1XFSCTL(3) Library Functions Manual XFSCTL(3)
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6 xfsctl - control XFS filesystems and individual files
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9 #include <xfs/xfs.h>
10 int xfsctl(const char *path, int fd, int cmd, void *ptr);
12 int platform_test_xfs_fd(int fd);
14 int platform_test_xfs_path(const char *path);
15
17 Some functionality specific to the XFS filesystem is accessible to
18 applications through platform-specific system call interfaces. These
19 operations can be divided into two sections - operations that operate
20 on individual files, and operations that operate on the filesystem
21 itself. Care should be taken when issuing xfsctl() calls to ensure the
22 target path and file descriptor (both must be supplied) do indeed rep‐
23 resent a file from an XFS filesystem. The statfs(2) and fstatfs(2)
24 system calls can be used to determine whether or not an arbitrary path
25 or file descriptor belong to an XFS filesystem. These are not portable
26 however, so the routines platform_test_xfs_fd() and plat‐
27 form_test_xfs_path() provide a platform-independent mechanism.
28 File Operations
30 In order to effect an operation on an individual file, the pathname and
31 descriptor arguments passed to xfsctl identifies the file being oper‐
32 ated on. The final argument described below refers to the final argu‐
33 ment of xfsctl. All of the data structures and macros mentioned below
34 are defined in the <xfs/xfs_fs.h> header file.
35 XFS_IOC_ALLOCSP
37 XFS_IOC_ALLOCSP64
38 XFS_IOC_FREESP
39 XFS_IOC_FREESP64
40 Alter storage space associated with a section of the ordinary
41 file specified. The section is specified by a variable of type
42 xfs_flock64_t, pointed to by the final argument. The data type
43 xfs_flock64_t contains the following members: l_whence is 0, 1,
44 or 2 to indicate that the relative offset l_start will be mea‐
45 sured from the start of the file, the current position, or the
46 end of the file, respectively (i.e., l_start is the offset from
47 the position specified in l_whence). If the offset specified is
48 before the current end of file, any data previously written into
49 this section is no longer accessible. If the offset specified
50 is beyond the current end of file, the file is grown and filled
51 with zeroes. The l_len field is currently ignored, and should
52 be set to zero.
53 XFS_IOC_ALLOCSP, XFS_IOC_ALLOCSP64, XFS_IOC_FREESP and
55 XFS_IOC_FREESP64 operations are all identical.
56 XFS_IOC_FSSETDM
58 Set the di_dmevmask and di_dmstate fields in an XFS on-disk
59 inode. The only legitimate values for these fields are those
60 previously returned in the bs_dmevmask and bs_dmstate fields of
61 the bulkstat structure. The data referred to by the final argu‐
62 ment is a struct fsdmidata. This structure's members are
63 fsd_dmevmask and fsd_dmstate. The di_dmevmask field is set to
64 the value in fsd_dmevmask. The di_dmstate field is set to the
65 value in fsd_dmstate. This command is restricted to root or to
66 processes with device management capabilities. Its sole purpose
67 is to allow backup and restore programs to restore the aforemen‐
68 tioned critical on-disk inode fields.
69 XFS_IOC_DIOINFO
71 Get information required to perform direct I/O on the specified
72 file descriptor. Direct I/O is performed directly to and from a
73 user's data buffer. Since the kernel's buffer cache is no
74 longer between the two, the user's data buffer must conform to
75 the same type of constraints as required for accessing a raw
76 disk partition. The final argument points to a variable of type
77 struct dioattr, which contains the following members: d_mem is
78 the memory alignment requirement of the user's data buffer.
79 d_miniosz specifies block size, minimum I/O request size, and
80 I/O alignment. The size of all I/O requests must be a multiple
81 of this amount and the value of the seek pointer at the time of
82 the I/O request must also be an integer multiple of this amount.
83 d_maxiosz is the maximum I/O request size which can be performed
84 on the file descriptor. If an I/O request does not meet these
85 constraints, the read(2) or write(2) will fail with EINVAL. All
86 I/O requests are kept consistent with any data brought into the
87 cache with an access through a non-direct I/O file descriptor.
