linux-kernel - Re: [PATCH V3 01/27] kfifo: add kfifo_alloc

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Message-Id: <20251112112914.459baa16c4e9117d67f53011@linux-foundation.org>
Date: Wed, 12 Nov 2025 11:29:14 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Ming Lei <ming.lei@...hat.com>
Cc: Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org, Caleb Sander
 Mateos <csander@...estorage.com>, Uday Shankar <ushankar@...estorage.com>,
 Stefani Seibold <stefani@...bold.net>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 01/27] kfifo: add kfifo_alloc_node() helper for NUMA
 awareness

On Wed, 12 Nov 2025 17:37:39 +0800 Ming Lei <ming.lei@...hat.com> wrote:

> Add __kfifo_alloc_node() by refactoring and reusing __kfifo_alloc(),
> and define kfifo_alloc_node() macro to support NUMA-aware memory
> allocation.
> 
> The new __kfifo_alloc_node() function accepts a NUMA node parameter
> and uses kmalloc_array_node() instead of kmalloc_array() for
> node-specific allocation. The existing __kfifo_alloc() now calls
> __kfifo_alloc_node() with NUMA_NO_NODE to maintain backward
> compatibility.
> 
> This enables users to allocate kfifo buffers on specific NUMA nodes,
> which is important for performance in NUMA systems where the kfifo
> will be primarily accessed by threads running on specific nodes.

I was about to ask "please don't add infrastructure without users", but
I see a "01/27" there.  I wander over to lkml but I can't find 02-27
there either.  Maybe something went wrong.

I prefer to be cc'ed on the entire series, please.

> --- a/include/linux/kfifo.h
> +++ b/include/linux/kfifo.h
> @@ -369,6 +369,30 @@ __kfifo_int_must_check_helper( \
>  }) \
>  )
>  
> +/**
> + * kfifo_alloc_node - dynamically allocates a new fifo buffer on a NUMA node
> + * @fifo: pointer to the fifo
> + * @size: the number of elements in the fifo, this must be a power of 2
> + * @gfp_mask: get_free_pages mask, passed to kmalloc()
> + * @node: NUMA node to allocate memory on
> + *
> + * This macro dynamically allocates a new fifo buffer with NUMA node awareness.
> + *
> + * The number of elements will be rounded-up to a power of 2.
> + * The fifo will be release with kfifo_free().
> + * Return 0 if no error, otherwise an error code.
> + */
> +#define kfifo_alloc_node(fifo, size, gfp_mask, node) \
> +__kfifo_int_must_check_helper( \
> +({ \
> +	typeof((fifo) + 1) __tmp = (fifo); \
> +	struct __kfifo *__kfifo = &__tmp->kfifo; \
> +	__is_kfifo_ptr(__tmp) ? \
> +	__kfifo_alloc_node(__kfifo, size, sizeof(*__tmp->type), gfp_mask, node) : \
> +	-EINVAL; \
> +}) \
> +)

Well this is an eyesore.  Do we really need it?  It seems to be here so
we can check for a programming bug?  Well, don't add programming bugs!

I'm actually not enjoying the existence of __is_kfifo_ptr() at all. 
What  is it all doing?  It's a FIFO for heck's sake, why is this so hard.

> @@ -902,6 +926,9 @@ __kfifo_uint_must_check_helper( \
>  extern int __kfifo_alloc(struct __kfifo *fifo, unsigned int size,
>  	size_t esize, gfp_t gfp_mask);
>  
> +extern int __kfifo_alloc_node(struct __kfifo *fifo, unsigned int size,
> +	size_t esize, gfp_t gfp_mask, int node);
> +

Nit: please align things like this:

extern int __kfifo_alloc_node(struct __kfifo *fifo, unsigned int size,
			      size_t esize, gfp_t gfp_mask, int node);

(several places)