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=-21.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS 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 753CDC433B4 for ; Wed, 7 Apr 2021 12:39:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4C1A861359 for ; Wed, 7 Apr 2021 12:39:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241768AbhDGMjm (ORCPT ); Wed, 7 Apr 2021 08:39:42 -0400 Received: from mail.kernel.org ([198.145.29.99]:51280 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1352298AbhDGMjj (ORCPT ); Wed, 7 Apr 2021 08:39:39 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 6E369611EE; Wed, 7 Apr 2021 12:39:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1617799170; bh=MbNYP3O2fuqdUVinNSa/jvtpmiBwOxrIr8MwmQfS1dA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=oHWYy1CZHUe2GfzNgqT7dtwQnGcVvlObCi9+6T9zzXrcxITQxhcE9X+uW4unbqMvx XSnFYSwEunGlUiqtF8kUs6cNXyV0yBY3ShgQcpXSgzgBXHdBIZ4iZNVZYqAR52MKED qv5iEEAWgSVum8HGCjFok14EvvKCuoJXudoQkdAirQothBiMNGHnbh76/J1NknrM9H l0EV9Q22zHdmjYfsSQShJhD1coyd3Bq6KwVpY3Zx6djykPk4OdMr5aMYvmSB4872jA Jwc994w6BCvx/NOBy/YWN63q8+UOyGigwI3nK9xlMggJVI2ljOCgi8fWRhNDL5rQV5 XL8rDySoOkmNA== Date: Wed, 7 Apr 2021 15:39:26 +0300 From: Leon Romanovsky To: Gal Pressman Cc: Jason Gunthorpe , Doug Ledford , Yossi Leybovich , linux-rdma@vger.kernel.org, Alexander Matushevsky , Jason Gunthorpe , Peter Xu , Mike Kravetz , Andrew Morton Subject: Re: [PATCH for-next v2] RDMA/nldev: Add copy-on-fork attribute to get sys command Message-ID: References: <20210407101606.80737-1-galpress@amazon.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210407101606.80737-1-galpress@amazon.com> Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On Wed, Apr 07, 2021 at 01:16:05PM +0300, Gal Pressman wrote: > The new attribute indicates that the kernel copies DMA pages on fork, > hence libibverbs' fork support through madvise and MADV_DONTFORK is not > needed. > > The introduced attribute is always reported as supported since the > kernel has the patch that added the copy-on-fork behavior. This allows > the userspace library to identify older vs newer kernel versions. > Extra care should be taken when backporting this patch as it relies on > the fact that the copy-on-fork patch is merged, hence no check for > support is added. > > Don't backport this patch unless you also have the following series: > 70e806e4e645 ("mm: Do early cow for pinned pages during fork() for ptes") > and 4eae4efa2c29 ("hugetlb: do early cow when page pinned on src mm"). > > Copy-on-fork attribute is read-only, trying to change it through the set > sys command will result in an error. > > Fixes: 70e806e4e645 ("mm: Do early cow for pinned pages during fork() for ptes") > Fixes: 4eae4efa2c29 ("hugetlb: do early cow when page pinned on src mm") > Signed-off-by: Gal Pressman > --- > PR was sent: > https://github.com/linux-rdma/rdma-core/pull/975 > > Changelog - > v1->v2: https://lore.kernel.org/linux-rdma/20210405114722.98904-1-galpress@amazon.com/ > * Remove nla_put_u8() return value check > * Add commit hashes to commit message and code comment > --- > drivers/infiniband/core/nldev.c | 14 +++++++++++++- > include/uapi/rdma/rdma_netlink.h | 2 ++ > 2 files changed, 15 insertions(+), 1 deletion(-) > > diff --git a/drivers/infiniband/core/nldev.c b/drivers/infiniband/core/nldev.c > index b8dc002a2478..6b2235926f74 100644 > --- a/drivers/infiniband/core/nldev.c > +++ b/drivers/infiniband/core/nldev.c > @@ -146,6 +146,7 @@ static const struct nla_policy nldev_policy[RDMA_NLDEV_ATTR_MAX] = { > [RDMA_NLDEV_ATTR_UVERBS_DRIVER_ID] = { .type = NLA_U32 }, > [RDMA_NLDEV_NET_NS_FD] = { .type = NLA_U32 }, > [RDMA_NLDEV_SYS_ATTR_NETNS_MODE] = { .type = NLA_U8 }, > + [RDMA_NLDEV_SYS_ATTR_COPY_ON_FORK] = { .type = NLA_U8 }, > }; > > static int put_driver_name_print_type(struct sk_buff *msg, const char *name, > @@ -1697,6 +1698,16 @@ static int nldev_sys_get_doit(struct sk_buff *skb, struct nlmsghdr *nlh, > nlmsg_free(msg); > return err; > } > + > + /* > + * Copy-on-fork is supported. > + * See commits: > + * 70e806e4e645 ("mm: Do early cow for pinned pages during fork() for ptes") > + * 4eae4efa2c29 ("hugetlb: do early cow when page pinned on src mm") > + * for more details. Don't backport this without them. > + */ > + nla_put_u8(msg, RDMA_NLDEV_SYS_ATTR_COPY_ON_FORK, 1); > + > nlmsg_end(msg, nlh); > return rdma_nl_unicast(sock_net(skb->sk), msg, NETLINK_CB(skb).portid); > } > @@ -1710,7 +1721,8 @@ static int nldev_set_sys_set_doit(struct sk_buff *skb, struct nlmsghdr *nlh, > > err = nlmsg_parse(nlh, 0, tb, RDMA_NLDEV_ATTR_MAX - 1, > nldev_policy, extack); > - if (err || !tb[RDMA_NLDEV_SYS_ATTR_NETNS_MODE]) > + if (err || !tb[RDMA_NLDEV_SYS_ATTR_NETNS_MODE] || > + tb[RDMA_NLDEV_SYS_ATTR_COPY_ON_FORK]) Why do we fail if user supplies RDMA_NLDEV_SYS_ATTR_COPY_ON_FORK? Thanks