From patchwork Tue Apr 9 19:22:49 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 13623161 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 8A1D415820A for ; Tue, 9 Apr 2024 19:24:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712690692; cv=none; b=NGkB0g1rtKh4bJWG1W1sJstrrCXKXaRvppqM8OPn0w7IANxO2QwYcBxcBh7KYyt37ZZqc1x/wiivb1RV0R8kTCBrUwlxfnAsuHaW6DYAyTrW63bnLoJNVAGTKN49lC7Guz+hLkApYNiR3qSWOIr21eL5orsz4e/d0ZjJ3IksZpQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712690692; c=relaxed/simple; bh=f2r6XGWVgx08KSMlFSZ6qHtz58Yi8+jxNoK6fRu4Nds=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=cGHmpAku06njxg7qsVXA/2XGpZzZvm+dbn/jHcOaP6DrkoPyZQWDIS3Cx+wad1RmeyhoANgMHMmEQ/xrpyc/TFhkw7/XCEGS0jA9exFt2yQOyr+z2zENKaIWykbP7ptSXKYGZOTVflNHEcFl6TO2tkK3WFL3nY/DavHzyNCFze4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none 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=O9vD3Zya; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none 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="O9vD3Zya" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1712690689; 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=kfmOqlR3LeI6JA5XUUI6YoG07vX8W74qIyKiUchjaJU=; b=O9vD3ZyaUBaIrZbiSV80Vt6m2bTKwKi/KMR88KN3Miq3IgK1G8hdCFed3nDh9REmSvu/Wj f8YaNdEOi99DPgEq2zCbrxCtaazNog44/o5DnAEcgu0Yhj6yFOYQeuBR1MZckZn2P+zZzt 94zjHOYO+ED/6LPjXSHUGRJVc/wk2sw= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-97-N-WWN3PRODGQvvQK2vZjIQ-1; Tue, 09 Apr 2024 15:24:44 -0400 X-MC-Unique: N-WWN3PRODGQvvQK2vZjIQ-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (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 mimecast-mx02.redhat.com (Postfix) with ESMTPS id B730680B51A; Tue, 9 Apr 2024 19:24:42 +0000 (UTC) Received: from t14s.redhat.com (unknown [10.39.192.106]) by smtp.corp.redhat.com (Postfix) with ESMTP id DCED040B4979; Tue, 9 Apr 2024 19:24:33 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, linux-doc@vger.kernel.org, cgroups@vger.kernel.org, linux-sh@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, David Hildenbrand , Andrew Morton , "Matthew Wilcox (Oracle)" , Peter Xu , Ryan Roberts , Yin Fengwei , Yang Shi , Zi Yan , Jonathan Corbet , Hugh Dickins , Yoshinori Sato , Rich Felker , John Paul Adrian Glaubitz , Chris Zankel , Max Filippov , Muchun Song , Miaohe Lin , Naoya Horiguchi , Richard Chang Subject: [PATCH v1 06/18] mm: make folio_mapcount() return 0 for small typed folios Date: Tue, 9 Apr 2024 21:22:49 +0200 Message-ID: <20240409192301.907377-7-david@redhat.com> In-Reply-To: <20240409192301.907377-1-david@redhat.com> References: <20240409192301.907377-1-david@redhat.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.2 We already handle it properly for large folios. Let's also return "0" for small typed folios, like page_mapcount() currently would. Consequently, folio_mapcount() will never return negative values for typed folios, but may return negative values for underflows. Signed-off-by: David Hildenbrand Signed-off-by: David Hildenbrand --- include/linux/mm.h | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index daf687f0e8e5..d453232bba62 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1260,12 +1260,19 @@ static inline int folio_large_mapcount(const struct folio *folio) * references the entire folio counts exactly once, even when such special * page table entries are comprised of multiple ordinary page table entries. * + * Will report 0 for pages which cannot be mapped into userspace, such as + * slab, page tables and similar. + * * Return: The number of times this folio is mapped. */ static inline int folio_mapcount(const struct folio *folio) { - if (likely(!folio_test_large(folio))) - return atomic_read(&folio->_mapcount) + 1; + int mapcount; + + if (likely(!folio_test_large(folio))) { + mapcount = atomic_read(&folio->_mapcount); + return page_type_has_type(mapcount) ? 0 : mapcount + 1; + } return folio_large_mapcount(folio); }