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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 44B3E10A1E63 for ; Fri, 27 Mar 2026 02:14:36 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id AAF576B009F; Thu, 26 Mar 2026 22:14:35 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A870F6B00A0; Thu, 26 Mar 2026 22:14:35 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9C4CA6B00A1; Thu, 26 Mar 2026 22:14:35 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 8B7636B009F for ; Thu, 26 Mar 2026 22:14:35 -0400 (EDT) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id B29ED5DB42 for ; Fri, 27 Mar 2026 02:14:33 +0000 (UTC) X-FDA: 84590224026.14.CD8131A Received: from out-181.mta1.migadu.com (out-181.mta1.migadu.com [95.215.58.181]) by imf21.hostedemail.com (Postfix) with ESMTP id 008241C0004 for ; Fri, 27 Mar 2026 02:14:31 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=lWTo7Sxh; spf=pass (imf21.hostedemail.com: domain of usama.arif@linux.dev designates 95.215.58.181 as permitted sender) smtp.mailfrom=usama.arif@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1774577672; 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-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=HoJOR/NIUvMGOPs6vSvgMHM3cn3cr848MTO9YNsr9oY=; b=Xkf2wUQe/WYzhxsVsQWla1yOZbdvXG2w3ui2QpJ9niTl03ens1uBWF7kInzRV1UkEXN1Lx fqxm+PrpcjflOv6hwp5GvLmvn0vck1IpHV08dWjpdIQCieXlPCATv52ZzL9LTXYKJPHcRc AJ/QdA2ti2FsQIyXXYYaDqLyOZ+gt8w= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=lWTo7Sxh; spf=pass (imf21.hostedemail.com: domain of usama.arif@linux.dev designates 95.215.58.181 as permitted sender) smtp.mailfrom=usama.arif@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1774577672; a=rsa-sha256; cv=none; b=1KKWmZrDJVO0cPl7GVQr/Uj0qtC6zvdAwjlFD8G3w8ffc0XPcpsaFNFf/IHeHF8WaxBPP/ 5qWjmr3svnDx64D7kWzhZHUXdnInU2RWfjiFxXXMnD/BQVwL6lHRwEN7rnj2+IydMnXiwA 8e+PnQ6wZX0XUyFguJafg+iz4gnJ0/c= 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=1774577669; 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: in-reply-to:in-reply-to:references:references; bh=HoJOR/NIUvMGOPs6vSvgMHM3cn3cr848MTO9YNsr9oY=; b=lWTo7SxhC2/el6n5yFl/mHGjsk9IDwHTkAjGiFljw5zNKe4kG/HDpe+AsO9ZpB7Xn6yD+M lcl/hkBeI86GVj/xnEw8geiYoIXVZyBgQnR/YjKR6jzAP1uj+D4R7LeXEfle4CWzYnGNLi 3qFtTl8j3HQslYlUdM8vuHjTd+DqRMA= From: Usama Arif To: Andrew Morton , david@kernel.org, Lorenzo Stoakes , willy@infradead.org, linux-mm@kvack.org Cc: fvdl@google.com, hannes@cmpxchg.org, riel@surriel.com, shakeel.butt@linux.dev, kas@kernel.org, baohua@kernel.org, dev.jain@arm.com, baolin.wang@linux.alibaba.com, npache@redhat.