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)