From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793306232; b=MNAeS4rZEKO8dZLPi+TpG1QO2iD3rPAqdWbjz3Xj88QZXojEXlkSWx0O9EliZ4MN5sm9 nHQRjLTWIN0SyL3/CUU2NSoGfiqzzllZfGLnEBtScExI7t+FNPyXKLWIf2dISa9Vj2BUh TNqLFqPFSKtfV5cXpKVDyKNo0ex2Y4wWhOgPfL8kv8/ckMrjc9cHoSe+grdDo/Sj8Zfp3 CUL/qAMFEO5IbMgga3CWy2i/yqcK0M+qp0Zf/B4/XcA7vgh6+mOT7+Xs/BXkP7ezIDOmq LTlheJ93YdpId4gJQ32KyxGdYthMCwaXP4OKYgNjjWYyY/wOA+kyPkIf6bev5bHUmow== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793306232; h=Received:DKIM-Signature:From:Date:Subject:MIME-Version:Content-Type: Content-Transfer-Encoding:Message-Id:References:In-Reply-To:To:Cc: X-Mailer:X-Developer-Signature:X-Developer-Key; bh=tNxobpWlUXNjZHphvvtOgvNQKSqjJiSYupG+wXJMVoE=; b=DGPqAshNIfsQX1VfLR6HgllLAEggmpb7TVziihBvghn2ZwD/Q58kAGVzOMB/JpfrDbWz BvvlNg0POBhuvScpYnbhWu5jrKSwQ3p0zKvI3EcSwI5ngEQKT8VeYfGFPNTN17b2YpCcC HWCIy1tj+4C+CdYphdnoNkEcNxrunb/nPMFWiu/FIy/8651LFNMIclSeqe+ythQEHcADI jaSAZAUxF19OzQLay115KZFDTCgjkRE+sImLejZzpVXvPvZDXunMo8BAzjeMPdfbpiA2V LMcg4bbLW/q+NLtLgctXPIZ/zcPLgY6WKtAftm/QnUs6z8qg8YKcXNQnQ4kitAfvYyA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=dnPvAICq; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1109E606A32A; Thu, 29 Oct 2026 20:37:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=dnPvAICq 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-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list 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 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