zsmalloc: use page->private instead of page->first_page

We are going to rework how compound_head() work. It will not use
page->first_page as we have it now.

The only other user of page->first_page beyond compound pages is
zsmalloc.

Let's use page->private instead of page->first_page here. It occupies
the same storage space.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 2858b20dce763741ff2e165fd4c09b98b5a12966..9f15bdd9163c2360edf2e070023b6099b683a85c 100644 (file)
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -16,7 +16,7 @@
  * struct page(s) to form a zspage.
  *
  * Usage of struct page fields:
- *     page->first_page: points to the first component (0-order) page
+ *     page->private: points to the first component (0-order) page
  *     page->index (union with page->freelist): offset of the first object
  *             starting in this page. For the first page, this is
  *             always 0, so we use this field (aka freelist) to point
@@ -26,8 +26,7 @@
  *
  *     For _first_ page only:
  *
- *     page->private (union with page->first_page): refers to the
- *             component page after the first page
+ *     page->private: refers to the component page after the first page
  *             If the page is first_page for huge object, it stores handle.
  *             Look at size_class->huge.
  *     page->freelist: points to the first free object in zspage.
@@ -774,7 +773,7 @@ static struct page *get_first_page(struct page *page)
        if (is_first_page(page))
                return page;
        else
-               return page->first_page;
+               return (struct page *)page_private(page);
 }
 
 static struct page *get_next_page(struct page *page)
@@ -959,7 +958,7 @@ static struct page *alloc_zspage(struct size_class *class, gfp_t flags)
         * Allocate individual pages and link them together as:
         * 1. first page->private = first sub-page
         * 2. all sub-pages are linked together using page->lru
-        * 3. each sub-page is linked to the first page using page->first_page
+        * 3. each sub-page is linked to the first page using page->private
         *
         * For each size class, First/Head pages are linked together using
         * page->lru. Also, we set PG_private to identify the first page
@@ -984,7 +983,7 @@ static struct page *alloc_zspage(struct size_class *class, gfp_t flags)
                if (i == 1)
                        set_page_private(first_page, (unsigned long)page);
                if (i >= 1)
-                       page->first_page = first_page;
+                       set_page_private(page, (unsigned long)first_page);
                if (i >= 2)
                        list_add(&page->lru, &prev_page->lru);
                if (i == class->pages_per_zspage - 1)   /* last page */