Revert "mm: use early_pfn_to_nid in page_ext_init"

This reverts commit fe53ca54270a ("mm: use early_pfn_to_nid in
page_ext_init").

When booting a system with "page_owner=on",

start_kernel
  page_ext_init
    invoke_init_callbacks
      init_section_page_ext
        init_page_owner
          init_early_allocated_pages
            init_zones_in_node
              init_pages_in_zone
                lookup_page_ext
                  page_to_nid

The issue here is that page_to_nid() will not work since some page flags
have no node information until later in page_alloc_init_late() due to
DEFERRED_STRUCT_PAGE_INIT.  Hence, it could trigger an out-of-bounds
access with an invalid nid.

  UBSAN: Undefined behaviour in ./include/linux/mm.h:1104:50
  index 7 is out of range for type 'zone [5]'

Also, kernel will panic since flags were poisoned earlier with,

CONFIG_DEBUG_VM_PGFLAGS=y
CONFIG_NODE_NOT_IN_PAGE_FLAGS=n

start_kernel
  setup_arch
    pagetable_init
      paging_init
        sparse_init
          sparse_init_nid
            memblock_alloc_try_nid_raw

It did not handle it well in init_pages_in_zone() which ends up calling
page_to_nid().

  page:ffffea0004200000 is uninitialized and poisoned
  raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
  raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
  page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
  page_owner info is not active (free page?)
  kernel BUG at include/linux/mm.h:990!
  RIP: 0010:init_page_owner+0x486/0x520

This means that assumptions behind commit fe53ca54270a ("mm: use
early_pfn_to_nid in page_ext_init") are incomplete.  Therefore, revert
the commit for now.  A proper way to move the page_owner initialization
to sooner is to hook into memmap initialization.

Link: http://lkml.kernel.org/r/20190115202812.75820-1-cai@lca.pw
Signed-off-by: Qian Cai <cai@lca.pw>
Acked-by: Michal Hocko <mhocko@kernel.org>
Cc: Pasha Tatashin <Pavel.Tatashin@microsoft.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Yang Shi <yang.shi@linaro.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 3 insertions, 4 deletions

diff --git a/init/main.c b/init/main.c
index e2e80ca3165a..c86a1c8f19f4 100644
--- a/init/main.c
+++ b/init/main.c
@@ -695,7 +695,6 @@ asmlinkage __visible void __init start_kernel(void)
                 initrd_start = 0;
         }
 #endif
-        page_ext_init();
         kmemleak_init();
         setup_per_cpu_pageset();
         numa_policy_init();
@@ -1131,6 +1130,8 @@ static noinline void __init kernel_init_freeable(void)
         sched_init_smp();
 
         page_alloc_init_late();
+        /* Initialize page ext after all struct pages are initialized. */
+        page_ext_init();
 
         do_basic_setup();
 
diff --git a/mm/page_ext.c b/mm/page_ext.c
index ae44f7adbe07..8c78b8d45117 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -398,10 +398,8 @@ void __init page_ext_init(void)
                          * We know some arch can have a nodes layout such as
                          * -------------pfn-------------->
                          * N0 | N1 | N2 | N0 | N1 | N2|....
-                         *
-                         * Take into account DEFERRED_STRUCT_PAGE_INIT.
                          */
-                        if (early_pfn_to_nid(pfn) != nid)
+                        if (pfn_to_nid(pfn) != nid)
                                 continue;
                         if (init_section_page_ext(pfn, nid))
                                 goto oom;