From: Miaohe Lin <linmiaohe@xxxxxxxxxx> Subject: mm/memory-failure.c: fix race with changing page compound again Patch series "A few fixup patches for memory failure", v2. This series contains a few patches to fix the race with changing page compound page, make non-LRU movable pages unhandlable and so on. More details can be found in the respective changelogs. There is a race window where we got the compound_head, the hugetlb page could be freed to buddy, or even changed to another compound page just before we try to get hwpoison page. Think about the below race window: CPU 1 CPU 2 memory_failure_hugetlb struct page *head = compound_head(p); hugetlb page might be freed to buddy, or even changed to another compound page. get_hwpoison_page -- page is not what we want now... If this race happens, just bail out. Also MF_MSG_DIFFERENT_PAGE_SIZE is introduced to record this event. [akpm@xxxxxxxxxxxxxxxxxxxx: s@/**@/*@, per Naoya Horiguchi] Link: https://lkml.kernel.org/r/20220312074613.4798-1-linmiaohe@xxxxxxxxxx Link: https://lkml.kernel.org/r/20220312074613.4798-2-linmiaohe@xxxxxxxxxx Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx> Acked-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx> Cc: Tony Luck <tony.luck@xxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: Yang Shi <shy828301@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/mm.h | 1 + include/ras/ras_event.h | 1 + mm/memory-failure.c | 12 ++++++++++++ 3 files changed, 14 insertions(+) --- a/include/linux/mm.h~mm-memory-failurec-fix-race-with-changing-page-compound-again +++ a/include/linux/mm.h @@ -3239,6 +3239,7 @@ enum mf_action_page_type { MF_MSG_BUDDY, MF_MSG_DAX, MF_MSG_UNSPLIT_THP, + MF_MSG_DIFFERENT_PAGE_SIZE, MF_MSG_UNKNOWN, }; --- a/include/ras/ras_event.h~mm-memory-failurec-fix-race-with-changing-page-compound-again +++ a/include/ras/ras_event.h @@ -374,6 +374,7 @@ TRACE_EVENT(aer_event, EM ( MF_MSG_BUDDY, "free buddy page" ) \ EM ( MF_MSG_DAX, "dax page" ) \ EM ( MF_MSG_UNSPLIT_THP, "unsplit thp" ) \ + EM ( MF_MSG_DIFFERENT_PAGE_SIZE, "different page size" ) \ EMe ( MF_MSG_UNKNOWN, "unknown page" ) /* --- a/mm/memory-failure.c~mm-memory-failurec-fix-race-with-changing-page-compound-again +++ a/mm/memory-failure.c @@ -732,6 +732,7 @@ static const char * const action_page_ty [MF_MSG_BUDDY] = "free buddy page", [MF_MSG_DAX] = "dax page", [MF_MSG_UNSPLIT_THP] = "unsplit thp", + [MF_MSG_DIFFERENT_PAGE_SIZE] = "different page size", [MF_MSG_UNKNOWN] = "unknown page", }; @@ -1532,6 +1533,17 @@ static int memory_failure_hugetlb(unsign } lock_page(head); + + /* + * The page could have changed compound pages due to race window. + * If this happens just bail out. + */ + if (!PageHuge(p) || compound_head(p) != head) { + action_result(pfn, MF_MSG_DIFFERENT_PAGE_SIZE, MF_IGNORED); + res = -EBUSY; + goto out; + } + page_flags = head->flags; if (hwpoison_filter(p)) { _
