xfs: get rid of indirections in the quotaops implementation

Currently we call from the nicely abstracted linux quotaops into a ugly
multiplexer just to split the calls out at the same boundary again.
Rewrite the quota ops handling to remove that obfucation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Christoph Hellwig 2009-02-09 08:47:34 +01:00 committed by Christoph Hellwig
parent c9a192dcf9
commit fcafb71b57
12 changed files with 181 additions and 262 deletions

View file

@ -33,6 +33,7 @@ xfs-$(CONFIG_XFS_QUOTA) += $(addprefix quota/, \
xfs_qm_syscalls.o \
xfs_qm_bhv.o \
xfs_qm.o)
xfs-$(CONFIG_XFS_QUOTA) += linux-2.6/xfs_quotaops.o
ifeq ($(CONFIG_XFS_QUOTA),y)
xfs-$(CONFIG_PROC_FS) += quota/xfs_qm_stats.o

View file

@ -147,17 +147,6 @@
#define SYNCHRONIZE() barrier()
#define __return_address __builtin_return_address(0)
/*
* IRIX (BSD) quotactl makes use of separate commands for user/group,
* whereas on Linux the syscall encodes this information into the cmd
* field (see the QCMD macro in quota.h). These macros help keep the
* code portable - they are not visible from the syscall interface.
*/
#define Q_XSETGQLIM XQM_CMD(8) /* set groups disk limits */
#define Q_XGETGQUOTA XQM_CMD(9) /* get groups disk limits */
#define Q_XSETPQLIM XQM_CMD(10) /* set projects disk limits */
#define Q_XGETPQUOTA XQM_CMD(11) /* get projects disk limits */
#define dfltprid 0
#define MAXPATHLEN 1024

View file

@ -0,0 +1,157 @@
/*
* Copyright (c) 2008, Christoph Hellwig
* All Rights Reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it would be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "xfs.h"
#include "xfs_dmapi.h"
#include "xfs_sb.h"
#include "xfs_inum.h"
#include "xfs_ag.h"
#include "xfs_mount.h"
#include "xfs_quota.h"
#include "xfs_log.h"
#include "xfs_trans.h"
#include "xfs_bmap_btree.h"
#include "xfs_inode.h"
#include "quota/xfs_qm.h"
#include <linux/quota.h>
STATIC int
xfs_quota_type(int type)
{
switch (type) {
case USRQUOTA:
return XFS_DQ_USER;
case GRPQUOTA:
return XFS_DQ_GROUP;
default:
return XFS_DQ_PROJ;
}
}
STATIC int
xfs_fs_quota_sync(
struct super_block *sb,
int type)
{
struct xfs_mount *mp = XFS_M(sb);
if (!XFS_IS_QUOTA_RUNNING(mp))
return -ENOSYS;
return -xfs_sync_inodes(mp, SYNC_DELWRI);
}
STATIC int
xfs_fs_get_xstate(
struct super_block *sb,
struct fs_quota_stat *fqs)
{
struct xfs_mount *mp = XFS_M(sb);
if (!XFS_IS_QUOTA_RUNNING(mp))
return -ENOSYS;
return -xfs_qm_scall_getqstat(mp, fqs);
}
STATIC int
xfs_fs_set_xstate(
struct super_block *sb,
unsigned int uflags,
int op)
{
struct xfs_mount *mp = XFS_M(sb);
unsigned int flags = 0;
if (sb->s_flags & MS_RDONLY)
return -EROFS;
if (!XFS_IS_QUOTA_RUNNING(mp))
return -ENOSYS;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (uflags & XFS_QUOTA_UDQ_ACCT)
flags |= XFS_UQUOTA_ACCT;
if (uflags & XFS_QUOTA_PDQ_ACCT)
flags |= XFS_PQUOTA_ACCT;
if (uflags & XFS_QUOTA_GDQ_ACCT)
flags |= XFS_GQUOTA_ACCT;
if (uflags & XFS_QUOTA_UDQ_ENFD)
flags |= XFS_UQUOTA_ENFD;
if (uflags & (XFS_QUOTA_PDQ_ENFD|XFS_QUOTA_GDQ_ENFD))
flags |= XFS_OQUOTA_ENFD;
switch (op) {
case Q_XQUOTAON:
return -xfs_qm_scall_quotaon(mp, flags);
case Q_XQUOTAOFF:
if (!XFS_IS_QUOTA_ON(mp))
return -EINVAL;
return -xfs_qm_scall_quotaoff(mp, flags);
case Q_XQUOTARM:
if (XFS_IS_QUOTA_ON(mp))
return -EINVAL;
return -xfs_qm_scall_trunc_qfiles(mp, flags);
}
return -EINVAL;
}
STATIC int
xfs_fs_get_xquota(
struct super_block *sb,
int type,
qid_t id,
struct fs_disk_quota *fdq)
{
struct xfs_mount *mp = XFS_M(sb);
if (!XFS_IS_QUOTA_RUNNING(mp))
return -ENOSYS;
if (!XFS_IS_QUOTA_ON(mp))
return -ESRCH;
return -xfs_qm_scall_getquota(mp, id, xfs_quota_type(type), fdq);
}
STATIC int
xfs_fs_set_xquota(
struct super_block *sb,
int type,
qid_t id,
struct fs_disk_quota *fdq)
{
struct xfs_mount *mp = XFS_M(sb);
if (sb->s_flags & MS_RDONLY)
return -EROFS;
if (!XFS_IS_QUOTA_RUNNING(mp))
return -ENOSYS;
if (!XFS_IS_QUOTA_ON(mp))
return -ESRCH;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
return -xfs_qm_scall_setqlim(mp, id, xfs_quota_type(type), fdq);
}
struct quotactl_ops xfs_quotactl_operations = {
.quota_sync = xfs_fs_quota_sync,
.get_xstate = xfs_fs_get_xstate,
.set_xstate = xfs_fs_set_xstate,
.get_xquota = xfs_fs_get_xquota,
.set_xquota = xfs_fs_set_xquota,
};

