From b33e18f61bd18227a456016a77b1a968f5bc1d65 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Tue, 27 Oct 2015 14:19:39 +0900 Subject: [PATCH] fs/writeback, rcu: Don't use list_entry_rcu() for pointer offsetting in bdi_split_work_to_wbs() bdi_split_work_to_wbs() uses list_for_each_entry_rcu_continue() to walk @bdi->wb_list. To set up the initial iteration condition, it uses list_entry_rcu() to calculate the entry pointer corresponding to the list head; however, this isn't an actual RCU dereference and using list_entry_rcu() for it ended up breaking a proposed list_entry_rcu() change because it was feeding an non-lvalue pointer into the macro. Don't use the RCU variant for simple pointer offsetting. Use list_entry() instead. Reported-by: Ingo Molnar Signed-off-by: Tejun Heo Cc: Darren Hart Cc: David Howells Cc: Dipankar Sarma Cc: Eric Dumazet Cc: Frederic Weisbecker Cc: Josh Triplett Cc: Lai Jiangshan Cc: Linus Torvalds Cc: Mathieu Desnoyers Cc: Oleg Nesterov Cc: Patrick Marlier Cc: Paul McKenney Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner Cc: pranith kumar Link: http://lkml.kernel.org/r/20151027051939.GA19355@mtj.duckdns.org Signed-off-by: Ingo Molnar --- fs/fs-writeback.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 29e4599f6fc1..7378169e90be 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -779,8 +779,8 @@ static void bdi_split_work_to_wbs(struct backing_dev_info *bdi, bool skip_if_busy) { struct bdi_writeback *last_wb = NULL; - struct bdi_writeback *wb = list_entry_rcu(&bdi->wb_list, - struct bdi_writeback, bdi_node); + struct bdi_writeback *wb = list_entry(&bdi->wb_list, + struct bdi_writeback, bdi_node); might_sleep(); restart: -- 2.20.1