From: Naoya Horiguchi <[email protected]> The call to get_user_pages_fast is only to get the pointer to a struct page of a given address, pinning it is memory-poisoning handler's job, so drop the refcount grabbed by get_user_pages_fast().
Note that the target page is still pinned after this put_page() because the current process should have refcount from mapping. Signed-off-by: Naoya Horiguchi <[email protected]> Signed-off-by: Oscar Salvador <[email protected]> --- mm/madvise.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-) diff --git v5.8-rc1-mmots-2020-06-20-21-44/mm/madvise.c v5.8-rc1-mmots-2020-06-20-21-44_patched/mm/madvise.c index dd1d43cf026d..275b08edd428 100644 --- v5.8-rc1-mmots-2020-06-20-21-44/mm/madvise.c +++ v5.8-rc1-mmots-2020-06-20-21-44_patched/mm/madvise.c @@ -893,16 +893,24 @@ static int madvise_inject_error(int behavior, */ size = page_size(compound_head(page)); - if (PageHWPoison(page)) { - put_page(page); + /* + * 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); + + if (PageHWPoison(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(pfn, MF_COUNT_INCREASED); + ret = soft_offline_page(pfn, 0); if (ret) return ret; continue; @@ -910,14 +918,6 @@ 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; -- 2.17.1
