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

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Message-ID: <aRUypQzcovGikrV0@fedora>
Date: Thu, 13 Nov 2025 09:21:41 +0800
From: Ming Lei <ming.lei@...hat.com>
To: Andrew Morton <akpm@...ux-foundation.org>
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, Nov 12, 2025 at 11:29:14AM -0800, Andrew Morton wrote:
> 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.

It can be found in lore:

https://lore.kernel.org/all/20251112093808.2134129-1-ming.lei@redhat.com/

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

OK.

> 
> > --- 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.

It is basically a clone of existing kfifo_alloc().

Do we need to clean kfifo_alloc() first? Otherwise I'd keep the same
pattern with existing definitions.

> 
> > @@ -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);

OK.

Thanks,
Ming