Ubuntu Manpage: xfsctl - control XFS filesystems and individual files

Provided by: xfslibs-dev_5.3.0-1ubuntu2_amd64

NAME

       xfsctl - control XFS filesystems and individual files

C SYNOPSIS

       #include <xfs/xfs.h>

       int xfsctl(const char *path, int fd, int cmd, void *ptr);

       int platform_test_xfs_fd(int fd);
       int platform_test_xfs_path(const char *path);

DESCRIPTION

Some functionality specific to the XFS filesystem is accessible to applications through
platform-specific system call interfaces. These operations can be divided into two
sections - operations that operate on individual files, and operations that operate on the
filesystem itself. Care should be taken when issuing xfsctl() calls to ensure the target
path and file descriptor (both must be supplied) do indeed represent a file from an XFS
filesystem. The statfs(2) and fstatfs(2) system calls can be used to determine whether or
not an arbitrary path or file descriptor belong to an XFS filesystem. These are not
portable however, so the routines platform_test_xfs_fd() and platform_test_xfs_path()
provide a platform-independent mechanism.

File Operations
In order to effect an operation on an individual file, the pathname and descriptor
arguments passed to xfsctl identifies the file being operated on. The final argument
described below refers to the final argument of xfsctl. All of the data structures and
macros mentioned below are defined in the <xfs/xfs_fs.h> header file.

XFS_IOC_ALLOCSP
XFS_IOC_ALLOCSP64
XFS_IOC_FREESP
XFS_IOC_FREESP64
Alter storage space associated with a section of the ordinary file specified. The
section is specified by a variable of type xfs_flock64_t, pointed to by the final
argument. The data type xfs_flock64_t contains the following members: l_whence is
0, 1, or 2 to indicate that the relative offset l_start will be measured from the
start of the file, the current position, or the end of the file, respectively
(i.e., l_start is the offset from the position specified in l_whence). If the
offset specified is before the current end of file, any data previously written
into this section is no longer accessible. If the offset specified is beyond the
current end of file, the file is grown and filled with zeroes. The l_len field is
currently ignored, and should be set to zero.

XFS_IOC_ALLOCSP, XFS_IOC_ALLOCSP64, XFS_IOC_FREESP and XFS_IOC_FREESP64 operations
are all identical.

XFS_IOC_FSSETDM
Set the di_dmevmask and di_dmstate fields in an XFS on-disk inode. The only
legitimate values for these fields are those previously returned in the bs_dmevmask
and bs_dmstate fields of the bulkstat structure. The data referred to by the final
argument is a struct fsdmidata. This structure's members are fsd_dmevmask and
fsd_dmstate. The di_dmevmask field is set to the value in fsd_dmevmask. The
di_dmstate field is set to the value in fsd_dmstate. This command is restricted to
root or to processes with device management capabilities. Its sole purpose is to
allow backup and restore programs to restore the aforementioned critical on-disk
inode fields.

XFS_IOC_DIOINFO
Get information required to perform direct I/O on the specified file descriptor.
Direct I/O is performed directly to and from a user's data buffer. Since the
kernel's buffer cache is no longer between the two, the user's data buffer must
conform to the same type of constraints as required for accessing a raw disk
partition. The final argument points to a variable of type struct dioattr, which
contains the following members: d_mem is the memory alignment requirement of the
user's data buffer. d_miniosz specifies block size, minimum I/O request size, and
I/O alignment. The size of all I/O requests must be a multiple of this amount and
the value of the seek pointer at the time of the I/O request must also be an
integer multiple of this amount. d_maxiosz is the maximum I/O request size which
can be performed on the file descriptor. If an I/O request does not meet these
constraints, the read(2) or write(2) will fail with EINVAL. All I/O requests are
kept consistent with any data brought into the cache with an access through a non-
direct I/O file descriptor.

