Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756150AbbLWEZX (ORCPT ); Tue, 22 Dec 2015 23:25:23 -0500 Received: from h2.hallyn.com ([78.46.35.8]:53770 "EHLO h2.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755836AbbLWEXf (ORCPT ); Tue, 22 Dec 2015 23:23:35 -0500 From: serge.hallyn@ubuntu.com To: linux-kernel@vger.kernel.org Cc: adityakali@google.com, tj@kernel.org, linux-api@vger.kernel.org, containers@lists.linux-foundation.org, cgroups@vger.kernel.org, lxc-devel@lists.linuxcontainers.org, akpm@linux-foundation.org, ebiederm@xmission.com, gregkh@linuxfoundation.org, lizefan@huawei.com, hannes@cmpxchg.org, "Serge E. Hallyn" Subject: [PATCH 5/8] kernfs: define kernfs_node_dentry Date: Tue, 22 Dec 2015 22:23:26 -0600 Message-Id: <1450844609-9194-6-git-send-email-serge.hallyn@ubuntu.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1450844609-9194-1-git-send-email-serge.hallyn@ubuntu.com> References: <1450844609-9194-1-git-send-email-serge.hallyn@ubuntu.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3906 Lines: 130 From: Aditya Kali Add a new kernfs api is added to lookup the dentry for a particular kernfs path. Signed-off-by: Aditya Kali Signed-off-by: Serge E. Hallyn --- Changelog: 20151116 - Don't allow user namespaces to bind new subsystems 20151118 - postpone the FS_USERNS_MOUNT flag until the last patch, until we can convince ourselves it is safe. 20151207 - Switch to walking up the kernfs path from kn root. 20151208 - Split out the kernfs change - Style changes - Switch from pr_crit to WARN_ON - Reorder arguments to kernfs_obtain_root - rename kernfs_obtain_root to kernfs_node_dentry --- fs/kernfs/mount.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/kernfs.h | 2 ++ 2 files changed, 69 insertions(+) diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c index 8eaf417..7224296 100644 --- a/fs/kernfs/mount.c +++ b/fs/kernfs/mount.c @@ -14,6 +14,7 @@ #include #include #include +#include #include "kernfs-internal.h" @@ -62,6 +63,72 @@ struct kernfs_root *kernfs_root_from_sb(struct super_block *sb) return NULL; } +/* + * find the next ancestor in the path down to @child, where @parent was the + * ancestor whose descendant we want to find. + * + * Say the path is /a/b/c/d. @child is d, @parent is NULL. We return the root + * node. If @parent is b, then we return the node for c. + * Passing in d as @parent is not ok. + */ +static struct kernfs_node * +find_next_ancestor(struct kernfs_node *child, struct kernfs_node *parent) +{ + if (child == parent) { + pr_crit_once("BUG in find_next_ancestor: called with parent == child"); + return NULL; + } + + while (child->parent != parent) { + if (!child->parent) + return NULL; + child = child->parent; + } + + return child; +} + +/** + * kernfs_node_dentry - get a dentry for the given kernfs_node + * @kn: kernfs_node for which a dentry is needed + * @sb: the kernfs super_block + */ +struct dentry *kernfs_node_dentry(struct kernfs_node *kn, + struct super_block *sb) +{ + struct dentry *dentry; + struct kernfs_node *knparent = NULL; + + BUG_ON(sb->s_op != &kernfs_sops); + + dentry = dget(sb->s_root); + + /* Check if this is the root kernfs_node */ + if (!kn->parent) + return dentry; + + knparent = find_next_ancestor(kn, NULL); + if (WARN_ON(!knparent)) + return ERR_PTR(-EINVAL); + + do { + struct dentry *dtmp; + struct kernfs_node *kntmp; + + if (kn == knparent) + return dentry; + kntmp = find_next_ancestor(kn, knparent); + if (WARN_ON(!kntmp)) + return ERR_PTR(-EINVAL); + dtmp = lookup_one_len(kntmp->name, dentry, strlen(kntmp->name)); + dput(dentry); + if (IS_ERR(dtmp)) + return dtmp; + knparent = kntmp; + dentry = dtmp; + } while (1); +} + static int kernfs_fill_super(struct super_block *sb, unsigned long magic) { struct kernfs_super_info *info = kernfs_info(sb); diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h index 716bfde..c06c442 100644 --- a/include/linux/kernfs.h +++ b/include/linux/kernfs.h @@ -284,6 +284,8 @@ struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry); struct kernfs_root *kernfs_root_from_sb(struct super_block *sb); struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn); +struct dentry *kernfs_node_dentry(struct kernfs_node *kn, + struct super_block *sb); struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops, unsigned int flags, void *priv); void kernfs_destroy_root(struct kernfs_root *root); -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/