Re: [PATCH v1 13/19] zsmalloc: factor page chain functionality out

On Sat, Mar 12, 2016 at 11:09:36AM +0800, xuyiping wrote:

On 2016/3/11 15:30, Minchan Kim wrote:

quoted

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

As a minor refactoring, it makes OBJ_ALLOCATED_TAG assign
more clear in obj_malloc(it could be another patch but it's
trivial so I want to put together in this patch).

Signed-off-by: Minchan Kim <minchan@kernel.org>
---
 mm/zsmalloc.c | 78 ++++++++++++++++++++++++++++++++++-------------------------
 1 file changed, 45 insertions(+), 33 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index bfc6a048afac..f86f8aaeb902 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c

@@ -977,7 +977,9 @@ 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;
+	INIT_LIST_HEAD(&first_page->lru);
+	set_zspage_inuse(first_page, 0);

 	while (page) {
 		struct page *next_page;

@@ -1022,13 +1024,44 @@ static void init_zspage(struct size_class *class, struct page *first_page)
 	set_freeobj(first_page, 0);
 }

+static void create_page_chain(struct page *pages[], int nr_pages)
+{
+	int i;
+	struct page *page;
+	struct page *prev_page = NULL;
+	struct page *first_page = NULL;
+
+	for (i = 0; i < nr_pages; i++) {
+		page = pages[i];
+
+		INIT_LIST_HEAD(&page->lru);
+		if (i == 0) {
+			SetPagePrivate(page);
+			set_page_private(page, 0);
+			first_page = page;
+		}
+
+		if (i == 1)
+			set_page_private(first_page, (unsigned long)page);
+		if (i >= 1)
+			set_page_private(page, (unsigned long)first_page);
+		if (i >= 2)
+			list_add(&page->lru, &prev_page->lru);
+		if (i == nr_pages - 1)
+			SetPagePrivate2(page);
+
+		prev_page = page;
+	}
+}
+
 /*
  * Allocate a zspage for the given size class
  */
 static struct page *alloc_zspage(struct size_class *class, gfp_t flags)
 {
-	int i, error;
+	int i;
 	struct page *first_page = NULL, *uninitialized_var(prev_page);
+	struct page *pages[ZS_MAX_PAGES_PER_ZSPAGE];

 	/*
 	 * Allocate individual pages and link them together as:

@@ -1041,43 +1074,23 @@ static struct page *alloc_zspage(struct size_class *class, gfp_t flags)

	*uninitialized_var(prev_page) in alloc_zspage is not in use more.

True.
It says why we should avoid uninitialized_var if possible.
If we didn't use uninitialized_var, compiler could warn about it
when I did build test.

Thanks.