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Commit 938aaa4f authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

sysctl: Initial support for auto-unregistering sysctl tables. 



Add nreg to ctl_table_header.  When nreg drops to 0 the ctl_table_header
will be unregistered.

Factor out drop_sysctl_table from unregister_sysctl_table, and add
the logic for decrementing nreg.

Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
parent 3cc3e046

fs/proc/proc_sysctl.c

+19 −9
Original line number Original line Diff line number Diff line
@@ -29,6 +29,7 @@ static struct ctl_table root_table[1]; 
static struct ctl_table_root sysctl_table_root;

static struct ctl_table_root sysctl_table_root;

static struct ctl_table_header root_table_header = {

static struct ctl_table_header root_table_header = {

	{{.count = 1,

	{{.count = 1,

	  .nreg = 1,

	  .ctl_table = root_table,

	  .ctl_table = root_table,

	  .ctl_entry = LIST_HEAD_INIT(sysctl_table_root.default_set.list),}},

	  .ctl_entry = LIST_HEAD_INIT(sysctl_table_root.default_set.list),}},

	.root = &sysctl_table_root,

	.root = &sysctl_table_root,
@@ -938,6 +939,7 @@ struct ctl_table_header *__register_sysctl_table( 
	header->unregistering = NULL;

	header->unregistering = NULL;

	header->root = root;

	header->root = root;

	header->count = 1;

	header->count = 1;

	header->nreg = 1;

	if (sysctl_check_table(path, table))

	if (sysctl_check_table(path, table))

		goto fail;

		goto fail;
@@ -1192,6 +1194,20 @@ struct ctl_table_header *register_sysctl_table(struct ctl_table *table) 
}

}

EXPORT_SYMBOL(register_sysctl_table);

EXPORT_SYMBOL(register_sysctl_table);





static void drop_sysctl_table(struct ctl_table_header *header)

{

	if (--header->nreg)

		return;



	start_unregistering(header);

	if (!--header->parent->count) {

		WARN_ON(1);

		kfree_rcu(header->parent, rcu);

	}

	if (!--header->count)

		kfree_rcu(header, rcu);

}



/**

/**

 * unregister_sysctl_table - unregister a sysctl table hierarchy

 * unregister_sysctl_table - unregister a sysctl table hierarchy

 * @header: the header returned from register_sysctl_table

 * @header: the header returned from register_sysctl_table
@@ -1224,13 +1240,7 @@ void unregister_sysctl_table(struct ctl_table_header * header) 
	}

	}





	spin_lock(&sysctl_lock);

	spin_lock(&sysctl_lock);

	start_unregistering(header);

	drop_sysctl_table(header);

	if (!--header->parent->count) {

		WARN_ON(1);

		kfree_rcu(header->parent, rcu);

	}

	if (!--header->count)

		kfree_rcu(header, rcu);

	spin_unlock(&sysctl_lock);

	spin_unlock(&sysctl_lock);

}

}

EXPORT_SYMBOL(unregister_sysctl_table);

EXPORT_SYMBOL(unregister_sysctl_table);

include/linux/sysctl.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -1032,6 +1032,7 @@ struct ctl_table_header 
			struct list_head ctl_entry;

			struct list_head ctl_entry;

			int used;

			int used;

			int count;

			int count;

			int nreg;

		};

		};

		struct rcu_head rcu;

		struct rcu_head rcu;

	};

	};