Re: [PATCH 2/2] maple_tree: refactor mas_wr_store_type()

["Liam R. Howlett" <Liam.Howlett@oracle.com>]

* Sidhartha Kumar <sidhartha.kumar@oracle.com> [241011 17:44]:
> In mas_wr_store_type(), we check if new_end < mt_slots[wr_mas->type]. If
> this check fails, we know that ,after this, new_end is >= mt_min_slots.
> Checking this again when we detect a wr_node_store later in the function
> is reduntant. Because this check is part of an OR statement, the statement
> will always evaluate to true, therefore we can just get rid of it.
> 
> We also refactor mas_wr_store_type() to return the store type rather
> than set it directly as it greatly cleans up the function.
> 
> Suggested-by: Liam Howlett <liam.howlett@oracle.com>
> Suggested-by: Wei Yang <richard.weiyang@gmail.com>
> Signed-off-by: Sidhartha <sidhartha.kumar@oracle.com>

Reviewed-by: Liam Howlett <liam.howlett@oracle.com>

> ---
> 
> Hi Andrew, could you please drop
> "maple_tree: remove conditionals to detect wr_node_store" in mm-unstable
> before applying this patch
> 
>  lib/maple_tree.c | 72 +++++++++++++++++-------------------------------
>  1 file changed, 25 insertions(+), 47 deletions(-)
> 
> diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> index b3b1d4b8126b..a5e982e482dd 100644
> --- a/lib/maple_tree.c
> +++ b/lib/maple_tree.c
> @@ -4191,24 +4191,22 @@ static inline int mas_prealloc_calc(struct ma_state *mas, void *entry)
>  }
>  
>  /*
> - * mas_wr_store_type() - Set the store type for a given
> + * mas_wr_store_type() - Determine the store type for a given
>   * store operation.
>   * @wr_mas: The maple write state
> + *
> + * Return: the type of store needed for the operation
>   */
> -static inline void mas_wr_store_type(struct ma_wr_state *wr_mas)
> +static inline enum store_type mas_wr_store_type(struct ma_wr_state *wr_mas)
>  {
>  	struct ma_state *mas = wr_mas->mas;
>  	unsigned char new_end;
>  
> -	if (unlikely(mas_is_none(mas) || mas_is_ptr(mas))) {
> -		mas->store_type = wr_store_root;
> -		return;
> -	}
> +	if (unlikely(mas_is_none(mas) || mas_is_ptr(mas)))
> +		return wr_store_root;
>  
> -	if (unlikely(!mas_wr_walk(wr_mas))) {
> -		mas->store_type = wr_spanning_store;
> -		return;
> -	}
> +	if (unlikely(!mas_wr_walk(wr_mas)))
> +		return wr_spanning_store;
>  
>  	/* At this point, we are at the leaf node that needs to be altered. */
>  	mas_wr_end_piv(wr_mas);
> @@ -4216,50 +4214,30 @@ static inline void mas_wr_store_type(struct ma_wr_state *wr_mas)
>  		mas_wr_extend_null(wr_mas);
>  
>  	new_end = mas_wr_new_end(wr_mas);
> -	if ((wr_mas->r_min == mas->index) && (wr_mas->r_max == mas->last)) {
> -		mas->store_type = wr_exact_fit;
> -		return;
> -	}
> +	if ((wr_mas->r_min == mas->index) && (wr_mas->r_max == mas->last))
> +		return wr_exact_fit;
>  
> -	if (unlikely(!mas->index && mas->last == ULONG_MAX)) {
> -		mas->store_type = wr_new_root;
> -		return;
> -	}
> +	if (unlikely(!mas->index && mas->last == ULONG_MAX))
> +		return wr_new_root;
>  
>  	/* Potential spanning rebalance collapsing a node */
>  	if (new_end < mt_min_slots[wr_mas->type]) {
> -		if (!mte_is_root(mas->node) && !(mas->mas_flags & MA_STATE_BULK)) {
> -			mas->store_type = wr_rebalance;
> -			return;
> -		}
> -		mas->store_type = wr_node_store;
> -		return;
> +		if (!mte_is_root(mas->node) && !(mas->mas_flags & MA_STATE_BULK))
> +			return  wr_rebalance;
> +		return wr_node_store;
>  	}
>  
> -	if (new_end >= mt_slots[wr_mas->type]) {
> -		mas->store_type = wr_split_store;
> -		return;
> -	}
> +	if (new_end >= mt_slots[wr_mas->type])
> +		return wr_split_store;
>  
> -	if (!mt_in_rcu(mas->tree) && (mas->offset == mas->end)) {
> -		mas->store_type = wr_append;
> -		return;
> -	}
> +	if (!mt_in_rcu(mas->tree) && (mas->offset == mas->end))
> +		return wr_append;
>  
>  	if ((new_end == mas->end) && (!mt_in_rcu(mas->tree) ||
> -		(wr_mas->offset_end - mas->offset == 1))) {
> -		mas->store_type = wr_slot_store;
> -		return;
> -	}
> -
> -	if (mte_is_root(mas->node) || (new_end >= mt_min_slots[wr_mas->type]) ||
> -		(mas->mas_flags & MA_STATE_BULK)) {
> -		mas->store_type = wr_node_store;
> -		return;
> -	}
> +		(wr_mas->offset_end - mas->offset == 1)))
> +		return wr_slot_store;
>  
> -	mas->store_type = wr_invalid;
> -	MAS_WARN_ON(mas, 1);
> +	return wr_node_store;
>  }
>  
>  /**
> @@ -4274,7 +4252,7 @@ static inline void mas_wr_preallocate(struct ma_wr_state *wr_mas, void *entry)
>  	int request;
>  
>  	mas_wr_prealloc_setup(wr_mas);
> -	mas_wr_store_type(wr_mas);
> +	mas->store_type = mas_wr_store_type(wr_mas);
>  	request = mas_prealloc_calc(mas, entry);
>  	if (!request)
>  		return;
> @@ -5446,7 +5424,7 @@ void *mas_store(struct ma_state *mas, void *entry)
>  	 * overwrite multiple entries within a self-balancing B-Tree.
>  	 */
>  	mas_wr_prealloc_setup(&wr_mas);
> -	mas_wr_store_type(&wr_mas);
> +	mas->store_type = mas_wr_store_type(&wr_mas);
>  	if (mas->mas_flags & MA_STATE_PREALLOC) {
>  		mas_wr_store_entry(&wr_mas);
>  		MAS_WR_BUG_ON(&wr_mas, mas_is_err(mas));
> @@ -5549,7 +5527,7 @@ int mas_preallocate(struct ma_state *mas, void *entry, gfp_t gfp)
>  	int request;
>  
>  	mas_wr_prealloc_setup(&wr_mas);
> -	mas_wr_store_type(&wr_mas);
> +	mas->store_type = mas_wr_store_type(&wr_mas);
>  	request = mas_prealloc_calc(mas, entry);
>  	if (!request)
>  		return ret;
> -- 
> 2.43.0
>