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NAME | C SYNOPSIS | DESCRIPTION | SEE ALSO | COLOPHON |
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XFSCTL(3) Library Functions Manual XFSCTL(3)
xfsctl - control XFS filesystems and individual files
#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);
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.
These ioctls are no longer supported as of Linux 5.17.
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. This ioctl is not supported as of Linux
5.5.
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. XFS_IOC_FSSETDM_BY_HANDLE is not supported
as of Linux 5.5.
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_fsgeometry(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.
ioctl_xfs_fsgetxattr(2), ioctl_xfs_fsgeometry(2),
ioctl_xfs_fsbulkstat(2), ioctl_xfs_scrub_metadata(2),
ioctl_xfs_fsinumbers(2), ioctl_xfs_fscounts(2),
ioctl_xfs_getresblks(2), ioctl_xfs_getbmap(2),
ioctl_xfs_goingdown(2), fstatfs(2), statfs(2), xfs(5),
xfs_info(8).
This page is part of the xfsprogs (utilities for XFS filesystems)
project. Information about the project can be found at
⟨http://xfs.org/⟩. If you have a bug report for this manual page,
send it to linux-xfs@vger.kernel.org. This page was obtained from
the project's upstream Git repository
⟨https://git.kernel.org/pub/scm/fs/xfs/xfsprogs-dev.git⟩ on
2025-08-11. (At that time, the date of the most recent commit
that was found in the repository was 2025-06-23.) If you discover
any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a
mail to man-pages@man7.org
XFSCTL(3)
Pages that refer to this page: open(2), handle(3), projects(5), projid(5), xfs(5), xfs_io(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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