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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 351DCECAAA1 for ; Mon, 24 Oct 2022 14:23:29 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8259F8E0002; Mon, 24 Oct 2022 10:23:28 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7D53B8E0001; Mon, 24 Oct 2022 10:23:28 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6C38A8E0002; Mon, 24 Oct 2022 10:23:28 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 60B2C8E0001 for ; Mon, 24 Oct 2022 10:23:28 -0400 (EDT) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 2EF9940407 for ; Mon, 24 Oct 2022 14:23:28 +0000 (UTC) X-FDA: 80056060896.02.0A231DA Received: from outbound-smtp47.blacknight.com (outbound-smtp47.blacknight.com [46.22.136.64]) by imf16.hostedemail.com (Postfix) with ESMTP id 75154180035 for ; Mon, 24 Oct 2022 14:23:27 +0000 (UTC) Received: from mail.blacknight.com (pemlinmail03.blacknight.ie [81.17.254.16]) by outbound-smtp47.blacknight.com (Postfix) with ESMTPS id 92792FB01C for ; Mon, 24 Oct 2022 15:23:25 +0100 (IST) Received: (qmail 2363 invoked from network); 24 Oct 2022 14:23:25 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.198.246]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 24 Oct 2022 14:23:25 -0000 Date: Mon, 24 Oct 2022 15:23:21 +0100 From: Mel Gorman To: Tvrtko Ursulin Cc: "Matthew Wilcox (Oracle)" , Hugh Dickins , Linux MM , Matthew Auld , "Intel-gfx@lists.freedesktop.org" Subject: Re: mm/huge_memory: do not clobber swp_entry_t during THP split Message-ID: <20221024142321.f2etddxtqa47bib7@techsingularity.net> References: <1596edbb-02ad-6bdf-51b8-15c2d2e08b76@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1596edbb-02ad-6bdf-51b8-15c2d2e08b76@linux.intel.com> ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=none; spf=pass (imf16.hostedemail.com: domain of mgorman@techsingularity.net designates 46.22.136.64 as permitted sender) smtp.mailfrom=mgorman@techsingularity.net; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1666621407; a=rsa-sha256; cv=none; b=nM/lAAQ+MAnkfOMVWJjJ5kV7b57+1K+pyGGo+pU/Uahlv0I5/90YxhJoRHL7xm+qz3hrt5 x3swdKVDZKB2AKUjwLsT9Nmo+d0Gd945pG4sM5JrvBpIfEyyrh595/bSajLeS7q+g82hj7 r6BrDovvFVBotqrTuJMhwkjGlhFuUXU= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1666621407; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=j9KZ/n/rVM7Uzpt5Z1NAaUAzmHc8Z69k+WxcIf9knjU=; b=ATjdOv/mWiVzwW5z79QUr+Sdd7el4XEg7JI1gtXWPdbOUc5pYpvVR8CslW8UeiAxAcorr7 JGxs7xmJhFlv+4C1o1rdv106wtXqV3nFTBQbHaYPIIuhfLWNsUliRg2dTK/UEbz/Q4dYlH LvIJHUNpauABCagbZQ/ZHSEVhVkv3e8= X-Rspamd-Queue-Id: 75154180035 Authentication-Results: imf16.hostedemail.com; dkim=none; spf=pass (imf16.hostedemail.com: domain of mgorman@techsingularity.net designates 46.22.136.64 as permitted sender) smtp.mailfrom=mgorman@techsingularity.net; dmarc=none X-Rspam-User: X-Rspamd-Server: rspam09 X-Stat-Signature: 3dspd993niwoyu9idy8eatqejmtwcw6o X-HE-Tag: 1666621407-509537 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Oct 24, 2022 at 02:04:50PM +0100, Tvrtko Ursulin wrote: > > Hi Mel, mm experts, > > With 6.1-rc2 we started hitting the WARN_ON added in 71e2d666ef85 ("mm/huge_memory: do not clobber swp_entry_t during THP split") in i915 automated CI: > Thanks for the report. As shmem pages pages are allocated via vma_alloc_folio and are compound pages, can you try the following patch please? If it still triggers, please post the new oops as it'll include the tail page information. --8<-- From: Hugh Dickins Subject: [PATCH] mm: prep_compound_tail() clear page->private Although page allocation always clears page->private in the first page or head page of an allocation, it has never made a point of clearing page->private in the tails (though 0 is often what is already there). But now commit 71e2d666ef85 ("mm/huge_memory: do not clobber swp_entry_t during THP split") issues a warning when page_tail->private is found to be non-0 (unless it's swapcache). Change that warning to dump page_tail (which also dumps head), instead of just the head: so far we have seen dead000000000122, dead000000000003, dead000000000001 or 0000000000000002 in the raw output for tail private. We could just delete the warning, but today's consensus appears to want page->private to be 0, unless there's a good reason for it to be set: so now clear it in prep_compound_tail() (more general than just for THP; but not for high order allocation, which makes no pass down the tails). Fixes: 71e2d666ef85 ("mm/huge_memory: do not clobber swp_entry_t during THP split") Signed-off-by: Hugh Dickins Cc: Mel Gorman Cc: Matthew Wilcox (Oracle) Cc: --- mm/huge_memory.c | 2 +- mm/page_alloc.c | 1 + 2 files changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 03fc7e5edf07..561a42567477 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2462,7 +2462,7 @@ static void __split_huge_page_tail(struct page *head, int tail, * Fix up and warn once if private is unexpectedly set. */ if (!folio_test_swapcache(page_folio(head))) { - VM_WARN_ON_ONCE_PAGE(page_tail->private != 0, head); + VM_WARN_ON_ONCE_PAGE(page_tail->private != 0, page_tail); page_tail->private = 0; } diff --git a/mm/page_alloc.c b/mm/page_alloc.c index b5a6c815ae28..218b28ee49ed 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -807,6 +807,7 @@ static void prep_compound_tail(struct page *head, int tail_idx) p->mapping = TAIL_MAPPING; set_compound_head(p, head); + set_page_private(p, 0); } void prep_compound_page(struct page *page, unsigned int order) -- 2.35.3