From: Bob Peterson rpeterso@redhat.com

Before this patch, functions save_callbacks and restore_callbacks called function lock_sock and release_sock to prevent other processes from messing with the struct sock while the callbacks were saved and restored. However, function add_sock calls write_lock_bh prior to calling it save_callbacks, which disables preempts. So the call to lock_sock would try to schedule when we can't schedule.

Cc: stable@vger.kernel.org # 4.9.x Fixes: b81171cb6869 ("DLM: Save and restore socket callbacks properly") Signed-off-by: Bob Peterson rpeterso@redhat.com Signed-off-by: David Teigland teigland@redhat.com Signed-off-by: Alexander Aring aahringo@redhat.com --- fs/dlm/lowcomms.c | 4 ---- 1 file changed, 4 deletions(-)

diff --git a/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c index 0d8aaf9c61be..9a9fc5ce1166 100644 --- a/fs/dlm/lowcomms.c +++ b/fs/dlm/lowcomms.c @@ -519,24 +519,20 @@ static void lowcomms_error_report(struct sock *sk) /* Note: sk_callback_lock must be locked before calling this function. */ static void save_callbacks(struct connection *con, struct sock *sk) { - lock_sock(sk); con->orig_data_ready = sk->sk_data_ready; con->orig_state_change = sk->sk_state_change; con->orig_write_space = sk->sk_write_space; con->orig_error_report = sk->sk_error_report; - release_sock(sk); }

static void restore_callbacks(struct connection *con, struct sock *sk) { write_lock_bh(&sk->sk_callback_lock); - lock_sock(sk); sk->sk_user_data = NULL; sk->sk_data_ready = con->orig_data_ready; sk->sk_state_change = con->orig_state_change; sk->sk_write_space = con->orig_write_space; sk->sk_error_report = con->orig_error_report; - release_sock(sk); write_unlock_bh(&sk->sk_callback_lock); }