linux-kernel - Re: [RFC v3] genalloc:support memory-allocation with bytes-alignment to genalloc

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Date:	Mon, 3 Aug 2015 18:18:35 -0500
From:	Scott Wood <scottwood@...escale.com>
To:	Zhao Qiang <qiang.zhao@...escale.com>
CC:	<lauraa@...eaurora.org>, <linux-kernel@...r.kernel.org>,
	<linuxppc-dev@...ts.ozlabs.org>, <akpm@...ux-foundation.org>,
	<olof@...om.net>, <catalin.marinas@....com>, <X.xie@...escale.com>
Subject: Re: [RFC v3] genalloc:support memory-allocation with
 bytes-alignment to genalloc

On Mon, 2015-08-03 at 16:35 +0800, Zhao Qiang wrote:
> 
> @@ -73,6 +74,13 @@ struct gen_pool_chunk {
>       unsigned long bits[0];          /* bitmap for allocating memory chunk */
>  };
>  
> +/*
> + *  General purpose special memory pool data descriptor.
> + */

It's not "general purpose".  It's for gen_pool_first_fit_align (and could be 
reused by any future algorithms that need alignment but nothing else).

> +struct data_align {
> +     int align;              /* alignment by bytes for starting address */
> +};

struct genpool_data_align


> diff --git a/lib/genalloc.c b/lib/genalloc.c
> index d214866..e0b737c 100644
> --- a/lib/genalloc.c
> +++ b/lib/genalloc.c
> @@ -269,6 +269,24 @@ EXPORT_SYMBOL(gen_pool_destroy);
>   */
>  unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
>  {
> +     return gen_pool_alloc_data(pool, size, NULL);
> +}
> +EXPORT_SYMBOL(gen_pool_alloc);

This should pass in pool->data, not NULL.

> +
> +/**
> + * gen_pool_alloc_data - allocate special memory from the pool
> + * @pool: pool to allocate from
> + * @size: number of bytes to allocate from the pool
> + * @data: data passed to algorithm
> + *
> + * Allocate the requested number of bytes from the specified pool.
> + * Uses the pool allocation function (with first-fit algorithm by default).
> + * Can not be used in NMI handler on architectures without
> + * NMI-safe cmpxchg implementation.
> + */
> +unsigned long gen_pool_alloc_data(struct gen_pool *pool, size_t size,
> +             void *data)
> +{
>       struct gen_pool_chunk *chunk;
>       unsigned long addr = 0;
>       int order = pool->min_alloc_order;
> @@ -290,7 +308,7 @@ unsigned long gen_pool_alloc(struct gen_pool *pool, 
> size_t size)
>               end_bit = chunk_size(chunk) >> order;
>  retry:
>               start_bit = pool->algo(chunk->bits, end_bit, start_bit, nbits,
> -                             pool->data);
> +                             pool->data, pool);


This should pass in data, not pool->data.  Currently you don't use the data 
argument at all.


> +unsigned long gen_pool_first_fit_align(unsigned long *map, unsigned long 
> size,
> +             unsigned long start, unsigned int nr, void *data,
> +             struct gen_pool *pool)
> +{
> +     struct data_align *alignment;
> +     unsigned long align_mask;
> +     int order;
> +
> +     if (data == NULL)
> +             return -EINVAL;

Unnecessary check.  If this happens it will happen quickly on the developer's 
machine, so let it oops and be obvious.

> +
> +     alignment = (struct data_align *)data;

Unnecessary cast.

-Scott

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