Manipulate disk quotas
#include <sys/quota.h> #include <xfs/xqm.h> int quotactl(int cmd, const char *special, int id, caddr_t addr);
The quota system can be used to set per-user and per-group limits on the amount of disk space used on a filesystem. For each user and/or group, a soft limit and a hard limit can be set for each filesystem. The hard limit can't be exceeded. The soft limit can be exceeded, but warnings will ensue. Moreover, the user can't exceed the soft limit for more than one week (by default) at a time; after this time, the soft limit counts as a hard limit.
The quotactl() call manipulates disk quotas. The cmd argument indicates a command to be applied to the user or group ID specified in id. To initialize the cmd argument, use the QCMD(subcmd, type) macro. The type value is either USRQUOTA, for user quotas, or GRPQUOTA, for group quotas. The subcmd value is described below.
The special argument is a pointer to a null-terminated string containing the pathname of the (mounted) block special device for the filesystem being manipulated.
The addr argument is the address of an optional, command-specific, data structure that is copied in or out of the system. The interpretation of addr is given with each command below.
The subcmd value is one of the following:
Q_QUOTAON
Turn on quotas for a filesystem. The id argument is the identification number of the quota format to be used. Currently, there are three supported quota formats:
QFMT_VFS_OLD
The original quota format.
QFMT_VFS_V0
The standard VFS v0 quota format, which can handle 32-bit UIDs and GIDs and quota limits up to 2^42 bytes and 2^32 inodes.
QFMT_VFS_V1
A quota format that can handle 32-bit UIDs and GIDs and quota limits of 2^64 bytes and 2^64 inodes.
The addr argument points to the pathname of a file containing the quotas for the filesystem. The quota file must exist; it is normally created with the quotacheck(8) program. This operation requires privilege (CAP_SYS_ADMIN).
Q_QUOTAOFF
Turn off quotas for a filesystem. The addr and id arguments are ignored. This operation requires privilege (CAP_SYS_ADMIN).
Q_GETQUOTA
Get disk quota limits and current usage for user or group id. The addr argument is a pointer to a dqblk structure defined in <sys/quota.h> as follows:
/* uint64_t is an unsigned 64-bit integer;
uint32_t is an unsigned 32-bit integer */
struct dqblk { /* Definition since Linux 2.4.22 */
uint64_t dqb_bhardlimit; /* absolute limit on disk
quota blocks alloc */
uint64_t dqb_bsoftlimit; /* preferred limit on
disk quota blocks */
uint64_t dqb_curspace; /* current quota block
count */
uint64_t dqb_ihardlimit; /* maximum number of
allocated inodes */
uint64_t dqb_isoftlimit; /* preferred inode limit */
uint64_t dqb_curinodes; /* current number of
allocated inodes */
uint64_t dqb_btime; /* time limit for excessive
disk use */
uint64_t dqb_itime; /* time limit for excessive
files */
uint32_t dqb_valid; /* bit mask of QIF_*
constants */
};
/* Flags in dqb_valid that indicate which fields in
dqblk structure are valid. */
#define QIF_BLIMITS 1
#define QIF_SPACE 2
#define QIF_ILIMITS 4
#define QIF_INODES 8
#define QIF_BTIME 16
#define QIF_ITIME 32
#define QIF_LIMITS (QIF_BLIMITS | QIF_ILIMITS)
#define QIF_USAGE (QIF_SPACE | QIF_INODES)
#define QIF_TIMES (QIF_BTIME | QIF_ITIME)
#define QIF_ALL (QIF_LIMITS | QIF_USAGE | QIF_TIMES)
The dqb_valid field is a bit mask that is set to indicate the entries in the dqblk structure that are valid. Currently, the kernel fills in all entries of the dqblk structure and marks them as valid in the dqb_valid field. Unprivileged users may retrieve only their own quotas; a privileged user (CAP_SYS_ADMIN) can retrieve the quotas of any user.
Q_SETQUOTA
Set quota information for user or group id, using the information supplied in the dqblk structure pointed to by addr. The dqb_valid field of the dqblk structure indicates which entries in the structure have been set by the caller. This operation supersedes the Q_SETQLIM and Q_SETUSE operations in the previous quota interfaces. This operation requires privilege (CAP_SYS_ADMIN).
