tracing: Change remove_event_file_dir() to clear "d_subdirs"->i_private
authorOleg Nesterov <oleg@redhat.com>
Sun, 28 Jul 2013 18:35:27 +0000 (20:35 +0200)
committerSteven Rostedt <rostedt@goodmis.org>
Tue, 30 Jul 2013 02:57:11 +0000 (22:57 -0400)
commitbf682c3159c4d298d1126a56793ed3f5e80395f7
tree119fe382412dbb356ded3bd708f93e8fae86550c
parentf6a84bdc75b5c11621dec58db73fe102cbaf40cc
tracing: Change remove_event_file_dir() to clear "d_subdirs"->i_private

Change remove_event_file_dir() to clear ->i_private for every
file we are going to remove.

We need to check file->dir != NULL because event_create_dir()
can fail. debugfs_remove_recursive(NULL) is fine but the patch
moves it under the same check anyway for readability.

spin_lock(d_lock) and "d_inode != NULL" check are not needed
afaics, but I do not understand this code enough.

tracing_open_generic_file() and tracing_release_generic_file()
can go away, ftrace_enable_fops and ftrace_event_filter_fops()
use tracing_open_generic() but only to check tracing_disabled.

This fixes all races with event_remove() or instance_delete().
f_op->read/write/whatever can never use the freed file/call,
all event/* files were changed to check and use ->i_private
under event_mutex.

Note: this doesn't not fix other problems, event_remove() can
destroy the active ftrace_event_call, we need more changes but
those changes are completely orthogonal.

Link: http://lkml.kernel.org/r/20130728183527.GB16723@redhat.com
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
kernel/trace/trace_events.c