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 06C91FC5937 for ; Thu, 26 Feb 2026 11:33:40 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6B80F6B0098; Thu, 26 Feb 2026 06:33:39 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 66EF86B0099; Thu, 26 Feb 2026 06:33:39 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 592336B009B; Thu, 26 Feb 2026 06:33:39 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 3CCD26B0098 for ; Thu, 26 Feb 2026 06:33:39 -0500 (EST) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 0B26F1B7B82 for ; Thu, 26 Feb 2026 11:33:39 +0000 (UTC) X-FDA: 84486397758.01.634E01B Received: from out-182.mta1.migadu.com (out-182.mta1.migadu.com [95.215.58.182]) by imf14.hostedemail.com (Postfix) with ESMTP id 3F836100005 for ; Thu, 26 Feb 2026 11:33:36 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=qqWTnMAd; spf=pass (imf14.hostedemail.com: domain of usama.arif@linux.dev designates 95.215.58.182 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=1772105617; 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=sEWb6ULyOrXRVye+x+KftZvBAQkL33Q0arTZiVRMt8I=; b=7xKR1p+DE3ZZzMGav1/qIqqur+aR9W1dk505WV9XbjinuSQKrjErRQPtKxCpg3bU25DWbu P3Bz4Xu2Sy2kaDgpfrwrLUskzx67AQDW+03P87tBkHPZF8HuaP5gBW+Zp7/4LFTytavMUw YCwqzaWDZm0c4zKLBce3EdohsLfa188= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=qqWTnMAd; spf=pass (imf14.hostedemail.com: domain of usama.arif@linux.dev designates 95.215.58.182 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=1772105617; a=rsa-sha256; cv=none; b=NrqTddgScjqJRffJiXLSUVcgH9LNe8F/zI211uMsocpRCiT1G7iwxe1LRk3grrjAjjeJvT 4Wdq8IBGvj4uIhTcVtqqS6hhpqTFY9YD0EdGIv5o3IJalvfIJIQb8i8pWkSMOAwc1/iMnJ JNucj1XhdgYX7SCLTh7im5O+E8xQ8Ho= 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=1772105615; 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=sEWb6ULyOrXRVye+x+KftZvBAQkL33Q0arTZiVRMt8I=; b=qqWTnMAdq5dg5CvpyeLbGUPbMz61dA9xpNIaerVTAxRFPXhdC6tgbMB8GUGdaSb1pEj7AQ +ksDSA5ARHrYo0OCNpPhXKcjyhuY8ZIczmUrM/O9mt6vELpp8Kp9v5Y2Nt8i4eNS5HVweF CbjSJodzFuIWJHz06nT0yacW4sZIjPs= From: Usama Arif To: Andrew Morton , david@kernel.org, lorenzo.stoakes@oracle.com, 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: [RFC v2 06/21] mm: thp: handle split failure in wp_huge_pmd() Date: Thu, 26 Feb 2026 03:23:35 -0800 Message-ID: <20260226113233.3987674-7-usama.arif@linux.dev> In-Reply-To: <20260226113233.3987674-1-usama.arif@linux.dev> References: <20260226113233.3987674-1-usama.arif@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: 75jrquqyx7a5d1jr5xbcgpb1nyu1emyh X-Rspam-User: X-Rspamd-Queue-Id: 3F836100005 X-Rspamd-Server: rspam01 X-HE-Tag: 1772105616-846943 X-HE-Meta: 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 VikBuS2L D7TEWVIVOeuJ0G+Kb/h9zfExuDskPfdSHze9iNbiwUpBlhVxajYPxcogdnBR07lmhE77pL8r0+PxAByc2pzWhG1GIIo2mOUd3uBlTON9CoF14OrcfTH/w24e5ZgiRpO2aNk2kyY3QzcI1VnQUTv8w5nzB1YgWNGzJzG5G15FJO2iIJGLkkdELSEUbUYATIiq2egMSymVV/o8s4QPqvBoyb3iszLBIO0TVyHg9El1shZ2b758nrR6YgzOuFbFMWrvrFDlvS04YbuLFcXeVbuwZdbJNfg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: wp_huge_pmd() splits the PMD when COW or write-notify must be handled at PTE level (e.g., shared/file VMAs, userfaultfd). It then returns VM_FAULT_FALLBACK so the fault handler retries at PTE granularity. If the split fails, the PMD is still huge. The PTE fault path cannot handle a huge PMD entry. Return VM_FAULT_OOM on split failure, which signals the fault handler to invoke the OOM killer or return -ENOMEM to userspace. This is similar to what __handle_mm_fault would do if p4d_alloc or pud_alloc fails. Signed-off-by: Usama Arif --- mm/memory.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 7ba1221c63792..51d2717e3f1b4 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -6161,8 +6161,13 @@ static inline vm_fault_t wp_huge_pmd(struct vm_fault *vmf) } split: - /* COW or write-notify handled on pte level: split pmd. */ - __split_huge_pmd(vma, vmf->pmd, vmf->address, false); + /* + * COW or write-notify handled on pte level: split pmd. + * If split fails, the PMD is still huge so falling back + * to PTE handling would be incorrect. + */ + if (__split_huge_pmd(vma, vmf->pmd, vmf->address, false)) + return VM_FAULT_OOM; return VM_FAULT_FALLBACK; } -- 2.47.3