btrfs: add tracepoints for outstanding extents mods

This is handy for tracing problems with modifying the outstanding
extents counters.

Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/btrfs_inode.h

@@ -274,6 +274,8 @@ static inline void btrfs_mod_outstanding_extents(struct btrfs_inode *inode,
 	inode->outstanding_extents += mod;
 	if (btrfs_is_free_space_inode(inode))
 		return;
+	trace_btrfs_inode_mod_outstanding_extents(inode->root, btrfs_ino(inode),
+						  mod);
 }
 
 static inline void btrfs_mod_reserved_extents(struct btrfs_inode *inode, int mod)

include/trace/events/btrfs.h

@@ -1695,6 +1695,27 @@ DEFINE_EVENT(btrfs__prelim_ref, btrfs_prelim_ref_insert,
 	TP_ARGS(fs_info, oldref, newref, tree_size)
 );
 
+TRACE_EVENT(btrfs_inode_mod_outstanding_extents,
+	TP_PROTO(struct btrfs_root *root, u64 ino, int mod),
+
+	TP_ARGS(root, ino, mod),
+
+	TP_STRUCT__entry_btrfs(
+		__field(	u64, root_objectid	)
+		__field(	u64, ino		)
+		__field(	int, mod		)
+	),
+
+	TP_fast_assign_btrfs(root->fs_info,
+		__entry->root_objectid	= root->objectid;
+		__entry->ino		= ino;
+		__entry->mod		= mod;
+	),
+
+	TP_printk_btrfs("root=%llu(%s) ino=%llu mod=%d",
+			show_root_type(__entry->root_objectid),
+			(unsigned long long)__entry->ino, __entry->mod)
+);
 #endif /* _TRACE_BTRFS_H */
 
 /* This part must be outside protection */