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 <[email protected]> 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 <[email protected]> Tested-by: Naoya Horiguchi <[email protected]> Reviewed-by: Naoya Horiguchi <[email protected]> Cc: <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> 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
