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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.
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
Get additional attributes associated with files in XFS file
systems. The final argument points to a variable of type
struct fsxattr, whose fields include: fsx_xflags (extended
flag bits), fsx_extsize (nominal extent size in file system
blocks), fsx_nextents (number of data extents in the file). A
fsx_extsize value returned indicates that a preferred extent
size was previously set on the file, a fsx_extsize of zero
indicates that the defaults for that filesystem will be used.
A fsx_cowextsize value returned indicates that a preferred
copy on write extent size was previously set on the file,
whereas a fsx_cowextsize of zero indicates that the defaults
for that filesystem will be used. The current default for
fsx_cowextsize is 128 blocks. Currently the meaningful bits
for the fsx_xflags field are:
Bit 0 (0x1) - XFS_XFLAG_REALTIME
The file is a realtime file.
Bit 1 (0x2) - XFS_XFLAG_PREALLOC
The file has preallocated space.
Bit 3 (0x8) - XFS_XFLAG_IMMUTABLE
The file is immutable - it cannot be modified,
deleted or renamed, no link can be created to this
file and no data can be written to the file. Only
the superuser or a process possessing the
CAP_LINUX_IMMUTABLE capability can set or clear this
flag.
Bit 4 (0x10) - XFS_XFLAG_APPEND
The file is append-only - it can only be open in
append mode for writing. Only the superuser or a
process possessing the CAP_LINUX_IMMUTABLE
capability can set or clear this flag.
Bit 5 (0x20) - XFS_XFLAG_SYNC
All writes to the file are synchronous.
Bit 6 (0x40) - XFS_XFLAG_NOATIME
When the file is accessed, its atime record is not
modified.
Bit 7 (0x80) - XFS_XFLAG_NODUMP
The file should be skipped by backup utilities.
Bit 8 (0x100) - XFS_XFLAG_RTINHERIT
Realtime inheritance bit - new files created in the
directory will be automatically realtime, and new
directories created in the directory will inherit
the inheritance bit.
Bit 9 (0x200) - XFS_XFLAG_PROJINHERIT
Project inheritance bit - new files and directories
created in the directory will inherit the parents
project ID. New directories also inherit the
project inheritance bit.
Bit 10 (0x400) - XFS_XFLAG_NOSYMLINKS
Can only be set on a directory and disallows
creation of symbolic links in that directory.
Bit 11 (0x800) - XFS_XFLAG_EXTSIZE
Extent size bit - if a basic extent size value is
set on the file then the allocator will allocate in
multiples of the set size for this file (see
XFS_IOC_FSSETXATTR below).
Bit 12 (0x1000) - XFS_XFLAG_EXTSZINHERIT
Extent size inheritance bit - new files and
directories created in the directory will inherit
the parents basic extent size value (see
XFS_IOC_FSSETXATTR below). Can only be set on a
directory.
Bit 13 (0x2000) - XFS_XFLAG_NODEFRAG
No defragment file bit - the file should be skipped
during a defragmentation operation. When applied to
a directory, new files and directories created will
inherit the no-defrag bit.
Bit 14 (0x4000) - XFS_XFLAG_FILESTREAM
Filestream allocator bit - allows a directory to
reserve an allocation group for exclusive use by
files created within that directory. Files being
written in other directories will not use the same
allocation group and so files within different
directories will not interleave extents on disk. The
reservation is only active while files are being
created and written into the directory.
Bit 15 (0x8000) - XFS_XFLAG_DAX
If the filesystem lives on directly accessible
persistent memory, reads and writes to this file
will go straight to the persistent memory, bypassing
the page cache. A file cannot be reflinked and have
the XFS_XFLAG_DAX set at the same time. That is to
say that DAX files cannot share blocks.
Bit 16 (0x10000) - XFS_XFLAG_COWEXTSIZE
Copy on Write Extent size bit - if a CoW extent size
value is set on the file, the allocator will
allocate extents for staging a copy on write
operation in multiples of the set size for this file
(see XFS_IOC_FSSETXATTR below). If the CoW extent
size is set on a directory, then new file and
directories created in the directory will inherit
the parent's CoW extent size value.
Bit 31 (0x80000000) - XFS_XFLAG_HASATTR
The file has extended attributes associated with it.
XFS_IOC_FSGETXATTRA
Identical to XFS_IOC_FSGETXATTR except that the fsx_nextents
field contains the number of attribute extents in the file.
XFS_IOC_FSSETXATTR
Set additional attributes associated with files in XFS file
systems. The final argument points to a variable of type
struct fsxattr, but only the following fields are used in this
call: fsx_xflags, fsx_extsize, fsx_cowextsize, and fsx_projid.
The fsx_xflags realtime file bit and the file's extent size
may be changed only when the file is empty, except in the case
of a directory where the extent size can be set at any time
(this value is only used for regular file allocations, so
should only be set on a directory in conjunction with the
XFS_XFLAG_EXTSZINHERIT flag). The copy on write extent size,
fsx_cowextsize, can be set at any time.
