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 47FCC10A62D1 for ; Fri, 27 Mar 2026 02:15:07 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id AFE846B00A9; Thu, 26 Mar 2026 22:15:06 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AD61B6B00AB; Thu, 26 Mar 2026 22:15:06 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A13926B00AC; Thu, 26 Mar 2026 22:15:06 -0400 (EDT) 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 8F9BE6B00A9 for ; Thu, 26 Mar 2026 22:15:06 -0400 (EDT) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 5D40813C472 for ; Fri, 27 Mar 2026 02:15:06 +0000 (UTC) X-FDA: 84590225412.20.48B52F7 Received: from out-179.mta0.migadu.com (out-179.mta0.migadu.com [91.218.175.179]) by imf13.hostedemail.com (Postfix) with ESMTP id A789120003 for ; Fri, 27 Mar 2026 02:15:04 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=c+UwEtgW; spf=pass (imf13.hostedemail.com: domain of usama.arif@linux.dev designates 91.218.175.179 as permitted sender) smtp.mailfrom=usama.arif@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=c+UwEtgW; spf=pass (imf13.hostedemail.com: domain of usama.arif@linux.dev designates 91.218.175.179 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=1774577704; a=rsa-sha256; cv=none; b=B2zNsUTl8FZEFNdXydV4yZpkigJdHhswhDJuTRPCzj8j3ic25ZswQG176dGFUrtLsdYE8e UwapbLM7+PxxIl7nlT6ojTnuBfNZvn6I5cU4kkIjA/CnMVZO2C/H+PIwMaVVeINdCAqbwE D7bdsKBleDuVk+l66md5IgQHQ7b81kY= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1774577704; 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=giSfT9S4Y3Fs6MBCHHOkpgsjb4flU8mTLfNnlsB/wxU=; b=dxBokh7qDr1iqF3vLzNQ99OxNMIXSBURxI+QJ2ZD0O5FiBhlRJvIl/refkYaSkDh0hu4Sy FIlwH4UCeMOHUk94eLOPCkcNotJjCp5UtM6zfe8fXjvErFye+8KPN2Tkt464MHBEzfC4KJ orOWkFh04zztwmvCLJPGM36qUN1zRzw= 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=1774577702; 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=giSfT9S4Y3Fs6MBCHHOkpgsjb4flU8mTLfNnlsB/wxU=; b=c+UwEtgWwyc5ExZqiso+pcfyt+iKbZ1QmoTTRB8NhGDZKpUwyzQzLx5Oi6hXFvtdq5ago3 ODRA0nas4eR1mjjEDHyY5MY9At3yhrqG1QJr6rpr5PRO3un578DMuu2R03YOspCxOxZ+jD EPix5NId6vnIBtCHcU6MJtVrfHvraLA= 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 08/24] mm: thp: handle split failure in follow_pmd_mask() Date: Thu, 26 Mar 2026 19:08:50 -0700 Message-ID: <20260327021403.214713-9-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-Server: rspam01 X-Rspamd-Queue-Id: A789120003 X-Stat-Signature: ypdzgfyqj9omuwejizkcuhjr4dpatiin X-Rspam-User: X-HE-Tag: 1774577704-304169 X-HE-Meta: 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 YwbnaA6h 26TtrcQkYwI3AdIKMkt58indM6rHdhJ+1DYRnDmH/9Y6Op7MtOV6QXudNFm93dE2mo6nU69HKDAPTAF1i/Z1EciV9WuuLMwT6G75dhtShVoxf4uXsfoOlNdpuN9cyEtNgoYyrEQZmUBkiXEXh4xGPggPdDzMOOySG+am8CT0vMIRewRCDKJXuQOuXQE4/uTRPp7K4qPh9GONPebNDkaljMz/3L0bm58BFc7EEv59OL2xZoFWxX+aXV2Ahjg== 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 ad9ded39609cb..07c6b0483c322 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); -- 2.52.0