kthread: Generalize pf_io_worker so it can point to struct kthread

The point of using set_child_tid to hold the kthread pointer was that
it already did what is necessary.  There are now restrictions on when
set_child_tid can be initialized and when set_child_tid can be used in
schedule_tail.  Which indicates that continuing to use set_child_tid
to hold the kthread pointer is a bad idea.

Instead of continuing to use the set_child_tid field of task_struct
generalize the pf_io_worker field of task_struct and use it to hold
the kthread pointer.

Rename pf_io_worker (which is a void * pointer) to worker_private so
it can be used to store kthreads struct kthread pointer.  Update the
kthread code to store the kthread pointer in the worker_private field.
Remove the places where set_child_tid had to be dealt with carefully
because kthreads also used it.

Link: https://lkml.kernel.org/r/CAHk-=wgtFAA9SbVYg0gR1tqPMC17-NYcs0GQkaYg1bGhh1uJQQ@mail.gmail.com
Link: https://lkml.kernel.org/r/87a6grvqy8.fsf_-_@email.froward.int.ebiederm.org
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/io-wq.h b/fs/io-wq.h
index 41bf37674a49..c7c23947cbcd 100644
--- a/fs/io-wq.h
+++ b/fs/io-wq.h
@@ -200,6 +200,6 @@ static inline void io_wq_worker_running(struct task_struct *tsk)
 static inline bool io_wq_current_is_worker(void)
 {
 	return in_task() && (current->flags & PF_IO_WORKER) &&
-		current->pf_io_worker;
+		current->worker_private;
 }
 #endif