linux-kernel - [PATCH v9 2/7] lib/stackdepot: Move stack_record struct definition into the header

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Date: Wed, 14 Feb 2024 18:01:52 +0100
From: Oscar Salvador <osalvador@...e.de>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	Michal Hocko <mhocko@...e.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Marco Elver <elver@...gle.com>,
	Andrey Konovalov <andreyknvl@...il.com>,
	Alexander Potapenko <glider@...gle.com>,
	Oscar Salvador <osalvador@...e.de>
Subject: [PATCH v9 2/7] lib/stackdepot: Move stack_record struct definition into the header

In order to move the heavy lifting into page_owner code, this one
needs to have access to the stack_record structure, which right now
sits in lib/stackdepot.c.
Move it to the stackdepot.h header so page_owner can access
stack_record's struct fields.

Signed-off-by: Oscar Salvador <osalvador@...e.de>
Reviewed-by: Marco Elver <elver@...gle.com>
Reviewed-by: Vlastimil Babka <vbabka@...e.cz>
---
 include/linux/stackdepot.h | 47 ++++++++++++++++++++++++++++++++++++++
 lib/stackdepot.c           | 45 +-----------------------------------
 2 files changed, 48 insertions(+), 44 deletions(-)

diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h
index adcbb8f23600..c4b5ad57c066 100644
--- a/include/linux/stackdepot.h
+++ b/include/linux/stackdepot.h
@@ -30,6 +30,53 @@ typedef u32 depot_stack_handle_t;
  */
 #define STACK_DEPOT_EXTRA_BITS 5
 
+#define DEPOT_HANDLE_BITS (sizeof(depot_stack_handle_t) * 8)
+
+#define DEPOT_POOL_ORDER 2 /* Pool size order, 4 pages */
+#define DEPOT_POOL_SIZE (1LL << (PAGE_SHIFT + DEPOT_POOL_ORDER))
+#define DEPOT_STACK_ALIGN 4
+#define DEPOT_OFFSET_BITS (DEPOT_POOL_ORDER + PAGE_SHIFT - DEPOT_STACK_ALIGN)
+#define DEPOT_POOL_INDEX_BITS (DEPOT_HANDLE_BITS - DEPOT_OFFSET_BITS - \
+			       STACK_DEPOT_EXTRA_BITS)
+
+#ifdef CONFIG_STACKDEPOT
+/* Compact structure that stores a reference to a stack. */
+union handle_parts {
+	depot_stack_handle_t handle;
+	struct {
+		/* pool_index is offset by 1 */
+		u32 pool_index	: DEPOT_POOL_INDEX_BITS;
+		u32 offset	: DEPOT_OFFSET_BITS;
+		u32 extra	: STACK_DEPOT_EXTRA_BITS;
+	};
+};
+
+struct stack_record {
+	struct list_head hash_list;	/* Links in the hash table */
+	u32 hash;			/* Hash in hash table */
+	u32 size;			/* Number of stored frames */
+	union handle_parts handle;	/* Constant after initialization */
+	refcount_t count;
+	union {
+		unsigned long entries[CONFIG_STACKDEPOT_MAX_FRAMES];	/* Frames */
+		struct {
+			/*
+			 * An important invariant of the implementation is to
+			 * only place a stack record onto the freelist iff its
+			 * refcount is zero. Because stack records with a zero
+			 * refcount are never considered as valid, it is safe to
+			 * union @entries and freelist management state below.
+			 * Conversely, as soon as an entry is off the freelist
+			 * and its refcount becomes non-zero, the below must not
+			 * be accessed until being placed back on the freelist.
+			 */
+			struct list_head free_list;	/* Links in the freelist */
+			unsigned long rcu_state;	/* RCU cookie */
+		};
+	};
+};
+#endif
+
 typedef u32 depot_flags_t;
 
 /*
diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index c043a4186bc5..4a661a6777da 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -36,55 +36,12 @@
 #include <linux/memblock.h>
 #include <linux/kasan-enabled.h>
 
-#define DEPOT_HANDLE_BITS (sizeof(depot_stack_handle_t) * 8)
-
-#define DEPOT_POOL_ORDER 2 /* Pool size order, 4 pages */
-#define DEPOT_POOL_SIZE (1LL << (PAGE_SHIFT + DEPOT_POOL_ORDER))
-#define DEPOT_STACK_ALIGN 4
-#define DEPOT_OFFSET_BITS (DEPOT_POOL_ORDER + PAGE_SHIFT - DEPOT_STACK_ALIGN)
-#define DEPOT_POOL_INDEX_BITS (DEPOT_HANDLE_BITS - DEPOT_OFFSET_BITS - \
-			       STACK_DEPOT_EXTRA_BITS)
 #define DEPOT_POOLS_CAP 8192
-/* The pool_index is offset by 1 so the first record does not have a 0 handle. */
+/* The pool_index is offset by 1 so the first record does not have a 0 handle */
 #define DEPOT_MAX_POOLS \
 	(((1LL << (DEPOT_POOL_INDEX_BITS)) - 1 < DEPOT_POOLS_CAP) ? \
 	 (1LL << (DEPOT_POOL_INDEX_BITS)) - 1 : DEPOT_POOLS_CAP)
 
-/* Compact structure that stores a reference to a stack. */
-union handle_parts {
-	depot_stack_handle_t handle;
-	struct {
-		u32 pool_index	: DEPOT_POOL_INDEX_BITS; /* pool_index is offset by 1 */
-		u32 offset	: DEPOT_OFFSET_BITS;
-		u32 extra	: STACK_DEPOT_EXTRA_BITS;
-	};
-};
-
-struct stack_record {
-	struct list_head hash_list;	/* Links in the hash table */
-	u32 hash;			/* Hash in hash table */
-	u32 size;			/* Number of stored frames */
-	union handle_parts handle;	/* Constant after initialization */
-	refcount_t count;
-	union {
-		unsigned long entries[CONFIG_STACKDEPOT_MAX_FRAMES];	/* Frames */
-		struct {
-			/*
-			 * An important invariant of the implementation is to
-			 * only place a stack record onto the freelist iff its
-			 * refcount is zero. Because stack records with a zero
-			 * refcount are never considered as valid, it is safe to
-			 * union @entries and freelist management state below.
-			 * Conversely, as soon as an entry is off the freelist
-			 * and its refcount becomes non-zero, the below must not
-			 * be accessed until being placed back on the freelist.
-			 */
-			struct list_head free_list;	/* Links in the freelist */
-			unsigned long rcu_state;	/* RCU cookie */
-		};
-	};
-};
-
 static bool stack_depot_disabled;
 static bool __stack_depot_early_init_requested __initdata = IS_ENABLED(CONFIG_STACKDEPOT_ALWAYS_INIT);
 static bool __stack_depot_early_init_passed __initdata;
-- 
2.43.0