View file

@ -68,7 +68,6 @@
#include <linux/freezer.h>
#include <linux/parser.h>
static struct quotactl_ops xfs_quotactl_operations;
static struct super_operations xfs_super_operations;
static kmem_zone_t *xfs_ioend_zone;
mempool_t *xfs_ioend_pool;
@ -1333,57 +1332,6 @@ xfs_fs_show_options(
return -xfs_showargs(XFS_M(mnt->mnt_sb), m);
}
STATIC int
xfs_fs_quotasync(
struct super_block *sb,
int type)
{
return -XFS_QM_QUOTACTL(XFS_M(sb), Q_XQUOTASYNC, 0, NULL);
}
STATIC int
xfs_fs_getxstate(
struct super_block *sb,
struct fs_quota_stat *fqs)
{
return -XFS_QM_QUOTACTL(XFS_M(sb), Q_XGETQSTAT, 0, (caddr_t)fqs);
}
STATIC int
xfs_fs_setxstate(
struct super_block *sb,
unsigned int flags,
int op)
{
return -XFS_QM_QUOTACTL(XFS_M(sb), op, 0, (caddr_t)&flags);
}
STATIC int
xfs_fs_getxquota(
struct super_block *sb,
int type,
qid_t id,
struct fs_disk_quota *fdq)
{
return -XFS_QM_QUOTACTL(XFS_M(sb),
(type == USRQUOTA) ? Q_XGETQUOTA :
((type == GRPQUOTA) ? Q_XGETGQUOTA :
Q_XGETPQUOTA), id, (caddr_t)fdq);
}
STATIC int
xfs_fs_setxquota(
struct super_block *sb,
int type,
qid_t id,
struct fs_disk_quota *fdq)
{
return -XFS_QM_QUOTACTL(XFS_M(sb),
(type == USRQUOTA) ? Q_XSETQLIM :
((type == GRPQUOTA) ? Q_XSETGQLIM :
Q_XSETPQLIM), id, (caddr_t)fdq);
}
/*
* This function fills in xfs_mount_t fields based on mount args.
* Note: the superblock _has_ now been read in.
@ -1466,7 +1414,9 @@ xfs_fs_fill_super(
sb_min_blocksize(sb, BBSIZE);
sb->s_xattr = xfs_xattr_handlers;
sb->s_export_op = &xfs_export_operations;
#ifdef CONFIG_XFS_QUOTA
sb->s_qcop = &xfs_quotactl_operations;
#endif
sb->s_op = &xfs_super_operations;
error = xfs_dmops_get(mp);
@ -1609,14 +1559,6 @@ static struct super_operations xfs_super_operations = {
.show_options = xfs_fs_show_options,
};
static struct quotactl_ops xfs_quotactl_operations = {
.quota_sync = xfs_fs_quotasync,
.get_xstate = xfs_fs_getxstate,
.set_xstate = xfs_fs_setxstate,
.get_xquota = xfs_fs_getxquota,
.set_xquota = xfs_fs_setxquota,
};
static struct file_system_type xfs_fs_type = {
.owner = THIS_MODULE,
.name = "xfs",

