[PATCH v6 19/37] mm: create new codetag references during page splitting

[Suren Baghdasaryan]

When a high-order page is split into smaller ones, each newly split
page should get its codetag. After the split each split page will be
referencing the original codetag. The codetag's "bytes" counter
remains the same because the amount of allocated memory has not
changed, however the "calls" counter gets increased to keep the
counter correct when these individual pages get freed.

Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
---
 include/linux/alloc_tag.h   |  9 +++++++++
 include/linux/pgalloc_tag.h | 30 ++++++++++++++++++++++++++++++
 mm/huge_memory.c            |  2 ++
 mm/page_alloc.c             |  2 ++
 4 files changed, 43 insertions(+)

diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h
index 28c0005edae1..bc9b1b99a55b 100644
--- a/include/linux/alloc_tag.h
+++ b/include/linux/alloc_tag.h
@@ -106,6 +106,15 @@ static inline void __alloc_tag_ref_set(union codetag_ref *ref, struct alloc_tag
 	this_cpu_inc(tag->counters->calls);
 }
 
+static inline void alloc_tag_ref_set(union codetag_ref *ref, struct alloc_tag *tag)
+{
+	alloc_tag_add_check(ref, tag);
+	if (!ref || !tag)
+		return;
+
+	__alloc_tag_ref_set(ref, tag);
+}
+
 static inline void alloc_tag_add(union codetag_ref *ref, struct alloc_tag *tag, size_t bytes)
 {
 	alloc_tag_add_check(ref, tag);
diff --git a/include/linux/pgalloc_tag.h b/include/linux/pgalloc_tag.h
index 66bd021eb46e..093edf98c3d7 100644
--- a/include/linux/pgalloc_tag.h
+++ b/include/linux/pgalloc_tag.h
@@ -67,11 +67,41 @@ static inline void pgalloc_tag_sub(struct page *page, unsigned int nr)
 	}
 }
 
+static inline void pgalloc_tag_split(struct page *page, unsigned int nr)
+{
+	int i;
+	struct page_ext *page_ext;
+	union codetag_ref *ref;
+	struct alloc_tag *tag;
+
+	if (!mem_alloc_profiling_enabled())
+		return;
+
+	page_ext = page_ext_get(page);
+	if (unlikely(!page_ext))
+		return;
+
+	ref = codetag_ref_from_page_ext(page_ext);
+	if (!ref->ct)
+		goto out;
+
+	tag = ct_to_alloc_tag(ref->ct);
+	page_ext = page_ext_next(page_ext);
+	for (i = 1; i < nr; i++) {
+		/* Set new reference to point to the original tag */
+		alloc_tag_ref_set(codetag_ref_from_page_ext(page_ext), tag);
+		page_ext = page_ext_next(page_ext);
+	}
+out:
+	page_ext_put(page_ext);
+}
+
 #else /* CONFIG_MEM_ALLOC_PROFILING */
 
 static inline void pgalloc_tag_add(struct page *page, struct task_struct *task,
 				   unsigned int nr) {}
 static inline void pgalloc_tag_sub(struct page *page, unsigned int nr) {}
+static inline void pgalloc_tag_split(struct page *page, unsigned int nr) {}
 
 #endif /* CONFIG_MEM_ALLOC_PROFILING */
 
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index c77cedf45f3a..b29f9ef0fcb2 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -38,6 +38,7 @@
 #include <linux/sched/sysctl.h>
 #include <linux/memory-tiers.h>
 #include <linux/compat.h>
+#include <linux/pgalloc_tag.h>
 
 #include <asm/tlb.h>
 #include <asm/pgalloc.h>
@@ -2924,6 +2925,7 @@ static void __split_huge_page(struct page *page, struct list_head *list,
 	/* Caller disabled irqs, so they are still disabled here */
 
 	split_page_owner(head, order, new_order);
+	pgalloc_tag_split(head, 1 << order);
 
 	/* See comment in __split_huge_page_tail() */
 	if (folio_test_anon(folio)) {
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 9c86ef2a0296..fd1cc5b80a56 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2666,6 +2666,7 @@ void split_page(struct page *page, unsigned int order)
 	for (i = 1; i < (1 << order); i++)
 		set_page_refcounted(page + i);
 	split_page_owner(page, order, 0);
+	pgalloc_tag_split(page, 1 << order);
 	split_page_memcg(page, order, 0);
 }
 EXPORT_SYMBOL_GPL(split_page);
@@ -4863,6 +4864,7 @@ static void *make_alloc_exact(unsigned long addr, unsigned int order,
 		struct page *last = page + nr;
 
 		split_page_owner(page, order, 0);
+		pgalloc_tag_split(page, 1 << order);
 		split_page_memcg(page, order, 0);
 		while (page < --last)
 			set_page_refcounted(last);
-- 
2.44.0.291.gc1ea87d7ee-goog