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, Vlastimil Babka , lance.yang@linux.dev, linux-kernel@vger.kernel.org, kernel-team@meta.com, maddy@linux.ibm.com, mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, linux-s390@vger.kernel.org, Usama Arif Subject: [v3 03/24] mm: thp: handle split failure in copy_huge_pmd() Date: Thu, 26 Mar 2026 19:08:45 -0700 Message-ID: <20260327021403.214713-4-usama.arif@linux.dev> In-Reply-To: <20260327021403.214713-1-usama.arif@linux.dev> References: <20260327021403.214713-1-usama.arif@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 008241C0004 X-Stat-Signature: ai7cknou7bh3ciqd58cedx8s3hd7ort7 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1774577671-931756 X-HE-Meta: U2FsdGVkX1+loAIb0GL3eATSrRsbJMLPw16Lj9O/zOE+CMhrjaEGJzU6MKAAVaGa6SG+Q3HZCKFlzjITScWz5tdkXYiEMw47NtO3nxBdKP6mCyWnAnCOPGpZ1fd7mxPKkfcI379HmhYWGXMwTFpdZRVaHgoTxsw61yn1kYf9QI8iXCAzJPLjh1ZiGPLk97Sgbt1+G4Ya4jwOhMHuNtJDtoqaAx6jngujLlNP7EBQlaM3eKYssYPfk/IoR0fXcAxNoEOP7GMiILELH3PGAoSmPaNGvOSXeM7DZ6LFQb13dJfB3XJWqYcIOn8XizorXG9R5hOwGOsbhhKYXMsAEdDSVedDA7FxbLKI9/NYHZXP1JC+CTQQbEq1uLURl5v21ipXG9U1PYvfJd5XQXaP9uTJefhr5IdMKbZjv9f+mxEesbK2wwKL//CjsCGOXLKQAjvs42J4nns4oqMUs1FZ8VHOvFfNyxzHF1Kn+pTHY1qH1gEogPnm3gYlPXIUX/7bl+CjOd+nXrqcflNeUMbTGKNDbHnpKhnnAgbLanLQsosbPwcrP77eG18GNlgU+ng1xRjY+fYWDCUypMg+X6clsUC8pSC6bIPCtQMQ15vdg+vPElk3e868nC1gk1jiJNrPku7rMScUdgA/ujTxIpA9jk5vKC1ae5tjFR3USZ1e8A0hkoigls8kD45u6c5qN1hGycUBO7D/oQKbDPqUViUExlNyJyQdS5qwpLbrxaPNF1FLmG+ta3SqFOrGuWw8Zq2aXnWrrNElfQrHXUtn5ojmV9n0FPDyV6MS9bMWcCYmaOYuXAgD/RR4Ip1KXOa6mkqeT7Y8/x7uuKVcLeFRCT+W4OrWrqwDQErnal0OuDujInR3Ztpmn2lfQ94337Rj2qveNSteMcUf4FlpdVeKCohS8SffwlKOvCJF51uhg9zUmnEBFrJ/6nWYdp5FCD0Z36vBbiZscgLn7KRKmyTDkz0R3tY KUnmlbsY 5J38ShPum9uUPbHF40gD57hXvr5FJNqzy8y7D9gaeiOMouDxQRZwrmXo6kcSjLjMCuZHYK9QiQSXZAz0F72/RzAeLYWJF26BLeQifbuX29rW2OyUURXPs7wGkw0mVJAqfSOvMHdr0gIigtXhXC8h0D9xPiQVvsqCou4QFuxq8QhQHVG41ghORDSQaTOeOVLs67ogYsQtww5jpbeA= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: copy_huge_pmd() splits the source PMD when a folio is pinned and can't be COW-shared at PMD granularity. It then returns -EAGAIN so copy_pmd_range() falls through to copy_pte_range(). If the split fails, the PMD is still huge. Returning -EAGAIN would cause copy_pmd_range() to call copy_pte_range(), which would dereference the huge PMD entry as if it were a pointer to a PTE page table. Return -ENOMEM on split failure instead (which is already done in copy_huge_pmd() if pte_alloc_one() fails), which causes copy_page_range() to abort the fork with -ENOMEM, similar to how copy_pmd_range() would be aborted if pmd_alloc() and copy_pte_range() fail. Signed-off-by: Usama Arif --- mm/huge_memory.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 99f3b8b24c682..8ad43897bdf80 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1913,7 +1913,13 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, pte_free(dst_mm, pgtable); spin_unlock(src_ptl); spin_unlock(dst_ptl); - __split_huge_pmd(src_vma, src_pmd, addr, false); + /* + * If split fails, the PMD is still huge so copy_pte_range + * (via -EAGAIN) would misinterpret it as a page table + * pointer. Return -ENOMEM directly to copy_pmd_range. + */ + if (__split_huge_pmd(src_vma, src_pmd, addr, false)) + return -ENOMEM; return -EAGAIN; } add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); -- 2.52.0