NACK/Cmnt: [SRU][F:linux-bluefield][PATCH] netfilter: flowtable: Use rw sem as flow block lock

[Stefan Bader]

On 18.05.21 23:43, Daniel Jurgens wrote:
> From: Paul Blakey <paulb at mellanox.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1927251
> 
> Currently flow offload threads are synchronized by the flow block mutex.
> Use rw lock instead to increase flow insertion (read) concurrency.
> 
> Signed-off-by: Paul Blakey <paulb at mellanox.com>
> Reviewed-by: Oz Shlomo <ozsh at mellanox.com>
> Signed-off-by: Pablo Neira Ayuso <pablo at netfilter.org>
> (backported from commit 422c032afcf57d5e8109a54912e22ffc53d99068)
> Signed-off-by: Daniel Jurgens <danielj at nvidia.com>
> 
> ---
>   include/net/netfilter/nf_flow_table.h |  2 +-
>   net/netfilter/nf_flow_table_core.c    | 11 +++++------
>   net/netfilter/nf_flow_table_offload.c |  4 ++--
>   3 files changed, 8 insertions(+), 9 deletions(-)
> 
> diff --git a/include/net/netfilter/nf_flow_table.h b/include/net/netfilter/nf_flow_table.h
> index 3a46b3c..e27b73f 100644
> --- a/include/net/netfilter/nf_flow_table.h
> +++ b/include/net/netfilter/nf_flow_table.h
> @@ -73,7 +73,7 @@ struct nf_flowtable {
>   	struct delayed_work		gc_work;
>   	unsigned int			flags;
>   	struct flow_block		flow_block;
> -	struct mutex			flow_block_lock; /* Guards flow_block */
> +	struct rw_semaphore		flow_block_lock; /* Guards flow_block */
>   	u32				flow_timeout;
>   	possible_net_t			net;
>   };
> diff --git a/net/netfilter/nf_flow_table_core.c b/net/netfilter/nf_flow_table_core.c
> index 5144e31..0c409aa 100644
> --- a/net/netfilter/nf_flow_table_core.c
> +++ b/net/netfilter/nf_flow_table_core.c
> @@ -398,7 +398,7 @@ int nf_flow_table_offload_add_cb(struct nf_flowtable *flow_table,
>   	struct flow_block_cb *block_cb;
>   	int err = 0;
>   
> -	mutex_lock(&flow_table->flow_block_lock);
> +	down_write(&flow_table->flow_block_lock);
>   	block_cb = flow_block_cb_lookup(block, cb, cb_priv);
>   	if (block_cb) {
>   		err = -EEXIST;
> @@ -414,7 +414,7 @@ int nf_flow_table_offload_add_cb(struct nf_flowtable *flow_table,
>   	list_add_tail(&block_cb->list, &block->cb_list);
>   
>   unlock:
> -	mutex_unlock(&flow_table->flow_block_lock);
> +	up_write(&flow_table->flow_block_lock);
>   	return err;
>   }
>   EXPORT_SYMBOL_GPL(nf_flow_table_offload_add_cb);
> @@ -425,13 +425,13 @@ void nf_flow_table_offload_del_cb(struct nf_flowtable *flow_table,
>   	struct flow_block *block = &flow_table->flow_block;
>   	struct flow_block_cb *block_cb;
>   
> -	mutex_lock(&flow_table->flow_block_lock);
> +	down_write(&flow_table->flow_block_lock);
>   	block_cb = flow_block_cb_lookup(block, cb, cb_priv);
>   	if (block_cb)
>   		list_del(&block_cb->list);
>   	else
>   		WARN_ON(true);
> -	mutex_unlock(&flow_table->flow_block_lock);
> +	up_write(&flow_table->flow_block_lock);
>   }
>   EXPORT_SYMBOL_GPL(nf_flow_table_offload_del_cb);
>   
> @@ -561,7 +561,7 @@ int nf_flow_table_init(struct nf_flowtable *flowtable)
>   
>   	INIT_DEFERRABLE_WORK(&flowtable->gc_work, nf_flow_offload_work_gc);
>   	flow_block_init(&flowtable->flow_block);
> -	mutex_init(&flowtable->flow_block_lock);
> +	init_rwsem(&flowtable->flow_block_lock);
>   
>   	err = rhashtable_init(&flowtable->rhashtable,
>   			      &nf_flow_offload_rhash_params);
> @@ -627,7 +627,6 @@ void nf_flow_table_free(struct nf_flowtable *flow_table)
>   		nf_flow_table_iterate(flow_table, nf_flow_offload_gc_step,
>   				      flow_table);
>   	rhashtable_destroy(&flow_table->rhashtable);
> -	mutex_destroy(&flow_table->flow_block_lock);
>   }
>   EXPORT_SYMBOL_GPL(nf_flow_table_free);
>   
> diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c
> index 26a950d..46bffaa 100644
> --- a/net/netfilter/nf_flow_table_offload.c
> +++ b/net/netfilter/nf_flow_table_offload.c
> @@ -698,7 +698,7 @@ static int nf_flow_offload_tuple(struct nf_flowtable *flowtable,
>   	if (cmd == FLOW_CLS_REPLACE)
>   		cls_flow.rule = flow_rule->rule;
>   
> -	mutex_lock(&flowtable->flow_block_lock);
> +	down_read(&flowtable->flow_block_lock);
>   	list_for_each_entry(block_cb, block_cb_list, list) {
>   		err = block_cb->cb(TC_SETUP_CLSFLOWER, &cls_flow,
>   				   block_cb->cb_priv);
> @@ -707,7 +707,7 @@ static int nf_flow_offload_tuple(struct nf_flowtable *flowtable,
>   
>   		i++;
>   	}
> -	mutex_unlock(&flowtable->flow_block_lock);
> +	up_read(&flowtable->flow_block_lock);
>   
>   	if (cmd == FLOW_CLS_STATS)
>   		memcpy(stats, &cls_flow.stats, sizeof(*stats));
> 
There was a NACK which appears to be meant for this but not as a reply to the 
thread.

-Stefan


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