From nobody Sun Feb 8 23:34:55 2026 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 B0C7F27990B for ; Mon, 28 Apr 2025 18:13:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745864039; cv=none; b=WcL3zUTtFmA+c4lk83mfayxO91zQRRwg896CzjIF0J/A4bgxdOOzeS/oWCh7IErjm+6xFo8kR5IMDwe8hNXFXrekpJvs9F8Wk87h/5NL3UciC/rIX1mPJXADHsjXyo6rG2Ibfld4xbajF3YYhHcSdHqJwZZUzF5kAda2rxho27c= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745864039; c=relaxed/simple; bh=7WQuzYTgoOktNa7BaRZ3rNS0qZfI1nMj9imLpll+iM8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iT6U7g9Gp6gj0duOBbIzygSv6H410dhDwUSDlsCH5TEwYsEvbN1Zw26JBn6rJzkgrQHYMWYMEiTb8kPhPWOuCcDpr6N8UHlM9xuwn3qtTiKFVZXm1VDoFbMArreBC37mnKAELyQCCBW+cXv4SjbqyD1Aa9wJW6Tl7KCrbl54qzg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=M65X4IAr; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="M65X4IAr" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1745864036; 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=fcQozjNet+vZ+AD/dmAuUysFjwKpw68qmsV5tnNH5oA=; b=M65X4IAryyDsjeZSrqm/WmAAXRoLlIuu3LrRzt869BUB0W2d50DURJGd1LiKC96SkxMaxa OVLV3e3N10DM32+vZ9o3LXKAZpDkvp86teb0PKv+mFWdvmmLcEpEtjk9Thc7zLyCs92Zlw isr6p2JF29SwAWWvTJMNdHCRGIYJe1g= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-466-FS__RpNxNRuCkqrFoFCq5w-1; Mon, 28 Apr 2025 14:13:53 -0400 X-MC-Unique: FS__RpNxNRuCkqrFoFCq5w-1 X-Mimecast-MFC-AGG-ID: FS__RpNxNRuCkqrFoFCq5w_1745864028 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 7A17719560AD; Mon, 28 Apr 2025 18:13:48 +0000 (UTC) Received: from h1.redhat.com (unknown [10.22.65.12]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id AC2B1180045B; Mon, 28 Apr 2025 18:13:41 +0000 (UTC) From: Nico Pache To: linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: akpm@linux-foundation.org, corbet@lwn.net, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, david@redhat.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, ryan.roberts@arm.com, willy@infradead.org, peterx@redhat.com, ziy@nvidia.com, wangkefeng.wang@huawei.com, usamaarif642@gmail.com, sunnanyong@huawei.com, vishal.moola@gmail.com, thomas.hellstrom@linux.intel.com, yang@os.amperecomputing.com, kirill.shutemov@linux.intel.com, aarcange@redhat.com, raquini@redhat.com, dev.jain@arm.com, anshuman.khandual@arm.com, catalin.marinas@arm.com, tiwai@suse.de, will@kernel.org, dave.hansen@linux.intel.com, jack@suse.cz, cl@gentwo.org, jglisse@google.com, surenb@google.com, zokeefe@google.com, hannes@cmpxchg.org, rientjes@google.com, mhocko@suse.com, rdunlap@infradead.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com Subject: [PATCH v5 08/12] khugepaged: skip collapsing mTHP to smaller orders Date: Mon, 28 Apr 2025 12:12:14 -0600 Message-ID: <20250428181218.85925-9-npache@redhat.com> In-Reply-To: <20250428181218.85925-1-npache@redhat.com> References: <20250428181218.85925-1-npache@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Content-Type: text/plain; charset="utf-8" khugepaged may try to collapse a mTHP to a smaller mTHP, resulting in some pages being unmapped. Skip these cases until we have a way to check if its ok to collapse to a smaller mTHP size (like in the case of a partially mapped folio). This patch is inspired by Dev Jain's work on khugepaged mTHP support [1]. [1] https://lore.kernel.org/lkml/20241216165105.56185-11-dev.jain@arm.com/ Co-developed-by: Dev Jain Signed-off-by: Dev Jain Signed-off-by: Nico Pache Reviewed-by: Baolin Wang --- mm/khugepaged.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 3a846cd70c66..86d1153ce9e8 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -625,7 +625,12 @@ static int __collapse_huge_page_isolate(struct vm_area= _struct *vma, folio =3D page_folio(page); VM_BUG_ON_FOLIO(!folio_test_anon(folio), folio); =20 - /* See hpage_collapse_scan_pmd(). */ + if (order !=3D HPAGE_PMD_ORDER && folio_order(folio) >=3D order) { + result =3D SCAN_PTE_MAPPED_HUGEPAGE; + goto out; + } + + /* See khugepaged_scan_pmd(). */ if (folio_maybe_mapped_shared(folio)) { ++shared; if (order !=3D HPAGE_PMD_ORDER || (cc->is_khugepaged && --=20 2.48.1