[RFC PATCH v3 04/21] mm/zsmalloc: add alternatives of frequently used helper functions

[Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>]

get_first_page(), get_next_page(), is_first_page() are frequently used
throughout zsmalloc code. As replacing them all at once would be hard to
review, add alternative helpers and gradually replace its users to
use new functions.

Signed-off-by: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
---
 mm/zsmalloc.c | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 4c9f9a2cb681..c511539bee8c 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -502,6 +502,11 @@ static __maybe_unused int is_first_page(struct page *page)
 	return PagePrivate(page);
 }
 
+static __maybe_unused int is_first_zsdesc(struct zsdesc *zsdesc)
+{
+	return PagePrivate(zsdesc_page(zsdesc));
+}
+
 /* Protected by pool->lock */
 static inline int get_zspage_inuse(struct zspage *zspage)
 {
@@ -514,7 +519,7 @@ static inline void mod_zspage_inuse(struct zspage *zspage, int val)
 	zspage->inuse += val;
 }
 
-static inline struct page *get_first_page(struct zspage *zspage)
+static __maybe_unused inline struct page *get_first_page(struct zspage *zspage)
 {
 	struct page *first_page = zsdesc_page(zspage->first_zsdesc);
 
@@ -522,6 +527,14 @@ static inline struct page *get_first_page(struct zspage *zspage)
 	return first_page;
 }
 
+static __maybe_unused struct zsdesc *get_first_zsdesc(struct zspage *zspage)
+{
+	struct zsdesc *first_zsdesc = zspage->first_zsdesc;
+
+	VM_BUG_ON_PAGE(!is_first_zsdesc(first_zsdesc), zsdesc_page(first_zsdesc));
+	return first_zsdesc;
+}
+
 static inline unsigned int get_first_obj_offset(struct page *page)
 {
 	return page->page_type;
@@ -810,7 +823,7 @@ static struct zspage *get_zspage(struct page *page)
 	return zspage;
 }
 
-static struct page *get_next_page(struct page *page)
+static __maybe_unused struct page *get_next_page(struct page *page)
 {
 	struct zspage *zspage = get_zspage(page);
 
@@ -820,6 +833,16 @@ static struct page *get_next_page(struct page *page)
 	return (struct page *)page->index;
 }
 
+static __maybe_unused struct zsdesc *get_next_zsdesc(struct zsdesc *zsdesc)
+{
+	struct zspage *zspage = get_zspage(zsdesc_page(zsdesc));
+
+	if (unlikely(ZsHugePage(zspage)))
+		return NULL;
+
+	return zsdesc->next;
+}
+
 /**
  * obj_to_location - get (<page>, <obj_idx>) from encoded object value
  * @obj: the encoded object value
-- 
2.39.3