perf/core: Simplify perf_event_alloc()

Using the previous simplifications, transition perf_event_alloc() to
the cleanup way of things -- reducing error path magic.

[ mingo: Ported it to recent kernels. ]

Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Reviewed-by: Ravi Bangoria <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: Peter Zijlstra

kernel/events/core.c

@@ -5410,6 +5410,8 @@ static void __free_event(struct perf_event *event)
 	call_rcu(&event->rcu_head, free_event_rcu);
 }
 
+DEFINE_FREE(__free_event, struct perf_event *, if (_T) __free_event(_T))
+
 /* vs perf_event_alloc() success */
 static void _free_event(struct perf_event *event)
 {
@@ -12291,7 +12293,6 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
 		 void *context, int cgroup_fd)
 {
 	struct pmu *pmu;
-	struct perf_event *event;
 	struct hw_perf_event *hwc;
 	long err = -EINVAL;
 	int node;
@@ -12306,8 +12307,8 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
 	}
 
 	node = (cpu >= 0) ? cpu_to_node(cpu) : -1;
-	event = kmem_cache_alloc_node(perf_event_cache, GFP_KERNEL | __GFP_ZERO,
-				      node);
+	struct perf_event *event __free(__free_event) =
+		kmem_cache_alloc_node(perf_event_cache, GFP_KERNEL | __GFP_ZERO, node);
 	if (!event)
 		return ERR_PTR(-ENOMEM);
 
@@ -12414,65 +12415,53 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
 	 * See perf_output_read().
 	 */
 	if (has_inherit_and_sample_read(attr) && !(attr->sample_type & PERF_SAMPLE_TID))
-		goto err;
+		return ERR_PTR(-EINVAL);
 
 	if (!has_branch_stack(event))
 		event->attr.branch_sample_type = 0;
 
 	pmu = perf_init_event(event);
-	if (IS_ERR(pmu)) {
-		err = PTR_ERR(pmu);
-		goto err;
-	}
+	if (IS_ERR(pmu))
+		return (void*)pmu;
 
 	/*
 	 * Disallow uncore-task events. Similarly, disallow uncore-cgroup
 	 * events (they don't make sense as the cgroup will be different
 	 * on other CPUs in the uncore mask).
 	 */
-	if (pmu->task_ctx_nr == perf_invalid_context && (task || cgroup_fd != -1)) {
-		err = -EINVAL;
-		goto err;
-	}
+	if (pmu->task_ctx_nr == perf_invalid_context && (task || cgroup_fd != -1))
+		return ERR_PTR(-EINVAL);
 
 	if (event->attr.aux_output &&
 	    (!(pmu->capabilities & PERF_PMU_CAP_AUX_OUTPUT) ||
-	     event->attr.aux_pause || event->attr.aux_resume)) {
-		err = -EOPNOTSUPP;
-		goto err;
-	}
+	     event->attr.aux_pause || event->attr.aux_resume))
+		return ERR_PTR(-EOPNOTSUPP);
 
-	if (event->attr.aux_pause && event->attr.aux_resume) {
-		err = -EINVAL;
-		goto err;
-	}
+	if (event->attr.aux_pause && event->attr.aux_resume)
+		return ERR_PTR(-EINVAL);
 
 	if (event->attr.aux_start_paused) {
-		if (!(pmu->capabilities & PERF_PMU_CAP_AUX_PAUSE)) {
-			err = -EOPNOTSUPP;
-			goto err;
-		}
+		if (!(pmu->capabilities & PERF_PMU_CAP_AUX_PAUSE))
+			return ERR_PTR(-EOPNOTSUPP);
 		event->hw.aux_paused = 1;
 	}
 
 	if (cgroup_fd != -1) {
 		err = perf_cgroup_connect(cgroup_fd, event, attr, group_leader);
 		if (err)
-			goto err;
+			return ERR_PTR(err);
 	}
 
 	err = exclusive_event_init(event);
 	if (err)
-		goto err;
+		return ERR_PTR(err);
 
 	if (has_addr_filter(event)) {
 		event->addr_filter_ranges = kcalloc(pmu->nr_addr_filters,
 						    sizeof(struct perf_addr_filter_range),
 						    GFP_KERNEL);
-		if (!event->addr_filter_ranges) {
-			err = -ENOMEM;
-			goto err;
-		}
+		if (!event->addr_filter_ranges)
+			return ERR_PTR(-ENOMEM);
 
 		/*
 		 * Clone the parent's vma offsets: they are valid until exec()
@@ -12496,23 +12485,19 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
 		if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) {
 			err = get_callchain_buffers(attr->sample_max_stack);
 			if (err)
-				goto err;
+				return ERR_PTR(err);
 			event->attach_state |= PERF_ATTACH_CALLCHAIN;
 		}
 	}
 
 	err = security_perf_event_alloc(event);
 	if (err)
-		goto err;
+		return ERR_PTR(err);
 
 	/* symmetric to unaccount_event() in _free_event() */
 	account_event(event);
 
-	return event;
-
-err:
-	__free_event(event);
-	return ERR_PTR(err);
+	return_ptr(event);
 }
 
 static int perf_copy_attr(struct perf_event_attr __user *uattr,