diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 89f8462f337e907dc0305fa51edc606cdc208ef0..3cff0a233cd14b4c6767aa9b4ffbae07f3be5adb 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -435,7 +435,7 @@ int kernfs_add_one(struct kernfs_node *kn)
goto out_unlock;
ret = -ENOENT;
- if (!kernfs_active(parent))
+ if ((parent->flags & KERNFS_ACTIVATED) && !kernfs_active(parent))
goto out_unlock;
kn->hash = kernfs_name_hash(kn->name, kn->ns);
@@ -451,9 +451,19 @@ int kernfs_add_one(struct kernfs_node *kn)
ps_iattrs->ia_ctime = ps_iattrs->ia_mtime = CURRENT_TIME;
}
- /* Mark the entry added into directory tree */
- atomic_sub(KN_DEACTIVATED_BIAS, &kn->active);
- ret = 0;
+ mutex_unlock(&kernfs_mutex);
+
+ /*
+ * Activate the new node unless CREATE_DEACTIVATED is requested.
+ * If not activated here, the kernfs user is responsible for
+ * activating the node with kernfs_activate(). A node which hasn't
+ * been activated is not visible to userland and its removal won't
+ * trigger deactivation.
+ */
+ if (!(kernfs_root(kn)->flags & KERNFS_ROOT_CREATE_DEACTIVATED))
+ kernfs_activate(kn);
+ return 0;
+
out_unlock:
mutex_unlock(&kernfs_mutex);
return ret;
@@ -528,13 +538,14 @@ EXPORT_SYMBOL_GPL(kernfs_find_and_get_ns);
/**
* kernfs_create_root - create a new kernfs hierarchy
* @scops: optional syscall operations for the hierarchy
+ * @flags: KERNFS_ROOT_* flags
* @priv: opaque data associated with the new directory
*
* Returns the root of the new hierarchy on success, ERR_PTR() value on
* failure.
*/
struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
- void *priv)
+ unsigned int flags, void *priv)
{
struct kernfs_root *root;
struct kernfs_node *kn;
@@ -553,14 +564,17 @@ struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
return ERR_PTR(-ENOMEM);
}
- atomic_sub(KN_DEACTIVATED_BIAS, &kn->active);
kn->priv = priv;
kn->dir.root = root;
root->syscall_ops = scops;
+ root->flags = flags;
root->kn = kn;
init_waitqueue_head(&root->deactivate_waitq);
+ if (!(root->flags & KERNFS_ROOT_CREATE_DEACTIVATED))
+ kernfs_activate(kn);
+
return root;
}
@@ -783,6 +797,40 @@ static struct kernfs_node *kernfs_next_descendant_post(struct kernfs_node *pos,
return pos->parent;
}
+/**
+ * kernfs_activate - activate a node which started deactivated
+ * @kn: kernfs_node whose subtree is to be activated
+ *
+ * If the root has KERNFS_ROOT_CREATE_DEACTIVATED set, a newly created node
+ * needs to be explicitly activated. A node which hasn't been activated
+ * isn't visible to userland and deactivation is skipped during its
+ * removal. This is useful to construct atomic init sequences where
+ * creation of multiple nodes should either succeed or fail atomically.
+ *
+ * The caller is responsible for ensuring that this function is not called
+ * after kernfs_remove*() is invoked on @kn.
+ */
+void kernfs_activate(struct kernfs_node *kn)
+{
+ struct kernfs_node *pos;
+
+ mutex_lock(&kernfs_mutex);
+
+ pos = NULL;
+ while ((pos = kernfs_next_descendant_post(pos, kn))) {
+ if (!pos || (pos->flags & KERNFS_ACTIVATED))
+ continue;
+
+ WARN_ON_ONCE(pos->parent && RB_EMPTY_NODE(&pos->rb));
+ WARN_ON_ONCE(atomic_read(&pos->active) != KN_DEACTIVATED_BIAS);
+
+ atomic_sub(KN_DEACTIVATED_BIAS, &pos->active);
+ pos->flags |= KERNFS_ACTIVATED;
+ }
+
+ mutex_unlock(&kernfs_mutex);
+}
+
static void __kernfs_remove(struct kernfs_node *kn)
{
struct kernfs_node *pos;
@@ -817,7 +865,16 @@ static void __kernfs_remove(struct kernfs_node *kn)
*/
kernfs_get(pos);
- kernfs_drain(pos);
+ /*
+ * Drain iff @kn was activated. This avoids draining and
+ * its lockdep annotations for nodes which have never been
+ * activated and allows embedding kernfs_remove() in create
+ * error paths without worrying about draining.