88 XFS_IOC_FSGETXATTR
90 Get additional attributes associated with files in XFS file sys‐
91 tems. The final argument points to a variable of type struct
92 fsxattr, whose fields include: fsx_xflags (extended flag bits),
93 fsx_extsize (nominal extent size in file system blocks),
94 fsx_nextents (number of data extents in the file). A fsx_ext‐
95 size value returned indicates that a preferred extent size was
96 previously set on the file, a fsx_extsize of zero indicates that
97 the defaults for that filesystem will be used. Currently the
98 meaningful bits for the fsx_xflags field are:
99 Bit 0 (0x1) - XFS_XFLAG_REALTIME
100 The file is a realtime file.
101 Bit 1 (0x2) - XFS_XFLAG_PREALLOC
102 The file has preallocated space.
103 Bit 3 (0x8) - XFS_XFLAG_IMMUTABLE
104 The file is immutable - it cannot be modified, deleted
105 or renamed, no link can be created to this file and no
106 data can be written to the file. Only the superuser
107 or a process possessing the CAP_LINUX_IMMUTABLE capa‐
108 bility can set or clear this flag.
109 Bit 4 (0x10) - XFS_XFLAG_APPEND
110 The file is append-only - it can only be open in
111 append mode for writing. Only the superuser or a
112 process possessing the CAP_LINUX_IMMUTABLE capability
113 can set or clear this flag.
114 Bit 5 (0x20) - XFS_XFLAG_SYNC
115 All writes to the file are synchronous.
116 Bit 6 (0x40) - XFS_XFLAG_NOATIME
117 When the file is accessed, its atime record is not
118 modified.
119 Bit 7 (0x80) - XFS_XFLAG_NODUMP
120 The file should be skipped by backup utilities.
121 Bit 8 (0x100) - XFS_XFLAG_RTINHERIT
122 Realtime inheritance bit - new files created in the
123 directory will be automatically realtime, and new
124 directories created in the directory will inherit the
125 inheritance bit.
126 Bit 9 (0x200) - XFS_XFLAG_PROJINHERIT
127 Project inheritance bit - new files and directories
128 created in the directory will inherit the parents
129 project ID. New directories also inherit the project
130 inheritance bit.
131 Bit 10 (0x400) - XFS_XFLAG_NOSYMLINKS
132 Can only be set on a directory and disallows creation
133 of symbolic links in that directory.
134 Bit 11 (0x800) - XFS_XFLAG_EXTSIZE
135 Extent size bit - if a basic extent size value is set
136 on the file then the allocator will allocate in multi‐
137 ples of the set size for this file (see
138 XFS_IOC_FSSETXATTR below).
139 Bit 12 (0x1000) - XFS_XFLAG_EXTSZINHERIT
140 Extent size inheritance bit - new files and directo‐
141 ries created in the directory will inherit the parents
142 basic extent size value (see XFS_IOC_FSSETXATTR
143 below). Can only be set on a directory.
144 Bit 13 (0x2000) - XFS_XFLAG_NODEFRAG
145 No defragment file bit - the file should be skipped
146 during a defragmentation operation. When applied to a
147 directory, new files and directories created will
148 inherit the no-defrag bit.
149 Bit 14 (0x4000) - XFS_XFLAG_FILESTREAM
150 Filestream allocator bit - allows a directory to
151 reserve an allocation group for exclusive use by files
152 created within that directory. Files being written in
153 other directories will not use the same allocation
154 group and so files within different directories will
155 not interleave extents on disk. The reservation is
156 only active while files are being created and written
157 into the directory.
158 Bit 31 (0x80000000) - XFS_XFLAG_HASATTR
159 The file has extended attributes associated with it.
160 XFS_IOC_FSGETXATTRA
161 Identical to XFS_IOC_FSGETXATTR except that the fsx_nextents
162 field contains the number of attribute extents in the file.
163 XFS_IOC_FSSETXATTR
166 Set additional attributes associated with files in XFS file sys‐
167 tems. The final argument points to a variable of type struct
168 fsxattr, but only the following fields are used in this call:
169 fsx_xflags, fsx_extsize and fsx_projid. The fsx_xflags realtime
170 file bit and the file's extent size may be changed only when the
171 file is empty, except in the case of a directory where the
172 extent size can be set at any time (this value is only used for
173 regular file allocations, so should only be set on a directory
174 in conjunction with the XFS_XFLAG_EXTSZINHERIT flag).
