Hello Jianguo,
In the commit a49ecbcd7b0d5a1cda, it talks about HugeTLB page being
freed into buddy allocator instead of hugepage_freelists. But if
I look the code closely for the function unmap_and_move_huge_page()
it only calls putback_active_hugepage() which puts the page into the
huge page active list to free up the source HugeTLB page after any
successful migration. I might be missing something here, so can you
please point me where we release the HugeTLB page into buddy allocator
directly during migration ?
commit a49ecbcd7b0d5a1cda7d60e03df402dd0ef76ac8
Author: Jianguo Wu <wujianguo@xxxxxxxxxx>
Date: Wed Dec 18 17:08:54 2013 -0800
mm/memory-failure.c: recheck PageHuge() after hugetlb page migrate successfully
After a successful hugetlb page migration by soft offline, the source
page will either be freed into hugepage_freelists or buddy(over-commit
page). If page is in buddy, page_hstate(page) will be NULL. It will
hit a NULL pointer dereference in dequeue_hwpoisoned_huge_page().
BUG: unable to handle kernel NULL pointer dereference at 0000000000000058
IP: [<ffffffff81163761>] dequeue_hwpoisoned_huge_page+0x131/0x1d0
PGD c23762067 PUD c24be2067 PMD 0
Oops: 0000 [#1] SMP
So check PageHuge(page) after call migrate_pages() successfully.
Signed-off-by: Jianguo Wu <wujianguo@xxxxxxxxxx>
Tested-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Reviewed-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index b7c1716..db08af9 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1505,10 +1505,16 @@ static int soft_offline_huge_page(struct page *page, int flags)
if (ret > 0)
ret = -EIO;
} else {
- set_page_hwpoison_huge_page(hpage);
- dequeue_hwpoisoned_huge_page(hpage);
- atomic_long_add(1 << compound_order(hpage),
- &num_poisoned_pages);
+ /* overcommit hugetlb page will be freed to buddy */
+ if (PageHuge(page)) {
+ set_page_hwpoison_huge_page(hpage);
+ dequeue_hwpoisoned_huge_page(hpage);
+ atomic_long_add(1 << compound_order(hpage),
+ &num_poisoned_pages);
+ } else {
+ SetPageHWPoison(page);
+ atomic_long_inc(&num_poisoned_pages);
+ }
}
return ret;
}
Regards
Anshuman
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