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Date:   Tue, 10 Oct 2023 14:15:58 -0400
From:   "Liam R. Howlett" <Liam.Howlett@Oracle.com>
To:     Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        maple-tree@lists.infradead.org, akpm@linux-foundation.org,
        willy@infradead.org, zhangpeng.00@bytedance.com
Subject: Re: [PATCH 2/3] maple_tree: use preallocations in mas_store_gfp()
Message-ID: <20231010181558.2xebit6nsu3lqk2m@revolver>
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References: <20231009201639.920512-1-sidhartha.kumar@oracle.com>
 <20231009201639.920512-3-sidhartha.kumar@oracle.com>
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* Sidhartha Kumar <sidhartha.kumar@oracle.com> [231009 16:16]:
> Preallocate maple nodes before call to mas_wr_store_entry(). If a new
> node is not needed, go directly to mas_wr_store_entry(), otherwise
> allocate the needed nodes and set the MA_STATE_PREALLOC flag.


The way I'd like to see this working is to preallocate nodes prior to
writing, but also to end in a state where we can call the store
operation to continue the operation.  Both of these parts need to be
together in a patch set if they cannot be in the same patch.

Thanks,
Liam

> 
> Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
> ---
>  lib/maple_tree.c | 22 +++++++++++++++++++---
>  1 file changed, 19 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> index e239197a57fc..25ae66e585f4 100644
> --- a/lib/maple_tree.c
> +++ b/lib/maple_tree.c
> @@ -5478,17 +5478,33 @@ int mas_prealloc_calc(struct ma_wr_state *wr_mas)
>  int mas_store_gfp(struct ma_state *mas, void *entry, gfp_t gfp)
>  {
>  	MA_WR_STATE(wr_mas, mas, entry);
> +	int request;
>  
>  	mas_wr_store_setup(&wr_mas);
> -	trace_ma_write(__func__, mas, 0, entry);
> -retry:
> +	wr_mas.content = mas_start(mas);
> +
> +	request = mas_prealloc_calc(&wr_mas);
> +	if (!request)
> +		goto store_entry;
> +
> +	mas_node_count_gfp(mas, request, gfp);
> +	if (unlikely(mas_is_err(mas))) {
> +		mas_set_alloc_req(mas, 0);
> +		mas_destroy(mas);
> +		mas_reset(mas);
> +		return xa_err(mas->node);
> +	}
> +	mas->mas_flags |= MA_STATE_PREALLOC;
> +
> +store_entry:
>  	mas_wr_store_entry(&wr_mas);
>  	if (unlikely(mas_nomem(mas, gfp)))
> -		goto retry;
> +		goto store_entry;
>  
>  	if (unlikely(mas_is_err(mas)))
>  		return xa_err(mas->node);
>  
> +	trace_ma_write(__func__, mas, 0, entry);
>  	return 0;
>  }
>  EXPORT_SYMBOL_GPL(mas_store_gfp);
> -- 
> 2.41.0
>