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[PATCH v8 01/11] x86/mm: setting fields in deferred pages

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Without deferred struct page feature (CONFIG_DEFERRED_STRUCT_PAGE_INIT),
flags and other fields in "struct page"es are never changed prior to first
initializing struct pages by going through __init_single_page().

With deferred struct page feature enabled, however, we set fields in
register_page_bootmem_info that are subsequently clobbered right after in
free_all_bootmem:

        mem_init() {
                register_page_bootmem_info();
                free_all_bootmem();
                ...
        }

When register_page_bootmem_info() is called only non-deferred struct pages
are initialized. But, this function goes through some reserved pages which
might be part of the deferred, and thus are not yet initialized.

  mem_init
   register_page_bootmem_info
    register_page_bootmem_info_node
     get_page_bootmem
      .. setting fields here ..
      such as: page->freelist = (void *)type;

  free_all_bootmem()
   free_low_memory_core_early()
    for_each_reserved_mem_region()
     reserve_bootmem_region()
      init_reserved_page() <- Only if this is deferred reserved page
       __init_single_pfn()
        __init_single_page()
            memset(0) <-- Loose the set fields here

We end-up with issue where, currently we do not observe problem as memory
is explicitly zeroed. But, if flag asserts are changed we can start hitting
issues.

Also, because in this patch series we will stop zeroing struct page memory
during allocation, we must make sure that struct pages are properly
initialized prior to using them.

The deferred-reserved pages are initialized in free_all_bootmem().
Therefore, the fix is to switch the above calls.

Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: Steven Sistare <steven.sistare@oracle.com>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Reviewed-by: Bob Picco <bob.picco@oracle.com>
---
 arch/x86/mm/init_64.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 048fbe8fc274..42b4b7a585c2 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1173,12 +1173,17 @@ void __init mem_init(void)
 
 	/* clear_bss() already clear the empty_zero_page */
 
-	register_page_bootmem_info();
-
 	/* this will put all memory onto the freelists */
 	free_all_bootmem();
 	after_bootmem = 1;
 
+	/* Must be done after boot memory is put on freelist, because here we
+	 * might set fields in deferred struct pages that have not yet been
+	 * initialized, and free_all_bootmem() initializes all the reserved
+	 * deferred pages for us.
+	 */
+	register_page_bootmem_info();
+
 	/* Register memory areas for /proc/kcore */
 	kclist_add(&kcore_vsyscall, (void *)VSYSCALL_ADDR,
 			 PAGE_SIZE, KCORE_OTHER);
-- 
2.14.1

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[PATCH v7 00/11] complete deferred page initialization Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
  [PATCH v8 03/11] mm: deferred_init_memmap improvements Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
  [PATCH v8 02/11] sparc64/mm: setting fields in deferred pages Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
  [PATCH v8 11/11] mm: stop zeroing memory during allocation in vmemmap Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
  [PATCH v8 05/11] mm: defining memblock_virt_alloc_try_nid_raw Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
  [PATCH v8 09/11] x86/kasan: explicitly zero kasan shadow memory Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
  [PATCH v8 08/11] mm: zero reserved and unavailable struct pages Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
  [PATCH v8 07/11] sparc64: optimized struct page zeroing Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
  [PATCH v8 06/11] mm: zero struct pages during initialization Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
  [PATCH v8 04/11] sparc64: simplify vmemmap_populate Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
  [PATCH v8 01/11] x86/mm: setting fields in deferred pages Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
  [PATCH v8 10/11] arm64/kasan: explicitly zero kasan shadow memory Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
    Re: [PATCH v8 10/11] arm64/kasan: explicitly zero kasan shadow memory Mark Rutland <mark.rutland@arm.com> - 2017-09-15 03:20 +0200
      Re: [PATCH v8 10/11] arm64/kasan: explicitly zero kasan shadow memory Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 03:40 +0200
        Re: [PATCH v8 10/11] arm64/kasan: explicitly zero kasan shadow memory Mark Rutland <mark.rutland@arm.com> - 2017-09-15 22:40 +0200
          Re: [PATCH v8 10/11] arm64/kasan: explicitly zero kasan shadow memory Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 23:30 +0200
            Re: [PATCH v8 10/11] arm64/kasan: explicitly zero kasan shadow memory Mark Rutland <mark.rutland@arm.com> - 2017-09-16 00:20 +0200
  [PATCH v8 00/11] complete deferred page initialization Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:50 +0200

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