[RFC PATCH 08/30] lib: introduce page allocation tagging

[Suren Baghdasaryan <surenb@google.com>]

Introduce CONFIG_PAGE_ALLOC_TAGGING which provides helper functions to
easily instrument page allocators and adds a page_ext field to store a
pointer to the allocation tag associated with the code that allocated
the page.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Co-developed-by: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---
 include/linux/pgalloc_tag.h | 28 ++++++++++++++++++++++++++++
 lib/Kconfig.debug           | 11 +++++++++++
 lib/Makefile                |  1 +
 lib/pgalloc_tag.c           | 22 ++++++++++++++++++++++
 mm/page_ext.c               |  6 ++++++
 5 files changed, 68 insertions(+)
 create mode 100644 include/linux/pgalloc_tag.h
 create mode 100644 lib/pgalloc_tag.c

diff --git a/include/linux/pgalloc_tag.h b/include/linux/pgalloc_tag.h
new file mode 100644
index 000000000000..f525abfe51d4
--- /dev/null
+++ b/include/linux/pgalloc_tag.h
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * page allocation tagging
+ */
+#ifndef _LINUX_PGALLOC_TAG_H
+#define _LINUX_PGALLOC_TAG_H
+
+#include <linux/alloc_tag.h>
+#include <linux/page_ext.h>
+
+extern struct page_ext_operations page_alloc_tagging_ops;
+struct page_ext *lookup_page_ext(const struct page *page);
+
+static inline union codetag_ref *get_page_tag_ref(struct page *page)
+{
+	struct page_ext *page_ext = lookup_page_ext(page);
+
+	return page_ext ? (void *)page_ext + page_alloc_tagging_ops.offset
+			: NULL;
+}
+
+static inline void pgalloc_tag_dec(struct page *page, unsigned int order)
+{
+	if (page)
+		alloc_tag_sub(get_page_tag_ref(page), PAGE_SIZE << order);
+}
+
+#endif /* _LINUX_PGALLOC_TAG_H */
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 795bf6993f8a..6686648843b3 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -978,6 +978,17 @@ config ALLOC_TAGGING
 	select CODE_TAGGING
 	select LAZY_PERCPU_COUNTER
 
+config PAGE_ALLOC_TAGGING
+	bool "Enable page allocation tagging"
+	default n
+	select ALLOC_TAGGING
+	select PAGE_EXTENSION
+	help
+	  Instrument page allocators to track allocation source code and
+	  collect statistics on the number of allocations and their total size
+	  initiated at that code location. The mechanism can be used to track
+	  memory leaks with a low performance impact.
+
 source "lib/Kconfig.kasan"
 source "lib/Kconfig.kfence"
 
diff --git a/lib/Makefile b/lib/Makefile
index dc00533fc5c8..99f732156673 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -229,6 +229,7 @@ obj-$(CONFIG_FUNCTION_ERROR_INJECTION) += error-inject.o
 
 obj-$(CONFIG_CODE_TAGGING) += codetag.o
 obj-$(CONFIG_ALLOC_TAGGING) += alloc_tag.o
+obj-$(CONFIG_PAGE_ALLOC_TAGGING) += pgalloc_tag.o
 
 lib-$(CONFIG_GENERIC_BUG) += bug.o
 
diff --git a/lib/pgalloc_tag.c b/lib/pgalloc_tag.c
new file mode 100644
index 000000000000..7d97372ca0df
--- /dev/null
+++ b/lib/pgalloc_tag.c
@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/pgalloc_tag.h>
+#include <linux/seq_file.h>
+
+static __init bool need_page_alloc_tagging(void)
+{
+	return true;
+}
+
+static __init void init_page_alloc_tagging(void)
+{
+}
+
+struct page_ext_operations page_alloc_tagging_ops = {
+	.size = sizeof(union codetag_ref),
+	.need = need_page_alloc_tagging,
+	.init = init_page_alloc_tagging,
+};
+EXPORT_SYMBOL(page_alloc_tagging_ops);
+
diff --git a/mm/page_ext.c b/mm/page_ext.c
index 3dc715d7ac29..a22f514ff4da 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -9,6 +9,7 @@
 #include <linux/page_owner.h>
 #include <linux/page_idle.h>
 #include <linux/page_table_check.h>
+#include <linux/pgalloc_tag.h>
 
 /*
  * struct page extension
@@ -76,6 +77,9 @@ static struct page_ext_operations *page_ext_ops[] __initdata = {
 #if defined(CONFIG_PAGE_IDLE_FLAG) && !defined(CONFIG_64BIT)
 	&page_idle_ops,
 #endif
+#ifdef CONFIG_PAGE_ALLOC_TAGGING
+	&page_alloc_tagging_ops,
+#endif
 #ifdef CONFIG_PAGE_TABLE_CHECK
 	&page_table_check_ops,
 #endif
@@ -152,6 +156,7 @@ struct page_ext *lookup_page_ext(const struct page *page)
 					MAX_ORDER_NR_PAGES);
 	return get_entry(base, index);
 }
+EXPORT_SYMBOL(lookup_page_ext);
 
 static int __init alloc_node_page_ext(int nid)
 {
@@ -221,6 +226,7 @@ struct page_ext *lookup_page_ext(const struct page *page)
 		return NULL;
 	return get_entry(section->page_ext, pfn);
 }
+EXPORT_SYMBOL(lookup_page_ext);
 
 static void *__meminit alloc_page_ext(size_t size, int nid)
 {
-- 
2.37.2.672.g94769d06f0-goog