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

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: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 8634c422

drivers/base/core.c

+0 −17
Original line number Diff line number Diff line
@@ -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

+0 −72
Original line number Diff line number Diff line
@@ -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

+0 −23
Original line number Diff line number Diff line
@@ -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

+0 −2
Original line number Diff line number Diff line
@@ -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

+0 −6
Original line number Diff line number Diff line
@@ -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; }