zsmalloc: simplify init_zspage free obj linking

Change zsmalloc init_zspage() logic to iterate through each object on each
of its pages, checking the offset to verify the object is on the current
page before linking it into the zspage.

The current zsmalloc init_zspage free object linking code has logic that
relies on there only being one page per zspage when PAGE_SIZE is a
multiple of class->size.  It calculates the number of objects for the
current page, and iterates through all of them plus one, to account for
the assumed partial object at the end of the page.  While this currently
works, the logic can be simplified to just link the object at each
successive offset until the offset is larger than PAGE_SIZE, which does
not rely on PAGE_SIZE being a multiple of class->size.

Signed-off-by: Dan Streetman <ddstreet@ieee.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Seth Jennings <sjennings@variantweb.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 5538c562377580947916b3366898f1eb5f53768e)
Signed-off-by: Alex Shi <alex.shi@linaro.org>

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index a4556ec316e4e9bc2e94fe962bd966307b963c19..00c28039b06aa064b0d2260e98bda4bc8411a6e0 100644 (file)
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -594,7 +594,7 @@ static void init_zspage(struct page *first_page, struct size_class *class)
        while (page) {
                struct page *next_page;
                struct link_free *link;
-               unsigned int i, objs_on_page;
+               unsigned int i = 1;
 
                /*
                 * page->index stores offset of first object starting
@@ -607,14 +607,10 @@ static void init_zspage(struct page *first_page, struct size_class *class)
 
                link = (struct link_free *)kmap_atomic(page) +
                                                off / sizeof(*link);
-               objs_on_page = (PAGE_SIZE - off) / class->size;
 
-               for (i = 1; i <= objs_on_page; i++) {
-                       off += class->size;
-                       if (off < PAGE_SIZE) {
-                               link->next = obj_location_to_handle(page, i);
-                               link += class->size / sizeof(*link);
-                       }
+               while ((off += class->size) < PAGE_SIZE) {
+                       link->next = obj_location_to_handle(page, i++);
+                       link += class->size / sizeof(*link);
                }
 
                /*
@@ -626,7 +622,7 @@ static void init_zspage(struct page *first_page, struct size_class *class)
                link->next = obj_location_to_handle(next_page, 0);
                kunmap_atomic(link);
                page = next_page;
-               off = (off + class->size) % PAGE_SIZE;
+               off %= PAGE_SIZE;
        }
 }