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 42F85FC5930 for ; Thu, 26 Feb 2026 11:33:51 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A208F6B00A2; Thu, 26 Feb 2026 06:33:50 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A01CD6B00A4; Thu, 26 Feb 2026 06:33:50 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 925516B00A5; Thu, 26 Feb 2026 06:33:50 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 7F8EE6B00A2 for ; Thu, 26 Feb 2026 06:33:50 -0500 (EST) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 47911BC24B for ; Thu, 26 Feb 2026 11:33:50 +0000 (UTC) X-FDA: 84486398220.26.0452A81 Received: from out-183.mta0.migadu.com (out-183.mta0.migadu.com [91.218.175.183]) by imf22.hostedemail.com (Postfix) with ESMTP id B3B46C000A for ; Thu, 26 Feb 2026 11:33:48 +0000 (UTC) Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=udE+houD; spf=pass (imf22.hostedemail.com: domain of usama.arif@linux.dev designates 91.218.175.183 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=1772105628; 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=voiqUydpep5c50p71jeWeFdopCgnIpO6zR1blEnFY9U=; b=lvqKrBbs7nHPf8R62cfcjN74aiZWS4Knh7QcKbvvkk8Y4avoTDIM6VCaChRkHe2U5eZ1gF w0PEksP21HsBdVGtSb4/v/rEwJA3U4+MqlzuRdilBR3qpl3hjn9p7EjDF/PBaj7WTtHbil +FxpGfJCoDOvmP0qhvIyxCJwr9bw1Pk= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=udE+houD; spf=pass (imf22.hostedemail.com: domain of usama.arif@linux.dev designates 91.218.175.183 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=1772105628; a=rsa-sha256; cv=none; b=Q3cbmZlBl8xD+sIjrsoWoPJW/Xzm9V0BzlIrYCFHx2MUDZI7ZRy2Oa+iKZUb2Me1uH/23w zgRFWU1J6BJkLlafzrSKbKO7qDQjiAHVYB9ox0rfinezpLmlBh9Zj/eKmNiW+hhy3vHs0C MiYzWz0gaEOE5l0u6D8EoPX1l5o4nTY= 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=1772105626; 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=voiqUydpep5c50p71jeWeFdopCgnIpO6zR1blEnFY9U=; b=udE+houDLGseN1f6IYvibBzYYzpJnrx63S12MifUCk13f0DjLpLexn7cLE+r93BBzXNqZW GMm8b+RjhZzqazJYt7NxsX82x6AVbHVcuPZhuNhuFnkbnvwr1QnAXR2LjKKpKiQSa6Xdhz 62qhsCiwM2CIlMTRP3nK9ID7G97Ovc0= 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 08/21] mm: thp: handle split failure in follow_pmd_mask() Date: Thu, 26 Feb 2026 03:23:37 -0800 Message-ID: <20260226113233.3987674-9-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-Rspamd-Server: rspam05 X-Rspam-User: X-Rspamd-Queue-Id: B3B46C000A X-Stat-Signature: 9d9sd5mywmqw9hxda8r8rx638w1dousw X-HE-Tag: 1772105628-623825 X-HE-Meta: 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: follow_pmd_mask() splits a huge PMD when FOLL_SPLIT_PMD is set, so GUP can pin individual pages at PTE granularity. If the split fails, the PMD is still huge and follow_page_pte() cannot process it. Return ERR_PTR(-ENOMEM) on split failure, which causes the GUP caller to get -ENOMEM. -ENOMEM is already returned in follow_pmd_mask if pte_alloc_one fails (which is the reason why split_huge_pmd could fail), hence this is a safe change. Signed-off-by: Usama Arif --- mm/gup.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/mm/gup.c b/mm/gup.c index 8e7dc2c6ee738..792b2e7319dd0 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -928,8 +928,16 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma, return follow_page_pte(vma, address, pmd, flags); } if (pmd_trans_huge(pmdval) && (flags & FOLL_SPLIT_PMD)) { + int ret; + spin_unlock(ptl); - split_huge_pmd(vma, pmd, address); + /* + * If split fails, the PMD is still huge and + * we cannot proceed to follow_page_pte. + */ + ret = split_huge_pmd(vma, pmd, address); + if (ret) + return ERR_PTR(ret); /* If pmd was left empty, stuff a page table in there quickly */ return pte_alloc(mm, pmd) ? ERR_PTR(-ENOMEM) : follow_page_pte(vma, address, pmd, flags); -- 2.47.3