[PATCH v4 19/36] 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. The original codetag is reused for these
pages but it's recorded as 0-byte allocation because original codetag
already accounts for the original high-order allocated page.

Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
---
 include/linux/pgalloc_tag.h | 30 ++++++++++++++++++++++++++++++
 mm/huge_memory.c            |  2 ++
 mm/page_alloc.c             |  2 ++
 3 files changed, 34 insertions(+)

diff --git a/include/linux/pgalloc_tag.h b/include/linux/pgalloc_tag.h
index b49ab955300f..9e6ad8e0e4aa 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 order)
 	}
 }
 
+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 order) {}
 static inline void pgalloc_tag_sub(struct page *page, unsigned int order) {}
+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 94c958f7ebb5..86daae671319 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>
@@ -2899,6 +2900,7 @@ 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, nr);
+	pgalloc_tag_split(head, nr);
 
 	/* See comment in __split_huge_page_tail() */
 	if (PageAnon(head)) {
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 58c0e8b948a4..4bc5b4720fee 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2621,6 +2621,7 @@ 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, 1 << order);
+	pgalloc_tag_split(page, 1 << order);
 	split_page_memcg(page, 1 << order);
 }
 EXPORT_SYMBOL_GPL(split_page);
@@ -4806,6 +4807,7 @@ static void *make_alloc_exact(unsigned long addr, unsigned int order,
 		struct page *last = page + nr;
 
 		split_page_owner(page, 1 << order);
+		pgalloc_tag_split(page, 1 << order);
 		split_page_memcg(page, 1 << order);
 		while (page < --last)
 			set_page_refcounted(last);
-- 
2.44.0.rc0.258.g7320e95886-goog