| From ea015218f2f7ace2dad9cedd21ed95bdba2886d7 Mon Sep 17 00:00:00 2001 |
| From: "Eric W. Biederman" <ebiederm@xmission.com> |
| Date: Wed, 13 May 2015 16:09:29 -0500 |
| Subject: kernfs: Add support for always empty directories. |
| |
| From: "Eric W. Biederman" <ebiederm@xmission.com> |
| |
| commit ea015218f2f7ace2dad9cedd21ed95bdba2886d7 upstream. |
| |
| Add a new function kernfs_create_empty_dir that can be used to create |
| directory that can not be modified. |
| |
| Update the code to use make_empty_dir_inode when reporting a |
| permanently empty directory to the vfs. |
| |
| Update the code to not allow adding to permanently empty directories. |
| |
| Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| fs/kernfs/dir.c | 38 +++++++++++++++++++++++++++++++++++++- |
| fs/kernfs/inode.c | 2 ++ |
| include/linux/kernfs.h | 3 +++ |
| 3 files changed, 42 insertions(+), 1 deletion(-) |
| |
| --- a/fs/kernfs/dir.c |
| +++ b/fs/kernfs/dir.c |
| @@ -592,6 +592,9 @@ int kernfs_add_one(struct kernfs_node *k |
| goto out_unlock; |
| |
| ret = -ENOENT; |
| + if (parent->flags & KERNFS_EMPTY_DIR) |
| + goto out_unlock; |
| + |
| if ((parent->flags & KERNFS_ACTIVATED) && !kernfs_active(parent)) |
| goto out_unlock; |
| |
| @@ -783,6 +786,38 @@ struct kernfs_node *kernfs_create_dir_ns |
| return ERR_PTR(rc); |
| } |
| |
| +/** |
| + * kernfs_create_empty_dir - create an always empty directory |
| + * @parent: parent in which to create a new directory |
| + * @name: name of the new directory |
| + * |
| + * Returns the created node on success, ERR_PTR() value on failure. |
| + */ |
| +struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent, |
| + const char *name) |
| +{ |
| + struct kernfs_node *kn; |
| + int rc; |
| + |
| + /* allocate */ |
| + kn = kernfs_new_node(parent, name, S_IRUGO|S_IXUGO|S_IFDIR, KERNFS_DIR); |
| + if (!kn) |
| + return ERR_PTR(-ENOMEM); |
| + |
| + kn->flags |= KERNFS_EMPTY_DIR; |
| + kn->dir.root = parent->dir.root; |
| + kn->ns = NULL; |
| + kn->priv = NULL; |
| + |
| + /* link in */ |
| + rc = kernfs_add_one(kn); |
| + if (!rc) |
| + return kn; |
| + |
| + kernfs_put(kn); |
| + return ERR_PTR(rc); |
| +} |
| + |
| static struct dentry *kernfs_iop_lookup(struct inode *dir, |
| struct dentry *dentry, |
| unsigned int flags) |
| @@ -1254,7 +1289,8 @@ int kernfs_rename_ns(struct kernfs_node |
| mutex_lock(&kernfs_mutex); |
| |
| error = -ENOENT; |
| - if (!kernfs_active(kn) || !kernfs_active(new_parent)) |
| + if (!kernfs_active(kn) || !kernfs_active(new_parent) || |
| + (new_parent->flags & KERNFS_EMPTY_DIR)) |
| goto out; |
| |
| error = 0; |
| --- a/fs/kernfs/inode.c |
| +++ b/fs/kernfs/inode.c |
| @@ -296,6 +296,8 @@ static void kernfs_init_inode(struct ker |
| case KERNFS_DIR: |
| inode->i_op = &kernfs_dir_iops; |
| inode->i_fop = &kernfs_dir_fops; |
| + if (kn->flags & KERNFS_EMPTY_DIR) |
| + make_empty_dir_inode(inode); |
| break; |
| case KERNFS_FILE: |
| inode->i_size = kn->attr.size; |
| --- a/include/linux/kernfs.h |
| +++ b/include/linux/kernfs.h |
| @@ -45,6 +45,7 @@ enum kernfs_node_flag { |
| KERNFS_LOCKDEP = 0x0100, |
| KERNFS_SUICIDAL = 0x0400, |
| KERNFS_SUICIDED = 0x0800, |
| + KERNFS_EMPTY_DIR = 0x1000, |
| }; |
| |
| /* @flags for kernfs_create_root() */ |
| @@ -285,6 +286,8 @@ void kernfs_destroy_root(struct kernfs_r |
| struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent, |
| const char *name, umode_t mode, |
| void *priv, const void *ns); |
| +struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent, |
| + const char *name); |
| struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent, |
| const char *name, |
| umode_t mode, loff_t size, |