[v2,27/33] zsmalloc: Stop using slab fields in struct page

Commit Message

Vlastimil Babka Dec. 1, 2021, 6:15 p.m. UTC

From: "Matthew Wilcox (Oracle)" <[e-mail]>

The ->freelist and ->units members of struct page are for the use of slab
only.  I'm not particularly familiar with zsmalloc, so generate the same
code by using page->index to store 'page' (page->index and page->freelist
are at the same offset in struct page).  This should be cleaned up
properly at some point by somebody who is familiar with zsmalloc.

Signed-off-by: Matthew Wilcox (Oracle) <[e-mail]>
Signed-off-by: Vlastimil Babka <[e-mail]>
Cc: Minchan Kim <[e-mail]>
Cc: Nitin Gupta <[e-mail]>
Cc: Sergey Senozhatsky <[e-mail]>
---
 mm/zsmalloc.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

Comments

Minchan Kim Dec. 1, 2021, 11:34 p.m. UTC | #1

On Wed, Dec 01, 2021 at 07:15:04PM +0100, Vlastimil Babka wrote:
> From: "Matthew Wilcox (Oracle)" <[e-mail]>
> 
> The ->freelist and ->units members of struct page are for the use of slab
> only.  I'm not particularly familiar with zsmalloc, so generate the same
> code by using page->index to store 'page' (page->index and page->freelist
> are at the same offset in struct page).  This should be cleaned up
> properly at some point by somebody who is familiar with zsmalloc.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <[e-mail]>
> Signed-off-by: Vlastimil Babka <[e-mail]>
Acked-by: Minchan Kim <[e-mail]>

Johannes Weiner Dec. 14, 2021, 2:58 p.m. UTC | #2

On Wed, Dec 01, 2021 at 07:15:04PM +0100, Vlastimil Babka wrote:
> From: "Matthew Wilcox (Oracle)" <[e-mail]>
> 
> The ->freelist and ->units members of struct page are for the use of slab
> only.  I'm not particularly familiar with zsmalloc, so generate the same
> code by using page->index to store 'page' (page->index and page->freelist
> are at the same offset in struct page).  This should be cleaned up
> properly at some point by somebody who is familiar with zsmalloc.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <[e-mail]>
> Signed-off-by: Vlastimil Babka <[e-mail]>
> Cc: Minchan Kim <[e-mail]>
> Cc: Nitin Gupta <[e-mail]>
> Cc: Sergey Senozhatsky <[e-mail]>

Acked-by: Johannes Weiner <[e-mail]>

Patch

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index b897ce3b399a..0d3b65939016 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -17,10 +17,10 @@ 
  *
  * Usage of struct page fields:
  *	page->private: points to zspage
- *	page->freelist(index): links together all component pages of a zspage
+ *	page->index: links together all component pages of a zspage
  *		For the huge page, this is always 0, so we use this field
  *		to store handle.
- *	page->units: first object offset in a subpage of zspage
+ *	page->page_type: first object offset in a subpage of zspage
  *
  * Usage of struct page flags:
  *	PG_private: identifies the first component page
@@ -489,12 +489,12 @@  static inline struct page *get_first_page(struct zspage *zspage)
 
 static inline int get_first_obj_offset(struct page *page)
 {
-	return page->units;
+	return page->page_type;
 }
 
 static inline void set_first_obj_offset(struct page *page, int offset)
 {
-	page->units = offset;
+	page->page_type = offset;
 }
 
 static inline unsigned int get_freeobj(struct zspage *zspage)
@@ -827,7 +827,7 @@  static struct page *get_next_page(struct page *page)
 	if (unlikely(PageHugeObject(page)))
 		return NULL;
 
-	return page->freelist;
+	return (struct page *)page->index;
 }
 
 /**
@@ -901,7 +901,7 @@  static void reset_page(struct page *page)
 	set_page_private(page, 0);
 	page_mapcount_reset(page);
 	ClearPageHugeObject(page);
-	page->freelist = NULL;
+	page->index = 0;
 }
 
 static int trylock_zspage(struct zspage *zspage)
@@ -1027,7 +1027,7 @@  static void create_page_chain(struct size_class *class, struct zspage *zspage,
 
 	/*
 	 * Allocate individual pages and link them together as:
-	 * 1. all pages are linked together using page->freelist
+	 * 1. all pages are linked together using page->index
 	 * 2. each sub-page point to zspage using page->private
 	 *
 	 * we set PG_private to identify the first page (i.e. no other sub-page
@@ -1036,7 +1036,7 @@  static void create_page_chain(struct size_class *class, struct zspage *zspage,
 	for (i = 0; i < nr_pages; i++) {
 		page = pages[i];
 		set_page_private(page, (unsigned long)zspage);
-		page->freelist = NULL;
+		page->index = 0;
 		if (i == 0) {
 			zspage->first_page = page;
 			SetPagePrivate(page);
@@ -1044,7 +1044,7 @@  static void create_page_chain(struct size_class *class, struct zspage *zspage,
 					class->pages_per_zspage == 1))
 				SetPageHugeObject(page);
 		} else {
-			prev_page->freelist = page;
+			prev_page->index = (unsigned long)page;
 		}
 		prev_page = page;
 	}