btrfs: backref, add tracepoints for prelim_ref insertion and merging

This patch adds a tracepoint event for prelim_ref insertion and
merging.  For each, the ref being inserted or merged and the count
of tree nodes is issued.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/backref.h

@@ -72,4 +72,16 @@ int btrfs_check_shared(struct btrfs_root *root, u64 inum, u64 bytenr);
 
 int __init btrfs_prelim_ref_init(void);
 void btrfs_prelim_ref_exit(void);
+
+struct prelim_ref {
+	struct rb_node rbnode;
+	u64 root_id;
+	struct btrfs_key key_for_search;
+	int level;
+	int count;
+	struct extent_inode_elem *inode_list;
+	u64 parent;
+	u64 wanted_disk_byte;
+};
+
 #endif

fs/btrfs/super.c

@@ -61,6 +61,7 @@
 #include "tests/btrfs-tests.h"
 
 #include "qgroup.h"
+#include "backref.h"
 #define CREATE_TRACE_POINTS
 #include <trace/events/btrfs.h>
 

include/trace/events/btrfs.h

@@ -26,6 +26,7 @@ struct btrfs_work;
 struct __btrfs_workqueue;
 struct btrfs_qgroup_extent_record;
 struct btrfs_qgroup;
+struct prelim_ref;
 
 #define show_ref_type(type)						\
 	__print_symbolic(type,						\
@@ -1636,6 +1637,63 @@ TRACE_EVENT(qgroup_meta_reserve,
 		show_root_type(__entry->refroot), __entry->diff)
 );
 
+DECLARE_EVENT_CLASS(btrfs__prelim_ref,
+	TP_PROTO(const struct btrfs_fs_info *fs_info,
+		 const struct prelim_ref *oldref,
+		 const struct prelim_ref *newref, u64 tree_size),
+	TP_ARGS(fs_info, newref, oldref, tree_size),
+
+	TP_STRUCT__entry_btrfs(
+		__field(	u64,  root_id		)
+		__field(	u64,  objectid		)
+		__field(	 u8,  type		)
+		__field(	u64,  offset		)
+		__field(	int,  level		)
+		__field(	int,  old_count		)
+		__field(	u64,  parent		)
+		__field(	u64,  bytenr		)
+		__field(	int,  mod_count		)
+		__field(	u64,  tree_size		)
+	),
+
+	TP_fast_assign_btrfs(fs_info,
+		__entry->root_id	= oldref->root_id;
+		__entry->objectid	= oldref->key_for_search.objectid;
+		__entry->type		= oldref->key_for_search.type;
+		__entry->offset		= oldref->key_for_search.offset;
+		__entry->level		= oldref->level;
+		__entry->old_count	= oldref->count;
+		__entry->parent		= oldref->parent;
+		__entry->bytenr		= oldref->wanted_disk_byte;
+		__entry->mod_count	= newref ? newref->count : 0;
+		__entry->tree_size	= tree_size;
+	),
+
+	TP_printk_btrfs("root_id=%llu key=[%llu,%u,%llu] level=%d count=[%d+%d=%d] parent=%llu wanted_disk_byte=%llu nodes=%llu",
+			(unsigned long long)__entry->root_id,
+			(unsigned long long)__entry->objectid, __entry->type,
+			(unsigned long long)__entry->offset, __entry->level,
+			__entry->old_count, __entry->mod_count,
+			__entry->old_count + __entry->mod_count,
+			(unsigned long long)__entry->parent,
+			(unsigned long long)__entry->bytenr,
+			(unsigned long long)__entry->tree_size)
+);
+
+DEFINE_EVENT(btrfs__prelim_ref, btrfs_prelim_ref_merge,
+	TP_PROTO(const struct btrfs_fs_info *fs_info,
+		 const struct prelim_ref *oldref,
+		 const struct prelim_ref *newref, u64 tree_size),
+	TP_ARGS(fs_info, oldref, newref, tree_size)
+);
+
+DEFINE_EVENT(btrfs__prelim_ref, btrfs_prelim_ref_insert,
+	TP_PROTO(const struct btrfs_fs_info *fs_info,
+		 const struct prelim_ref *oldref,
+		 const struct prelim_ref *newref, u64 tree_size),
+	TP_ARGS(fs_info, oldref, newref, tree_size)
+);
+
 #endif /* _TRACE_BTRFS_H */
 
 /* This part must be outside protection */