IOCTL-XFS-AG-GEOMETRY(2)

NAME
ioctl_xfs_ag_geometry - query XFS allocation group geometry information

SYNOPSIS
#include <xfs/xfs_fs.h>

int ioctl(int fd, XFS_IOC_AG_GEOMETRY, struct xfs_ag_geometry *arg);

DESCRIPTION
This XFS ioctl retrieves the geometry information for a given allocation group. The geometry information is conveyed in a structure of the following form:

struct xfs_ag_geometry {
	uint32_t  ag_number;
	uint32_t  ag_length;
	uint32_t  ag_freeblks;
	uint32_t  ag_icount;
	uint32_t  ag_ifree;
	uint32_t  ag_sick;
	uint32_t  ag_checked;
	uint32_t  ag_flags;
	uint64_t  ag_reserved[12];
};

ag_number
    The caller must set this field to the index of the allocation group that the caller wishes to learn about.

ag_length
    The length of the allocation group is returned in this field, in units of filesystem blocks.

ag_freeblks
    The number of free blocks in the allocation group is returned in this field, in units of filesystem blocks.

ag_icount
    The number of inode records allocated in this allocation group is returned in this field.

ag_ifree
    The number of unused inode records (of the space allocated) in this allocation group is returned in this field.

ag_flags
    The caller can set this field to change the operational behavior of the ioctl. Currently no flags are defined, so this field must be zero.

ag_reserved
    All reserved fields will be set to zero on return.

The fields ag_sick and ag_checked indicate the relative health of various allocation group metadata:

•   If a given sick flag is set in ag_sick, then that piece of metadata has been observed to be damaged. The same bit will be set in ag_checked.

•   If a given sick flag is set in ag_checked and is not set in ag_sick, then that piece of metadata has been checked and is not faulty.

•   If a given sick flag is not set in ag_checked, then no conclusion can be made.

The following flags apply to these fields:

    XFS_AG_GEOM_SICK_SB
        Allocation group superblock.

    XFS_AG_GEOM_SICK_AGF
        Free space header.

    XFS_AG_GEOM_SICK_AGFL
        Free space reserve list.

    XFS_AG_GEOM_SICK_AGI
        Inode header.

    XFS_AG_GEOM_SICK_BNOBT or XFS_AG_GEOM_SICK_CNTBT
        Free space btrees.

    XFS_AG_GEOM_SICK_INOBT or XFS_AG_GEOM_SICK_FINOBT
        Inode btrees.

    XFS_AG_GEOM_SICK_RMAPBT
        Reverse mapping btree.

    XFS_AG_GEOM_SICK_REFCNTBT
        Reference count btree.

RETURN VALUE
On error, -1 is returned, and errno is set to indicate the error.

ERRORS
Error codes can be one of, but are not limited to, the following:

EFSBADCRC
    Metadata checksum validation failed while performing the query.

EFSCORRUPTED
    Metadata corruption was encountered while performing the query.

EINVAL
    The specified allocation group number is not valid for this filesystem.

EIO An I/O error was encountered while performing the query.

CONFORMING TO
This API is specific to XFS filesystem on the Linux kernel.

SEE ALSO
ioctl(2)