[lkml]   [2020]   [Feb]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    Patch in this message
    Subject[PATCH 5.5 055/367] mm/sparse.c: reset sections mem_map when fully deactivated
    From: Pingfan Liu <>

    commit 1f503443e7df8dc8366608b4d810ce2d6669827c upstream.

    After commit ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug"),
    when a mem section is fully deactivated, section_mem_map still records
    the section's start pfn, which is not used any more and will be
    reassigned during re-addition.

    In analogy with alloc/free pattern, it is better to clear all fields of

    Beside this, it breaks the user space tool "makedumpfile" [1], which
    makes assumption that a hot-removed section has mem_map as NULL, instead
    of checking directly against SECTION_MARKED_PRESENT bit. (makedumpfile
    will be better to change the assumption, and need a patch)

    The bug can be reproduced on IBM POWERVM by "drmgr -c mem -r -q 5" ,
    trigger a crash, and save vmcore by makedumpfile

    [1]: makedumpfile, commit e73016540293 ("[v1.6.7] Update version")

    Signed-off-by: Pingfan Liu <>
    Acked-by: Michal Hocko <>
    Acked-by: David Hildenbrand <>
    Cc: Dan Williams <>
    Cc: Oscar Salvador <>
    Cc: Baoquan He <>
    Cc: Qian Cai <>
    Cc: Kazuhito Hagio <>
    Cc: <>
    Signed-off-by: Andrew Morton <>
    Signed-off-by: Linus Torvalds <>
    Signed-off-by: Greg Kroah-Hartman <>

    mm/sparse.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/mm/sparse.c
    +++ b/mm/sparse.c
    @@ -789,7 +789,7 @@ static void section_deactivate(unsigned
    ms->usage = NULL;
    memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
    - ms->section_mem_map = sparse_encode_mem_map(NULL, section_nr);
    + ms->section_mem_map = (unsigned long)NULL;

    if (section_is_early && memmap)

     \ /
      Last update: 2020-02-10 14:08    [W:3.985 / U:0.008 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site