Q_GETINFO
Get information (like grace times) about quotafile. The addr argument should be a pointer to a dqinfo structure. This structure is defined in <sys/quota.h> as follows:
/* uint64_t is an unsigned 64-bit integer;
uint32_t is an unsigned 32-bit integer */
struct dqinfo { /* Defined since kernel 2.4.22 */
uint64_t dqi_bgrace; /* Time before block soft limit
becomes hard limit */
uint64_t dqi_igrace; /* Time before inode soft limit
becomes hard limit */
uint32_t dqi_flags; /* Flags for quotafile
(DQF_*) */
uint32_t dqi_valid;
};
/* Bits for dqi_flags */
/* Quota format QFMT_VFS_OLD */
#define V1_DQF_RSQUASH 1 /* Root squash enabled */
/* Other quota formats have no dqi_flags bits defined */
/* Flags in dqi_valid that indicate which fields in
dqinfo structure are valid. */
# define IIF_BGRACE 1
# define IIF_IGRACE 2
# define IIF_FLAGS 4
# define IIF_ALL (IIF_BGRACE | IIF_IGRACE | IIF_FLAGS)
The dqi_valid field in the dqinfo structure indicates the entries in the structure that are valid. Currently, the kernel fills in all entries of the dqinfo structure and marks them all as valid in the dqi_valid field. The id argument is ignored.
Q_SETINFO
Set information about quotafile. The addr argument should be a pointer to a dqinfo structure. The dqi_valid field of the dqinfo structure indicates the entries in the structure that have been set by the caller. This operation supersedes the Q_SETGRACE and Q_SETFLAGS operations in the previous quota interfaces. The id argument is ignored. This operation requires privilege (CAP_SYS_ADMIN).
Q_GETFMT
Get quota format used on the specified filesystem. The addr argument should be a pointer to a 4-byte buffer where the format number will be stored.
Q_SYNC
Update the on-disk copy of quota usages for a filesystem. If special is NULL, then all filesystems with active quotas are sync'ed. The addr and id arguments are ignored.
Q_GETSTATS
Get statistics and other generic information about the quota subsystem. The addr argument should be a pointer to a dqstats structure in which data should be stored. This structure is defined in <sys/quota.h>. The special and id arguments are ignored. This operation is obsolete and not supported by recent kernels. Files in /proc/sys/fs/quota/ carry the information instead.
For XFS filesystems making use of the XFS Quota Manager (XQM), the above commands are bypassed and the following commands are used:
Q_XQUOTAON
Turn on quotas for an XFS filesystem. XFS provides the ability to turn on/off quota limit enforcement with quota accounting. Therefore, XFS expects addr to be a pointer to an unsigned int that contains either the flags XFS_QUOTA_UDQ_ACCT and/or XFS_QUOTA_UDQ_ENFD (for user quota), or XFS_QUOTA_GDQ_ACCT and/or XFS_QUOTA_GDQ_ENFD (for group quota), as defined in <xfs/xqm.h>. This operation requires privilege (CAP_SYS_ADMIN).
Q_XQUOTAOFF
Turn off quotas for an XFS filesystem. As with Q_QUOTAON, XFS filesystems expect a pointer to an unsigned int that specifies whether quota accounting and/or limit enforcement need to be turned off. This operation requires privilege (CAP_SYS_ADMIN).
Q_XGETQUOTA
Get disk quota limits and current usage for user id. The addr argument is a pointer to an fs_disk_quota structure (defined in <xfs/xqm.h>). Unprivileged users may retrieve only their own quotas; a privileged user (CAP_SYS_ADMIN) may retrieve the quotas of any user.
Q_XSETQLIM
Set disk quota limits for user id. The addr argument is a pointer to an fs_disk_quota structure (defined in <xfs/xqm.h>). This operation requires privilege (CAP_SYS_ADMIN).
Q_XGETQSTAT
Returns an fs_quota_stat structure containing XFS filesystem-specific quota information. This is useful for finding out how much space is used to store quota information, and also to get quotaon/off status of a given local XFS filesystem.
Q_XQUOTARM
Free the disk space taken by disk quotas. Quotas must have already been turned off.
There is no command equivalent to Q_SYNC for XFS since sync(1) writes quota information to disk (in addition to the other filesystem metadata that it writes out).
On success, quotactl() returns 0; on error -1 is returned, and errno is set to indicate the error.
EFAULT
addr or special is invalid.
EINVAL
cmd or type is invalid.
ENOENT
The file specified by special or addr does not exist.
ENOSYS
The kernel has not been compiled with the CONFIG_QUOTA option.
ENOTBLK
special is not a block device.
EPERM
The caller lacked the required privilege (CAP_SYS_ADMIN) for the specified operation.
ESRCH
No disk quota is found for the indicated user. Quotas have not been turned on for this filesystem.
If cmd is Q_SETQUOTA, quotactl() may also set errno to:
ERANGE
Specified limits are out of range allowed by quota format.
If cmd is Q_QUOTAON, quotactl() may also set errno to:
EACCES
The quota file pointed to by addr exists, but is not a regular file; or, the quota file pointed to by addr exists, but is not on the filesystem pointed to by special.
EBUSY
Q_QUOTAON attempted, but another Q_QUOTAON had already been performed.
EINVAL
The quota file is corrupted.
ESRCH
Specified quota format was not found.
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