Re: [PATCH] mm: Introduce page_size()

[Kirill Tkhai <ktkhai@virtuozzo.com>]

Hi, Matthew,

On 10.05.2019 21:12, Matthew Wilcox wrote:
> From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> 
> It's unnecessarily hard to find out the size of a potentially large page.
> Replace 'PAGE_SIZE << compound_order(page)' with 'page_size(page)'.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>  arch/arm/mm/flush.c                           | 3 +--
>  arch/arm64/mm/flush.c                         | 3 +--
>  arch/ia64/mm/init.c                           | 2 +-
>  drivers/staging/android/ion/ion_system_heap.c | 4 ++--
>  drivers/target/tcm_fc/tfc_io.c                | 3 +--
>  fs/io_uring.c                                 | 2 +-
>  include/linux/hugetlb.h                       | 2 +-
>  include/linux/mm.h                            | 9 +++++++++
>  lib/iov_iter.c                                | 2 +-
>  mm/kasan/common.c                             | 8 +++-----
>  mm/nommu.c                                    | 2 +-
>  mm/page_vma_mapped.c                          | 3 +--
>  mm/rmap.c                                     | 6 ++----
>  mm/slob.c                                     | 2 +-
>  mm/slub.c                                     | 4 ++--
>  net/xdp/xsk.c                                 | 2 +-
>  16 files changed, 29 insertions(+), 28 deletions(-)
> 
> diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
> index 58469623b015..c68a120de28b 100644
> --- a/arch/arm/mm/flush.c
> +++ b/arch/arm/mm/flush.c
> @@ -207,8 +207,7 @@ void __flush_dcache_page(struct address_space *mapping, struct page *page)
>  	 * coherent with the kernels mapping.
>  	 */
>  	if (!PageHighMem(page)) {
> -		size_t page_size = PAGE_SIZE << compound_order(page);
> -		__cpuc_flush_dcache_area(page_address(page), page_size);
> +		__cpuc_flush_dcache_area(page_address(page), page_size(page));
>  	} else {
>  		unsigned long i;
>  		if (cache_is_vipt_nonaliasing()) {
> diff --git a/arch/arm64/mm/flush.c b/arch/arm64/mm/flush.c
> index 5c9073bace83..280fdbc3bfa5 100644
> --- a/arch/arm64/mm/flush.c
> +++ b/arch/arm64/mm/flush.c
> @@ -67,8 +67,7 @@ void __sync_icache_dcache(pte_t pte)
>  	struct page *page = pte_page(pte);
>  
>  	if (!test_and_set_bit(PG_dcache_clean, &page->flags))
> -		sync_icache_aliases(page_address(page),
> -				    PAGE_SIZE << compound_order(page));
> +		sync_icache_aliases(page_address(page), page_size(page));
>  }
>  EXPORT_SYMBOL_GPL(__sync_icache_dcache);
>  
> diff --git a/arch/ia64/mm/init.c b/arch/ia64/mm/init.c
> index d28e29103bdb..cc4061cd9899 100644
> --- a/arch/ia64/mm/init.c
> +++ b/arch/ia64/mm/init.c
> @@ -63,7 +63,7 @@ __ia64_sync_icache_dcache (pte_t pte)
>  	if (test_bit(PG_arch_1, &page->flags))
>  		return;				/* i-cache is already coherent with d-cache */
>  
> -	flush_icache_range(addr, addr + (PAGE_SIZE << compound_order(page)));
> +	flush_icache_range(addr, addr + page_size(page));
>  	set_bit(PG_arch_1, &page->flags);	/* mark page as clean */
>  }
>  
> diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c
> index aa8d8425be25..b83a1d16bd89 100644
> --- a/drivers/staging/android/ion/ion_system_heap.c
> +++ b/drivers/staging/android/ion/ion_system_heap.c
> @@ -120,7 +120,7 @@ static int ion_system_heap_allocate(struct ion_heap *heap,
>  		if (!page)
>  			goto free_pages;
>  		list_add_tail(&page->lru, &pages);
> -		size_remaining -= PAGE_SIZE << compound_order(page);
> +		size_remaining -= page_size(page);
>  		max_order = compound_order(page);
>  		i++;
>  	}
> @@ -133,7 +133,7 @@ static int ion_system_heap_allocate(struct ion_heap *heap,
>  
>  	sg = table->sgl;
>  	list_for_each_entry_safe(page, tmp_page, &pages, lru) {
> -		sg_set_page(sg, page, PAGE_SIZE << compound_order(page), 0);
> +		sg_set_page(sg, page, page_size(page), 0);
>  		sg = sg_next(sg);
>  		list_del(&page->lru);
>  	}
> diff --git a/drivers/target/tcm_fc/tfc_io.c b/drivers/target/tcm_fc/tfc_io.c
> index 1eb1f58e00e4..83c1ec65dbcc 100644
> --- a/drivers/target/tcm_fc/tfc_io.c
> +++ b/drivers/target/tcm_fc/tfc_io.c
> @@ -148,8 +148,7 @@ int ft_queue_data_in(struct se_cmd *se_cmd)
>  					   page, off_in_page, tlen);
>  			fr_len(fp) += tlen;
>  			fp_skb(fp)->data_len += tlen;
> -			fp_skb(fp)->truesize +=
> -					PAGE_SIZE << compound_order(page);
> +			fp_skb(fp)->truesize += page_size(page);
>  		} else {
>  			BUG_ON(!page);
>  			from = kmap_atomic(page + (mem_off >> PAGE_SHIFT));
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index fdc18321d70c..2c37da095517 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -2891,7 +2891,7 @@ static int io_uring_mmap(struct file *file, struct vm_area_struct *vma)
>  	}
>  
>  	page = virt_to_head_page(ptr);
> -	if (sz > (PAGE_SIZE << compound_order(page)))
> +	if (sz > page_size(page))
>  		return -EINVAL;
>  
>  	pfn = virt_to_phys(ptr) >> PAGE_SHIFT;
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index edf476c8cfb9..2e909072a41f 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -472,7 +472,7 @@ static inline pte_t arch_make_huge_pte(pte_t entry, struct vm_area_struct *vma,
>  static inline struct hstate *page_hstate(struct page *page)
>  {
>  	VM_BUG_ON_PAGE(!PageHuge(page), page);
> -	return size_to_hstate(PAGE_SIZE << compound_order(page));
> +	return size_to_hstate(page_size(page));
>  }
>  
>  static inline unsigned hstate_index_to_shift(unsigned index)
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 0e8834ac32b7..0208f77bab63 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -772,6 +772,15 @@ static inline void set_compound_order(struct page *page, unsigned int order)
>  	page[1].compound_order = order;
>  }
>  
> +/*
> + * Returns the number of bytes in this potentially compound page.
> + * Must be called with the head page, not a tail page.
> + */
> +static inline unsigned long page_size(struct page *page)
> +{

Maybe we should underline commented head page limitation with VM_BUG_ON()?

Kirill