diff options
| -rw-r--r-- | fs/kernfs/dir.c | 118 | ||||
| -rw-r--r-- | include/linux/kernfs.h | 7 |
2 files changed, 123 insertions, 2 deletions
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index 37dd6408f5f6..1aeb57969bff 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -396,6 +396,7 @@ struct kernfs_node *kernfs_new_node(struct kernfs_root *root, const char *name, atomic_set(&kn->count, 1); atomic_set(&kn->active, KN_DEACTIVATED_BIAS); + kn->deact_depth = 1; RB_CLEAR_NODE(&kn->rb); kn->name = name; @@ -461,6 +462,7 @@ int kernfs_add_one(struct kernfs_node *kn, struct kernfs_node *parent) /* Mark the entry added into directory tree */ atomic_sub(KN_DEACTIVATED_BIAS, &kn->active); + kn->deact_depth--; ret = 0; out_unlock: mutex_unlock(&kernfs_mutex); @@ -561,6 +563,7 @@ struct kernfs_root *kernfs_create_root(struct kernfs_dir_ops *kdops, void *priv) } atomic_sub(KN_DEACTIVATED_BIAS, &kn->active); + kn->deact_depth--; kn->priv = priv; kn->dir.root = root; @@ -773,7 +776,8 @@ static void __kernfs_deactivate(struct kernfs_node *kn) /* prevent any new usage under @kn by deactivating all nodes */ pos = NULL; while ((pos = kernfs_next_descendant_post(pos, kn))) { - if (atomic_read(&pos->active) >= 0) { + if (!pos->deact_depth++) { + WARN_ON_ONCE(atomic_read(&pos->active) < 0); atomic_add(KN_DEACTIVATED_BIAS, &pos->active); pos->flags |= KERNFS_JUST_DEACTIVATED; } @@ -797,6 +801,118 @@ static void __kernfs_deactivate(struct kernfs_node *kn) } } +static void __kernfs_reactivate(struct kernfs_node *kn) +{ + struct kernfs_node *pos; + + lockdep_assert_held(&kernfs_mutex); + + pos = NULL; + while ((pos = kernfs_next_descendant_post(pos, kn))) { + if (!--pos->deact_depth) { + WARN_ON_ONCE(atomic_read(&pos->active) >= 0); + atomic_sub(KN_DEACTIVATED_BIAS, &pos->active); + } + WARN_ON_ONCE(pos->deact_depth < 0); + } + + /* some nodes reactivated, kick get_active waiters */ + wake_up_all(&kernfs_root(kn)->deactivate_waitq); +} + +static void __kernfs_deactivate_self(struct kernfs_node *kn) +{ + /* + * Take out ourself out of the active ref dependency chain and + * deactivate. If we're called without an active ref, lockdep will + * complain. + */ + kernfs_put_active(kn); + __kernfs_deactivate(kn); +} + +static void __kernfs_reactivate_self(struct kernfs_node *kn) +{ + __kernfs_reactivate(kn); + /* + * Restore active ref dropped by deactivate_self() so that it's + * balanced on return. put_active() will soon be called on @kn, so + * this can't break anything regardless of @kn's state. + */ + atomic_inc(&kn->active); + if (kernfs_lockdep(kn)) + rwsem_acquire(&kn->dep_map, 0, 1, _RET_IP_); +} + +/** + * kernfs_deactivate - deactivate subtree of a node + * @kn: kernfs_node to deactivate subtree of + * + * Deactivate the subtree of @kn. On return, there's no active operation + * going on under @kn and creation or renaming of a node under @kn is + * blocked until @kn is reactivated or removed. This function can be + * called multiple times and nests properly. Each invocation should be + * paired with kernfs_reactivate(). + * + * For a kernfs user which uses simple locking, the subsystem lock would + * nest inside active reference. This becomes problematic if the user + * tries to remove nodes while holding the subystem lock as it would create + * a reverse locking dependency from the subsystem lock to active ref. + * This function can be used to break such reverse dependency. The user + * can call this function outside the subsystem lock and then proceed to + * invoke kernfs_remove() while holding the subsystem lock without + * introducing such reverse dependency. + */ +void kernfs_deactivate(struct kernfs_node *kn) +{ + mutex_lock(&kernfs_mutex); + __kernfs_deactivate(kn); + mutex_unlock(&kernfs_mutex); +} + +/** + * kernfs_reactivate - reactivate subtree of a node + * @kn: kernfs_node to reactivate subtree of + * + * Undo kernfs_deactivate(). + */ +void kernfs_reactivate(struct kernfs_node *kn) +{ + mutex_lock(&kernfs_mutex); + __kernfs_reactivate(kn); + mutex_unlock(&kernfs_mutex); +} + +/** + * kernfs_deactivate_self - deactivate subtree of a node from its own method + * @kn: the self kernfs_node to deactivate subtree of + * + * The caller must be running off of a kernfs operation which is invoked + * with an active reference - e.g. one of kernfs_ops. Once this function + * is called, @kn may be removed by someone else while the enclosing method + * is in progress. Other than that, this function is equivalent to + * kernfs_deactivate() and should be paired with kernfs_reactivate_self(). + */ +void kernfs_deactivate_self(struct kernfs_node *kn) +{ + mutex_lock(&kernfs_mutex); + __kernfs_deactivate_self(kn); + mutex_unlock(&kernfs_mutex); +} + +/** + * kernfs_reactivate_self - reactivate subtree of a node from its own method + * @kn: the self kernfs_node to reactivate subtree of + * + * Undo kernfs_deactivate_self(). + */ +void kernfs_reactivate_self(struct kernfs_node *kn) +{ + mutex_lock(&kernfs_mutex); + __kernfs_reactivate_self(kn); + mutex_unlock(&kernfs_mutex); +} + static void __kernfs_remove(struct kernfs_node *kn) { struct kernfs_root *root = kernfs_root(kn); diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h index 9b5a4bb88c64..ac8693027058 100644 --- a/include/linux/kernfs.h +++ b/include/linux/kernfs.h @@ -80,6 +80,8 @@ struct kernfs_elem_attr { struct kernfs_node { atomic_t count; atomic_t active; + int deact_depth; + unsigned int hash; /* ns + name hash */ #ifdef CONFIG_DEBUG_LOCK_ALLOC struct lockdep_map dep_map; #endif @@ -90,7 +92,6 @@ struct kernfs_node { struct rb_node rb; const void *ns; /* namespace tag */ - unsigned int hash; /* ns + name hash */ union { struct kernfs_elem_dir dir; struct kernfs_elem_symlink symlink; @@ -233,6 +234,10 @@ 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_deactivate(struct kernfs_node *kn); +void kernfs_reactivate(struct kernfs_node *kn); +void kernfs_deactivate_self(struct kernfs_node *kn); +void kernfs_reactivate_self(struct kernfs_node *kn); void kernfs_remove(struct kernfs_node *kn); int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name, const void *ns); |