View file

@ -93,6 +93,7 @@ extern void xfs_blkdev_issue_flush(struct xfs_buftarg *);
extern const struct export_operations xfs_export_operations;
extern struct xattr_handler *xfs_xattr_handlers[];
extern struct quotactl_ops xfs_quotactl_operations;
#define XFS_M(sb) ((struct xfs_mount *)((sb)->s_fs_info))

View file

@ -19,6 +19,7 @@
#define XFS_SYNC_H 1
struct xfs_mount;
struct xfs_perag;
typedef struct bhv_vfs_sync_work {
struct list_head w_list;

View file

@ -173,6 +173,16 @@ extern void xfs_qm_dqdetach(xfs_inode_t *);
extern int xfs_qm_dqpurge_all(xfs_mount_t *, uint);
extern void xfs_qm_dqrele_all_inodes(xfs_mount_t *, uint);
/* quota ops */
extern int xfs_qm_scall_trunc_qfiles(xfs_mount_t *, uint);
extern int xfs_qm_scall_getquota(xfs_mount_t *, xfs_dqid_t, uint,
fs_disk_quota_t *);
extern int xfs_qm_scall_setqlim(xfs_mount_t *, xfs_dqid_t, uint,
fs_disk_quota_t *);
extern int xfs_qm_scall_getqstat(xfs_mount_t *, fs_quota_stat_t *);
extern int xfs_qm_scall_quotaon(xfs_mount_t *, uint);
extern int xfs_qm_scall_quotaoff(xfs_mount_t *, uint);
/* vop stuff */
extern int xfs_qm_vop_dqalloc(xfs_mount_t *, xfs_inode_t *,
uid_t, gid_t, prid_t, uint,
@ -190,10 +200,6 @@ extern int xfs_qm_vop_chown_reserve(xfs_trans_t *, xfs_inode_t *,
extern void xfs_qm_freelist_append(xfs_frlist_t *, xfs_dquot_t *);
extern void xfs_qm_freelist_unlink(xfs_dquot_t *);
/* system call interface */
extern int xfs_qm_quotactl(struct xfs_mount *, int, int,
xfs_caddr_t);
#ifdef DEBUG
extern int xfs_qm_internalqcheck(xfs_mount_t *);
#else

View file

@ -235,7 +235,6 @@ struct xfs_qmops xfs_qmcore_xfs = {
.xfs_dqvopchownresv = xfs_qm_vop_chown_reserve,
.xfs_dqstatvfs = xfs_qm_statvfs,
.xfs_dqsync = xfs_qm_sync,
.xfs_quotactl = xfs_qm_quotactl,
.xfs_dqtrxops = &xfs_trans_dquot_ops,
};
EXPORT_SYMBOL(xfs_qmcore_xfs);

