Commit a9f138b0 authored by Greg Kroah-Hartman's avatar Greg Kroah-Hartman

Revert "kernfs, sysfs, driver-core: implement kernfs_remove_self() and its wrappers"

This reverts commit 1ae06819.

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>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: 's avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 8634c422
......@@ -570,23 +570,6 @@ void device_remove_file(struct device *dev,
}
EXPORT_SYMBOL_GPL(device_remove_file);
/**
* device_remove_file_self - remove sysfs attribute file from its own method.
* @dev: device.
* @attr: device attribute descriptor.
*
* See kernfs_remove_self() for details.
*/
bool device_remove_file_self(struct device *dev,
const struct device_attribute *attr)
{
if (dev)
return sysfs_remove_file_self(&dev->kobj, &attr->attr);
else
return false;
}
EXPORT_SYMBOL_GPL(device_remove_file_self);
/**
* device_create_bin_file - create sysfs binary attribute file for device.
* @dev: device.
......
......@@ -985,78 +985,6 @@ void kernfs_remove(struct kernfs_node *kn)
mutex_unlock(&kernfs_mutex);
}
/**
* kernfs_remove_self - remove a kernfs_node from its own method
* @kn: the self kernfs_node to remove
*
* The caller must be running off of a kernfs operation which is invoked
* with an active reference - e.g. one of kernfs_ops. This can be used to
* implement a file operation which deletes itself.
*
* For example, the "delete" file for a sysfs device directory can be
* implemented by invoking kernfs_remove_self() on the "delete" file
* itself. This function breaks the circular dependency of trying to
* deactivate self while holding an active ref itself. It isn't necessary
* to modify the usual removal path to use kernfs_remove_self(). The
* "delete" implementation can simply invoke kernfs_remove_self() on self
* before proceeding with the usual removal path. kernfs will ignore later
* kernfs_remove() on self.
*
* kernfs_remove_self() can be called multiple times concurrently on the
* same kernfs_node. Only the first one actually performs removal and
* returns %true. All others will wait until the kernfs operation which
* won self-removal finishes and return %false. Note that the losers wait
* for the completion of not only the winning kernfs_remove_self() but also
* the whole kernfs_ops which won the arbitration. This can be used to
* guarantee, for example, all concurrent writes to a "delete" file to
* finish only after the whole operation is complete.
*/
bool kernfs_remove_self(struct kernfs_node *kn)
{
bool ret;
mutex_lock(&kernfs_mutex);
__kernfs_deactivate_self(kn);
/*
* SUICIDAL is used to arbitrate among competing invocations. Only
* the first one will actually perform removal. When the removal
* is complete, SUICIDED is set and the active ref is restored
* while holding kernfs_mutex. The ones which lost arbitration
* waits for SUICDED && drained which can happen only after the
* enclosing kernfs operation which executed the winning instance
* of kernfs_remove_self() finished.
*/
if (!(kn->flags & KERNFS_SUICIDAL)) {
kn->flags |= KERNFS_SUICIDAL;
__kernfs_remove(kn);
kn->flags |= KERNFS_SUICIDED;
ret = true;
} else {
wait_queue_head_t *waitq = &kernfs_root(kn)->deactivate_waitq;
DEFINE_WAIT(wait);
while (true) {
prepare_to_wait(waitq, &wait, TASK_UNINTERRUPTIBLE);
if ((kn->flags & KERNFS_SUICIDED) &&
atomic_read(&kn->active) == KN_DEACTIVATED_BIAS)
break;
mutex_unlock(&kernfs_mutex);
schedule();
mutex_lock(&kernfs_mutex);
}
finish_wait(waitq, &wait);
WARN_ON_ONCE(!RB_EMPTY_NODE(&kn->rb));
ret = false;
}
__kernfs_reactivate_self(kn);
mutex_unlock(&kernfs_mutex);
return ret;
}
/**
* kernfs_remove_by_name_ns - find a kernfs_node by name and remove it
* @parent: parent of the target
......
......@@ -372,29 +372,6 @@ void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
}
EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
/**
* sysfs_remove_file_self - remove an object attribute from its own method
* @kobj: object we're acting for
* @attr: attribute descriptor
*
* See kernfs_remove_self() for details.
*/
bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
{
struct kernfs_node *parent = kobj->sd;
struct kernfs_node *kn;
bool ret;
kn = kernfs_find_and_get(parent, attr->name);
if (WARN_ON_ONCE(!kn))
return false;
ret = kernfs_remove_self(kn);
kernfs_put(kn);
return ret;
}
void sysfs_remove_files(struct kobject *kobj, const struct attribute **ptr)
{
int i;
......
......@@ -560,8 +560,6 @@ extern int device_create_file(struct device *device,
const struct device_attribute *entry);
extern void device_remove_file(struct device *dev,
const struct device_attribute *attr);
extern bool device_remove_file_self(struct device *dev,
const struct device_attribute *attr);
extern int __must_check device_create_bin_file(struct device *dev,
const struct bin_attribute *attr);
extern void device_remove_bin_file(struct device *dev,
......
......@@ -43,8 +43,6 @@ enum kernfs_node_flag {
KERNFS_HAS_MMAP = 0x0080,
KERNFS_LOCKDEP = 0x0100,
KERNFS_STATIC_NAME = 0x0200,
KERNFS_SUICIDAL = 0x0400,
KERNFS_SUICIDED = 0x0800,
};
/* type-specific structures for kernfs_node union members */
......@@ -241,7 +239,6 @@ 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);
bool kernfs_remove_self(struct kernfs_node *kn);
int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
const void *ns);
int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
......@@ -299,9 +296,6 @@ kernfs_create_link(struct kernfs_node *parent, const char *name,
static inline void kernfs_remove(struct kernfs_node *kn) { }
static inline bool kernfs_remove_self(struct kernfs_node *kn)
{ return false; }
static inline int kernfs_remove_by_name_ns(struct kernfs_node *kn,
const char *name, const void *ns)
{ return -ENOSYS; }
......
......@@ -198,7 +198,6 @@ int __must_check sysfs_chmod_file(struct kobject *kobj,
const struct attribute *attr, umode_t mode);
void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
const void *ns);
bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr);
void sysfs_remove_files(struct kobject *kobj, const struct attribute **attr);
int __must_check sysfs_create_bin_file(struct kobject *kobj,
......@@ -302,12 +301,6 @@ static inline void sysfs_remove_file_ns(struct kobject *kobj,
{
}
static inline bool sysfs_remove_file_self(struct kobject *kobj,
const struct attribute *attr)
{
return false;
}
static inline void sysfs_remove_files(struct kobject *kobj,
const struct attribute **attr)
{
......
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