[PATCH 2/2] trace_event_filter: factorize filter creation

[Tejun Heo <tj@kernel.org>]

There are four places where new filter for a given filter string is
created, which involves several different steps.  This patch factors
those steps into create_[system_]filter() functions which in turn make
use of create_filter_{start|finish}() for common parts.

The only functional change is that if replace_filter_string() is
requested and fails, creation fails without any side effect instead of
being ignored.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
These two are on top of the current linus/master bbbc4791cd "Merge
branch 'staging-linus' of git://git.kernel.org/.../gregkh/staging" as
tip seems to be lagging behind for the moment.

Thank you.

 kernel/trace/trace_events_filter.c |  274 ++++++++++++++++++-------------------
 1 file changed, 137 insertions(+), 137 deletions(-)

Index: work/kernel/trace/trace_events_filter.c
===================================================================
--- work.orig/kernel/trace/trace_events_filter.c
+++ work/kernel/trace/trace_events_filter.c
@@ -1727,11 +1727,114 @@ static int replace_system_preds(struct e
 	return -ENOMEM;
 }
 
-int apply_event_filter(struct ftrace_event_call *call, char *filter_string)
+static int create_filter_start(char *filter_str, bool set_str,
+			       struct filter_parse_state **psp,
+			       struct event_filter **filterp)
 {
-	struct filter_parse_state *ps;
 	struct event_filter *filter;
-	struct event_filter *tmp;
+	struct filter_parse_state *ps = NULL;
+	int err = 0;
+
+	WARN_ON_ONCE(*psp || *filterp);
+
+	/* allocate everything, and if any fails, free all and fail */
+	filter = __alloc_filter();
+	if (filter && set_str)
+		err = replace_filter_string(filter, filter_str);
+
+	ps = kzalloc(sizeof(*ps), GFP_KERNEL);
+
+	if (!filter || !ps || err) {
+		kfree(ps);
+		__free_filter(filter);
+		return -ENOMEM;
+	}
+
+	/* we're committed to creating a new filter */
+	*filterp = filter;
+	*psp = ps;
+
+	parse_init(ps, filter_ops, filter_str);
+	err = filter_parse(ps);
+	if (err && set_str)
+		append_filter_err(ps, filter);
+	return err;
+}
+
+static void create_filter_finish(struct filter_parse_state *ps)
+{
+	if (ps) {
+		filter_opstack_clear(ps);
+		postfix_clear(ps);
+		kfree(ps);
+	}
+}
+
+/**
+ * create_filter - create a filter for a ftrace_event_call
+ * @call: ftrace_event_call to create a filter for
+ * @filter_str: filter string
+ * @set_str: remember @filter_str and enable detailed error in filter
+ * @filterp: out param for created filter (must be %NULL on entry, may not
+ *	     be %NULL after failure)
+ *
+ * Creates a filter for @call with @filter_str.  If @set_str is %true,
+ * @filter_str is copied and recorded in the new filter.
+ *
+ * On success, returns 0 and *@filterp points to the new filter.  On
+ * failure, returns -errno and *@filterp may point to %NULL or to a new
+ * filter.  In the latter case, the returned filter contains error
+ * information if @set_str is %true and the caller is responsible for
+ * freeing it.
+ */
+static int create_filter(struct ftrace_event_call *call,
+			 char *filter_str, bool set_str,
+			 struct event_filter **filterp)
+{
+	struct filter_parse_state *ps = NULL;
+	int err;
+
+	err = create_filter_start(filter_str, set_str, &ps, filterp);
+	if (!err) {
+		err = replace_preds(call, *filterp, ps, filter_str, false);
+		if (err && set_str)
+			append_filter_err(ps, *filterp);
+	}
+	create_filter_finish(ps);
+
+	return err;
+}
+
+/**
+ * create_system_filter - create a filter for an event_subsystem
+ * @system: event_subsystem to create a filter for
+ * @filter_str: filter string
+ * @filterp: out param for created filter (must be %NULL on entry, may not
+ *	     be %NULL after failure)
+ *
+ * Identical to create_filter() except that it creates a subsystem filter
+ * and always remembers @filter_str.
+ */
+static int create_system_filter(struct event_subsystem *system,
+				char *filter_str, struct event_filter **filterp)
+{
+	struct filter_parse_state *ps = NULL;
+	int err;
+
+	err = create_filter_start(filter_str, true, &ps, filterp);
+	if (!err) {
+		err = replace_system_preds(system, ps, filter_str);
+		if (err)
+			append_filter_err(ps, *filterp);
+	}
+	create_filter_finish(ps);
+
+	return err;
+}
+
+int apply_event_filter(struct ftrace_event_call *call, char *filter_string)
+{
+	struct event_filter *filter = NULL;
 	int err = 0;
 
