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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/core.c

@@ -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.

fs/kernfs/dir.c

@@ -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

fs/sysfs/file.c

@@ -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;

include/linux/device.h

@@ -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,

include/linux/kernfs.h

@@ -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; }

include/linux/sysfs.h

@@ -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)
 {