• G
    mm/hugetlb: fix memory offline with hugepage size > memory block size · 2247bb33
    Gerald Schaefer 提交于
    Patch series "mm/hugetlb: memory offline issues with hugepages", v4.
    
    This addresses several issues with hugepages and memory offline.  While
    the first patch fixes a panic, and is therefore rather important, the
    last patch is just a performance optimization.
    
    The second patch fixes a theoretical issue with reserved hugepages,
    while still leaving some ugly usability issue, see description.
    
    This patch (of 3):
    
    dissolve_free_huge_pages() will either run into the VM_BUG_ON() or a
    list corruption and addressing exception when trying to set a memory
    block offline that is part (but not the first part) of a "gigantic"
    hugetlb page with a size > memory block size.
    
    When no other smaller hugetlb page sizes are present, the VM_BUG_ON()
    will trigger directly.  In the other case we will run into an addressing
    exception later, because dissolve_free_huge_page() will not work on the
    head page of the compound hugetlb page which will result in a NULL
    hstate from page_hstate().
    
    To fix this, first remove the VM_BUG_ON() because it is wrong, and then
    use the compound head page in dissolve_free_huge_page().  This means
    that an unused pre-allocated gigantic page that has any part of itself
    inside the memory block that is going offline will be dissolved
    completely.  Losing an unused gigantic hugepage is preferable to failing
    the memory offline, for example in the situation where a (possibly
    faulty) memory DIMM needs to go offline.
    
    Fixes: c8721bbb ("mm: memory-hotplug: enable memory hotplug to handle hugepage")
    Link: http://lkml.kernel.org/r/20160926172811.94033-2-gerald.schaefer@de.ibm.comSigned-off-by: NGerald Schaefer <gerald.schaefer@de.ibm.com>
    Acked-by: NMichal Hocko <mhocko@suse.com>
    Acked-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
    Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
    Cc: Vlastimil Babka <vbabka@suse.cz>
    Cc: Mike Kravetz <mike.kravetz@oracle.com>
    Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com>
    Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
    Cc: Rui Teng <rui.teng@linux.vnet.ibm.com>
    Cc: Dave Hansen <dave.hansen@linux.intel.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
    2247bb33
hugetlb.c 119.7 KB