XFS_IOC_GETBMAP
Get the block map for a segment of a file in an XFS file
system. The final argument points to an arry of variables of
type struct getbmap. All sizes and offsets in the structure
are in units of 512 bytes. The structure fields include:
bmv_offset (file offset of segment), bmv_block (starting block
of segment), bmv_length (length of segment), bmv_count (number
of array entries, including the first), and bmv_entries
(number of entries filled in). The first structure in the
array is a header, and the remaining structures in the array
contain block map information on return. The header controls
iterative calls to the XFS_IOC_GETBMAP command. The caller
fills in the bmv_offset and bmv_length fields of the header to
indicate the area of interest in the file, and fills in the
bmv_count field to indicate the length of the array. If the
bmv_length value is set to -1 then the length of the
interesting area is the rest of the file. On return from a
call, the header is updated so that the command can be reused
to obtain more information, without re-initializing the
structures. Also on return, the bmv_entries field of the
header is set to the number of array entries actually filled
in. The non-header structures will be filled in with
bmv_offset, bmv_block, and bmv_length. If a region of the
file has no blocks (is a hole in the file) then the bmv_block
field is set to -1.
XFS_IOC_GETBMAPA
Identical to XFS_IOC_GETBMAP except that information about the
attribute fork of the file is returned.
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
This interface is used to extract a list of valid inode
numbers from an XFS filesystem. It is intended to be called
iteratively, to obtain the entire set of inodes. The
information is passed in and out via a structure of type
xfs_fsop_bulkreq_t pointed to by the final argument. lastip
is a pointer to a variable containing the last inode number
returned, initially it should be zero. icount is the size of
the array of structures specified by ubuffer. ubuffer is the
address of an array of structures, of type xfs_inogrp_t. This
structure has the following elements: xi_startino (starting
inode number), xi_alloccount (count of bits set in
xi_allocmask), and xi_allocmask (mask of allocated inodes in
this group). The bitmask is 64 bits long, and the least
significant bit corresponds to inode xi_startino. Each bit is
set if the corresponding inode is in use. ocount is a pointer
to a count of returned values, filled in by the call. An
output ocount value of zero means that the inode table has
been exhausted.
XFS_IOC_FSBULKSTAT
This interface is used to extract inode information (stat
information) "in bulk" from a filesystem. It is intended to
be called iteratively, to obtain information about the entire
set of inodes in a filesystem. The information is passed in
and out via a structure of type xfs_fsop_bulkreq_t pointed to
by the final argument. lastip is a pointer to a variable
containing the last inode number returned, initially it should
be zero. icount indicates the size of the array of structures
specified by ubuffer. ubuffer is the address of an array of
structures of type xfs_bstat_t. Many of the elements in the
structure are the same as for the stat structure. The
structure has the following elements: bs_ino (inode number),
bs_mode (type and mode), bs_nlink (number of links), bs_uid
(user id), bs_gid (group id), bs_rdev (device value),
bs_blksize (block size of the filesystem), bs_size (file size
in bytes), bs_atime (access time), bs_mtime (modify time),
bs_ctime (inode change time), bs_blocks (number of blocks used
by the file), bs_xflags (extended flags), bs_extsize (extent
size), bs_extents (number of extents), bs_gen (generation
count), bs_projid_lo (project id - low word), bs_projid_hi
(project id - high word, used when projid32bit feature is
enabled), bs_dmevmask (DMIG event mask), bs_dmstate (DMIG
state information), and bs_aextents (attribute extent count).
ocount is a pointer to a count of returned values, filled in
by the call. An output ocount value of zero means that the
inode table has been exhausted.
XFS_IOC_FSBULKSTAT_SINGLE
This interface is a variant of the XFS_IOC_FSBULKSTAT
interface, used to obtain information about a single inode.
for an open file in the filesystem of interest. The same
structure is used to pass information in and out of the
kernel, except no output count parameter is used (should be
initialized to zero). An error is returned if the inode
number is invalid.
XFS_IOC_THAW
XFS_IOC_FREEZE
XFS_IOC_GET_RESBLKS
XFS_IOC_SET_RESBLKS
XFS_IOC_FSGROWFSDATA
XFS_IOC_FSGROWFSLOG
XFS_IOC_FSGROWFSRT
XFS_IOC_FSCOUNTS
These interfaces are used to implement various filesystem
internal operations on XFS filesystems. For
XFS_IOC_FSGEOMETRY (get filesystem mkfs time information), the
output structure is of type xfs_fsop_geom_t. For
XFS_FS_COUNTS (get filesystem dynamic global information), the
output structure is of type xfs_fsop_counts_t. The remainder
of these operations will not be described further as they are
not of general use to applications.
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, see
⟨http://oss.sgi.com/bugzilla/buglist.cgi?product=XFS⟩. This page was
obtained from the project's upstream Git repository
⟨git://oss.sgi.com/xfs/cmds/xfsprogs⟩ on 2018-02-02. (At that time,
the date of the most recent commit that was found in the repository
was 2017-11-27.) 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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