On Tue, Jan 12, 2021 at 1:54 AM Oscar Salvador osalvador@suse.de wrote:
On Tue, Jan 12, 2021 at 01:34:58AM -0800, Dan Williams wrote:
The conversion to move pfn_to_online_page() internal to soft_offline_page() missed that the get_user_pages() reference needs to be dropped when pfn_to_online_page() fails.
I would be more specific here wrt. get_user_pages (madvise). soft_offline_page gets called from more places besides madvise_*.
Sure.
When soft_offline_page() is handed a pfn_valid() && !pfn_to_online_page() pfn the kernel hangs at dax-device shutdown due to a leaked reference.
Fixes: feec24a6139d ("mm, soft-offline: convert parameter to pfn") Cc: Andrew Morton akpm@linux-foundation.org Cc: Naoya Horiguchi nao.horiguchi@gmail.com Cc: David Hildenbrand david@redhat.com Cc: Michal Hocko mhocko@kernel.org Cc: Oscar Salvador osalvador@suse.de Cc: stable@vger.kernel.org Signed-off-by: Dan Williams dan.j.williams@intel.com
LGTM, thanks for catching this:
Reviewed-by: Oscar Salvador osalvador@suse.de
A nit below.
mm/memory-failure.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-)
diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 5a38e9eade94..78b173c7190c 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -1885,6 +1885,12 @@ static int soft_offline_free_page(struct page *page) return rc; }
+static void put_ref_page(struct page *page) +{
if (page)put_page(page);+}
I am not sure this warrants a function. I would probably go with "if (ref_page).." in the two corresponding places, but not feeling strong here.
I'll take another look, it felt cluttered...
/**
- soft_offline_page - Soft offline a page.
- @pfn: pfn to soft-offline
@@ -1910,20 +1916,26 @@ static int soft_offline_free_page(struct page *page) int soft_offline_page(unsigned long pfn, int flags) { int ret;
struct page *page; bool try_again = true;
struct page *page, *ref_page = NULL;WARN_ON_ONCE(!pfn_valid(pfn) && (flags & MF_COUNT_INCREASED));Did you see any scenario where this could happen? I understand that you are adding this because we will leak a reference in case pfn is not valid anymore.
I did not, more future proofing / documenting against refactoring that fails to consider that case.