From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EA44DC433EF for ; Fri, 10 Dec 2021 11:02:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240175AbhLJLGU (ORCPT ); Fri, 10 Dec 2021 06:06:20 -0500 Received: from out0.migadu.com ([94.23.1.103]:59313 "EHLO out0.migadu.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234606AbhLJLGT (ORCPT ); Fri, 10 Dec 2021 06:06:19 -0500 X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1639134163; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=crOYlgjr6TJQi4fWo9njLpi/uZBGieqA7+/rnQHOBK8=; b=TlsQaoW0afvqpwqbG9OMB38r8CsUgGwszyRJfd2I0pZk+9qAaNVT/oiWmS0IoI3regwT1L gdSVcoPFOT1ldGVqlcettgUBRjqMQaTNq5Tp7OMsZgosc03owNZ4tsc6j1D1Bha9kZKHtP aGEns7ikvMpyTpUqlcWLMxH/Umwi1l0= From: Naoya Horiguchi To: linux-mm@kvack.org Cc: Andrew Morton , luofei@unicloud.com, Naoya Horiguchi , linux-kernel@vger.kernel.org Subject: [PATCH v1] mm, hwpoison: fix condition in free hugetlb page path Date: Fri, 10 Dec 2021 20:02:08 +0900 Message-Id: <20211210110208.879740-1-naoya.horiguchi@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: naoya.horiguchi@linux.dev Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Naoya Horiguchi When a memory error hits a tail page of a free hugepage, __page_handle_poison() is expected to be called to isolate the error in 4kB unit, but it's not called due to the outdated if-condition in memory_failure_hugetlb(). This loses the chance to isolate the error in the finer unit, so it's not optimal. Drop the condition. This "(p != head && TestSetPageHWPoison(head)" condition is based on the old semantics of PageHWPoison on hugepage (where PG_hwpoison flag was set on the subpage), so it's not necessray any more. By getting to set PG_hwpoison on head page for hugepages, concurrent error events on different subpages in a single hugepage can be prevented by TestSetPageHWPoison(head) at the beginning of memory_failure_hugetlb(). So dropping the condition should not reopen the race window originally mentioned in commit b985194c8c0a ("hwpoison, hugetlb: lock_page/unlock_page does not match for handling a free hugepage") Reported-by: Fei Luo Signed-off-by: Naoya Horiguchi Cc: # v5.14+ --- I set v5.14+ for stable trees because the base code was greatly changed by commit 0ed950d1f281 ("mm,hwpoison: make get_hwpoison_page() call get_any_page()"), and this patch is not cleanly applicable, although the original issue was introduced more previously. --- mm/memory-failure.c | 21 +++++++-------------- 1 file changed, 7 insertions(+), 14 deletions(-) diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 8f0ee5b08696..68d9a35f8908 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -1521,24 +1521,17 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags) if (!(flags & MF_COUNT_INCREASED)) { res = get_hwpoison_page(p, flags); if (!res) { - /* - * Check "filter hit" and "race with other subpage." - */ lock_page(head); - if (PageHWPoison(head)) { - if ((hwpoison_filter(p) && TestClearPageHWPoison(p)) - || (p != head && TestSetPageHWPoison(head))) { + if (hwpoison_filter(p)) { + if (TestClearPageHWPoison(head)) num_poisoned_pages_dec(); - unlock_page(head); - return 0; - } + unlock_page(head); + return 0; } unlock_page(head); - res = MF_FAILED; - if (__page_handle_poison(p)) { - page_ref_inc(p); - res = MF_RECOVERED; - } + res = MF_RECOVERED; + if (!page_handle_poison(p, true, false)) + res = MF_FAILED; action_result(pfn, MF_MSG_FREE_HUGE, res); return res == MF_RECOVERED ? 0 : -EBUSY; } else if (res < 0) { -- 2.25.1