Commit 572438f9 authored by KAMEZAWA Hiroyuki's avatar KAMEZAWA Hiroyuki Committed by Linus Torvalds

mm: fix is_mem_section_removable() page_order BUG_ON check

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: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: default avatarWu Fengguang <fengguang.wu@intel.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.cz>
Acked-by: default avatarMel Gorman <mel@csn.ul.ie>
Cc: <stable@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 44e2aa93
......@@ -62,7 +62,7 @@ extern bool is_free_buddy_page(struct page *page);
*/
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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