3.19.8-ckt4 -stable review patch. If anyone has any objections, please let me
know.
------------------
From: "Eric W. Biederman" <ebied...@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" <ebied...@xmission.com>
Signed-off-by: Kamal Mostafa <ka...@canonical.com>
---
fs/kernfs/dir.c | 38 +++++++++++++++++++++++++++++++++++++-
fs/kernfs/inode.c | 2 ++
include/linux/kernfs.h | 3 +++
3 files changed, 42 insertions(+), 1 deletion(-)
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 2d881b3..48ed22d 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -587,6 +587,9 @@ int kernfs_add_one(struct kernfs_node *kn)
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;
@@ -778,6 +781,38 @@ struct kernfs_node *kernfs_create_dir_ns(struct
kernfs_node *parent,
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)
@@ -1249,7 +1284,8 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct
kernfs_node *new_parent,
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;
diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c
index 9852176..5b8ab29 100644
--- a/fs/kernfs/inode.c
+++ b/fs/kernfs/inode.c
@@ -309,6 +309,8 @@ static void kernfs_init_inode(struct kernfs_node *kn,
struct inode *inode)
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;
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index d4e01b3..cfc81c2 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -46,6 +46,7 @@ enum kernfs_node_flag {
KERNFS_STATIC_NAME = 0x0200,
KERNFS_SUICIDAL = 0x0400,
KERNFS_SUICIDED = 0x0800,
+ KERNFS_EMPTY_DIR = 0x1000,
};
/* @flags for kernfs_create_root() */
@@ -286,6 +287,8 @@ void kernfs_destroy_root(struct kernfs_root *root);
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,
--
1.9.1
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