drm: Simplify stacktrace handling

Replace the indirection through struct stack_trace by using the storage
array based interfaces.

The original code in all printing functions is really wrong. It allocates a
storage array on stack which is unused because depot_fetch_stack() does not
store anything in it. It overwrites the entries pointer in the stack_trace
struct so it points to the depot storage.

Signed-off-by: Thomas Gleixner <[e-mail]>
Reviewed-by: Josh Poimboeuf <[e-mail]>
Acked-by: Daniel Vetter <[e-mail]>
Cc: Andy Lutomirski <[e-mail]>
Cc: [e-mail]
Cc: Joonas Lahtinen <[e-mail]>
Cc: Maarten Lankhorst <[e-mail]>
Cc: [e-mail]
Cc: David Airlie <[e-mail]>
Cc: Jani Nikula <[e-mail]>
Cc: Rodrigo Vivi <[e-mail]>
Cc: Steven Rostedt <[e-mail]>
Cc: Alexander Potapenko <[e-mail]>
Cc: Alexey Dobriyan <[e-mail]>
Cc: Andrew Morton <[e-mail]>
Cc: Christoph Lameter <[e-mail]>
Cc: Pekka Enberg <[e-mail]>
Cc: [e-mail]
Cc: David Rientjes <[e-mail]>
Cc: Catalin Marinas <[e-mail]>
Cc: Dmitry Vyukov <[e-mail]>
Cc: Andrey Ryabinin <[e-mail]>
Cc: [e-mail]
Cc: Mike Rapoport <[e-mail]>
Cc: Akinobu Mita <[e-mail]>
Cc: Christoph Hellwig <[e-mail]>
Cc: [e-mail]
Cc: Robin Murphy <[e-mail]>
Cc: Marek Szyprowski <[e-mail]>
Cc: Johannes Thumshirn <[e-mail]>
Cc: David Sterba <[e-mail]>
Cc: Chris Mason <[e-mail]>
Cc: Josef Bacik <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: Mike Snitzer <[e-mail]>
Cc: Alasdair Kergon <[e-mail]>
Cc: Tom Zanussi <[e-mail]>
Cc: Miroslav Benes <[e-mail]>
Cc: [e-mail]
Link: https://lkml.kernel.org/r/[e-mail]

drivers/gpu/drm/drm_mm.c

···
 static noinline void save_stack(struct drm_mm_node *node)
 {
 	unsigned long entries[STACKDEPTH];
-	struct stack_trace trace = {
-		.entries = entries,
-		.max_entries = STACKDEPTH,
-		.skip = 1
-	};
+	unsigned int n;
 
-	save_stack_trace(&trace);
+	n = stack_trace_save(entries, ARRAY_SIZE(entries), 1);
 
 	/* May be called under spinlock, so avoid sleeping */
-	node->stack = depot_save_stack(&trace, GFP_NOWAIT);
+	node->stack = stack_depot_save(entries, n, GFP_NOWAIT);
 }
 
 static void show_leaks(struct drm_mm *mm)
 {
 	struct drm_mm_node *node;
-	unsigned long entries[STACKDEPTH];
+	unsigned long *entries;
+	unsigned int nr_entries;
 	char *buf;
 
 	buf = kmalloc(BUFSZ, GFP_KERNEL);
···
 		return;
 
 	list_for_each_entry(node, drm_mm_nodes(mm), node_list) {
-		struct stack_trace trace = {
-			.entries = entries,
-			.max_entries = STACKDEPTH
-		};
-
 		if (!node->stack) {
 			DRM_ERROR("node [%08llx + %08llx]: unknown owner\n",
 				  node->start, node->size);
 			continue;
 		}
 
-		depot_fetch_stack(node->stack, &trace);
-		snprint_stack_trace(buf, BUFSZ, &trace, 0);
+		nr_entries = stack_depot_fetch(node->stack, &entries);
+		stack_trace_snprint(buf, BUFSZ, entries, nr_entries, 0);
 		DRM_ERROR("node [%08llx + %08llx]: inserted at\n%s",
 			  node->start, node->size, buf);
 	}

drivers/gpu/drm/i915/i915_vma.c

···
 
 static void vma_print_allocator(struct i915_vma *vma, const char *reason)
 {
-	unsigned long entries[12];
-	struct stack_trace trace = {
-		.entries = entries,
-		.max_entries = ARRAY_SIZE(entries),
-	};
+	unsigned long *entries;
+	unsigned int nr_entries;
 	char buf[512];
 
 	if (!vma->node.stack) {
···
 		return;
 	}
 
-	depot_fetch_stack(vma->node.stack, &trace);
-	snprint_stack_trace(buf, sizeof(buf), &trace, 0);
+	nr_entries = stack_depot_fetch(vma->node.stack, &entries);
+	stack_trace_snprint(buf, sizeof(buf), entries, nr_entries, 0);
 	DRM_DEBUG_DRIVER("vma.node [%08llx + %08llx] %s: inserted at %s\n",
 			 vma->node.start, vma->node.size, reason, buf);
 }

drivers/gpu/drm/i915/intel_runtime_pm.c

···
 static noinline depot_stack_handle_t __save_depot_stack(void)
 {
 	unsigned long entries[STACKDEPTH];
-	struct stack_trace trace = {
-		.entries = entries,
-		.max_entries = ARRAY_SIZE(entries),
-		.skip = 1,
-	};
+	unsigned int n;
 
-	save_stack_trace(&trace);
-	return depot_save_stack(&trace, GFP_NOWAIT | __GFP_NOWARN);
+	n = stack_trace_save(entries, ARRAY_SIZE(entries), 1);
+	return stack_depot_save(entries, n, GFP_NOWAIT | __GFP_NOWARN);
 }
 
 static void __print_depot_stack(depot_stack_handle_t stack,
 				char *buf, int sz, int indent)
 {
-	unsigned long entries[STACKDEPTH];
-	struct stack_trace trace = {
-		.entries = entries,
-		.max_entries = ARRAY_SIZE(entries),
-	};
+	unsigned long *entries;
+	unsigned int nr_entries;
 
-	depot_fetch_stack(stack, &trace);
-	snprint_stack_trace(buf, sz, &trace, indent);
+	nr_entries = stack_depot_fetch(stack, &entries);
+	stack_trace_snprint(buf, sz, entries, nr_entries, indent);
 }
 
 static void init_intel_runtime_pm_wakeref(struct drm_i915_private *i915)