Re: [PATCH 1/3] mm: Remove last argument of reuse_swap_page()

[William Kucharski <william.kucharski@oracle.com>]

I really like the cleanups and the removal of code no one is using anyway.

For the series:

Reviewed-by: William Kucharski <william.kucharski@oracle.com>

> On Dec 20, 2021, at 1:59 PM, Matthew Wilcox (Oracle) <willy@infradead.org> wrote:
> 
> None of the callers care about the total_map_swapcount() any more.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
> include/linux/swap.h | 6 +++---
> mm/huge_memory.c     | 2 +-
> mm/khugepaged.c      | 2 +-
> mm/memory.c          | 2 +-
> mm/swapfile.c        | 8 +-------
> 5 files changed, 7 insertions(+), 13 deletions(-)
> 
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index d1ea44b31f19..bdccbf1efa61 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -514,7 +514,7 @@ extern int __swp_swapcount(swp_entry_t entry);
> extern int swp_swapcount(swp_entry_t entry);
> extern struct swap_info_struct *page_swap_info(struct page *);
> extern struct swap_info_struct *swp_swap_info(swp_entry_t entry);
> -extern bool reuse_swap_page(struct page *, int *);
> +extern bool reuse_swap_page(struct page *);
> extern int try_to_free_swap(struct page *);
> struct backing_dev_info;
> extern int init_swap_address_space(unsigned int type, unsigned long nr_pages);
> @@ -680,8 +680,8 @@ static inline int swp_swapcount(swp_entry_t entry)
> 	return 0;
> }
> 
> -#define reuse_swap_page(page, total_map_swapcount) \
> -	(page_trans_huge_mapcount(page, total_map_swapcount) == 1)
> +#define reuse_swap_page(page) \
> +	(page_trans_huge_mapcount(page, NULL) == 1)
> 
> static inline int try_to_free_swap(struct page *page)
> {
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index e5483347291c..b61fbe95c856 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1322,7 +1322,7 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf)
> 	 * We can only reuse the page if nobody else maps the huge page or it's
> 	 * part.
> 	 */
> -	if (reuse_swap_page(page, NULL)) {
> +	if (reuse_swap_page(page)) {
> 		pmd_t entry;
> 		entry = pmd_mkyoung(orig_pmd);
> 		entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index e99101162f1a..11794bdf513a 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -681,7 +681,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
> 			goto out;
> 		}
> 		if (!pte_write(pteval) && PageSwapCache(page) &&
> -				!reuse_swap_page(page, NULL)) {
> +				!reuse_swap_page(page)) {
> 			/*
> 			 * Page is in the swap cache and cannot be re-used.
> 			 * It cannot be collapsed into a THP.
> diff --git a/mm/memory.c b/mm/memory.c
> index 8f1de811a1dc..dd85fd07cb24 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3626,7 +3626,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> 	inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
> 	dec_mm_counter_fast(vma->vm_mm, MM_SWAPENTS);
> 	pte = mk_pte(page, vma->vm_page_prot);
> -	if ((vmf->flags & FAULT_FLAG_WRITE) && reuse_swap_page(page, NULL)) {
> +	if ((vmf->flags & FAULT_FLAG_WRITE) && reuse_swap_page(page)) {
> 		pte = maybe_mkwrite(pte_mkdirty(pte), vma);
> 		vmf->flags &= ~FAULT_FLAG_WRITE;
> 		ret |= VM_FAULT_WRITE;
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index e59e08ef46e1..a4f48189300a 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1668,12 +1668,8 @@ static int page_trans_huge_map_swapcount(struct page *page, int *total_mapcount,
> * to it.  And as a side-effect, free up its swap: because the old content
> * on disk will never be read, and seeking back there to write new content
> * later would only waste time away from clustering.
> - *
> - * NOTE: total_map_swapcount should not be relied upon by the caller if
> - * reuse_swap_page() returns false, but it may be always overwritten
> - * (see the other implementation for CONFIG_SWAP=n).
> */
> -bool reuse_swap_page(struct page *page, int *total_map_swapcount)
> +bool reuse_swap_page(struct page *page)
> {
> 	int count, total_mapcount, total_swapcount;
> 
> @@ -1682,8 +1678,6 @@ bool reuse_swap_page(struct page *page, int *total_map_swapcount)
> 		return false;
> 	count = page_trans_huge_map_swapcount(page, &total_mapcount,
> 					      &total_swapcount);
> -	if (total_map_swapcount)
> -		*total_map_swapcount = total_mapcount + total_swapcount;
> 	if (count == 1 && PageSwapCache(page) &&
> 	    (likely(!PageTransCompound(page)) ||
> 	     /* The remaining swap count will be freed soon */
> -- 
> 2.33.0
> 
>