[PATCH] rcu/kvfree: Refactor kvfree_rcu_queue_batch()

[PATCH] rcu/kvfree: Refactor kvfree_rcu_queue_batch()

[Uladzislau Rezki (Sony)]

Improve readability of kvfree_rcu_queue_batch() function
in away that, after a first batch queuing, the loop is break
and success value is returned to a caller.

There is no reason to loop and check batches further as all
outstanding objects have already been picked and attached to
a certain batch to complete an offloading.

Link: https://lore.kernel.org/lkml/ZvWUt2oyXRsvJRNc@pc636/T/
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
---
 kernel/rcu/tree.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index a60616e69b66..b1f883fcd918 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3607,11 +3607,12 @@ kvfree_rcu_queue_batch(struct kfree_rcu_cpu *krcp)
 			}
 
 			// One work is per one batch, so there are three
-			// "free channels", the batch can handle. It can
-			// be that the work is in the pending state when
-			// channels have been detached following by each
-			// other.
+			// "free channels", the batch can handle. Break
+			// the loop since it is done with this CPU thus
+			// queuing an RCU work is _always_ success here.
 			queued = queue_rcu_work(system_unbound_wq, &krwp->rcu_work);
+			WARN_ON_ONCE(!queued);
+			break;
 		}
 	}
 
-- 
2.39.5

Re: [PATCH] rcu/kvfree: Refactor kvfree_rcu_queue_batch()

[Vlastimil Babka]

On 9/30/24 13:37, Uladzislau Rezki (Sony) wrote:
> Improve readability of kvfree_rcu_queue_batch() function
> in away that, after a first batch queuing, the loop is break
> and success value is returned to a caller.
> 
> There is no reason to loop and check batches further as all
> outstanding objects have already been picked and attached to
> a certain batch to complete an offloading.
> 
> Link: https://lore.kernel.org/lkml/ZvWUt2oyXRsvJRNc@pc636/T/
> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

Applied to slab/for-next, thanks!

> ---
>  kernel/rcu/tree.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index a60616e69b66..b1f883fcd918 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -3607,11 +3607,12 @@ kvfree_rcu_queue_batch(struct kfree_rcu_cpu *krcp)
>  			}
>  
>  			// One work is per one batch, so there are three
> -			// "free channels", the batch can handle. It can
> -			// be that the work is in the pending state when
> -			// channels have been detached following by each
> -			// other.
> +			// "free channels", the batch can handle. Break
> +			// the loop since it is done with this CPU thus
> +			// queuing an RCU work is _always_ success here.
>  			queued = queue_rcu_work(system_unbound_wq, &krwp->rcu_work);
> +			WARN_ON_ONCE(!queued);
> +			break;
>  		}
>  	}
>