[PATCH 1/1] io_uring: fix locked_free_list caches_free()

[PATCH 1/1] io_uring: fix locked_free_list caches_free()

[Pavel Begunkov]

Don't forget to zero locked_free_nr, it's not a disaster but makes it
attempting to flush it with extra locking when there is nothing in the
list. Also, don't traverse a potentially long list freeing requests
under spinlock, splice the list and do it afterwards.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index bf9ad810c621..dedcf971e2d5 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -8710,12 +8710,13 @@ static void io_req_caches_free(struct io_ring_ctx *ctx, struct task_struct *tsk)
 		submit_state->free_reqs = 0;
 	}
 
-	io_req_cache_free(&submit_state->comp.free_list, NULL);
-
 	spin_lock_irq(&ctx->completion_lock);
-	io_req_cache_free(&submit_state->comp.locked_free_list, NULL);
+	list_splice_init(&cs->locked_free_list, &cs->free_list);
+	cs->locked_free_nr = 0;
 	spin_unlock_irq(&ctx->completion_lock);
 
+	io_req_cache_free(&submit_state->comp.free_list, NULL);
+
 	mutex_unlock(&ctx->uring_lock);
 }
 
-- 
2.24.0

Re: [PATCH 1/1] io_uring: fix locked_free_list caches_free()

[Pavel Begunkov]

On 23/02/2021 21:53, Pavel Begunkov wrote:
> Don't forget to zero locked_free_nr, it's not a disaster but makes it
> attempting to flush it with extra locking when there is nothing in the
> list. Also, don't traverse a potentially long list freeing requests
> under spinlock, splice the list and do it afterwards.

Err, it gone totally wrong, will resend

> 
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> ---
>  fs/io_uring.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index bf9ad810c621..dedcf971e2d5 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -8710,12 +8710,13 @@ static void io_req_caches_free(struct io_ring_ctx *ctx, struct task_struct *tsk)
>  		submit_state->free_reqs = 0;
>  	}
>  
> -	io_req_cache_free(&submit_state->comp.free_list, NULL);
> -
>  	spin_lock_irq(&ctx->completion_lock);
> -	io_req_cache_free(&submit_state->comp.locked_free_list, NULL);
> +	list_splice_init(&cs->locked_free_list, &cs->free_list);
> +	cs->locked_free_nr = 0;
>  	spin_unlock_irq(&ctx->completion_lock);
>  
> +	io_req_cache_free(&submit_state->comp.free_list, NULL);
> +
>  	mutex_unlock(&ctx->uring_lock);
>  }
>  
> 

-- 
Pavel Begunkov