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)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 29 Aug 2013 16:47:34 +0000 (09:47 -0700)
commit012dc156d6af49e02a30fcba7d688e251608d97c
tree9df8015705569ced239b24ae56872eabc2b15054
parentc6febdf258313a120acd1298dd1dd41442131a37
tracing: Change remove_event_file_dir() to clear "d_subdirs"->i_private

commit bf682c3159c4d298d1126a56793ed3f5e80395f7 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernel/trace/trace_events.c