When memory_failure() runs on a thp tail page after pmd is split, we trigger
the following VM_BUG_ON_PAGE():
[ 619.550520] page:ffffd7cd819b0040 count:0 mapcount:0 mapping: (null) index:0x1
[ 619.555486] flags: 0x1fffc000400000(hwpoison)
[ 619.556408] page dumped because: VM_BUG_ON_PAGE(!page_count(p))
[ 619.558998] ------------[ cut here ]------------
[ 619.561388] kernel BUG at /src/linux-dev/mm/memory-failure.c:1132!
memory_failure() passed refcount and page lock from tail page to head page,
which is not needed because we can pass any subpage to split_huge_page().
Signed-off-by: Naoya Horiguchi <[email protected]>
Fixes: 61f5d698cc97 ("mm: re-enable THP")
Cc: [email protected] # 4.5+
---
mm/memory-failure.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)
diff --git v4.8-rc8-mmotm-2016-09-27-16-08/mm/memory-failure.c v4.8-rc8-mmotm-2016-09-27-16-08_patched/mm/memory-failure.c
index de88f33..19e796d 100644
--- v4.8-rc8-mmotm-2016-09-27-16-08/mm/memory-failure.c
+++ v4.8-rc8-mmotm-2016-09-27-16-08_patched/mm/memory-failure.c
@@ -1112,10 +1112,10 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
}
if (!PageHuge(p) && PageTransHuge(hpage)) {
- lock_page(hpage);
- if (!PageAnon(hpage) || unlikely(split_huge_page(hpage))) {
- unlock_page(hpage);
- if (!PageAnon(hpage))
+ lock_page(p);
+ if (!PageAnon(p) || unlikely(split_huge_page(p))) {
+ unlock_page(p);
+ if (!PageAnon(p))
pr_err("Memory failure: %#lx: non anonymous thp\n",
pfn);
else
@@ -1126,9 +1126,7 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
put_hwpoison_page(p);
return -EBUSY;
}
- unlock_page(hpage);
- get_hwpoison_page(p);
- put_hwpoison_page(hpage);
+ unlock_page(p);
VM_BUG_ON_PAGE(!page_count(p), p);
hpage = compound_head(p);
}
--
2.7.0