| Date | Tue, 07 Dec 2010 16:43:29 -0800 | From | Greg KH <> | Subject | [023/127] mm: fix is_mem_section_removable() page_order BUG_ON check |
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2.6.32-stable review patch. If anyone has any objections, please let us know.
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From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
commit 572438f9b52236bd8938b1647cc15e027d27ef55 upstream.
page_order() is called by memory hotplug's user interface to check the section is removable or not. (is_mem_section_removable())
It calls page_order() withoug holding zone->lock. So, even if the caller does
if (PageBuddy(page)) ret = page_order(page) ... The caller may hit BUG_ON().
For fixing this, there are 2 choices. 1. add zone->lock. 2. remove BUG_ON().
is_mem_section_removable() is used for some "advice" and doesn't need to be 100% accurate. This is_removable() can be called via user program.. We don't want to take this important lock for long by user's request. So, this patch removes BUG_ON().
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Wu Fengguang <fengguang.wu@intel.com> Acked-by: Michal Hocko <mhocko@suse.cz> Acked-by: Mel Gorman <mel@csn.ul.ie> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- mm/internal.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/internal.h +++ b/mm/internal.h @@ -59,7 +59,7 @@ extern void prep_compound_page(struct pa */ static inline unsigned long page_order(struct page *page) { - VM_BUG_ON(!PageBuddy(page)); + /* PageBuddy() must be checked by the caller */ return page_private(page); }
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