 	mutex_lock(&event_mutex);
@@ -1748,49 +1851,30 @@ int apply_event_filter(struct ftrace_eve
 		goto out_unlock;
 	}
 
-	err = -ENOMEM;
-	ps = kzalloc(sizeof(*ps), GFP_KERNEL);
-	if (!ps)
-		goto out_unlock;
-
-	filter = __alloc_filter();
-	if (!filter) {
-		kfree(ps);
-		goto out_unlock;
-	}
-
-	replace_filter_string(filter, filter_string);
-
-	parse_init(ps, filter_ops, filter_string);
-	err = filter_parse(ps);
-	if (err) {
-		append_filter_err(ps, filter);
-		goto out;
-	}
+	err = create_filter(call, filter_string, true, &filter);
 
-	err = replace_preds(call, filter, ps, filter_string, false);
-	if (err) {
-		filter_disable(call);
-		append_filter_err(ps, filter);
-	} else
-		call->flags |= TRACE_EVENT_FL_FILTERED;
-out:
 	/*
 	 * Always swap the call filter with the new filter
 	 * even if there was an error. If there was an error
 	 * in the filter, we disable the filter and show the error
 	 * string
 	 */
-	tmp = call->filter;
-	rcu_assign_pointer(call->filter, filter);
-	if (tmp) {
-		/* Make sure the call is done with the filter */
-		synchronize_sched();
-		__free_filter(tmp);
+	if (filter) {
+		struct event_filter *tmp = call->filter;
+
+		if (!err)
+			call->flags |= TRACE_EVENT_FL_FILTERED;
+		else
+			filter_disable(call);
+
+		rcu_assign_pointer(call->filter, filter);
+
+		if (tmp) {
+			/* Make sure the call is done with the filter */
+			synchronize_sched();
+			__free_filter(tmp);
+		}
 	}
-	filter_opstack_clear(ps);
-	postfix_clear(ps);
-	kfree(ps);
 out_unlock:
 	mutex_unlock(&event_mutex);
 
@@ -1800,8 +1884,7 @@ out_unlock:
 int apply_subsystem_event_filter(struct event_subsystem *system,
 				 char *filter_string)
 {
-	struct filter_parse_state *ps;
-	struct event_filter *filter;
+	struct event_filter *filter = NULL;
 	int err = 0;
 
 	mutex_lock(&event_mutex);
@@ -1824,38 +1907,15 @@ int apply_subsystem_event_filter(struct 
 		goto out_unlock;
 	}
 
