mm/slub: use stackdepot to save stack trace in objects

Many stack traces are similar so there are many similar arrays.
Stackdepot saves each unique stack only once.

Replace field addrs in struct track with depot_stack_handle_t handle.  Use
stackdepot to save stack trace.

The benefits are smaller memory overhead and possibility to aggregate
per-cache statistics in the future using the stackdepot handle instead of
matching stacks manually.

[rdunlap@infradead.org: rename save_stack_trace()]
  Link: https://lkml.kernel.org/r/20210513051920.29320-1-rdunlap@infradead.org
[vbabka@suse.cz: fix lockdep splat]
  Link: https://lkml.kernel.org/r/20210516195150.26740-1-vbabka@suse.czLink: https://lkml.kernel.org/r/20210414163434.4376-1-glittao@gmail.com

Signed-off-by: Oliver Glitta <glittao@gmail.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

init/Kconfig

@@ -1847,6 +1847,7 @@ config SLUB_DEBUG
 	default y
 	bool "Enable SLUB debugging support" if EXPERT
 	depends on SLUB && SYSFS
+	select STACKDEPOT if STACKTRACE_SUPPORT
 	help
 	  SLUB has extensive debug support features. Disabling these can
 	  result in significant savings in code size. This also disables

mm/slub.c

@@ -26,6 +26,7 @@
 #include <linux/cpuset.h>
 #include <linux/mempolicy.h>
 #include <linux/ctype.h>
+#include <linux/stackdepot.h>
 #include <linux/debugobjects.h>
 #include <linux/kallsyms.h>
 #include <linux/kfence.h>
@@ -220,8 +221,8 @@ static inline bool kmem_cache_has_cpu_partial(struct kmem_cache *s)
 #define TRACK_ADDRS_COUNT 16
 struct track {
 	unsigned long addr;	/* Called from address */
-#ifdef CONFIG_STACKTRACE
-	unsigned long addrs[TRACK_ADDRS_COUNT];	/* Called from address */
+#ifdef CONFIG_STACKDEPOT
+	depot_stack_handle_t handle;
 #endif
 	int cpu;		/* Was running on cpu */
 	int pid;		/* Pid context */
@@ -625,22 +626,27 @@ static struct track *get_track(struct kmem_cache *s, void *object,
 	return kasan_reset_tag(p + alloc);
 }
 
+#ifdef CONFIG_STACKDEPOT
+static depot_stack_handle_t save_stack_depot_trace(gfp_t flags)
+{
+	unsigned long entries[TRACK_ADDRS_COUNT];
+	depot_stack_handle_t handle;
+	unsigned int nr_entries;
+
+	nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 4);
+	handle = stack_depot_save(entries, nr_entries, flags);
+	return handle;
+}
+#endif
+
 static void set_track(struct kmem_cache *s, void *object,
 			enum track_item alloc, unsigned long addr)
 {
 	struct track *p = get_track(s, object, alloc);
 
 	if (addr) {
-#ifdef CONFIG_STACKTRACE
-		unsigned int nr_entries;
-
-		metadata_access_enable();
-		nr_entries = stack_trace_save(kasan_reset_tag(p->addrs),
-					      TRACK_ADDRS_COUNT, 3);
-		metadata_access_disable();
-
-		if (nr_entries < TRACK_ADDRS_COUNT)
-			p->addrs[nr_entries] = 0;
+#ifdef CONFIG_STACKDEPOT
+		p->handle = save_stack_depot_trace(GFP_NOWAIT);
 #endif
 		p->addr = addr;
 		p->cpu = smp_processor_id();
@@ -667,14 +673,19 @@ static void print_track(const char *s, struct track *t, unsigned long pr_time)
 
 	pr_err("%s in %pS age=%lu cpu=%u pid=%d\n",
 	       s, (void *)t->addr, pr_time - t->when, t->cpu, t->pid);
-#ifdef CONFIG_STACKTRACE
+#ifdef CONFIG_STACKDEPOT
 	{
-		int i;
-		for (i = 0; i < TRACK_ADDRS_COUNT; i++)
-			if (t->addrs[i])
-				pr_err("\t%pS\n", (void *)t->addrs[i]);
-			else
-				break;
+		depot_stack_handle_t handle;
+		unsigned long *entries;
+		unsigned int nr_entries;
+
+		handle = READ_ONCE(t->handle);
+		if (!handle) {
+			pr_err("object allocation/free stack trace missing\n");
+		} else {
+			nr_entries = stack_depot_fetch(handle, &entries);
+			stack_trace_print(entries, nr_entries, 0);
+		}
 	}
 #endif
 }
@@ -4048,18 +4059,26 @@ void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct page *page)
 	objp = fixup_red_left(s, objp);
 	trackp = get_track(s, objp, TRACK_ALLOC);
 	kpp->kp_ret = (void *)trackp->addr;
-#ifdef CONFIG_STACKTRACE
-	for (i = 0; i < KS_ADDRS_COUNT && i < TRACK_ADDRS_COUNT; i++) {
-		kpp->kp_stack[i] = (void *)trackp->addrs[i];
-		if (!kpp->kp_stack[i])
-			break;
-	}
+#ifdef CONFIG_STACKDEPOT
+	{
+		depot_stack_handle_t handle;
+		unsigned long *entries;
+		unsigned int nr_entries;
 
-	trackp = get_track(s, objp, TRACK_FREE);
-	for (i = 0; i < KS_ADDRS_COUNT && i < TRACK_ADDRS_COUNT; i++) {
-		kpp->kp_free_stack[i] = (void *)trackp->addrs[i];
-		if (!kpp->kp_free_stack[i])
-			break;
+		handle = READ_ONCE(trackp->handle);
+		if (handle) {
+			nr_entries = stack_depot_fetch(handle, &entries);
+			for (i = 0; i < KS_ADDRS_COUNT && i < nr_entries; i++)
+				kpp->kp_stack[i] = (void *)entries[i];
+		}
+
+		trackp = get_track(s, objp, TRACK_FREE);
+		handle = READ_ONCE(trackp->handle);
+		if (handle) {
+			nr_entries = stack_depot_fetch(handle, &entries);
+			for (i = 0; i < KS_ADDRS_COUNT && i < nr_entries; i++)
+				kpp->kp_free_stack[i] = (void *)entries[i];
+		}
 	}
 #endif
 #endif