netdev - Re: [PATCHv2 net 0/3] net: add support for flex_array_resize in flex

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Date:   Tue, 11 Dec 2018 22:50:00 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     lucien.xin@...il.com
Cc:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        linux-sctp@...r.kernel.org, marcelo.leitner@...il.com,
        nhorman@...driver.com, dave.hansen@...ux.intel.com,
        rientjes@...gle.com, eparis@...hat.com, khorenko@...tuozzo.com
Subject: Re: [PATCHv2 net 0/3] net: add support for flex_array_resize in
 flex_array

From: Xin Long <lucien.xin@...il.com>
Date: Fri,  7 Dec 2018 14:30:32 +0800

> Without the support for the total_nr_elements's growing or shrinking
> dynamically, flex_array is not that 'flexible'. Like when users want
> to change the size, they have to redo flex_array_alloc and copy all
> the elements from the old to the new one.  The worse thing is every
> element's memory gets changed.
> 
> To implement flex_array_resize based on current code, the difficult
> thing is to process the size border of FLEX_ARRAY_BASE_BYTES_LEFT,
> where the base data memory may change to an array for the 2nd level
> data memory for growing, likewise for shrinking.
> 
> To make this part easier, we separate the base data memory and define
> FLEX_ARRAY_BASE_SIZE as a same value of FLEX_ARRAY_PART_SIZE, as Neil
> suggested.  When new size is crossing the border, the base memory is
> allocated as the array for the 2nd level data memory and its part[0]
> is pointed to the old base memory, and do the opposite for shrinking.
> 
> But it doesn't do any memory allocation or shrinking for elements in
> flex_array_resize, as which should be done by flex_array_prealloc or
> flex_array_shrink called by users.  No memory leaks can be caused by
> that.
> 
> SCTP has benefited a lot from flex_array_resize() for managing its
> stream memory so far.
> 
> v1->v2:
>   Cc LKML and more developers.

So I don't know what to do about this series.

One of the responses stated that it has been proposed to remove flex_array
and I don't know what to make of that, nor can I tell if that makes this
series inappropriate or not.