Commit 4a7b29f6 authored by Thomas Weißschuh's avatar Thomas Weißschuh Committed by Joel Granados
Browse files

sysctl: move sysctl type to ctl_table_header 



Move the SYSCTL_TABLE_TYPE_{DEFAULT,PERMANENTLY_EMPTY} enums from
ctl_table to ctl_table_header.
Removing the mutable member is necessary to constify static instances
of struct ctl_table.

Move the initialization of the sysctl_mount_point type into
init_header() where all the other header fields are also initialized.

As a side-effect the memory usage of the sysctl core is reduced.
Each ctl_table_header instance can manage multiple ctl_table instances
and is only allocated when the table is actually registered.
This saves 8 bytes of memory per ctl_table on 64bit, 4 due to the enum
field itself and 4 due to padding.

Signed-off-by: default avatarThomas Weißschuh <linux@weissschuh.net>
Signed-off-by: default avatarJoel Granados <j.granados@samsung.com>
parent eb32d3ad

fs/proc/proc_sysctl.c

+6 −4
Original line number Diff line number Diff line
@@ -31,7 +31,7 @@ static const struct inode_operations proc_sys_dir_operations; 


/* Support for permanently empty directories */

static struct ctl_table sysctl_mount_point[] = {

	{.type = SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY }

	{ }

};



/**
@@ -49,11 +49,11 @@ struct ctl_table_header *register_sysctl_mount_point(const char *path) 
EXPORT_SYMBOL(register_sysctl_mount_point);



#define sysctl_is_perm_empty_ctl_header(hptr)		\

	(hptr->ctl_table[0].type == SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY)

	(hptr->type == SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY)

#define sysctl_set_perm_empty_ctl_header(hptr)		\

	(hptr->ctl_table[0].type = SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY)

	(hptr->type = SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY)

#define sysctl_clear_perm_empty_ctl_header(hptr)	\

	(hptr->ctl_table[0].type = SYSCTL_TABLE_TYPE_DEFAULT)

	(hptr->type = SYSCTL_TABLE_TYPE_DEFAULT)



void proc_sys_poll_notify(struct ctl_table_poll *poll)

{
@@ -208,6 +208,8 @@ static void init_header(struct ctl_table_header *head, 
			node++;

		}

	}

	if (table == sysctl_mount_point)

		sysctl_set_perm_empty_ctl_header(head);

}



static void erase_header(struct ctl_table_header *head)

include/linux/sysctl.h

+11 −11
Original line number Diff line number Diff line
@@ -137,17 +137,6 @@ struct ctl_table { 
	void *data;

	int maxlen;

	umode_t mode;

	/**

	 * enum type - Enumeration to differentiate between ctl target types

	 * @SYSCTL_TABLE_TYPE_DEFAULT: ctl target with no special considerations

	 * @SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY: Used to identify a permanently

	 *                                       empty directory target to serve

	 *                                       as mount point.

	 */

	enum {

		SYSCTL_TABLE_TYPE_DEFAULT,

		SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY

	} type;

	proc_handler *proc_handler;	/* Callback for text formatting */

	struct ctl_table_poll *poll;

	void *extra1;
@@ -188,6 +177,17 @@ struct ctl_table_header { 
	struct ctl_dir *parent;

	struct ctl_node *node;

	struct hlist_head inodes; /* head for proc_inode->sysctl_inodes */

	/**

	 * enum type - Enumeration to differentiate between ctl target types

	 * @SYSCTL_TABLE_TYPE_DEFAULT: ctl target with no special considerations

	 * @SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY: Used to identify a permanently

	 *                                       empty directory target to serve

	 *                                       as mount point.

	 */

	enum {

		SYSCTL_TABLE_TYPE_DEFAULT,

		SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY,

	} type;

};



struct ctl_dir {