[RFC][PATCH v2 10/11] perf: core, lookup pmu via sysfs

[Lin Ming <ming.m.lin@intel.com>]

Add another pmu lookup method via sysfs.
Now we have 2 methods: type->pmu and sys_fd->pmu

Changes log,
Lookup pmu via sysfs (Ingo Molnar)

Signed-off-by: Lin Ming <ming.m.lin@intel.com>
---
 kernel/perf_event.c |   33 ++++++++++++++++++++++++++++++++-
 1 files changed, 32 insertions(+), 1 deletions(-)

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 8640610..0ab4a8b 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -4680,7 +4680,7 @@ static struct pmu *sw_perf_event_init(struct perf_event *event)
 	return pmu;
 }
 
-static struct pmu *perf_event_lookup_pmu(struct perf_event *event)
+static struct pmu *perf_event_lookup_pmu_by_type(struct perf_event *event)
 {
 	struct pmu *pmu = NULL;
 	int pmu_id = PERF_EVENT_ATTR_TYPE(&event->attr);
@@ -4708,6 +4708,37 @@ static struct pmu *perf_event_lookup_pmu(struct perf_event *event)
 	return pmu;
 }
 
+static struct pmu *perf_event_lookup_pmu_by_fd(struct perf_event *event)
+{
+	struct pmu *pmu = NULL;
+	struct kobject *kobj;
+	int sys_fd = PERF_EVENT_ATTR_FD(&event->attr);
+	struct file *file;
+	int fput_needed;
+
+	file = fget_light(sys_fd, &fput_needed);
+	if (!file)
+		return NULL;
+
+	kobj = sysfs_get_kobject(file);
+	if (kobj)
+		pmu = container_of(kobj, struct pmu, kobj);
+
+	fput_light(file, fput_needed);
+
+	return pmu;
+}
+
+static struct pmu *perf_event_lookup_pmu(struct perf_event *event)
+{
+	u32 type = event->attr.type;
+
+	if (type & PERF_EVENT_FD)
+		return perf_event_lookup_pmu_by_fd(event);
+	else
+		return perf_event_lookup_pmu_by_type(event);
+}
+
 /*
  * Allocate and initialize a event structure
  */