* Tejun Heo <t...@kernel.org> wrote:
> Subject: writeback: 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.
>
> Signed-off-by: Tejun Heo <t...@kernel.org>
> ---
> 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 29e4599..7378169 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();
Any objections against me applying this fix to tip:core/rcu so that I can push
the
recent RCU changes towards linux-next without triggering a build failure?
Thanks,
Ingo
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