include/linux/mmdebug.h
+++ b/include/linux/mmdebug.h
@@ -47,6 +47,15 @@ void vma_iter_dump_tree(const struct vma_iterator *vmi);
 			BUG();						\
 		}							\
 	} while (0)
+#define VM_WARN_ON_PAGE(cond, page)		({			\
+	int __ret_warn = !!(cond);					\
+									\
+	if (unlikely(__ret_warn)) {					\
+		dump_page(page, "VM_WARN_ON_PAGE(" __stringify(cond)")");\
+		WARN_ON(1);						\
+	}								\
+	unlikely(__ret_warn);						\
+})
 #define VM_WARN_ON_ONCE_PAGE(cond, page)	({			\
 	static bool __section(".data..once") __warned;			\
 	int __ret_warn_once = !!(cond);					\
@@ -122,6 +131,7 @@ void vma_iter_dump_tree(const struct vma_iterator *vmi);
 #define VM_BUG_ON_MM(cond, mm) VM_BUG_ON(cond)
 #define VM_WARN_ON(cond) BUILD_BUG_ON_INVALID(cond)
 #define VM_WARN_ON_ONCE(cond) BUILD_BUG_ON_INVALID(cond)
+#define VM_WARN_ON_PAGE(cond, page)  BUILD_BUG_ON_INVALID(cond)
 #define VM_WARN_ON_ONCE_PAGE(cond, page)  BUILD_BUG_ON_INVALID(cond)
 #define VM_WARN_ON_FOLIO(cond, folio)  BUILD_BUG_ON_INVALID(cond)
 #define VM_WARN_ON_ONCE_FOLIO(cond, folio)  BUILD_BUG_ON_INVALID(cond)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c0b048584769..3b99296eda5b 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3107,6 +3107,15 @@ void free_unref_folios(struct folio_batch *folios)
 	folio_batch_reinit(folios);
 }
 
+static void __split_page(struct page *page, unsigned int order)
+{
+	VM_WARN_ON_PAGE(PageCompound(page), page);
+
+	split_page_owner(page, order, 0);
+	pgalloc_tag_split(page_folio(page), order, 0);
+	split_page_memcg(page, order);
+}
+
 /*
  * split_page takes a non-compound higher-order page, and splits it into
  * n (1<<order) sub-pages: page[0..n]
@@ -3119,14 +3128,12 @@ void split_page(struct page *page, unsigned int order)
 {
 	int i;
 
-	VM_BUG_ON_PAGE(PageCompound(page), page);
-	VM_BUG_ON_PAGE(!page_count(page), page);
+	VM_WARN_ON_PAGE(!page_count(page), page);
 
 	for (i = 1; i < (1 << order); i++)
 		set_page_refcounted(page + i);
-	split_page_owner(page, order, 0);
-	pgalloc_tag_split(page_folio(page), order, 0);
-	split_page_memcg(page, order);
+
+	__split_page(page, order);
 }
 EXPORT_SYMBOL_GPL(split_page);
 
@@ -5389,9 +5396,7 @@ static void *make_alloc_exact(unsigned long addr, unsigned int order,
 		struct page *page = virt_to_page((void *)addr);
 		struct page *last = page + nr;
 
-		split_page_owner(page, order, 0);
-		pgalloc_tag_split(page_folio(page), order, 0);
-		split_page_memcg(page, order);
+		__split_page(page, order);
 		while (page < --last)
 			set_page_refcounted(last);