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.