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configfs: accessing item hierarchy during rmdir(2)

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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: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
This commit is contained in:
Joel Becker 2006-10-06 17:33:23 -07:00 committed by Mark Fasheh
parent 6d748924b7
commit 299894cc90
3 changed files with 41 additions and 1 deletions
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12
Documentation/filesystems/configfs/configfs.txt
View file

@ -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

29
fs/configfs/dir.c
View file

@ -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
@ -733,7 +755,7 @@ static void client_drop_item(struct config_item *parent_item,
*/
if (type->ct_group_ops && type->ct_group_ops->drop_item)
type->ct_group_ops->drop_item(to_config_group(parent_item),
item);
item);
else
config_item_put(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);
}

1
include/linux/configfs.h
View file

@ -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);
};