View file

@ -57,134 +57,15 @@
# define qdprintk(s, args...) do { } while (0)
#endif
STATIC int xfs_qm_scall_trunc_qfiles(xfs_mount_t *, uint);
STATIC int xfs_qm_scall_getquota(xfs_mount_t *, xfs_dqid_t, uint,
fs_disk_quota_t *);
STATIC int xfs_qm_scall_getqstat(xfs_mount_t *, fs_quota_stat_t *);
STATIC int xfs_qm_scall_setqlim(xfs_mount_t *, xfs_dqid_t, uint,
fs_disk_quota_t *);
STATIC int xfs_qm_scall_quotaon(xfs_mount_t *, uint);
STATIC int xfs_qm_scall_quotaoff(xfs_mount_t *, uint, boolean_t);
STATIC int xfs_qm_log_quotaoff(xfs_mount_t *, xfs_qoff_logitem_t **, uint);
STATIC int xfs_qm_log_quotaoff_end(xfs_mount_t *, xfs_qoff_logitem_t *,
uint);
STATIC uint xfs_qm_import_flags(uint);
STATIC uint xfs_qm_export_flags(uint);
STATIC uint xfs_qm_import_qtype_flags(uint);
STATIC uint xfs_qm_export_qtype_flags(uint);
STATIC void xfs_qm_export_dquot(xfs_mount_t *, xfs_disk_dquot_t *,
fs_disk_quota_t *);
/*
* The main distribution switch of all XFS quotactl system calls.
*/
int
xfs_qm_quotactl(
xfs_mount_t *mp,
int cmd,
int id,
xfs_caddr_t addr)
{
int error;
ASSERT(addr != NULL || cmd == Q_XQUOTASYNC);
/*
* The following commands are valid even when quotaoff.
*/
switch (cmd) {
case Q_XQUOTARM:
/*
* Truncate quota files. quota must be off.
*/
if (XFS_IS_QUOTA_ON(mp))
return XFS_ERROR(EINVAL);
if (mp->m_flags & XFS_MOUNT_RDONLY)
return XFS_ERROR(EROFS);
return (xfs_qm_scall_trunc_qfiles(mp,
xfs_qm_import_qtype_flags(*(uint *)addr)));
case Q_XGETQSTAT:
/*
* Get quota status information.
*/
return (xfs_qm_scall_getqstat(mp, (fs_quota_stat_t *)addr));
case Q_XQUOTAON:
/*
* QUOTAON - enabling quota enforcement.
* Quota accounting must be turned on at mount time.
*/
if (mp->m_flags & XFS_MOUNT_RDONLY)
return XFS_ERROR(EROFS);
return (xfs_qm_scall_quotaon(mp,
xfs_qm_import_flags(*(uint *)addr)));
case Q_XQUOTAOFF:
if (mp->m_flags & XFS_MOUNT_RDONLY)
return XFS_ERROR(EROFS);
break;
case Q_XQUOTASYNC:
return xfs_sync_inodes(mp, SYNC_DELWRI);
default:
break;
}
if (! XFS_IS_QUOTA_ON(mp))
return XFS_ERROR(ESRCH);
switch (cmd) {
case Q_XQUOTAOFF:
if (mp->m_flags & XFS_MOUNT_RDONLY)
return XFS_ERROR(EROFS);
error = xfs_qm_scall_quotaoff(mp,
xfs_qm_import_flags(*(uint *)addr),
B_FALSE);
break;
case Q_XGETQUOTA:
error = xfs_qm_scall_getquota(mp, (xfs_dqid_t)id, XFS_DQ_USER,
(fs_disk_quota_t *)addr);
break;
case Q_XGETGQUOTA:
error = xfs_qm_scall_getquota(mp, (xfs_dqid_t)id, XFS_DQ_GROUP,
(fs_disk_quota_t *)addr);
break;
case Q_XGETPQUOTA:
error = xfs_qm_scall_getquota(mp, (xfs_dqid_t)id, XFS_DQ_PROJ,
(fs_disk_quota_t *)addr);
break;
case Q_XSETQLIM:
if (mp->m_flags & XFS_MOUNT_RDONLY)
return XFS_ERROR(EROFS);
error = xfs_qm_scall_setqlim(mp, (xfs_dqid_t)id, XFS_DQ_USER,
(fs_disk_quota_t *)addr);
break;
case Q_XSETGQLIM:
if (mp->m_flags & XFS_MOUNT_RDONLY)
return XFS_ERROR(EROFS);
error = xfs_qm_scall_setqlim(mp, (xfs_dqid_t)id, XFS_DQ_GROUP,
(fs_disk_quota_t *)addr);
break;
case Q_XSETPQLIM:
if (mp->m_flags & XFS_MOUNT_RDONLY)
return XFS_ERROR(EROFS);
error = xfs_qm_scall_setqlim(mp, (xfs_dqid_t)id, XFS_DQ_PROJ,
(fs_disk_quota_t *)addr);
break;
default:
error = XFS_ERROR(EINVAL);
break;
}
return (error);
}
/*
* Turn off quota accounting and/or enforcement for all udquots and/or
* gdquots. Called only at unmount time.
@ -193,11 +74,10 @@ xfs_qm_quotactl(
* incore, and modifies the ondisk dquot directly. Therefore, for example,
