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=1793439849; b=RF0zLNU38Pmauq4ySVSojkeGTRtuXG5kRb+/iiHniq1EU3RFO/u6yJWm5boQH6BNHKW/ OTAJqRUzBv/yJPE2F989DySA3/V/fIw9rKSZ1CpJ7ipEK9iMi7aCNAYw4asSwvFI/KYVT MoTIeqmu+A2Hf+L/aLuhO+TsvcKm9g1ZyunxaMHMhkVgtoRChyNtqOzLgOyWVHTtHvbzv uTZzjwEn7lJBAfFvcfD7rqA687KTjDxWnctYlVVrQxV33LPshtaOY8f6cms3b1/E8EaW3 eAwb1JxjKUQybbk1ruCviIjIb79PTuRd0zpqtmwuDyWDfXxLfrEdtu+JqPygUtRvP7g== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793439849; 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=dD8bNaZIuViD1rMmSH8A86u/ZWtm1YEV/epD2uKBbxE=; b=CbilSzJ1EipERfxr4Jmd8EVvfyBp8glCxDhfNCzGy7XC6WwoxP9R8QqxqKfpUae+UGqK kUgPMCYcSiS2Aa1pOpRe4EcDq048o/aSlxLwR4ORhPcijEnrs3CqFmGEXqTwvp7wpfbf1 oGVf7xzXZ93wNLVRzaAUcI3zoPhZBPnODTOgbB3xP2uARNYCOxFVBuBF1Onfc5gUxgqnI XdrdeyJY3BqpaB43UsQxK+h0sx0ojr5m0blWJLA6SDN6pTD2Vl+zZiSFuIbFQMP5JQEYw PJKjZk4XN5ox+HG4WrFPU9Mxl+oyxiV6zQXFoTekro4wdWrCoATHXy645OC5Mla3Gog== 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=SBYWyFJB; 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 6B9F9606A31E; Sat, 31 Oct 2026 09:44:09 +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=SBYWyFJB Received: by smtp.kernel.org (Postfix) with ESMTPSA id BBBC31F0093A; Sat, 31 Oct 2026 09:43:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793439849; bh=dD8bNaZIuViD1rMmSH8A86u/ZWtm1YEV/epD2uKBbxE=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=SBYWyFJBjrqmvQU0SLK/yXNYDG03UfEHLHBfhq+cgw3Mp75MofH2A8dc6wPjeEDVv OgsCgMr8avGx4SVXvGmJOt4L0WLdm8QTqbVfd3IgM2F9nzP1NKoikT78JhjLalaX6y MJa8/PAIKKtuVGZ6zyGm2qn8asC2gEIT2/RlnUQdveNPyGdqArZM+nJ3oFiB4QJBUD FqHedcFM3LOFsdKvRRAW7qIWlFNsNLMIvP2f0hRzi9q6829DtyPX0OMj/JaKxv8REN 3jH/Ga4Nqjvn8Vw5Hr0RDErkQgv1hA578/T4CTyi0+/C11MmrghwGE7RVwyCq1+EpW sR34AEi7oNxPg== From: "David Hildenbrand (Arm)" Date: Sat, 31 Oct 2026 10:39:44 +0100 Subject: [PATCH v3 15/47] mm/khugepaged: always recheck the pmd in try_collapse_pte_mapped_thp() X-Mailing-List: linux-arch@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: <20261031-fixes_core-v3-15-d6437171ecc3@kernel.org> References: <20261031-fixes_core-v3-0-d6437171ecc3@kernel.org> In-Reply-To: <20261031-fixes_core-v3-0-d6437171ecc3@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, Muhammad Usama Anjum , "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1665; i=david@kernel.org; h=from:subject:message-id; bh=CS7nU47snOvzHXKT1Jq5YnXJ98oWY8rgSlPg1efCrZ0=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLKebk9PenzlJu+Me5oLPjgcPt+x3vBE0sRXv9/FJ7pPE V46WSm6vaOUhUGMg0FWTJElKPi+wcuX62qr3fiYYeawMoEMYeDiFICJnF7PyNBhvkr/s0eeQtOS xA+ZX8KZxEMW5rmvFv7Ty3PvlKhu4G9Ghhu37Loa9P4Ieh2Osa9PXXbdul0vIGFp3yn3w0uKr5Z OYAYA 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) Tested-by: Muhammad Usama Anjum 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 3a6f4b7b28453..81496887d827e 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