+ */
+ if (kn->flags & KERNFS_ACTIVATED)
+ kernfs_drain(pos);
+ else
+ WARN_ON_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS);
/*
* kernfs_unlink_sibling() succeeds once per node. Use it
diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 6211230814fd89dcc1a0a4b0acbabe000428e5b8..5c7fdd9c681118c68830c05973ff715569289d08 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -62,7 +62,7 @@ int __init sysfs_init(void)
{
int err;
- sysfs_root = kernfs_create_root(NULL, NULL);
+ sysfs_root = kernfs_create_root(NULL, 0, NULL);
if (IS_ERR(sysfs_root))
return PTR_ERR(sysfs_root);
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 5d5b7e94729435d773ae31c3ba1947bcf0b0624a..4520c86f5cb40d387ebb415737179811ac3e7dd2 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -38,6 +38,7 @@ enum kernfs_node_type {
#define KERNFS_FLAG_MASK ~KERNFS_TYPE_MASK
enum kernfs_node_flag {
+ KERNFS_ACTIVATED = 0x0010,
KERNFS_NS = 0x0020,
KERNFS_HAS_SEQ_SHOW = 0x0040,
KERNFS_HAS_MMAP = 0x0080,
@@ -47,6 +48,11 @@ enum kernfs_node_flag {
KERNFS_SUICIDED = 0x0800,
};
+/* @flags for kernfs_create_root() */
+enum kernfs_root_flag {
+ KERNFS_ROOT_CREATE_DEACTIVATED = 0x0001,
+};
+
/* type-specific structures for kernfs_node union members */
struct kernfs_elem_dir {
unsigned long subdirs;
@@ -128,6 +134,7 @@ struct kernfs_syscall_ops {
struct kernfs_root {
/* published fields */
struct kernfs_node *kn;
+ unsigned int flags; /* KERNFS_ROOT_* flags */
/* private fields, do not use outside kernfs proper */
struct ida ino_ida;
@@ -223,7 +230,7 @@ void kernfs_get(struct kernfs_node *kn);
void kernfs_put(struct kernfs_node *kn);
struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
- void *priv);
+ unsigned int flags, void *priv);
void kernfs_destroy_root(struct kernfs_root *root);
struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
@@ -239,6 +246,7 @@ struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
const char *name,
struct kernfs_node *target);
+void kernfs_activate(struct kernfs_node *kn);
void kernfs_remove(struct kernfs_node *kn);
void kernfs_break_active_protection(struct kernfs_node *kn);
void kernfs_unbreak_active_protection(struct kernfs_node *kn);
@@ -276,7 +284,8 @@ static inline void kernfs_get(struct kernfs_node *kn) { }
static inline void kernfs_put(struct kernfs_node *kn) { }
static inline struct kernfs_root *
-kernfs_create_root(struct kernfs_syscall_ops *scops, void *priv)
+kernfs_create_root(struct kernfs_syscall_ops *scops, unsigned int flags,
+ void *priv)
{ return ERR_PTR(-ENOSYS); }
static inline void kernfs_destroy_root(struct kernfs_root *root) { }
@@ -298,6 +307,8 @@ kernfs_create_link(struct kernfs_node *parent, const char *name,
struct kernfs_node *target)
{ return ERR_PTR(-ENOSYS); }
+static inline void kernfs_activate(struct kernfs_node *kn) { }
+
static inline void kernfs_remove(struct kernfs_node *kn) { }
static inline bool kernfs_remove_self(struct kernfs_node *kn)