mm/migrate: fix refcount handling when !hugepage_migration_supported()

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.com
Reported-by: Manoj Iyer <manoj.iyer@canonical.com>
Tested-by: Manoj Iyer <manoj.iyer@canonical.com>
Suggested-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Punit 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 2527dfeddb003d245ac2e2bd964134030426f777..342fac9ba89b0da3e207b1fdaef2be71c9837a24 100644 (file)
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1595,12 +1595,8 @@ static int soft_offline_huge_page(struct page *page, int flags)
        if (ret) {
                pr_info("soft offline: %#lx: migration failed %d, type %lx (%pGp)\n",
                        pfn, ret, page->flags, &page->flags);
-               /*
-                * We know that soft_offline_huge_page() tries to migrate
-                * only one hugepage pointed to by hpage, so we need not
-                * run through the pagelist here.
-                */
-               putback_active_hugepage(hpage);
+               if (!list_empty(&pagelist))
+                       putback_movable_pages(&pagelist);
                if (ret > 0)
                        ret = -EIO;
        } else {