Re: [PATCHv3 2/5] zsmalloc: use page->private instead of page->first_page

From: Vlastimil Babka
Date: Mon Aug 24 2015 - 11:04:50 EST


On 08/19/2015 11:21 AM, Kirill A. Shutemov wrote:
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->fisrt_page beyond compound pages is

^ typo

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@xxxxxxxxxxxxxxx>

Acked-by: Vlastimil Babka <vbabka@xxxxxxx>

---
mm/zsmalloc.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 0a7f81aa2249..a85754e69879 100644
--- 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.
@@ -770,7 +769,7 @@ 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)
@@ -955,7 +954,7 @@ 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
@@ -980,7 +979,7 @@ 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(first_page, (unsigned long)first_page);
if (i >= 2)
list_add(&page->lru, &prev_page->lru);
if (i == class->pages_per_zspage - 1) /* last page */


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