From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BFD1C60A2610 for ; Thu, 29 Oct 2026 20:37:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=rglVB+P/; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=dnPvAICq DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Cc:To:In-Reply-To:References :Message-Id:Content-Transfer-Encoding:Content-Type:MIME-Version:Subject:Date: From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Unsubscribe-Post: List-Owner; bh=tNxobpWlUXNjZHphvvtOgvNQKSqjJiSYupG+wXJMVoE=; b=rglVB+P/g7PuOl Dyx2JOGeDwhAoOxWpuFU4SBmCkoSmHAa1ofzwgxskt9aa7R99ssFprFU2dS3SkYSWUkCQD4UbiKmf 7Ulo9Wnvl+LPS2hxlqvaZr5Zz9IWRlKSEkRblpUtw/LIYrJET7AMr4fs7xJ/7NILNeRCtJayumEic pTaTt5613WtMVMwO9YQQbMlGbrCDnIQ+acNvaPNuGAgFaKeoNlxszt3ftyoTy4bX8jT27clT4bSEc 55Jxz/szbLGholq5aac7poyFCuGSF4hC+6QB5NC03AjYKb4XGMDNAJXxFs0NQ6GHwAri4V8eBwaMV TJwoRQ3MaOFOJpXOn58w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xMWs7-0000000AL0i-24Oh; Thu, 29 Oct 2026 20:37:15 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xMWs4-0000000AL0Z-3DkC for kexec@lists.infradead.org; Thu, 29 Oct 2026 20:37:13 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 3597B6020F; Thu, 29 Oct 2026 20:37:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 800E91F01816; Thu, 29 Oct 2026 20:36:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793306231; bh=tNxobpWlUXNjZHphvvtOgvNQKSqjJiSYupG+wXJMVoE=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=dnPvAICqs5R8ijwgTMhLfxbmgHzO9ja4TQwnVekFvzI4/Y7pZ5RiY6O6tVJsThGVV 0+fRYRkM1yM1n6cFK+iCf3ZqyzqyhwSxWilIYYeoHZzbo9N29g9v86q9A13gDR/zAg 8DtvbNaMzwDgGrBUQB5UExtEwWaK0Dn9sbaFts/LVGL/R1SW2YpAU0BrON2RUO4yYy cu/4SgzAJ0FHs5/Ri+ZxG/yPhlMK/kh2s08tuIv4giMR88cv5B14Ge4CBnqQ8xk6oa 1CwTQSEOwzHx7AbzR0KZQSktdzwEh8USZEjLO2tgQvbt5Dkn/jHz3doUQYIsiZKPxC 3UQpIdOeycdlw== From: "David Hildenbrand (Arm)" Date: Thu, 29 Oct 2026 21:33:10 +0100 Subject: [PATCH v2 15/47] mm/khugepaged: always recheck the pmd in try_collapse_pte_mapped_thp() X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261029-fixes_core-v2-15-a64ce7f83abb@kernel.org> References: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> In-Reply-To: <20261029-fixes_core-v2-0-a64ce7f83abb@kernel.org> To: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Pedro Falcato , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Dev Jain , Usama Arif , Kiryl Shutsemau , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, Josef Bacik , stable@vger.kernel.org, "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1608; i=david@kernel.org; h=from:subject:message-id; bh=KkwG8uxQMmQsjX2diZyIiRGRbeEH7cv/itYGtmQ0sPg=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLIer23LVcs0DZ+Vey1b3SqpnrEvsuh3u9sunSOS0y9ke OvO3DSho5SFQYyDQVZMkSUo+L7By5fraqvd+Jhh5rAygQxh4OIUgIl0pTD8Zglw/6lYZenzR8hk r8l90wVv172VFuh9dvaBH8e5W5P3izP8DzWJnPD4TI3eYUNe26sd69i/56mUL3HNdaxgFvxTHXi AAQA= X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" X-Spam-Status: No, score=-18.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 From: Josef Bacik try_collapse_pte_mapped_thp() drops the PTE lock after it has cleared the page table, and takes the PMD lock and the PTE lock to remove it. In between, MADV_DONTNEED with CONFIG_PT_RECLAIM can reclaim the page table. The pmd_same() check is supposed to handle this, but it is only done with CONFIG_SPLIT_PTE_PTLOCKS. Fix it by performing the check unconditionally. Fix generated by an LLM and sent by Josef Bacik in private. Fixes: 6375e95f381e ("mm: pgtable: reclaim empty PTE page in madvise(MADV_DONTNEED)") Cc: stable@vger.kernel.org Signed-off-by: Josef Bacik [ david: adjust description ] Reviewed-by: Gregory Price (Meta) Tested-by: Gregory Price (Meta) Signed-off-by: David Hildenbrand (Arm) --- mm/khugepaged.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 4b71d010b2af..f53c50507c83 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -2013,12 +2013,11 @@ static enum scan_result try_collapse_pte_mapped_thp(struct mm_struct *mm, unsign /* step 4: remove empty page table */ if (!pml) { pml = pmd_lock(mm, pmd); - if (ptl != pml) { + if (ptl != pml) spin_lock_nested(ptl, SINGLE_DEPTH_NESTING); - if (unlikely(!pmd_same(pgt_pmd, pmdp_get_lockless(pmd)))) { - flush_tlb_mm(mm); - goto unlock; - } + if (unlikely(!pmd_same(pgt_pmd, pmdp_get_lockless(pmd)))) { + flush_tlb_mm(mm); + goto unlock; } } pgt_pmd = pmdp_collapse_flush(vma, haddr, pmd); -- 2.43.0