Subject: Re: [PATCH net-next v2 4/9] hsr: Implement more robust duplicate discard for PRP

From: Simon Horman <[email-masked]>
Date: Wed, 28 Jan 2026 16:38:24 +0000

On Thu, Jan 22, 2026 at 03:56:59PM +0100, Felix Maurer wrote:

...

> diff --git a/net/hsr/hsr_framereg.c b/net/hsr/hsr_framereg.c

...

> +/* Get the currently active sequence number block. If there is no block yet, or
> + * the existing one is expired, a new block is created. The idea is to maintain
> + * a "sparse bitmap" where a bitmap for the whole sequence number space is
> + * split into blocks and not all blocks exist all the time. The blocks can
> + * expire after time (in low traffic situations) or when they are replaced in
> + * the backing fixed size buffer (in high traffic situations).
> + */
> +static struct hsr_seq_block *hsr_get_seq_block(struct hsr_node *node,
> +					       u16 block_idx)
> +{
> +	struct hsr_seq_block *block, *res;
> +
> +	block = xa_load(&node->seq_blocks, block_idx);
> +
> +	if (block && hsr_seq_block_is_old(block)) {
> +		hsr_forget_seq_block(node, block);
> +		block = NULL;
> +	}
> +
> +	if (!block) {
> +		block = &node->block_buf[node->next_block];
> +		hsr_forget_seq_block(node, block);
> +
> +		memset(block, 0, sizeof(*block));
> +		block->time = jiffies;
> +		block->block_idx = block_idx;
> +
> +		res = xa_store(&node->seq_blocks, block_idx, block, GFP_ATOMIC);
> +		if (xa_is_err(res))

Hi Felix,

I ran Claude Code over this with review-prompts [1] and it flags
that in the error path above, the following is needed so that the
block can be re-used.

			block->time = 0;

[1] https://github.com/masoncl/review-prompts/

> +			return NULL;
> +
> +		node->next_block =
> +			(node->next_block + 1) & (HSR_MAX_SEQ_BLOCKS - 1);
> +	}
> +
> +	return block;
> +}
> +

...