* it is an error to call this twice, without purging the cache.
*/
STATIC int
int
xfs_qm_scall_quotaoff(
xfs_mount_t *mp,
uint flags,
boolean_t force)
uint flags)
{
uint dqtype;
int error;
@ -205,8 +85,6 @@ xfs_qm_scall_quotaoff(
xfs_qoff_logitem_t *qoffstart;
int nculprits;
if (!force && !capable(CAP_SYS_ADMIN))
return XFS_ERROR(EPERM);
/*
* No file system can have quotas enabled on disk but not in core.
* Note that quota utilities (like quotaoff) _expect_
@ -375,7 +253,7 @@ out_error:
return (error);
}
STATIC int
int
xfs_qm_scall_trunc_qfiles(
xfs_mount_t *mp,
uint flags)
@ -383,8 +261,6 @@ xfs_qm_scall_trunc_qfiles(
int error = 0, error2 = 0;
xfs_inode_t *qip;
if (!capable(CAP_SYS_ADMIN))
return XFS_ERROR(EPERM);
if (!xfs_sb_version_hasquota(&mp->m_sb) || flags == 0) {
qdprintk("qtrunc flags=%x m_qflags=%x\n", flags, mp->m_qflags);
return XFS_ERROR(EINVAL);
@ -416,7 +292,7 @@ xfs_qm_scall_trunc_qfiles(
* effect immediately.
* (Switching on quota accounting must be done at mount time.)
*/
STATIC int
int
xfs_qm_scall_quotaon(
xfs_mount_t *mp,
uint flags)
@ -426,9 +302,6 @@ xfs_qm_scall_quotaon(
uint accflags;
__int64_t sbflags;
if (!capable(CAP_SYS_ADMIN))
return XFS_ERROR(EPERM);
flags &= (XFS_ALL_QUOTA_ACCT | XFS_ALL_QUOTA_ENFD);
/*
* Switching on quota accounting must be done at mount time.
@ -517,7 +390,7 @@ xfs_qm_scall_quotaon(
/*
* Return quota status information, such as uquota-off, enforcements, etc.
*/
STATIC int
int
xfs_qm_scall_getqstat(
xfs_mount_t *mp,
fs_quota_stat_t *out)
@ -582,7 +455,7 @@ xfs_qm_scall_getqstat(
/*
* Adjust quota limits, and start/stop timers accordingly.
*/
STATIC int
int
xfs_qm_scall_setqlim(
xfs_mount_t *mp,
xfs_dqid_t id,
@ -595,9 +468,6 @@ xfs_qm_scall_setqlim(
int error;
xfs_qcnt_t hard, soft;
if (!capable(CAP_SYS_ADMIN))
return XFS_ERROR(EPERM);
if ((newlim->d_fieldmask &
(FS_DQ_LIMIT_MASK|FS_DQ_TIMER_MASK|FS_DQ_WARNS_MASK)) == 0)
return (0);
@ -742,7 +612,7 @@ xfs_qm_scall_setqlim(
return error;
}
STATIC int
int
xfs_qm_scall_getquota(
xfs_mount_t *mp,
xfs_dqid_t id,
@ -934,30 +804,6 @@ xfs_qm_export_dquot(
#endif
}
STATIC uint
xfs_qm_import_qtype_flags(
uint uflags)
{
uint oflags = 0;
/*
* Can't be more than one, or none.
*/
if (((uflags & (XFS_GROUP_QUOTA | XFS_USER_QUOTA)) ==
(XFS_GROUP_QUOTA | XFS_USER_QUOTA)) ||
((uflags & (XFS_GROUP_QUOTA | XFS_PROJ_QUOTA)) ==
(XFS_GROUP_QUOTA | XFS_PROJ_QUOTA)) ||
((uflags & (XFS_USER_QUOTA | XFS_PROJ_QUOTA)) ==
(XFS_USER_QUOTA | XFS_PROJ_QUOTA)) ||
((uflags & (XFS_GROUP_QUOTA|XFS_USER_QUOTA|XFS_PROJ_QUOTA)) == 0))
return (0);
oflags |= (uflags & XFS_USER_QUOTA) ? XFS_DQ_USER : 0;
oflags |= (uflags & XFS_PROJ_QUOTA) ? XFS_DQ_PROJ : 0;
oflags |= (uflags & XFS_GROUP_QUOTA) ? XFS_DQ_GROUP: 0;
return oflags;
}
STATIC uint
xfs_qm_export_qtype_flags(
uint flags)
@ -978,26 +824,6 @@ xfs_qm_export_qtype_flags(
XFS_PROJ_QUOTA : XFS_GROUP_QUOTA;
}
STATIC uint
xfs_qm_import_flags(
uint uflags)
{
uint flags = 0;
if (uflags & XFS_QUOTA_UDQ_ACCT)
flags |= XFS_UQUOTA_ACCT;
if (uflags & XFS_QUOTA_PDQ_ACCT)
flags |= XFS_PQUOTA_ACCT;
if (uflags & XFS_QUOTA_GDQ_ACCT)
flags |= XFS_GQUOTA_ACCT;
if (uflags & XFS_QUOTA_UDQ_ENFD)
flags |= XFS_UQUOTA_ENFD;
if (uflags & (XFS_QUOTA_PDQ_ENFD|XFS_QUOTA_GDQ_ENFD))
flags |= XFS_OQUOTA_ENFD;
return (flags);
}
STATIC uint
xfs_qm_export_flags(
uint flags)

