From: Zi Yan <[email protected]> The loop in madvise_inject_error() reads its step size from a page after it is soft-offlined. It works because the page is: 1) a hugetlb page: the page size does not change; 2) a base page: the page size does not change; 3) a THP: soft-offline always splits THPs, thus, it is OK to use PAGE_SIZE as step size.
It will be a problem when soft-offline supports THP migrations. When a THP is migrated without split during soft-offlining, the THP is split after migration, thus, before and after soft-offlining page sizes do not match. This causes a THP to be unnecessarily soft-lined, at most, 511 times, wasting free space. Signed-off-by: Zi Yan <[email protected]> --- mm/madvise.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) diff --git a/mm/madvise.c b/mm/madvise.c index 47d8d8a25eae..49f6774db259 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -612,19 +612,22 @@ static long madvise_remove(struct vm_area_struct *vma, static int madvise_inject_error(int behavior, unsigned long start, unsigned long end) { - struct page *page; + struct page *page = NULL; + unsigned long page_size = PAGE_SIZE; if (!capable(CAP_SYS_ADMIN)) return -EPERM; - for (; start < end; start += PAGE_SIZE << - compound_order(compound_head(page))) { + for (; start < end; start += page_size) { int ret; ret = get_user_pages_fast(start, 1, 0, &page); if (ret != 1) return ret; + page_size = (PAGE_SIZE << compound_order(compound_head(page))) - + (PAGE_SIZE * (page - compound_head(page))); + if (PageHWPoison(page)) { put_page(page); continue; @@ -637,6 +640,12 @@ static int madvise_inject_error(int behavior, ret = soft_offline_page(page, MF_COUNT_INCREASED); if (ret) return ret; + /* + * Non hugetlb pages either have PAGE_SIZE + * or are split into PAGE_SIZE + */ + if (!PageHuge(page)) + page_size = PAGE_SIZE; continue; } pr_info("Injecting memory failure for pfn %#lx at process virtual address %#lx\n", @@ -645,6 +654,12 @@ static int madvise_inject_error(int behavior, ret = memory_failure(page_to_pfn(page), 0, MF_COUNT_INCREASED); if (ret) return ret; + /* + * Non hugetlb pages either have PAGE_SIZE + * or are split into PAGE_SIZE + */ + if (!PageHuge(page)) + page_size = PAGE_SIZE; } return 0; } -- 2.13.2