XFS_IOC_FSGETXATTR
XFS_IOC_FSGETXATTRA
XFS_IOC_FSSETXATTR
See ioctl_xfs_fsgetxattr(2) for more information.

XFS_IOC_GETBMAP
XFS_IOC_GETBMAPA
XFS_IOC_GETBMAPX
See ioctl_getbmap(2) for more information.

XFS_IOC_RESVSP
XFS_IOC_RESVSP64
This command is used to allocate space to a file. A range of bytes is specified
using a pointer to a variable of type xfs_flock64_t in the final argument. The
blocks are allocated, but not zeroed, and the file size does not change. If the
XFS filesystem is configured to flag unwritten file extents, performance will be
negatively affected when writing to preallocated space, since extra filesystem
transactions are required to convert extent flags on the range of the file written.
If xfs_info(8) reports unwritten=1, then the filesystem was made to flag unwritten
extents.

XFS_IOC_UNRESVSP
XFS_IOC_UNRESVSP64
This command is used to free space from a file. A range of bytes is specified
using a pointer to a variable of type xfs_flock64_t in the final argument. Partial
filesystem blocks are zeroed, and whole filesystem blocks are removed from the
file. The file size does not change.

XFS_IOC_ZERO_RANGE
This command is used to convert a range of a file to zeros without issuing data IO.
A range of bytes is specified using a pointer to a variable of type xfs_flock64_t
in the final argument. Blocks are preallocated for regions that span holes in the
file, and the entire range is converted to unwritten extents. This operation is a
fast method of overwriting any from the range specified with zeros without removing
any blocks or having to write zeros to disk. Any subsequent read in the given
range will return zeros until new data is written. This functionality requires
filesystems to support unwritten extents. If xfs_info(8) reports unwritten=1, then
the filesystem was made to flag unwritten extents.

XFS_IOC_PATH_TO_HANDLE
XFS_IOC_PATH_TO_FSHANDLE
XFS_IOC_FD_TO_HANDLE
XFS_IOC_OPEN_BY_HANDLE
XFS_IOC_READLINK_BY_HANDLE
XFS_IOC_ATTR_LIST_BY_HANDLE
XFS_IOC_ATTR_MULTI_BY_HANDLE
XFS_IOC_FSSETDM_BY_HANDLE
These are all interfaces that are used to implement various libhandle functions
(see open_by_handle(3)). They are all subject to change and should not be called
directly by applications.

Filesystem Operations
In order to effect one of the following operations, the pathname and descriptor arguments
passed to xfsctl() can be any open file in the XFS filesystem in question.

XFS_IOC_FSINUMBERS
See ioctl_xfs_fsinumbers(2) for more information.

XFS_IOC_FSGEOMETRY
See ioctl_xfs_fsop_geometry(2) for more information.

XFS_IOC_AG_GEOMETRY
See ioctl_xfs_ag_geometry(2) for more information.

XFS_IOC_FSBULKSTAT or XFS_IOC_FSBULKSTAT_SINGLE
See ioctl_xfs_fsbulkstat(2) for more information.

XFS_IOC_SCRUB_METADATA
See ioctl_xfs_scrub_metadata(2) for more information.

XFS_IOC_FSCOUNTS
See ioctl_xfs_fscounts(2) for more information.

XFS_IOC_GET_RESBLKS
XFS_IOC_SET_RESBLKS
See ioctl_xfs_getresblks(2) for more information. Save yourself a lot of
frustration and avoid these ioctls.

XFS_IOC_GOINGDOWN
See ioctl_xfs_goingdown(2) for more information.

XFS_IOC_THAW
XFS_IOC_FREEZE
XFS_IOC_FSGROWFSDATA
XFS_IOC_FSGROWFSLOG
XFS_IOC_FSGROWFSRT
These interfaces are used to implement various filesystem internal operations on
XFS filesystems. The remainder of these operations will not be described further
as they are not of general use to applications.

NAME

C SYNOPSIS

DESCRIPTION

SEE ALSO