On Tue, 2024-06-25 at 21:52 +0800, Yunsheng Lin wrote:
> There are many use cases that need minimum memory in order
> for forward progress, but more performant if more memory is
> available or need to probe the cache info to use any memory
> available for frag caoleasing reason.
>
> Currently skb_page_frag_refill() API is used to solve the
> above use cases, but caller needs to know about the internal
> detail and access the data field of 'struct page_frag' to
> meet the requirement of the above use cases and its
> implementation is similar to the one in mm subsystem.
>
> To unify those two page_frag implementations, introduce a
> prepare API to ensure minimum memory is satisfied and return
> how much the actual memory is available to the caller and a
> probe API to report the current available memory to caller
> without doing cache refilling. The caller needs to either call
> the commit API to report how much memory it actually uses, or
> not do so if deciding to not use any memory.
>
> As next patch is about to replace 'struct page_frag' with
> 'struct page_frag_cache' in linux/sched.h, which is included
> by the asm-offsets.s, using the virt_to_page() in the inline
> helper of page_frag_cache.h cause a "'vmemmap' undeclared"
> compiling error for asm-offsets.s, use a macro for probe API
> to avoid that compiling error.
>
> CC: Alexander Duyck <alexander.duyck@xxxxxxxxx>
> Signed-off-by: Yunsheng Lin <linyunsheng@xxxxxxxxxx>
> ---
> include/linux/page_frag_cache.h | 82 +++++++++++++++++++++++
> mm/page_frag_cache.c | 114 ++++++++++++++++++++++++++++++++
> 2 files changed, 196 insertions(+)
>
> diff --git a/include/linux/page_frag_cache.h b/include/linux/page_frag_cache.h
> index b33904d4494f..e95d44a36ec9 100644
> --- a/include/linux/page_frag_cache.h
> +++ b/include/linux/page_frag_cache.h
> @@ -4,6 +4,7 @@
> #define _LINUX_PAGE_FRAG_CACHE_H
>
> #include <linux/gfp_types.h>
> +#include <linux/mmdebug.h>
>
> #define PAGE_FRAG_CACHE_MAX_SIZE __ALIGN_MASK(32768, ~PAGE_MASK)
> #define PAGE_FRAG_CACHE_MAX_ORDER get_order(PAGE_FRAG_CACHE_MAX_SIZE)
> @@ -87,6 +88,9 @@ static inline unsigned int page_frag_cache_page_size(struct encoded_va *encoded_
>
> void page_frag_cache_drain(struct page_frag_cache *nc);
> void __page_frag_cache_drain(struct page *page, unsigned int count);
> +struct page *page_frag_alloc_pg(struct page_frag_cache *nc,
> + unsigned int *offset, unsigned int fragsz,
> + gfp_t gfp);
> void *__page_frag_alloc_va_align(struct page_frag_cache *nc,
> unsigned int fragsz, gfp_t gfp_mask,
> unsigned int align_mask);
> @@ -99,12 +103,90 @@ static inline void *page_frag_alloc_va_align(struct page_frag_cache *nc,
> return __page_frag_alloc_va_align(nc, fragsz, gfp_mask, -align);
> }
>
> +static inline unsigned int page_frag_cache_page_offset(const struct page_frag_cache *nc)
> +{
> + return page_frag_cache_page_size(nc->encoded_va) - nc->remaining;
> +}
> +
> static inline void *page_frag_alloc_va(struct page_frag_cache *nc,
> unsigned int fragsz, gfp_t gfp_mask)
> {
> return __page_frag_alloc_va_align(nc, fragsz, gfp_mask, ~0u);
> }
>
> +void *page_frag_alloc_va_prepare(struct page_frag_cache *nc, unsigned int *fragsz,
> + gfp_t gfp);
> +
> +static inline void *page_frag_alloc_va_prepare_align(struct page_frag_cache *nc,
> + unsigned int *fragsz,
> + gfp_t gfp,
> + unsigned int align)
> +{
> + WARN_ON_ONCE(!is_power_of_2(align) || align > PAGE_SIZE);
> + nc->remaining = nc->remaining & -align;
> + return page_frag_alloc_va_prepare(nc, fragsz, gfp);
> +}
> +
> +struct page *page_frag_alloc_pg_prepare(struct page_frag_cache *nc,
> + unsigned int *offset,
> + unsigned int *fragsz, gfp_t gfp);
> +
> +struct page *page_frag_alloc_prepare(struct page_frag_cache *nc,
> + unsigned int *offset,
> + unsigned int *fragsz,
> + void **va, gfp_t gfp);
> +
> +static inline struct encoded_va *__page_frag_alloc_probe(struct page_frag_cache *nc,
> + unsigned int *offset,
> + unsigned int *fragsz,
> + void **va)
> +{
> + struct encoded_va *encoded_va;
> +
> + *fragsz = nc->remaining;
> + encoded_va = nc->encoded_va;
> + *offset = page_frag_cache_page_size(encoded_va) - *fragsz;
> + *va = encoded_page_address(encoded_va) + *offset;
> +
> + return encoded_va;
> +}
> +
> +#define page_frag_alloc_probe(nc, offset, fragsz, va) \
> +({ \
> + struct page *__page = NULL; \
> + \
> + VM_BUG_ON(!*(fragsz)); \
> + if (likely((nc)->remaining >= *(fragsz))) \
> + __page = virt_to_page(__page_frag_alloc_probe(nc, \
> + offset, \
> + fragsz, \
> + va)); \
> + \
> + __page; \
> +})
> +
Why is this a macro instead of just being an inline? Are you trying to
avoid having to include a header due to the virt_to_page?
