From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-188.mta1.migadu.com (out-188.mta1.migadu.com [95.215.58.188]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 302933126C2 for ; Thu, 26 Feb 2026 11:33:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.188 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772105635; cv=none; b=kLsgu6fctpi0zTXz2ylZKgqnYAeAgdIfxlRsNyJfXrVgzjRRjqceYqKFa6gHx/+xJX/mHEVDYamN9BAm2QY/TcbzWGoo8bRuMcuJC5kNRCDsMZaabuImYH0utzsD4jmSK1vf7aMjxDcvdWPMgQ2g7CarHsmR/tGYlXuu/xYe3VM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772105635; c=relaxed/simple; bh=pUUXXPmW7bXhtmtKExGJnVno8KAfeEF+vOAxJbtyM4s=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Og+9ztqtVxX45cNk/qS3t4bSfv45VHNfWTaIZH572MnJF0VnGSYVZEfagfG7qKbJQL5czQZn9eQino4UWwL+EEFlbniC/jSncLocjTYqVr4AT1kBToEYkUoNgxWors1rAzwhvNvfKnFrQriRcRPwj3BklBRa/wtTGXrh/+KLUr0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=urU1JU88; arc=none smtp.client-ip=95.215.58.188 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="urU1JU88" 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=1772105632; 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=VYA2+HQ3PTBt5D8sdrhOr6HCB84Kriw+faUOIzAxMpw=; b=urU1JU881GY7kjUvIyBX3z3Lqlmyk50JU6TXPEMfQliw0OxBspGKG47gwOqyYchKYjdhOS 4MCdiw06/6qjaNTE/dJI2QINH/BZD+AyBh9OYXNlQ7Q+2vDLHhiRiXwTsCMMVh0aAiWh5C T/IMdVB4xvM/4LGbijfTnkgoLXbW/+E= 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 09/21] mm: handle walk_page_range() failure from THP split Date: Thu, 26 Feb 2026 03:23:38 -0800 Message-ID: <20260226113233.3987674-10-usama.arif@linux.dev> In-Reply-To: <20260226113233.3987674-1-usama.arif@linux.dev> References: <20260226113233.3987674-1-usama.arif@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT walk_pmd_range() splits a huge PMD when a page table walker with pte_entry or install_pte callbacks needs PTE-level granularity. If the split fails due to memory allocation failure in pte_alloc_one(), walk_pte_range() would encounter a huge PMD instead of a PTE page table. Break out of the loop on split failure and return -ENOMEM to the walker's caller. Callers that reach this path (those with pte_entry or install_pte set) such as mincore, hmm_range_fault and queue_pages_range already handle negative return values from walk_page_range(). Similar approach is taken when __pte_alloc() fails in walk_pmd_range(). Signed-off-by: Usama Arif --- mm/pagewalk.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/mm/pagewalk.c b/mm/pagewalk.c index a94c401ab2cfe..1ee9df7a4461d 100644 --- a/mm/pagewalk.c +++ b/mm/pagewalk.c @@ -147,9 +147,11 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end, continue; } - if (walk->vma) - split_huge_pmd(walk->vma, pmd, addr); - else if (pmd_leaf(*pmd) || !pmd_present(*pmd)) + if (walk->vma) { + err = split_huge_pmd(walk->vma, pmd, addr); + if (err) + break; + } else if (pmd_leaf(*pmd) || !pmd_present(*pmd)) continue; /* Nothing to do. */ err = walk_pte_range(pmd, addr, next, walk); -- 2.47.3