This problem is seen when machine is rebooted after kexec:
A message like this is printed:
==========================================================================
WARNING: CPU: 21 PID: 249 at linux/lib/list_debug.c:53__listd+0x83/0xa0
Modules linked in:
CPU: 21 PID: 249 Comm: pgdatinit0 Not tainted 4.14.0-rc6_pt_deferred #90
Hardware name: Oracle Corporation ORACLE SERVER X6-2/ASM,MOTHERBOARD,1U,
BIOS 3016
node 1 initialised, 32444607 pages in 1679ms
task: ffff880180e75a00 task.stack: ffffc9000cdb0000
RIP: 0010:__list_del_entry_valid+0x83/0xa0
RSP: 0000:ffffc9000cdb3d18 EFLAGS: 00010046
RAX: 0000000000000054 RBX: 0000000000000009 RCX: ffffffff81c5f3e8
RDX: 0000000000000000 RSI: 0000000000000086 RDI: 0000000000000046
RBP: ffffc9000cdb3d18 R08: 00000000fffffffe R09: 0000000000000154
R10: 0000000000000005 R11: 0000000000000153 R12: 0000000001fcdc00
R13: 0000000001fcde00 R14: ffff88207ffded00 R15: ffffea007f370000
FS: 0000000000000000(0000) GS:ffff881fffac0000(0000) knlGS:0
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000407ec09001 CR4: 00000000003606e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
free_one_page+0x103/0x390
__free_pages_ok+0x1cf/0x2d0
__free_pages+0x19/0x30
__free_pages_boot_core+0xae/0xba
deferred_free_range+0x60/0x94
deferred_init_memmap+0x324/0x372
kthread+0x109/0x140
? __free_pages_bootmem+0x2e/0x2e
? kthread_park+0x60/0x60
ret_from_fork+0x25/0x30
list_del corruption. next->prev should be ffffea007f428020, but was
ffffea007f1d8020
==========================================================================
The problem happens in this path:
page_alloc_init_late
deferred_init_memmap
deferred_init_range
__def_free
deferred_free_range
__free_pages_boot_core(page, order)
__free_pages()
__free_pages_ok()
free_one_page()
__free_one_page(page, pfn, zone, order, migratetype);
deferred_init_range() initializes one page at a time by calling
__init_single_page(), once it initializes pageblock_nr_pages pages, it
calls deferred_free_range() to free the initialized pages to the buddy
allocator. Eventually, we reach __free_one_page(), where we compute buddy
page:
buddy_pfn = __find_buddy_pfn(pfn, order);
buddy = page + (buddy_pfn - pfn);
buddy_pfn is computed as pfn ^ (1 << order), or pfn + pageblock_nr_pages.
Thefore, buddy page becomes a page one after the range that currently was
initialized, and we access this page in this function. Also, later when we
return back to deferred_init_range(), the buddy page is initialized again.
So, in order to avoid this issue, we must initialize the buddy page prior
to calling deferred_free_range().
Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
---
mm/page_alloc.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 97687b38da05..f3ea06db3eed 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1500,9 +1500,17 @@ static unsigned long deferred_init_range(int nid, int zid, unsigned long pfn,
__init_single_page(page, pfn, zid, nid);
nr_free++;
} else {
- nr_pages += __def_free(&nr_free, &free_base_pfn, &page);
page = pfn_to_page(pfn);
__init_single_page(page, pfn, zid, nid);
+ /*
+ * We must free previous range after initializing the
+ * first page of the next range. This is because first
+ * page may be accessed in __free_one_page(), when buddy
+ * page is computed:
+ * buddy_pfn = pfn + pageblock_nr_pages
+ */
+ deferred_free_range(free_base_pfn, nr_free);
+ nr_pages += nr_free;
free_base_pfn = pfn;
nr_free = 1;
cond_resched();
--
2.14.3
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