NAME

       ioctl_xfs_getresblks - query and set XFS free space reservation information

SYNOPSIS

       #include <xfs/xfs_fs.h>

       int ioctl(int fd, XFS_IOC_GET_RESBLKS, struct xfs_fsop_resblks *arg);
       int ioctl(int fd, XFS_IOC_SET_RESBLKS, struct xfs_fsop_resblks *arg);

DESCRIPTION

       Query  or  set  the  free space reservation information.  These blocks are reserved by the
       filesystem as a final attempt to prevent metadata  update  failures  due  to  insufficient
       space.   Only  the  system  administrator  can  use  these  ioctls, because overriding the
       defaults is extremely dangerous.

       This functionality is intended only for use by XFS filesystem developers.

       The reservation information is conveyed in a structure of the following form:

           struct xfs_fsop_resblks {
                __u64  resblks;
                __u64  resblks_avail;
           };

       resblks is the number of blocks that the  filesystem  will  try  to  maintain  to  prevent
       critical out of space situations.

       resblks_avail is the number of reserved blocks remaining.

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.

       EPERM  Caller does not have permission to call this ioctl.

CONFORMING TO

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

SEE ALSO

       ioctl(2)