• Punit Agrawal's avatar
    mm/migrate: fix refcount handling when !hugepage_migration_supported() · 9bf638a0
    Punit Agrawal authored
    [ Upstream commit 30809f55 ]
    
    On failing to migrate a page, soft_offline_huge_page() performs the
    necessary update to the hugepage ref-count.
    
    But when !hugepage_migration_supported() , unmap_and_move_hugepage()
    also decrements the page ref-count for the hugepage.  The combined
    behaviour leaves the ref-count in an inconsistent state.
    
    This leads to soft lockups when running the overcommitted hugepage test
    from mce-tests suite.
    
      Soft offlining pfn 0x83ed600 at process virtual address 0x400000000000
      soft offline: 0x83ed600: migration failed 1, type 1fffc00000008008 (uptodate|head)
      INFO: rcu_preempt detected stalls on CPUs/tasks:
       Tasks blocked on level-0 rcu_node (CPUs 0-7): P2715
        (detected by 7, t=5254 jiffies, g=963, c=962, q=321)
        thugetlb_overco R  running task        0  2715   2685 0x00000008
        Call trace:
          dump_backtrace+0x0/0x268
          show_stack+0x24/0x30
          sched_show_task+0x134/0x180
          rcu_print_detail_task_stall_rnp+0x54/0x7c
          rcu_check_callbacks+0xa74/0xb08
          update_process_times+0x34/0x60
          tick_sched_handle.isra.7+0x38/0x70
          tick_sched_timer+0x4c/0x98
          __hrtimer_run_queues+0xc0/0x300
          hrtimer_interrupt+0xac/0x228
          arch_timer_handler_phys+0x3c/0x50
          handle_percpu_devid_irq+0x8c/0x290
          generic_handle_irq+0x34/0x50
          __handle_domain_irq+0x68/0xc0
          gic_handle_irq+0x5c/0xb0
    
    Address this by changing the putback_active_hugepage() in
    soft_offline_huge_page() to putback_movable_pages().
    
    This only triggers on systems that enable memory failure handling
    (ARCH_SUPPORTS_MEMORY_FAILURE) but not hugepage migration
    (!ARCH_ENABLE_HUGEPAGE_MIGRATION).
    
    I imagine this wasn't triggered as there aren't many systems running
    this configuration.
    
    [akpm@linux-foundation.org: remove dead comment, per Naoya]
    Link: http://lkml.kernel.org/r/20170525135146.32011-1-punit.agrawal@arm.comReported-by: default avatarManoj Iyer <manoj.iyer@canonical.com>
    Tested-by: default avatarManoj Iyer <manoj.iyer@canonical.com>
    Suggested-by: default avatarNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
    Signed-off-by: default avatarPunit Agrawal <punit.agrawal@arm.com>
    Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
    Cc: Wanpeng Li <wanpeng.li@hotmail.com>
    Cc: Christoph Lameter <cl@linux.com>
    Cc: Mel Gorman <mgorman@techsingularity.net>
    Cc: <stable@vger.kernel.org>	[3.14+]
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
    9bf638a0
memory-failure.c 48.1 KB