Re: [PATCH tip/core/rcu 14/15] rcu/tree: Allocate a page when caller is preemptible

[Michal Hocko]

On Thu 01-10-20 09:27:09, Paul E. McKenney wrote:
[...]
> commit ea5c19d21233b5e8d3d06c0d4ecd6be9f2829dc3
> Author: Paul E. McKenney <paulmck@xxxxxxxxxx>
> Date:   Thu Oct 1 09:24:40 2020 -0700
> 
>     kvfree_rcu: Use __GFP_NOMEMALLOC for single-argument kvfree_rcu()
>     
>     This commit applies the __GFP_NOMEMALLOC gfp flag to memory allocations
>     carried out by the single-argument variant of kvfree_rcu(), thus avoiding
>     this can-sleep code path from dipping into the emergency reserves.
>     
>     Suggested-by: Michal Hocko <mhocko@xxxxxxxx>
>     Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>

LGTM. At least for this one I feel competent to give you
Acked-by: Michal Hocko <mhocko@xxxxxxxx>

> 
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 242f0f0..6132452 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -3364,7 +3364,8 @@ add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp,
>  {
>  	struct kvfree_rcu_bulk_data *bnode;
>  	bool can_alloc_page = preemptible();
> -	gfp_t gfp = (can_sleep ? GFP_KERNEL | __GFP_RETRY_MAYFAIL : GFP_ATOMIC) | __GFP_NOWARN;
> +	gfp_t gfp = (can_sleep ? GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOMEMALLOC
> +			       : GFP_ATOMIC) | __GFP_NOWARN;
>  	int idx;
>  
>  	*krcp = krc_this_cpu_lock(flags);

-- 
Michal Hocko
SUSE Labs