Commit 299894cc authored by Joel Becker's avatar Joel Becker Committed by Mark Fasheh
Browse files

configfs: accessing item hierarchy during rmdir(2) 



Add a notification callback, ops->disconnect_notify(). It has the same
prototype as ->drop_item(), but it will be called just before the item
linkage is broken. This way, configfs users who want to do work while
the object is still in the heirarchy have a chance.

Client drivers will still need to config_item_put() in their
->drop_item(), if they implement it.  They need do nothing in
->disconnect_notify().  They don't have to provide it if they don't
care.  But someone who wants to be notified before ci_parent is set to
NULL can now be notified.

Signed-off-by: default avatarJoel Becker <joel.becker@oracle.com>
Signed-off-by: default avatarMark Fasheh <mark.fasheh@oracle.com>
parent 6d748924

Documentation/filesystems/configfs/configfs.txt

+12 −0
Original line number Diff line number Diff line
@@ -238,6 +238,8 @@ config_item_type. 
		struct config_group *(*make_group)(struct config_group *group,

						   const char *name);

		int (*commit_item)(struct config_item *item);

		void (*disconnect_notify)(struct config_group *group,

					  struct config_item *item);

		void (*drop_item)(struct config_group *group,

				  struct config_item *item);

	};
@@ -268,6 +270,16 @@ the item in other threads, the memory is safe. It may take some time 
for the item to actually disappear from the subsystem's usage.  But it

is gone from configfs.



When drop_item() is called, the item's linkage has already been torn

down.  It no longer has a reference on its parent and has no place in

the item hierarchy.  If a client needs to do some cleanup before this

teardown happens, the subsystem can implement the

ct_group_ops->disconnect_notify() method.  The method is called after

configfs has removed the item from the filesystem view but before the

item is removed from its parent group.  Like drop_item(),

disconnect_notify() is void and cannot fail.  Client subsystems should

not drop any references here, as they still must do it in drop_item().



A config_group cannot be removed while it still has child items.  This

is implemented in the configfs rmdir(2) code.  ->drop_item() will not be

called, as the item has not been dropped.  rmdir(2) will fail, as the

fs/configfs/dir.c

+28 −1
Original line number Diff line number Diff line
@@ -713,6 +713,28 @@ static void configfs_detach_group(struct config_item *item) 
	configfs_detach_item(item);

}



/*

 * After the item has been detached from the filesystem view, we are

 * ready to tear it out of the hierarchy.  Notify the client before

 * we do that so they can perform any cleanup that requires

 * navigating the hierarchy.  A client does not need to provide this

 * callback.  The subsystem semaphore MUST be held by the caller, and

 * references must be valid for both items.  It also assumes the

 * caller has validated ci_type.

 */

static void client_disconnect_notify(struct config_item *parent_item,

				     struct config_item *item)

{

	struct config_item_type *type;



	type = parent_item->ci_type;

	BUG_ON(!type);



	if (type->ct_group_ops && type->ct_group_ops->disconnect_notify)

		type->ct_group_ops->disconnect_notify(to_config_group(parent_item),

						      item);

}



/*

 * Drop the initial reference from make_item()/make_group()

 * This function assumes that reference is held on item
@@ -842,11 +864,14 @@ out_unlink: 
	if (ret) {

		/* Tear down everything we built up */

		mutex_lock(&subsys->su_mutex);



		client_disconnect_notify(parent_item, item);

		if (group)

			unlink_group(group);

		else

			unlink_obj(item);

		client_drop_item(parent_item, item);



		mutex_unlock(&subsys->su_mutex);



		if (module_got)
@@ -911,11 +936,13 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry) 
		configfs_detach_group(item);



		mutex_lock(&subsys->su_mutex);

		client_disconnect_notify(parent_item, item);

		unlink_group(to_config_group(item));

	} else {

		configfs_detach_item(item);



		mutex_lock(&subsys->su_mutex);

		client_disconnect_notify(parent_item, item);

		unlink_obj(item);

	}

include/linux/configfs.h

+1 −0
Original line number Diff line number Diff line
@@ -169,6 +169,7 @@ struct configfs_group_operations { 
	struct config_item *(*make_item)(struct config_group *group, const char *name);

	struct config_group *(*make_group)(struct config_group *group, const char *name);

	int (*commit_item)(struct config_item *item);

	void (*disconnect_notify)(struct config_group *group, struct config_item *item);

	void (*drop_item)(struct config_group *group, struct config_item *item);

};

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