Re: [PATCH v3 09/16] zsmalloc: move struct zs_meta from mapping to freelist

Sergey Senozhatsky
2016-04-17T14:24:37Z

Hello,

On (03/30/16 16:12), Minchan Kim wrote:
> For supporting migration from VM, we need to have address_space
> on every page so zsmalloc shouldn't use page->mapping. So,
> this patch moves zs_meta from mapping to freelist.
>
> Signed-off-by: Minchan Kim <minchan@kernel.org>

a small get_zspage_meta() helper would make this patch shorter :)

Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>

-ss

> ---
> mm/zsmalloc.c | 22 +++++++++++-----------
> 1 file changed, 11 insertions(+), 11 deletions(-)
>
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index 807998462539..d4d33a819832 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -29,7 +29,7 @@
> * Look at size_class->huge.
> * page->lru: links together first pages of various zspages.
> * Basically forming list of zspages in a fullness group.
> - * page->mapping: override by struct zs_meta
> + * page->freelist: override by struct zs_meta
> *
> * Usage of struct page flags:
> * PG_private: identifies the first component page
> @@ -418,7 +418,7 @@ static int get_zspage_inuse(struct page *first_page)
>
> VM_BUG_ON_PAGE(!is_first_page(first_page), first_page);
>
> - m = (struct zs_meta *)&first_page->mapping;
> + m = (struct zs_meta *)&first_page->freelist;
>
> return m->inuse;
> }
> @@ -429,7 +429,7 @@ static void set_zspage_inuse(struct page *first_page, int val)
>
> VM_BUG_ON_PAGE(!is_first_page(first_page), first_page);
>
> - m = (struct zs_meta *)&first_page->mapping;
> + m = (struct zs_meta *)&first_page->freelist;
> m->inuse = val;
> }
>
> @@ -439,7 +439,7 @@ static void mod_zspage_inuse(struct page *first_page, int val)
>
> VM_BUG_ON_PAGE(!is_first_page(first_page), first_page);
>
> - m = (struct zs_meta *)&first_page->mapping;
> + m = (struct zs_meta *)&first_page->freelist;
> m->inuse += val;
> }
>
> @@ -449,7 +449,7 @@ static void set_freeobj(struct page *first_page, int idx)
>
> VM_BUG_ON_PAGE(!is_first_page(first_page), first_page);
>
> - m = (struct zs_meta *)&first_page->mapping;
> + m = (struct zs_meta *)&first_page->freelist;
> m->freeobj = idx;
> }
>
> @@ -459,7 +459,7 @@ static unsigned long get_freeobj(struct page *first_page)
>
> VM_BUG_ON_PAGE(!is_first_page(first_page), first_page);
>
> - m = (struct zs_meta *)&first_page->mapping;
> + m = (struct zs_meta *)&first_page->freelist;
> return m->freeobj;
> }
>
> @@ -471,7 +471,7 @@ static void get_zspage_mapping(struct page *first_page,
>
> VM_BUG_ON_PAGE(!is_first_page(first_page), first_page);
>
> - m = (struct zs_meta *)&first_page->mapping;
> + m = (struct zs_meta *)&first_page->freelist;
> *fullness = m->fullness;
> *class_idx = m->class;
> }
> @@ -484,7 +484,7 @@ static void set_zspage_mapping(struct page *first_page,
>
> VM_BUG_ON_PAGE(!is_first_page(first_page), first_page);
>
> - m = (struct zs_meta *)&first_page->mapping;
> + m = (struct zs_meta *)&first_page->freelist;
> m->fullness = fullness;
> m->class = class_idx;
> }
> @@ -946,7 +946,6 @@ static void reset_page(struct page *page)
> clear_bit(PG_private, &page->flags);
> clear_bit(PG_private_2, &page->flags);
> set_page_private(page, 0);
> - page->mapping = NULL;
> page->freelist = NULL;
> }
>
> @@ -1056,6 +1055,7 @@ static struct page *alloc_zspage(struct size_class *class, gfp_t flags)
>
> INIT_LIST_HEAD(&page->lru);
> if (i == 0) { /* first page */
> + page->freelist = NULL;
> SetPagePrivate(page);
> set_page_private(page, 0);
> first_page = page;
> @@ -2068,9 +2068,9 @@ static int __init zs_init(void)
>
> /*
> * A zspage's a free object index, class index, fullness group,
> - * inuse object count are encoded in its (first)page->mapping
> + * inuse object count are encoded in its (first)page->freelist
> * so sizeof(struct zs_meta) should be less than
> - * sizeof(page->mapping(i.e., unsigned long)).
> + * sizeof(page->freelist(i.e., void *)).
> */
> BUILD_BUG_ON(sizeof(struct zs_meta) > sizeof(unsigned long));
>
> --
> 1.9.1
>