f2fs: add f2fs_destroy_trace_ios to free radix tree

This patch removes radix tree after finishing tracing IOs.
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/super.c

@@ -1272,6 +1272,7 @@ static void __exit exit_f2fs_fs(void)
 	destroy_node_manager_caches();
 	destroy_inodecache();
 	kset_unregister(f2fs_kset);
+	f2fs_destroy_trace_ios();
 }
 
 module_init(init_f2fs_fs)

fs/f2fs/trace.c

@@ -11,6 +11,7 @@
 #include <linux/fs.h>
 #include <linux/f2fs_fs.h>
 #include <linux/sched.h>
+#include <linux/radix-tree.h>
 
 #include "f2fs.h"
 #include "trace.h"
@@ -120,3 +121,39 @@ void f2fs_build_trace_ios(void)
 {
 	spin_lock_init(&pids_lock);
 }
+
+#define PIDVEC_SIZE	128
+static unsigned int gang_lookup_pids(pid_t *results, unsigned long first_index,
+							unsigned int max_items)
+{
+	struct radix_tree_iter iter;
+	void **slot;
+	unsigned int ret = 0;
+
+	if (unlikely(!max_items))
+		return 0;
+
+	radix_tree_for_each_slot(slot, &pids, &iter, first_index) {
+		results[ret] = iter.index;
+		if (++ret == PIDVEC_SIZE)
+			break;
+	}
+	return ret;
+}
+
+void f2fs_destroy_trace_ios(void)
+{
+	pid_t pid[PIDVEC_SIZE];
+	pid_t next_pid = 0;
+	unsigned int found;
+
+	spin_lock(&pids_lock);
+	while ((found = gang_lookup_pids(pid, next_pid, PIDVEC_SIZE))) {
+		unsigned idx;
+
+		next_pid = pid[found - 1] + 1;
+		for (idx = 0; idx < found; idx++)
+			radix_tree_delete(&pids, pid[idx]);
+	}
+	spin_unlock(&pids_lock);
+}

fs/f2fs/trace.h

@@ -35,10 +35,12 @@ struct last_io_info {
 extern void f2fs_trace_pid(struct page *);
 extern void f2fs_trace_ios(struct page *, struct f2fs_io_info *, int);
 extern void f2fs_build_trace_ios(void);
+extern void f2fs_destroy_trace_ios(void);
 #else
 #define f2fs_trace_pid(p)
 #define f2fs_trace_ios(p, i, n)
 #define f2fs_build_trace_ios()
+#define f2fs_destroy_trace_ios()
 
 #endif
 #endif /* __F2FS_TRACE_H__ */