• zhong jiang's avatar
    mm/mempolicy.c: fix an incorrect rebind node in mpol_rebind_nodemask · 55b3118c
    zhong jiang authored
    commit 29b190fa774dd1b72a1a6f19687d55dc72ea83be upstream.
    
    mpol_rebind_nodemask() is called for MPOL_BIND and MPOL_INTERLEAVE
    mempoclicies when the tasks's cpuset's mems_allowed changes.  For
    policies created without MPOL_F_STATIC_NODES or MPOL_F_RELATIVE_NODES,
    it works by remapping the policy's allowed nodes (stored in v.nodes)
    using the previous value of mems_allowed (stored in
    w.cpuset_mems_allowed) as the domain of map and the new mems_allowed
    (passed as nodes) as the range of the map (see the comment of
    bitmap_remap() for details).
    
    The result of remapping is stored back as policy's nodemask in v.nodes,
    and the new value of mems_allowed should be stored in
    w.cpuset_mems_allowed to facilitate the next rebind, if it happens.
    
    However, 213980c0 ("mm, mempolicy: simplify rebinding mempolicies
    when updating cpusets") introduced a bug where the result of remapping
    is stored in w.cpuset_mems_allowed instead.  Thus, a mempolicy's
    allowed nodes can evolve in an unexpected way after a series of
    rebinding due to cpuset mems_allowed changes, possibly binding to a
    wrong node or a smaller number of nodes which may e.g.  overload them.
    This patch fixes the bug so rebinding again works as intended.
    
    [vbabka@suse.cz: new changlog]
      Link: http://lkml.kernel.org/r/ef6a69c6-c052-b067-8f2c-9d615c619bb9@suse.cz
    Link: http://lkml.kernel.org/r/1558768043-23184-1-git-send-email-zhongjiang@huawei.com
    Fixes: 213980c0 ("mm, mempolicy: simplify rebinding mempolicies when updating cpusets")
    Signed-off-by: default avatarzhong jiang <zhongjiang@huawei.com>
    Reviewed-by: default avatarVlastimil Babka <vbabka@suse.cz>
    Cc: Oscar Salvador <osalvador@suse.de>
    Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
    Cc: Michal Hocko <mhocko@suse.com>
    Cc: Mel Gorman <mgorman@techsingularity.net>
    Cc: Andrea Arcangeli <aarcange@redhat.com>
    Cc: Ralph Campbell <rcampbell@nvidia.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    55b3118c