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memory hotplug: fix next block calculation in is_removable 

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.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
KAMEZAWA Hiroyuki 2010-09-09 16:38:01 -07:00 committed by Linus Torvalds
parent bc69304574
commit 0dcc48c15f
1 changed files with 8 additions and 8 deletions
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16
mm/memory_hotplug.c
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@ -584,19 +584,19 @@ static inline int pageblock_free(struct page *page)
/* 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. */