Re: [RFC v11 02/14] mm: move the page fragment allocator from page_alloc into its own file

[Yunsheng Lin]

On 7/22/2024 1:58 AM, Alexander Duyck wrote:
> On Fri, Jul 19, 2024 at 2:37 AM Yunsheng Lin <linyunsheng@xxxxxxxxxx> wrote:

...

> > --- /dev/null
> > +++ b/include/linux/page_frag_cache.h
> > @@ -0,0 +1,32 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +
> > +#ifndef _LINUX_PAGE_FRAG_CACHE_H
> > +#define _LINUX_PAGE_FRAG_CACHE_H
> > +
> > +#include <linux/log2.h>
> > +#include <linux/types.h>
> > +#include <linux/mm_types_task.h>
>
> You don't need to include mm_types_task.h here. You can just use
> declare "struct page_frag_cache;" as we did before in gfp.h.
> Technically this should be included in mm_types.h so any callers
> making use of these functions would need to make sure to include that
> like we did for gfp.h before anyway.

The probe API is added as an inline helper in patch 11 according to
discussion in [1], so the definition of "struct page_frag_cache" is
needed, so I am not sure what is the point of using
"struct page_frag_cache;" here and then remove it and include
mm_types_task.h in patch 11.

1. 
https://lore.kernel.org/all/cb541985-a06d-7a71-9e6d-38827ccdf875@xxxxxxxxxx/

> > +#include <asm/page.h>
> > +
>
> Not sure why this is included here either. From what I can tell there
> isn't anything here using the contents of page.h. I suspect you should
> only need it for the get_order call which would be used in other
> files.

It seems unnecessay, will remove that.

> > +void page_frag_cache_drain(struct page_frag_cache *nc);
> > +void __page_frag_cache_drain(struct page *page, unsigned int count);
> > +void *__page_frag_alloc_align(struct page_frag_cache *nc, unsigned int fragsz,
> > +                             gfp_t gfp_mask, unsigned int align_mask);
> > +
> > +static inline void *page_frag_alloc_align(struct page_frag_cache *nc,
> > +                                         unsigned int fragsz, gfp_t gfp_mask,
> > +                                         unsigned int align)
> > +{
> > +       WARN_ON_ONCE(!is_power_of_2(align));
> > +       return __page_frag_alloc_align(nc, fragsz, gfp_mask, -align);
> > +}
> > +
> > +static inline void *page_frag_alloc(struct page_frag_cache *nc,
> > +                                   unsigned int fragsz, gfp_t gfp_mask)
> > +{
> > +       return __page_frag_alloc_align(nc, fragsz, gfp_mask, ~0u);
> > +}
> > +
> > +void page_frag_free(void *addr);
> > +
> > +#endif
>
> ...
>
> > diff --git a/mm/page_frag_test.c b/mm/page_frag_test.c
> > index cf2691f60b67..b7a5affb92f2 100644
> > --- a/mm/page_frag_test.c
> > +++ b/mm/page_frag_test.c
> > @@ -6,7 +6,6 @@
> >    * Copyright: linyunsheng@xxxxxxxxxx
> >    */
> >
> > -#include <linux/mm.h>
> >   #include <linux/module.h>
> >   #include <linux/slab.h>
> >   #include <linux/vmalloc.h>
> > @@ -16,6 +15,7 @@
> >   #include <linux/log2.h>
> >   #include <linux/completion.h>
> >   #include <linux/kthread.h>
> > +#include <linux/page_frag_cache.h>
> >
> >   #define OBJPOOL_NR_OBJECT_MAX  BIT(24)
>
> Rather than making users have to include page_frag_cache.h I think it
> would be better for us to just maintain the code as being accessible
> from mm.h. So it might be better to just add page_frag_cache.h to the
> includes there.

It would be better to list out why it is better that way as I am failing
to see it that way yet as I think it is better to use the explicit
header file instead the implicit header file.


>