f2fs: add spin_lock to cover radix operations in IO tracer

This patch adds spin_lock to cover radix tree operations in IO tracer.
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/super.c

@@ -1222,6 +1222,8 @@ static int __init init_f2fs_fs(void)
 {
 	int err;
 
+	f2fs_build_trace_ios();
+
 	err = init_inodecache();
 	if (err)
 		goto fail;

fs/f2fs/trace.c

@@ -15,7 +15,8 @@
 #include "f2fs.h"
 #include "trace.h"
 
-RADIX_TREE(pids, GFP_NOIO);
+RADIX_TREE(pids, GFP_ATOMIC);
+spinlock_t pids_lock;
 struct last_io_info last_io;
 
 static inline void __print_last_io(void)
@@ -58,9 +59,13 @@ void f2fs_trace_pid(struct page *page)
 
 	page->private = pid;
 
+	if (radix_tree_preload(GFP_NOFS))
+		return;
+
+	spin_lock(&pids_lock);
 	p = radix_tree_lookup(&pids, pid);
 	if (p == current)
-		return;
+		goto out;
 	if (p)
 		radix_tree_delete(&pids, pid);
 
@@ -69,7 +74,9 @@ void f2fs_trace_pid(struct page *page)
 	trace_printk("%3x:%3x %4x %-16s\n",
 			MAJOR(inode->i_sb->s_dev), MINOR(inode->i_sb->s_dev),
 			pid, current->comm);
-
+out:
+	spin_unlock(&pids_lock);
+	radix_tree_preload_end();
 }
 
 void f2fs_trace_ios(struct page *page, struct f2fs_io_info *fio, int flush)
@@ -108,3 +115,8 @@ void f2fs_trace_ios(struct page *page, struct f2fs_io_info *fio, int flush)
 	last_io.len = 1;
 	return;
 }
+
+void f2fs_build_trace_ios(void)
+{
+	spin_lock_init(&pids_lock);
+}

fs/f2fs/trace.h

@@ -34,9 +34,11 @@ 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);
 #else
 #define f2fs_trace_pid(p)
 #define f2fs_trace_ios(p, i, n)
+#define f2fs_build_trace_ios()
 
 #endif
 #endif /* __F2FS_TRACE_H__ */