• Nick Piggin's avatar
    [PATCH] core remove PageReserved · b5810039
    Nick Piggin authored
    
    
    Remove PageReserved() calls from core code by tightening VM_RESERVED
    handling in mm/ to cover PageReserved functionality.
    
    PageReserved special casing is removed from get_page and put_page.
    
    All setting and clearing of PageReserved is retained, and it is now flagged
    in the page_alloc checks to help ensure we don't introduce any refcount
    based freeing of Reserved pages.
    
    MAP_PRIVATE, PROT_WRITE of VM_RESERVED regions is tentatively being
    deprecated.  We never completely handled it correctly anyway, and is be
    reintroduced in future if required (Hugh has a proof of concept).
    
    Once PageReserved() calls are removed from kernel/power/swsusp.c, and all
    arch/ and driver code, the Set and Clear calls, and the PG_reserved bit can
    be trivially removed.
    
    Last real user of PageReserved is swsusp, which uses PageReserved to
    determine whether a struct page points to valid memory or not.  This still
    needs to be addressed (a generic page_is_ram() should work).
    
    A last caveat: the ZERO_PAGE is now refcounted and managed with rmap (and
    thus mapcounted and count towards shared rss).  These writes to the struct
    page could cause excessive cacheline bouncing on big systems.  There are a
    number of ways this could be addressed if it is an issue.
    Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
    
    Refcount bug fix for filemap_xip.c
    Signed-off-by: default avatarCarsten Otte <cotte@de.ibm.com>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
    b5810039
bootmem.c 11.1 KB