• Michal Hocko's avatar
    mm: consider zone which is not fully populated to have holes · 2d070eab
    Michal Hocko authored
    __pageblock_pfn_to_page has two users currently, set_zone_contiguous
    which checks whether the given zone contains holes and
    pageblock_pfn_to_page which then carefully returns a first valid page
    from the given pfn range for the given zone.  This doesn't handle zones
    which are not fully populated though.  Memory pageblocks can be offlined
    or might not have been onlined yet.  In such a case the zone should be
    considered to have holes otherwise pfn walkers can touch and play with
    offline pages.
    Current callers of pageblock_pfn_to_page in compaction seem to work
    properly right now because they only isolate PageBuddy
    (isolate_freepages_block) or PageLRU resp.  __PageMovable
    (isolate_migratepages_block) which will be always false for these pages.
    It would be safer to skip these pages altogether, though.
    In order to do this patch adds a new memory section state
    (SECTION_IS_ONLINE) which is set in memory_present (during boot time) or
    in online_pages_range during the memory hotplug.  Similarly
    offline_mem_sections clears the bit and it is called when the memory
    range is offlined.
    pfn_to_online_page helper is then added which check the mem section and
    only returns a page if it is onlined already.
    Use the new helper in __pageblock_pfn_to_page and skip the whole page
    block in such a case.
    [mhocko@suse.com: check valid section number in pfn_to_online_page (Vlastimil),
     mark sections online after all struct pages are initialized in
     online_pages_range (Vlastimil)]
      Link: http://lkml.kernel.org/r/20170518164210.GD18333@dhcp22.suse.cz
    Link: http://lkml.kernel.org/r/20170515085827.16474-8-mhocko@kernel.orgSigned-off-by: default avatarMichal Hocko <mhocko@suse.com>
    Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
    Cc: Andi Kleen <ak@linux.intel.com>
    Cc: Andrea Arcangeli <aarcange@redhat.com>
    Cc: Balbir Singh <bsingharora@gmail.com>
    Cc: Dan Williams <dan.j.williams@intel.com>
    Cc: Daniel Kiper <daniel.kiper@oracle.com>
    Cc: David Rientjes <rientjes@google.com>
    Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
    Cc: Igor Mammedov <imammedo@redhat.com>
    Cc: Jerome Glisse <jglisse@redhat.com>
    Cc: Joonsoo Kim <js1304@gmail.com>
    Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Cc: Mel Gorman <mgorman@suse.de>
    Cc: Reza Arbab <arbab@linux.vnet.ibm.com>
    Cc: Tobias Regnery <tobias.regnery@gmail.com>
    Cc: Toshi Kani <toshi.kani@hpe.com>
    Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
    Cc: Xishi Qiu <qiuxishi@huawei.com>
    Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
sparse.c 22.8 KB