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    mm: define PAGE_MAPPING_FLAGS · 3ca7b3c5
    Hugh Dickins 提交于
    At present we define PageAnon(page) by the low PAGE_MAPPING_ANON bit set
    in page->mapping, with the higher bits a pointer to the anon_vma; and have
    defined PageKsm(page) as that with NULL anon_vma.
    
    But KSM swapping will need to store a pointer there: so in preparation for
    that, now define PAGE_MAPPING_FLAGS as the low two bits, including
    PAGE_MAPPING_KSM (always set along with PAGE_MAPPING_ANON, until some
    other use for the bit emerges).
    
    Declare page_rmapping(page) to return the pointer part of page->mapping,
    and page_anon_vma(page) to return the anon_vma pointer when that's what it
    is.  Use these in a few appropriate places: notably, unuse_vma() has been
    testing page->mapping, but is better to be testing page_anon_vma() (cases
    may be added in which flag bits are set without any pointer).
    Signed-off-by: NHugh Dickins <hugh.dickins@tiscali.co.uk>
    Cc: Izik Eidus <ieidus@redhat.com>
    Cc: Andrea Arcangeli <aarcange@redhat.com>
    Cc: Nick Piggin <npiggin@suse.de>
    Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    Reviewed-by: NRik van Riel <riel@redhat.com>
    Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
    Cc: Andi Kleen <andi@firstfloor.org>
    Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Cc: Wu Fengguang <fengguang.wu@intel.com>
    Cc: Minchan Kim <minchan.kim@gmail.com>
    Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
    3ca7b3c5
rmap.h 4.7 KB