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

This reverts commit 1ae06819c77cff1ea2833c94f8c093fe8a5c79db.

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>

1 files changed, 0 insertions, 72 deletions

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index a8028be..1aeb579 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -986,78 +986,6 @@ void kernfs_remove(struct kernfs_node *kn)
 }
 
 /**
- * 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
  * @name: name of the kernfs_node to remove