• Hugh Dickins's avatar
    [PATCH] mm: follow_page with inner ptlock · deceb6cd
    Hugh Dickins authored
    Final step in pushing down common core's page_table_lock.  follow_page no
    longer wants caller to hold page_table_lock, uses pte_offset_map_lock itself;
    and so no page_table_lock is taken in get_user_pages itself.
    
    But get_user_pages (and get_futex_key) do then need follow_page to pin the
    page for them: take Daniel's suggestion of bitflags to follow_page.
    
    Need one for WRITE, another for TOUCH (it was the accessed flag before:
    vanished along with check_user_page_readable, but surely get_numa_maps is
    wrong to mark every page it finds as accessed), another for GET.
    
    And another, ANON to dispose of untouched_anonymous_page: it seems silly for
    that to descend a second time, let follow_page observe if there was no page
    table and return ZERO_PAGE if so.  Fix minor bug in that: check VM_LOCKED -
    make_pages_present ought to make readonly anonymous present.
    
    Give get_numa_maps a cond_resched while we're there.
    Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
    deceb6cd
nommu.c 27.6 KB