[PATCH 6/9] locking/lockdep: Fallback to folio_pool in alloc_list_entry when static pool is full

[Jim Cromie via B4 Relay]

From: Jim Cromie <jim.cromie@xxxxxxxxx>

Use struct folio_pool to dynamically expand lock dependency storage when
the static list_entries pool is exhausted, avoiding premature lockdep
disabling.

Signed-off-by: Jim Cromie <jim.cromie@xxxxxxxxx>
---
 kernel/locking/lockdep.c           | 35 ++++++++++++++++++++++++++++++++++-
 kernel/locking/lockdep_internals.h |  2 ++
 kernel/locking/lockdep_proc.c      | 16 ++++++++++++++--
 3 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 2d4c5bab5af8..f0f58db090ff 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -58,12 +58,37 @@
 #include <linux/context_tracking.h>
 #include <linux/console.h>
 #include <linux/kasan.h>
+#include <linux/folio_pool.h>
+
+DEFINE_STATIC_KEY_TRUE(lockdep_pool_key);
+static struct folio_pool lockdep_pool =
+	FOLIO_POOL_INIT_KEY(lockdep_pool, sizeof(struct lock_list),
+			    FOLIO_POOL_64K_ORDER, &lockdep_pool_key);
+
+static int __init setup_lockdep_folio_pool(char *str)
+{
+	bool enable;
+
+	if (!kstrtobool(str, &enable)) {
+		if (enable)
+			static_branch_enable(&lockdep_pool_key);
+		else
+			static_branch_disable(&lockdep_pool_key);
+	}
+	return 1;
+}
+__setup("lockdep.folio_pool=", setup_lockdep_folio_pool);
 
 #include <asm/sections.h>
 
 #include "lockdep_internals.h"
 #include "lock_events.h"
 
+void lockdep_pool_stats(unsigned int *nr_chunks, size_t *chunk_size, size_t *tail_used)
+{
+	folio_pool_stats(&lockdep_pool, nr_chunks, chunk_size, tail_used);
+}
+
 #include <trace/events/lock.h>
 
 #ifdef CONFIG_PROVE_LOCKING
@@ -1404,11 +1429,19 @@ static struct lock_list *alloc_list_entry(void)
 				      ARRAY_SIZE(list_entries));
 
 	if (idx >= ARRAY_SIZE(list_entries)) {
+		struct lock_list *p;
+
+		p = folio_pool_alloc_type(&lockdep_pool, struct lock_list,
+					  GFP_ATOMIC);
+		if (p) {
+			nr_list_entries++;
+			return p;
+		}
 		if (!debug_locks_off_graph_unlock())
 			return NULL;
 
 		nbcon_cpu_emergency_enter();
-		print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!");
+		print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low and folio_pool exhausted!");
 		dump_stack();
 		nbcon_cpu_emergency_exit();
 		return NULL;
diff --git a/kernel/locking/lockdep_internals.h b/kernel/locking/lockdep_internals.h
index 0e5e6ffe91a3..f802160c0dd5 100644
--- a/kernel/locking/lockdep_internals.h
+++ b/kernel/locking/lockdep_internals.h
@@ -159,6 +159,8 @@ extern unsigned long max_lock_class_idx;
 extern struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
 extern unsigned long lock_classes_in_use[];
 
+void lockdep_pool_stats(unsigned int *nr_chunks, size_t *chunk_size, size_t *tail_used);
+
 #ifdef CONFIG_PROVE_LOCKING
 extern unsigned long lockdep_count_forward_deps(struct lock_class *);
 extern unsigned long lockdep_count_backward_deps(struct lock_class *);
diff --git a/kernel/locking/lockdep_proc.c b/kernel/locking/lockdep_proc.c
index 1916db9aa46b..3e6f24ae9b34 100644
--- a/kernel/locking/lockdep_proc.c
+++ b/kernel/locking/lockdep_proc.c
@@ -288,8 +288,20 @@ static int lockdep_stats_show(struct seq_file *m, void *v)
 			nr_lock_classes, MAX_LOCKDEP_KEYS);
 	seq_printf(m, " dynamic-keys:                  %11lu\n",
 			nr_dynamic_keys);
-	seq_printf(m, " direct dependencies:           %11lu [max: %lu]\n",
-			nr_list_entries, MAX_LOCKDEP_ENTRIES);
+	{
+		unsigned int fp_chunks = 0;
+		size_t fp_chunk_sz = 0, fp_tail_used = 0;
+
+		lockdep_pool_stats(&fp_chunks, &fp_chunk_sz, &fp_tail_used);
+		if (fp_chunks) {
+			seq_printf(m, " direct dependencies:           %11lu [dynamic: %u x %zu kB, tail: %zu kB/%zu kB]\n",
+				   nr_list_entries, fp_chunks, fp_chunk_sz / 1024,
+				   fp_tail_used / 1024, fp_chunk_sz / 1024);
+		} else {
+			seq_printf(m, " direct dependencies:           %11lu [max: %lu]\n",
+				   nr_list_entries, MAX_LOCKDEP_ENTRIES);
+		}
+	}
 	seq_printf(m, " indirect dependencies:         %11lu\n",
 			sum_forward_deps);
 

-- 
2.55.0