From patchwork Wed Jun 28 16:29:56 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Shaohua Li X-Patchwork-Id: 9814881 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id E27A5603D7 for ; Wed, 28 Jun 2017 16:34:08 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D604826222 for ; Wed, 28 Jun 2017 16:34:08 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id CB25F2860C; Wed, 28 Jun 2017 16:34:08 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 66E5026222 for ; Wed, 28 Jun 2017 16:34:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752052AbdF1Qc0 (ORCPT ); Wed, 28 Jun 2017 12:32:26 -0400 Received: from mail.kernel.org ([198.145.29.99]:39192 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751922AbdF1QaJ (ORCPT ); Wed, 28 Jun 2017 12:30:09 -0400 Received: from shli-virt.localdomain (unknown [199.201.64.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 37F9B22BDD; Wed, 28 Jun 2017 16:30:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 37F9B22BDD Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=fail smtp.mailfrom=shli@fb.com From: Shaohua Li To: linux-kernel@vger.kernel.org, linux-block@vger.kernel.org Cc: tj@kernel.org, gregkh@linuxfoundation.org, hch@lst.de, axboe@fb.com, rostedt@goodmis.org, lizefan@huawei.com, Kernel-team@fb.com, Shaohua Li Subject: [PATCH V4 06/12] kernfs: add exportfs operations Date: Wed, 28 Jun 2017 09:29:56 -0700 Message-Id: <794fb2699d1b3cb85ff7746da20cb9890d42adea.1498666964.git.shli@fb.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: References: In-Reply-To: References: Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Shaohua Li Now we have the facilities to implement exportfs operations. The idea is cgroup can export the fhandle info to userspace, then userspace uses fhandle to find the cgroup name. Another example is userspace can get fhandle for a cgroup and BPF uses the fhandle to filter info for the cgroup. Signed-off-by: Shaohua Li Acked-by: Greg Kroah-Hartman --- fs/kernfs/mount.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/kernfs.h | 12 +++++++++++ kernel/cgroup/cgroup.c | 3 ++- 3 files changed, 70 insertions(+), 1 deletion(-) diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c index acd5426..fa32358 100644 --- a/fs/kernfs/mount.c +++ b/fs/kernfs/mount.c @@ -16,6 +16,7 @@ #include #include #include +#include #include "kernfs-internal.h" @@ -64,6 +65,59 @@ const struct super_operations kernfs_sops = { .show_path = kernfs_sop_show_path, }; +static struct inode *kernfs_fh_get_inode(struct super_block *sb, + u64 ino, u32 generation) +{ + struct kernfs_super_info *info = kernfs_info(sb); + struct inode *inode; + struct kernfs_node *kn; + + if (ino == 0) + return ERR_PTR(-ESTALE); + + kn = kernfs_find_and_get_node_by_ino(info->root, ino); + if (!kn) + return ERR_PTR(-ESTALE); + inode = kernfs_get_inode(sb, kn); + kernfs_put(kn); + if (IS_ERR(inode)) + return ERR_CAST(inode); + + if (generation && inode->i_generation != generation) { + /* we didn't find the right inode.. */ + iput(inode); + return ERR_PTR(-ESTALE); + } + return inode; +} + +static struct dentry *kernfs_fh_to_dentry(struct super_block *sb, struct fid *fid, + int fh_len, int fh_type) +{ + return generic_fh_to_dentry(sb, fid, fh_len, fh_type, + kernfs_fh_get_inode); +} + +static struct dentry *kernfs_fh_to_parent(struct super_block *sb, struct fid *fid, + int fh_len, int fh_type) +{ + return generic_fh_to_parent(sb, fid, fh_len, fh_type, + kernfs_fh_get_inode); +} + +static struct dentry *kernfs_get_parent_dentry(struct dentry *child) +{ + struct kernfs_node *kn = kernfs_dentry_node(child); + + return d_obtain_alias(kernfs_get_inode(child->d_sb, kn->parent)); +} + +static const struct export_operations kernfs_export_ops = { + .fh_to_dentry = kernfs_fh_to_dentry, + .fh_to_parent = kernfs_fh_to_parent, + .get_parent = kernfs_get_parent_dentry, +}; + /** * kernfs_root_from_sb - determine kernfs_root associated with a super_block * @sb: the super_block in question @@ -159,6 +213,8 @@ static int kernfs_fill_super(struct super_block *sb, unsigned long magic) sb->s_magic = magic; sb->s_op = &kernfs_sops; sb->s_xattr = kernfs_xattr_handlers; + if (info->root->flags & KERNFS_ROOT_SUPPORT_EXPORTOP) + sb->s_export_op = &kernfs_export_ops; sb->s_time_gran = 1; /* get root inode, initialize and unlock it */ diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h index 06a0c59..d149361 100644 --- a/include/linux/kernfs.h +++ b/include/linux/kernfs.h @@ -69,6 +69,12 @@ enum kernfs_root_flag { * following flag enables that behavior. */ KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK = 0x0002, + + /* + * The filesystem supports exportfs operation, so userspace can use + * fhandle to access nodes of the fs. + */ + KERNFS_ROOT_SUPPORT_EXPORTOP = 0x0004, }; /* type-specific structures for kernfs_node union members */ @@ -98,6 +104,12 @@ struct kernfs_elem_attr { /* represent a kernfs node */ union kernfs_node_id { struct { + /* + * blktrace will export this struct as a simplified 'struct + * fid' (which is a big data struction), so userspace can use + * it to find kernfs node. The layout must match the first two + * fields of 'struct fid' exactly. + */ u32 ino; u32 generation; }; diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index dbfd702..4a5cbe9 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -1691,7 +1691,8 @@ int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask, int ref_flags) &cgroup_kf_syscall_ops : &cgroup1_kf_syscall_ops; root->kf_root = kernfs_create_root(kf_sops, - KERNFS_ROOT_CREATE_DEACTIVATED, + KERNFS_ROOT_CREATE_DEACTIVATED | + KERNFS_ROOT_SUPPORT_EXPORTOP, root_cgrp); if (IS_ERR(root->kf_root)) { ret = PTR_ERR(root->kf_root);