From: Naoya Horiguchi <[email protected]> Currently madvise_inject_error() pins the target via get_user_pages_fast. The call to get_user_pages_fast is only to get the respective page of a given address, but it is the job of the memory-poisoning handler to deal with races, so drop the refcount grabbed by get_user_pages_fast.
Signed-off-by: Naoya Horiguchi <[email protected]> Signed-off-by: Oscar Salvador <[email protected]> --- mm/madvise.c | 25 +++++++++++-------------- 1 file changed, 11 insertions(+), 14 deletions(-) diff --git a/mm/madvise.c b/mm/madvise.c index 6e023414f5c1..fbe6d402232c 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -883,6 +883,16 @@ static int madvise_inject_error(int behavior, ret = get_user_pages_fast(start, 1, 0, &page); if (ret != 1) return ret; + /* + * The get_user_pages_fast() is just to get the pfn of the + * given address, and the refcount has nothing to do with + * what we try to test, so it should be released immediately. + * This is racy but it's intended because the real hardware + * errors could happen at any moment and memory error handlers + * must properly handle the race. + */ + put_page(page); + pfn = page_to_pfn(page); /* @@ -892,16 +902,11 @@ static int madvise_inject_error(int behavior, */ order = compound_order(compound_head(page)); - if (PageHWPoison(page)) { - put_page(page); - continue; - } - if (behavior == MADV_SOFT_OFFLINE) { pr_info("Soft offlining pfn %#lx at process virtual address %#lx\n", pfn, start); - ret = soft_offline_page(page, MF_COUNT_INCREASED); + ret = soft_offline_page(page, 0); if (ret) return ret; continue; @@ -909,14 +914,6 @@ static int madvise_inject_error(int behavior, pr_info("Injecting memory failure for pfn %#lx at process virtual address %#lx\n", pfn, start); - - /* - * Drop the page reference taken by get_user_pages_fast(). In - * the absence of MF_COUNT_INCREASED the memory_failure() - * routine is responsible for pinning the page to prevent it - * from being released back to the page allocator. - */ - put_page(page); ret = memory_failure(pfn, 0); if (ret) return ret; -- 2.12.3