-	err = -ENOMEM;
-	ps = kzalloc(sizeof(*ps), GFP_KERNEL);
-	if (!ps)
-		goto out_unlock;
-
-	filter = __alloc_filter();
-	if (!filter)
-		goto out;
-
-	replace_filter_string(filter, filter_string);
-	/*
-	 * No event actually uses the system filter
-	 * we can free it without synchronize_sched().
-	 */
-	__free_filter(system->filter);
-	system->filter = filter;
-
-	parse_init(ps, filter_ops, filter_string);
-	err = filter_parse(ps);
-	if (err) {
-		append_filter_err(ps, system->filter);
-		goto out;
+	err = create_system_filter(system, filter_string, &filter);
+	if (filter) {
+		/*
+		 * No event actually uses the system filter
+		 * we can free it without synchronize_sched().
+		 */
+		__free_filter(system->filter);
+		system->filter = filter;
 	}
-
-	err = replace_system_preds(system, ps, filter_string);
-	if (err)
-		append_filter_err(ps, system->filter);
-
-out:
-	filter_opstack_clear(ps);
-	postfix_clear(ps);
-	kfree(ps);
 out_unlock:
 	mutex_unlock(&event_mutex);
 
@@ -1876,8 +1936,7 @@ int ftrace_profile_set_filter(struct per
 			      char *filter_str)
 {
 	int err;
-	struct event_filter *filter;
-	struct filter_parse_state *ps;
+	struct event_filter *filter = NULL;
 	struct ftrace_event_call *call;
 
 	mutex_lock(&event_mutex);
@@ -1892,33 +1951,10 @@ int ftrace_profile_set_filter(struct per
 	if (event->filter)
 		goto out_unlock;
 
-	filter = __alloc_filter();
-	if (!filter) {
-		err = PTR_ERR(filter);
-		goto out_unlock;
-	}
-
-	err = -ENOMEM;
-	ps = kzalloc(sizeof(*ps), GFP_KERNEL);
-	if (!ps)
-		goto free_filter;
-
-	parse_init(ps, filter_ops, filter_str);
-	err = filter_parse(ps);
-	if (err)
-		goto free_ps;
-
-	err = replace_preds(call, filter, ps, filter_str, false);
+	err = create_filter(call, filter_str, false, &filter);
 	if (!err)
 		event->filter = filter;
-
-free_ps:
-	filter_opstack_clear(ps);
-	postfix_clear(ps);
-	kfree(ps);
-
-free_filter:
-	if (err)
+	else
 		__free_filter(filter);
 
 out_unlock:
@@ -1937,43 +1973,6 @@ out_unlock:
 #define CREATE_TRACE_POINTS
 #include "trace_events_filter_test.h"
 
-static int test_get_filter(char *filter_str, struct ftrace_event_call *call,
-			   struct event_filter **pfilter)
-{
-	struct event_filter *filter;
-	struct filter_parse_state *ps;
-	int err = -ENOMEM;
-
-	filter = __alloc_filter();
-	if (!filter)
-		goto out;
-
-	ps = kzalloc(sizeof(*ps), GFP_KERNEL);
-	if (!ps)
-		goto free_filter;
-
-	parse_init(ps, filter_ops, filter_str);
-	err = filter_parse(ps);
-	if (err)
-		goto free_ps;
-
-	err = replace_preds(call, filter, ps, filter_str, false);
-	if (!err)
-		*pfilter = filter;
-
- free_ps:
-	filter_opstack_clear(ps);
-	postfix_clear(ps);
-	kfree(ps);
-
- free_filter:
-	if (err)
-		__free_filter(filter);
-
- out:
-	return err;
-}
-
 #define DATA_REC(m, va, vb, vc, vd, ve, vf, vg, vh, nvisit) \
 { \
 	.filter = FILTER, \
@@ -2092,12 +2091,13 @@ static __init int ftrace_test_event_filt
 		struct test_filter_data_t *d = &test_filter_data[i];
 		int err;
 
-		err = test_get_filter(d->filter, &event_ftrace_test_filter,
-				      &filter);
+		err = create_filter(&event_ftrace_test_filter, d->filter,
+				    false, &filter);
 		if (err) {
 			printk(KERN_INFO
 			       "Failed to get filter for '%s', err %d\n",
 			       d->filter, err);
+			__free_filter(filter);
 			break;
 		}