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 X-Spam-Level: X-Spam-Status: No, score=-16.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 ED9CCC4338F for ; Mon, 16 Aug 2021 08:19:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CEEB861B03 for ; Mon, 16 Aug 2021 08:19:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234525AbhHPIUF (ORCPT ); Mon, 16 Aug 2021 04:20:05 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:52027 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231716AbhHPIUE (ORCPT ); Mon, 16 Aug 2021 04:20:04 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1629101973; 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=JJy1wTV0mXwECxuw+eS0iCkYTF/8HGBJnP6WAB8OQEQ=; b=dv5XzXbXG/1RW0hiPjXhLsjO07Bcisa+BspUep9TFqWGupPoPzrEsV5Igg3vac95dcVYNS DTnyOsNBTi4NsdpU5uodznPAqYP8XHlKsbVP/z9eQZssonRZe39ARMevmLQnc/vUwE/nqH R/wrlu4gChv5agGKlsaGeNr8BbZa3k4= 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-459-Qk4NXh_TM16hKZO6MpW73A-1; Mon, 16 Aug 2021 04:19:31 -0400 X-MC-Unique: Qk4NXh_TM16hKZO6MpW73A-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 99229107ACF5; Mon, 16 Aug 2021 08:19:29 +0000 (UTC) Received: from t480s.redhat.com (unknown [10.39.192.85]) by smtp.corp.redhat.com (Postfix) with ESMTP id 36C50620DE; Mon, 16 Aug 2021 08:19:23 +0000 (UTC) From: David Hildenbrand To: linux-man@vger.kernel.org Cc: David Hildenbrand , Pankaj Gupta , Alejandro Colomar , Michael Kerrisk , Andrew Morton , Michal Hocko , Oscar Salvador , Jann Horn , Mike Rapoport , Linux API , linux-mm@kvack.org Subject: [PATCH v2] madvise.2: Document MADV_POPULATE_READ and MADV_POPULATE_WRITE Date: Mon, 16 Aug 2021 10:19:22 +0200 Message-Id: <20210816081922.5155-1-david@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-man@vger.kernel.org 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. Further, commit eb2faa513c24 ("mm/madvise: report SIGBUS as -EFAULT for MADV_POPULATE_(READ|WRITE)"), part of v5.14-rc6, made sure that SIGBUS is converted to -EFAULT instead of -EINVAL. Let's document the behavior and error conditions of these new madvise() options. Acked-by: Pankaj Gupta 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 --- v1 -> v2: - Use semantic newlines in all cases - Add two missing " - Document -EFAULT handling - Rephrase some parts to make it more generic: VM_PFNMAP and VM_IO are only examples for special mappings --- man2/madvise.2 | 107 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 107 insertions(+) diff --git a/man2/madvise.2 b/man2/madvise.2 index f1f384c0c..f6cea9ad2 100644 --- a/man2/madvise.2 +++ b/man2/madvise.2 @@ -469,6 +469,72 @@ 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 memory. +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, +for example, +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 memory. +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, +for example, +marked with the kernel-internal +.B VM_PFNMAP +and +.BR VM_IO . +.IP +Note that with +.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 () @@ -490,6 +556,17 @@ A kernel resource was temporarily unavailable. .B EBADF The map exists, but the area maps something that isn't a file. .TP +.B EFAULT +.I advice +is +.B MADV_POPULATE_READ +or +.BR MADV_POPULATE_WRITE , +and populating (prefaulting) page tables failed because a +.B SIGBUS +would have been generated on actual memory access and the reason is not a +HW poisoned page. +.TP .B EINVAL .I addr is not page-aligned or @@ -533,6 +610,18 @@ 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 +or incompatible mappings such as +.B VM_IO +or +.BR VM_PFNMAP. +.TP .B EIO (for .BR MADV_WILLNEED ) @@ -548,6 +637,15 @@ 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 , +and populating (prefaulting) page tables failed because there was not enough +memory. +.TP .B EPERM .I advice is @@ -555,6 +653,15 @@ 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 populating (prefaulting) page tables failed because a HW poisoned page +was encountered. .SH VERSIONS Since Linux 3.18, .\" commit d3ac21cacc24790eb45d735769f35753f5b56ceb -- 2.31.1