From patchwork Mon Jul 12 08:39:17 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 12370557 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 87FF2C07E99 for ; Mon, 12 Jul 2021 08:39:33 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 191C860FE7 for ; Mon, 12 Jul 2021 08:39:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 191C860FE7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 23FAD6B008A; Mon, 12 Jul 2021 04:39:33 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2166A8D0002; Mon, 12 Jul 2021 04:39:33 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0B87D8D0001; Mon, 12 Jul 2021 04:39:33 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0102.hostedemail.com [216.40.44.102]) by kanga.kvack.org (Postfix) with ESMTP id CF1466B008A for ; Mon, 12 Jul 2021 04:39:32 -0400 (EDT) Received: from smtpin29.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id D8D66231B2 for ; Mon, 12 Jul 2021 08:39:31 +0000 (UTC) X-FDA: 78353286942.29.B428DEF Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf15.hostedemail.com (Postfix) with ESMTP id 8EDDDD00009F for ; Mon, 12 Jul 2021 08:39:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1626079171; 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; bh=nWJUYOez7eAAIVRuvZFT1uKCzfdN0rxKg/h1MnIYqcE=; b=NKVVXLn3mvXlhd8Zzvu6iANoK0wIPQJtxCJ5ODhc++6e97IOjzrUrSw2znWBWcDUQhhqeb lUy1ffc+ANGSdC0z/EW6smi64jDshWw1kps7CGLNA2SH90U7KjgYt4bPI7fEdw1JY/I43b h16zSEMfzSY/+ntsPSTCAUAA9uzaH8A= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-576-soJ3PwFuObWp_v98xq5Dog-1; Mon, 12 Jul 2021 04:39:27 -0400 X-MC-Unique: soJ3PwFuObWp_v98xq5Dog-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 53D3D1906810; Mon, 12 Jul 2021 08:39:21 +0000 (UTC) Received: from t480s.redhat.com (ovpn-113-111.rdu2.redhat.com [10.10.113.111]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6F9DA60CA0; Mon, 12 Jul 2021 08:39:18 +0000 (UTC) From: David Hildenbrand To: linux-man@vger.kernel.org Cc: David Hildenbrand , Alejandro Colomar , Michael Kerrisk , Andrew Morton , Michal Hocko , Oscar Salvador , Jann Horn , Mike Rapoport , Linux API , linux-mm@kvack.org Subject: [PATCH v1] madvise.2: Document MADV_POPULATE_READ and MADV_POPULATE_WRITE Date: Mon, 12 Jul 2021 10:39:17 +0200 Message-Id: <20210712083917.16361-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 8EDDDD00009F X-Stat-Signature: qdmykwe4rewt1uky4hggxewgk8zxxemz Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=NKVVXLn3; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf15.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=david@redhat.com X-HE-Tag: 1626079171-653923 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: MADV_POPULATE_READ and MADV_POPULATE_WRITE have been merged into upstream Linux via commit 4ca9b3859dac ("mm/madvise: introduce MADV_POPULATE_(READ|WRITE) to prefault page tables"), part of v5.14-rc1. Let's document the behavior and error conditions of these new madvise() options. Cc: Alejandro Colomar Cc: Michael Kerrisk Cc: Andrew Morton Cc: Michal Hocko Cc: Oscar Salvador Cc: Jann Horn Cc: Mike Rapoport Cc: Linux API Cc: linux-mm@kvack.org Signed-off-by: David Hildenbrand Acked-by: Pankaj Gupta --- man2/madvise.2 | 80 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 80 insertions(+) diff --git a/man2/madvise.2 b/man2/madvise.2 index f1f384c0c..3ec8c53a7 100644 --- a/man2/madvise.2 +++ b/man2/madvise.2 @@ -469,6 +469,59 @@ If a page is file-backed and dirty, it will be written back to the backing storage. The advice might be ignored for some pages in the range when it is not applicable. +.TP +.BR MADV_POPULATE_READ " (since Linux 5.14) +Populate (prefault) page tables readable for the whole range without actually +reading. Depending on the underlying mapping, map the shared zeropage, +preallocate memory or read the underlying file; files with holes might or +might not preallocate blocks. +Do not generate +.B SIGBUS +when populating fails, return an error instead. +.IP +If +.B MADV_POPULATE_READ +succeeds, all page tables have been populated (prefaulted) readable once. +If +.B MADV_POPULATE_READ +fails, some page tables might have been populated. +.IP +.B MADV_POPULATE_READ +cannot be applied to mappings without read permissions +and special mappings marked with the kernel-internal +.B VM_PFNMAP +and +.BR VM_IO . +.IP +Note that with +.BR MADV_POPULATE_READ , +the process can be killed at any moment when the system runs out of memory. +.TP +.BR MADV_POPULATE_WRITE " (since Linux 5.14) +Populate (prefault) page tables writable for the whole range without actually +writing. Depending on the underlying mapping, preallocate memory or read the +underlying file; files with holes will preallocate blocks. +Do not generate +.B SIGBUS +when populating fails, return an error instead. +.IP +If +.B MADV_POPULATE_WRITE +succeeds, all page tables have been populated (prefaulted) writable once. +If +.B MADV_POPULATE_WRITE +fails, some page tables might have been populated. +.IP +.B MADV_POPULATE_WRITE +cannot be applied to mappings without write permissions +and special mappings marked with the kernel-internal +.B VM_PFNMAP +and +.BR VM_IO . +.IP +Note that +.BR MADV_POPULATE_WRITE , +the process can be killed at any moment when the system runs out of memory. .SH RETURN VALUE On success, .BR madvise () @@ -533,6 +586,17 @@ or .BR VM_PFNMAP ranges. .TP +.B EINVAL +.I advice +is +.B MADV_POPULATE_READ +or +.BR MADV_POPULATE_WRITE , +but the specified address range includes ranges with insufficient permissions, +.B VM_IO +or +.BR VM_PFNMAP. +.TP .B EIO (for .BR MADV_WILLNEED ) @@ -548,6 +612,14 @@ Not enough memory: paging in failed. Addresses in the specified range are not currently mapped, or are outside the address space of the process. .TP +.B ENOMEM +.I advice +is +.B MADV_POPULATE_READ +or +.BR MADV_POPULATE_WRITE , +but populating (prefaulting) page tables failed. +.TP .B EPERM .I advice is @@ -555,6 +627,14 @@ is but the caller does not have the .B CAP_SYS_ADMIN capability. +.TP +.B EHWPOISON +.I advice +is +.B MADV_POPULATE_READ +or +.BR MADV_POPULATE_WRITE , +and a HW poisoned page is encountered. .SH VERSIONS Since Linux 3.18, .\" commit d3ac21cacc24790eb45d735769f35753f5b56ceb