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 <>
Acked-by: default avatarWu Fengguang <>
Acked-by: default avatarMichal Hocko <>
Acked-by: default avatarMel Gorman <>
Cc: <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 44e2aa93
......@@ -62,7 +62,7 @@ extern bool is_free_buddy_page(struct page *page);
static inline unsigned long page_order(struct page *page)
/* PageBuddy() must be checked by the caller */
return page_private(page);
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