[PATCH v1 12/19] zsmalloc: move struct zs_meta from mapping to freelist

[Minchan Kim]

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 <minc...@kernel.org>
---
 mm/zsmalloc.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index e23cd3b2dd71..bfc6a048afac 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
@@ -419,7 +419,7 @@ 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;
 }
@@ -430,7 +430,7 @@ 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;
 }
 
@@ -440,7 +440,7 @@ 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;
 }
 
@@ -450,7 +450,7 @@ 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;
 }
 
@@ -460,7 +460,7 @@ 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;
 }
 
@@ -472,7 +472,7 @@ 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;
 }
@@ -485,7 +485,7 @@ 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;
 }
@@ -941,7 +941,7 @@ 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;
        page_mapcount_reset(page);
 }
 
@@ -1051,6 +1051,7 @@ 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;
@@ -2066,9 +2067,9 @@ 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