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authorGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-01-13 14:09:38 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-01-13 14:09:38 -0800
commit9b0925a6ff64a33be45497e3c798bfee8790b102 (patch)
tree827aec07fe844addd8e1dd2d1f09b4bb855c9cd1
parenta9f138b0e537de55933335d580ebd38c2bc53c47 (diff)
Revert "kernfs: implement kernfs_{de|re}activate[_self]()"
This reverts commit 9f010c2ad5194a4b682e747984477850fabd03be. Tejun writes: I'm sorry but can you please revert the whole series? get_active() waiting while a node is deactivated has potential to lead to deadlock and that deactivate/reactivate interface is something fundamentally flawed and that cgroup will have to work with the remove_self() like everybody else. IOW, I think the first posting was correct. Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--fs/kernfs/dir.c118
-rw-r--r--include/linux/kernfs.h7
2 files changed, 2 insertions, 123 deletions
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 1aeb57969bff..37dd6408f5f6 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -396,7 +396,6 @@ 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;
@@ -462,7 +461,6 @@ 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);
@@ -563,7 +561,6 @@ 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;
@@ -776,8 +773,7 @@ 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 (!pos->deact_depth++) {
- WARN_ON_ONCE(atomic_read(&pos->active) < 0);
+ if (atomic_read(&pos->active) >= 0) {
atomic_add(KN_DEACTIVATED_BIAS, &pos->active);
pos->flags |= KERNFS_JUST_DEACTIVATED;
}
@@ -801,118 +797,6 @@ 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 ac8693027058..9b5a4bb88c64 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -80,8 +80,6 @@ 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
@@ -92,6 +90,7 @@ 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;
@@ -234,10 +233,6 @@ 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);