View file

@ -136,7 +136,6 @@ typedef int (*xfs_dqvopchownresv_t)(struct xfs_trans *, struct xfs_inode *,
struct xfs_dquot *, struct xfs_dquot *, uint);
typedef void (*xfs_dqstatvfs_t)(struct xfs_inode *, struct kstatfs *);
typedef int (*xfs_dqsync_t)(struct xfs_mount *, int flags);
typedef int (*xfs_quotactl_t)(struct xfs_mount *, int, int, xfs_caddr_t);
typedef struct xfs_qmops {
xfs_qminit_t xfs_qminit;
@ -154,7 +153,6 @@ typedef struct xfs_qmops {
xfs_dqvopchownresv_t xfs_dqvopchownresv;
xfs_dqstatvfs_t xfs_dqstatvfs;
xfs_dqsync_t xfs_dqsync;
xfs_quotactl_t xfs_quotactl;
struct xfs_dqtrxops *xfs_dqtrxops;
} xfs_qmops_t;
@ -188,8 +186,6 @@ typedef struct xfs_qmops {
(*(ip)->i_mount->m_qm_ops->xfs_dqstatvfs)(ip, statp)
#define XFS_QM_DQSYNC(mp, flags) \
(*(mp)->m_qm_ops->xfs_dqsync)(mp, flags)
#define XFS_QM_QUOTACTL(mp, cmd, id, addr) \
(*(mp)->m_qm_ops->xfs_quotactl)(mp, cmd, id, addr)
#ifdef HAVE_PERCPU_SB

View file

@ -126,7 +126,6 @@ static struct xfs_qmops xfs_qmcore_stub = {
.xfs_dqvopchownresv = (xfs_dqvopchownresv_t) fs_noerr,
.xfs_dqstatvfs = (xfs_dqstatvfs_t) fs_noval,
.xfs_dqsync = (xfs_dqsync_t) fs_noerr,
.xfs_quotactl = (xfs_quotactl_t) fs_nosys,
};
int

View file

@ -18,6 +18,8 @@
#ifndef __XFS_QUOTA_H__
#define __XFS_QUOTA_H__
struct xfs_trans;
/*
* The ondisk form of a dquot structure.
*/