zsmalloc: factor page chain functionality out

For page migration, we need to create page chain of zspage dynamically
so this patch factors it out from alloc_zspage.

Link: http://lkml.kernel.org/r/1464736881-24886-8-git-send-email-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 35 insertions, 24 deletions

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 5da80961ff3e..07485a2e5b96 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -960,7 +960,8 @@ static void init_zspage(struct size_class *class, struct page *first_page)
         unsigned long off = 0;
         struct page *page = first_page;
 
-        VM_BUG_ON_PAGE(!is_first_page(first_page), first_page);
+        first_page->freelist = NULL;
+        set_zspage_inuse(first_page, 0);
 
         while (page) {
                 struct page *next_page;
@@ -996,15 +997,16 @@ static void init_zspage(struct size_class *class, struct page *first_page)
                 page = next_page;
                 off %= PAGE_SIZE;
         }
+
+        set_freeobj(first_page, (unsigned long)location_to_obj(first_page, 0));
 }
 
-/*
- * Allocate a zspage for the given size class
- */
-static struct page *alloc_zspage(struct size_class *class, gfp_t flags)
+static void create_page_chain(struct page *pages[], int nr_pages)
 {
-        int i, error;
-        struct page *first_page = NULL, *uninitialized_var(prev_page);
+        int i;
+        struct page *page;
+        struct page *prev_page = NULL;
+        struct page *first_page = NULL;
 
         /*
          * Allocate individual pages and link them together as:
@@ -1017,20 +1019,14 @@ static struct page *alloc_zspage(struct size_class *class, gfp_t flags)
          * (i.e. no other sub-page has this flag set) and PG_private_2 to
          * identify the last page.
          */
-        error = -ENOMEM;
-        for (i = 0; i < class->pages_per_zspage; i++) {
-                struct page *page;
-
-                page = alloc_page(flags);
-                if (!page)
-                        goto cleanup;
+        for (i = 0; i < nr_pages; i++) {
+                page = pages[i];
 
                 INIT_LIST_HEAD(&page->lru);
-                if (i == 0) {   /* first page */
+                if (i == 0) {
                         SetPagePrivate(page);
                         set_page_private(page, 0);
                         first_page = page;
-                        set_zspage_inuse(first_page, 0);
                 }
                 if (i == 1)
                         set_page_private(first_page, (unsigned long)page);
@@ -1038,22 +1034,37 @@ static struct page *alloc_zspage(struct size_class *class, gfp_t flags)
                         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 */
+                if (i == nr_pages - 1)
                         SetPagePrivate2(page);
                 prev_page = page;
         }
+}
 
-        init_zspage(class, first_page);
+/*
+ * Allocate a zspage for the given size class
+ */
+static struct page *alloc_zspage(struct size_class *class, gfp_t flags)
+{
+        int i;
+        struct page *first_page = NULL;
+        struct page *pages[ZS_MAX_PAGES_PER_ZSPAGE];
 
-        set_freeobj(first_page, (unsigned long)location_to_obj(first_page, 0));
-        error = 0; /* Success */
+        for (i = 0; i < class->pages_per_zspage; i++) {
+                struct page *page;
 
-cleanup:
-        if (unlikely(error) && first_page) {
-                free_zspage(first_page);
-                first_page = NULL;
+                page = alloc_page(flags);
+                if (!page) {
+                        while (--i >= 0)
+                                __free_page(pages[i]);
+                        return NULL;
+                }
+                pages[i] = page;
         }
 
+        create_page_chain(pages, class->pages_per_zspage);
+        first_page = pages[0];
+        init_zspage(class, first_page);
+
         return first_page;
 }