linux-kernel - Re: [PATCH v5 03/10] maple_tree: Introduce interfaces __mt_dup() and mtree

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Date:   Tue, 17 Oct 2023 10:44:49 +0800
From:   Peng Zhang <zhangpeng.00@...edance.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Liam.Howlett@...cle.com, corbet@....net, akpm@...ux-foundation.org,
        brauner@...nel.org, surenb@...gle.com, michael.christie@...cle.com,
        mjguzik@...il.com, mathieu.desnoyers@...icios.com,
        npiggin@...il.com, peterz@...radead.org, oliver.sang@...el.com,
        mst@...hat.com, maple-tree@...ts.infradead.org, linux-mm@...ck.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org,
        Peng Zhang <zhangpeng.00@...edance.com>
Subject: Re: [PATCH v5 03/10] maple_tree: Introduce interfaces __mt_dup() and
 mtree_dup()



在 2023/10/16 22:10, Matthew Wilcox 写道:
> On Mon, Oct 16, 2023 at 11:22:19AM +0800, Peng Zhang wrote:
>> +++ b/lib/maple_tree.c
>> @@ -4,6 +4,10 @@
>>    * Copyright (c) 2018-2022 Oracle Corporation
>>    * Authors: Liam R. Howlett <Liam.Howlett@...cle.com>
>>    *	    Matthew Wilcox <willy@...radead.org>
>> + *
>> + * Algorithm for duplicating Maple Tree
>> + * Copyright (c) 2023 ByteDance
>> + * Author: Peng Zhang <zhangpeng.00@...edance.com>
> 
> You can't copyright an algorithm.  You can copyright the
> _implementation_ of an algorithm.  You have a significant chunk of code
> in this file, so adding your copyright is reasonable (although not
> legally required, AIUI).  Just leave out this line:
> 
> + * Algorithm for duplicating Maple Tree
Okay, I will make the correction, thank you.
> 
>> +/**
>> + * __mt_dup(): Duplicate an entire maple tree
>> + * @mt: The source maple tree
>> + * @new: The new maple tree
>> + * @gfp: The GFP_FLAGS to use for allocations
>> + *
>> + * This function duplicates a maple tree in Depth-First Search (DFS) pre-order
>> + * traversal. It uses memcopy() to copy nodes in the source tree and allocate
> 
> memcpy()?
Yes, thank you for pointing this out.
> 
>> +int __mt_dup(struct maple_tree *mt, struct maple_tree *new, gfp_t gfp)
>> +{
>> +	int ret = 0;
>> +	MA_STATE(mas, mt, 0, 0);
>> +	MA_STATE(new_mas, new, 0, 0);
>> +
>> +	mas_dup_build(&mas, &new_mas, gfp);
>> +
>> +	if (unlikely(mas_is_err(&mas))) {
>> +		ret = xa_err(mas.node);
>> +		if (ret == -ENOMEM)
>> +			mas_dup_free(&new_mas);
>> +	}
>> +
>> +	return ret;
>> +}
>> +EXPORT_SYMBOL(__mt_dup);
> 
> Why does it need to be exported?
I consider __mt_dup() as a general interface for Maple Tree,
uncertain whether it will be used by certain modules in the future.
> 
>