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Subject[PATCH] mm: skip checking poison pattern for page_to_nid()
Date
Kernel panic with page_owner=on

CONFIG_DEBUG_VM_PGFLAGS=y
PAGE_OWNER=y
NODE_NOT_IN_PAGE_FLAGS=n

This is due to f165b378bbd (mm: uninitialized struct page poisoning
sanity checking) shoots itself in the foot.

[ 11.917212] page:ffffea0004200000 is uninitialized and poisoned
[ 11.917220] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff
ffffffffffffffff
[ 11.921745] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff
ffffffffffffffff
[ 11.924523] page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
[ 11.926498] page_owner info is not active (free page?)
[ 12.329560] kernel BUG at include/linux/mm.h:990!
[ 12.337632] RIP: 0010:init_page_owner+0x486/0x520

At first,

start_kernel
setup_arch
pagetable_init
paging_init
sparse_init
sparse_init_nid
sparse_buffer_init
memblock_virt_alloc_try_nid_raw

It poisons all the allocated pages there.

memset(ptr, PAGE_POISON_PATTERN, size)

Later,

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
PF_POISONED_CHECK <--- panic here.

This because all allocated pages are not initialized until later.

init_pages_in_zone
__set_page_owner_handle

Fixes: f165b378bbd (mm: uninitialized struct page poisoning
sanity checking)
Signed-off-by: Qian Cai <cai@lca.pw>
---
include/linux/mm.h | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 5411de93a363..f083f366ea90 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -985,9 +985,7 @@ extern int page_to_nid(const struct page *page);
#else
static inline int page_to_nid(const struct page *page)
{
- struct page *p = (struct page *)page;
-
- return (PF_POISONED_CHECK(p)->flags >> NODES_PGSHIFT) & NODES_MASK;
+ return (page->flags >> NODES_PGSHIFT) & NODES_MASK;
}
#endif

--
2.17.2 (Apple Git-113)
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