• Konstantin Khlebnikov's avatar
    mm: strictly require elevated page refcount in isolate_lru_page() · 0c917313
    Konstantin Khlebnikov authored
    isolate_lru_page() must be called only with stable reference to the page,
    this is what is written in the comment above it, this is reasonable.
    
    current isolate_lru_page() users and its page extra reference sources:
    
     mm/huge_memory.c:
      __collapse_huge_page_isolate()	- reference from pte
    
     mm/memcontrol.c:
      mem_cgroup_move_parent()		- get_page_unless_zero()
      mem_cgroup_move_charge_pte_range()	- reference from pte
    
     mm/memory-failure.c:
      soft_offline_page()			- fixed, reference from get_any_page()
      delete_from_lru_cache() - reference from caller or get_page_unless_zero()
    	[ seems like there bug, because __memory_failure() can call
    	  page_action() for hpages tail, but it is ok for
    	  isolate_lru_page(), tail getted and not in lru]
    
     mm/memory_hotplug.c:
      do_migrate_range()			- fixed, get_page_unless_zero()
    
     mm/mempolicy.c:
      migrate_page_add()			- reference from pte
    
     mm/migrate.c:
      do_move_page_to_node_array()		- reference from follow_page()
    
     mlock.c:				- various external references
    
     mm/vmscan.c:
      putback_lru_page()			- reference from isolate_lru_page()
    
    It seems that all isolate_lru_page() users are ready now for this
    restriction.  So, let's replace redundant get_page_unless_zero() with
    get_page() and add page initial reference count check with VM_BUG_ON()
    Signed-off-by: default avatarKonstantin Khlebnikov <khlebnikov@openvz.org>
    Cc: Andi Kleen <andi@firstfloor.org>
    Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    Cc: Mel Gorman <mel@csn.ul.ie>
    Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
    Cc: Rik van Riel <riel@redhat.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    0c917313
vmscan.c 92.5 KB