From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
next_active_pageblock() is for finding next _used_ freeblock. It skips
several blocks when it finds there are a chunk of free pages lager than
pageblock. But it has 2 bugs.
1. We have no lock. page_order(page) - pageblock_order can be minus.
2. pageblocks_stride += is wrong. it should skip page_order(p) of pages.
Changelog: 2010/09/07
- fix range check of order returned by page_order().
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
---
mm/memory_hotplug.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
Index: kametest/mm/memory_hotplug.c
===================================================================
--- kametest.orig/mm/memory_hotplug.c
+++ kametest/mm/memory_hotplug.c
@@ -584,19 +584,19 @@ static inline int pageblock_free(struct
/* Return the start of the next active pageblock after a given page */
static struct page *next_active_pageblock(struct page *page)
{
- int pageblocks_stride;
-
/* Ensure the starting page is pageblock-aligned */
BUG_ON(page_to_pfn(page) & (pageblock_nr_pages - 1));
- /* Move forward by at least 1 * pageblock_nr_pages */
- pageblocks_stride = 1;
-
/* If the entire pageblock is free, move to the end of free page */
- if (pageblock_free(page))
- pageblocks_stride += page_order(page) - pageblock_order;
+ if (pageblock_free(page)) {
+ int order;
+ /* be careful. we don't have locks, page_order can be changed.*/
+ order = page_order(page);
+ if ((order < MAX_ORDER) && (order >= pageblock_order))
+ return page + (1 << order);
+ }
- return page + (pageblocks_stride * pageblock_nr_pages);
+ return page + pageblock_nr_pages;
}
/* Checks if this range of memory is likely to be hot-removable. */
--
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