drm/i915/gem: Remove per-client stats from debugfs/i915_gem_objects

Rather than trying to avoid the use-after-free possible with the current
context chasing, simply remove presentation of the per-client stats from
debugfs. While we know from bug reports that this debugfs/i915_gem_objects
has been used by chromeos (and chrome itself) for debug purposes, google
suggests that it is unparsed, so we are free to invoke debugfs is not
ABI and remove details from it.
Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210118110854.1873-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_debugfs.c

@@ -220,145 +220,6 @@ i915_debugfs_describe_obj(struct seq_file *m, struct drm_i915_gem_object *obj)
 		seq_printf(m, " (%s)", engine->name);
 }
 
-struct file_stats {
-	struct i915_address_space *vm;
-	unsigned long count;
-	u64 total;
-	u64 active, inactive;
-	u64 closed;
-};
-
-static int per_file_stats(int id, void *ptr, void *data)
-{
-	struct drm_i915_gem_object *obj = ptr;
-	struct file_stats *stats = data;
-	struct i915_vma *vma;
-
-	if (IS_ERR_OR_NULL(obj) || !kref_get_unless_zero(&obj->base.refcount))
-		return 0;
-
-	stats->count++;
-	stats->total += obj->base.size;
-
-	spin_lock(&obj->vma.lock);
-	if (!stats->vm) {
-		for_each_ggtt_vma(vma, obj) {
-			if (!drm_mm_node_allocated(&vma->node))
-				continue;
-
-			if (i915_vma_is_active(vma))
-				stats->active += vma->node.size;
-			else
-				stats->inactive += vma->node.size;
-
-			if (i915_vma_is_closed(vma))
-				stats->closed += vma->node.size;
-		}
-	} else {
-		struct rb_node *p = obj->vma.tree.rb_node;
-
-		while (p) {
-			long cmp;
-
-			vma = rb_entry(p, typeof(*vma), obj_node);
-			cmp = i915_vma_compare(vma, stats->vm, NULL);
-			if (cmp == 0) {
-				if (drm_mm_node_allocated(&vma->node)) {
-					if (i915_vma_is_active(vma))
-						stats->active += vma->node.size;
-					else
-						stats->inactive += vma->node.size;
-
-					if (i915_vma_is_closed(vma))
-						stats->closed += vma->node.size;
-				}
-				break;
-			}
-			if (cmp < 0)
-				p = p->rb_right;
-			else
-				p = p->rb_left;
-		}
-	}
-	spin_unlock(&obj->vma.lock);
-
-	i915_gem_object_put(obj);
-	return 0;
-}
-
-#define print_file_stats(m, name, stats) do { \
-	if (stats.count) \
-		seq_printf(m, "%s: %lu objects, %llu bytes (%llu active, %llu inactive, %llu closed)\n", \
-			   name, \
-			   stats.count, \
-			   stats.total, \
-			   stats.active, \
-			   stats.inactive, \
-			   stats.closed); \
-} while (0)
-
-static void print_context_stats(struct seq_file *m,
-				struct drm_i915_private *i915)
-{
-	struct file_stats kstats = {};
-	struct i915_gem_context *ctx, *cn;
-
-	spin_lock(&i915->gem.contexts.lock);
-	list_for_each_entry_safe(ctx, cn, &i915->gem.contexts.list, link) {
-		struct i915_gem_engines_iter it;
-		struct intel_context *ce;
-
-		if (!kref_get_unless_zero(&ctx->ref))
-			continue;
-
-		spin_unlock(&i915->gem.contexts.lock);
-
-		for_each_gem_engine(ce,
-				    i915_gem_context_lock_engines(ctx), it) {
-			if (intel_context_pin_if_active(ce)) {
-				rcu_read_lock();
-				if (ce->state)
-					per_file_stats(0,
-						       ce->state->obj, &kstats);
-				per_file_stats(0, ce->ring->vma->obj, &kstats);
-				rcu_read_unlock();
-				intel_context_unpin(ce);
-			}
-		}
-		i915_gem_context_unlock_engines(ctx);
-
-		mutex_lock(&ctx->mutex);
-		if (!IS_ERR_OR_NULL(ctx->file_priv)) {
-			struct file_stats stats = {
-				.vm = rcu_access_pointer(ctx->vm),
-			};
-			struct drm_file *file = ctx->file_priv->file;
-			struct task_struct *task;
-			char name[80];
-
-			rcu_read_lock();
-			idr_for_each(&file->object_idr, per_file_stats, &stats);
-			rcu_read_unlock();
-
-			rcu_read_lock();
-			task = pid_task(ctx->pid ?: file->pid, PIDTYPE_PID);
-			snprintf(name, sizeof(name), "%s",
-				 task ? task->comm : "<unknown>");
-			rcu_read_unlock();
-
-			print_file_stats(m, name, stats);
-		}
-		mutex_unlock(&ctx->mutex);
-
-		spin_lock(&i915->gem.contexts.lock);
-		list_safe_reset_next(ctx, cn, link);
-		i915_gem_context_put(ctx);
-	}
-	spin_unlock(&i915->gem.contexts.lock);
-
-	print_file_stats(m, "[k]contexts", kstats);
-}
-
 static int i915_gem_object_info(struct seq_file *m, void *data)
 {
 	struct drm_i915_private *i915 = node_to_i915(m->private);
@@ -372,9 +233,6 @@ static int i915_gem_object_info(struct seq_file *m, void *data)
 	for_each_memory_region(mr, i915, id)
 		seq_printf(m, "%s: total:%pa, available:%pa bytes\n",
 			   mr->name, &mr->total, &mr->avail);
-	seq_putc(m, '\n');
-
-	print_context_stats(m, i915);
 
 	return 0;
 }