tracing: Automatically mount tracefs on debugfs/tracing
As tools currently rely on the tracing directory in debugfs, we can not
just created a tracefs infrastructure and expect sysadmins to mount
the new tracefs to have their old tools work.
Instead, the debugfs tracing directory is still created and the tracefs
file system is mounted there when the debugfs filesystem is mounted.
No longer does the tracing infrastructure update the debugfs file system,
but instead interacts with the tracefs file system. But now, it still
appears to the user like nothing changed, except you also have the feature
of mounting just the tracing system without needing all of debugfs!
Note, because debugfs_create_dir() happens to end up setting the
dentry->d_op, we can not use d_set_d_op() but must manually assign the
new op, that has automount set, to the dentry returned. This can be
racy, but since this happens during the initcall sequence on boot up,
there should be nothing that races with it.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
1 file changed