175 XFS_IOC_GETBMAP
178 Get the block map for a segment of a file in an XFS file system.
179 The final argument points to an arry of variables of type struct
180 getbmap. All sizes and offsets in the structure are in units of
181 512 bytes. The structure fields include: bmv_offset (file off‐
182 set of segment), bmv_block (starting block of segment),
183 bmv_length (length of segment), bmv_count (number of array
184 entries, including the first), and bmv_entries (number of
185 entries filled in). The first structure in the array is a
186 header, and the remaining structures in the array contain block
187 map information on return. The header controls iterative calls
188 to the XFS_IOC_GETBMAP command. The caller fills in the
189 bmv_offset and bmv_length fields of the header to indicate the
190 area of interest in the file, and fills in the bmv_count field
191 to indicate the length of the array. If the bmv_length value is
192 set to -1 then the length of the interesting area is the rest of
193 the file. On return from a call, the header is updated so that
194 the command can be reused to obtain more information, without
195 re-initializing the structures. Also on return, the bmv_entries
196 field of the header is set to the number of array entries actu‐
197 ally filled in. The non-header structures will be filled in
198 with bmv_offset, bmv_block, and bmv_length. If a region of the
199 file has no blocks (is a hole in the file) then the bmv_block
200 field is set to -1.
201 XFS_IOC_GETBMAPA
204 Identical to XFS_IOC_GETBMAP except that information about the
205 attribute fork of the file is returned.
206 XFS_IOC_RESVSP
209 XFS_IOC_RESVSP64
211 This command is used to allocate space to a file. A range of
212 bytes is specified using a pointer to a variable of type
213 xfs_flock64_t in the final argument. The blocks are allocated,
214 but not zeroed, and the file size does not change. If the XFS
215 filesystem is configured to flag unwritten file extents, perfor‐
216 mance will be negatively affected when writing to preallocated
217 space, since extra filesystem transactions are required to con‐
218 vert extent flags on the range of the file written. If
219 xfs_info(8) reports unwritten=1, then the filesystem was made to
220 flag unwritten extents.
221 XFS_IOC_UNRESVSP
224 XFS_IOC_UNRESVSP64
226 This command is used to free space from a file. A range of
227 bytes is specified using a pointer to a variable of type
228 xfs_flock64_t in the final argument. Partial filesystem blocks
229 are zeroed, and whole filesystem blocks are removed from the
230 file. The file size does not change.
231 XFS_IOC_ZERO_RANGE
234 This command is used to convert a range of a file to zeros with‐
235 out issuing data IO. A range of bytes is specified using a
236 pointer to a variable of type xfs_flock64_t in the final argu‐
237 ment. Blocks are preallocated for regions that span holes in
238 the file, and the entire range is converted to unwritten
239 extents. This operation is a fast method of overwriting any
240 from the range specified with zeros without removing any blocks
241 or having to write zeros to disk. Any subsequent read in the
242 given range will return zeros until new data is written. This
243 functionality requires filesystems to support unwritten extents.
244 If xfs_info(8) reports unwritten=1, then the filesystem was made
245 to flag unwritten extents.
246 XFS_IOC_PATH_TO_HANDLE
250 XFS_IOC_PATH_TO_FSHANDLE
251 XFS_IOC_FD_TO_HANDLE
252 XFS_IOC_OPEN_BY_HANDLE
253 XFS_IOC_READLINK_BY_HANDLE
254 XFS_IOC_ATTR_LIST_BY_HANDLE
255 XFS_IOC_ATTR_MULTI_BY_HANDLE
256 XFS_IOC_FSSETDM_BY_HANDLE
257 These are all interfaces that are used to implement various lib‐
258 handle functions (see open_by_handle(3)). They are all subject
259 to change and should not be called directly by applications.
260 Filesystem Operations
262 In order to effect one of the following operations, the pathname and
263 descriptor arguments passed to xfsctl() can be any open file in the XFS
264 filesystem in question.
265 XFS_IOC_FSINUMBERS
267 This interface is used to extract a list of valid inode numbers
268 from an XFS filesystem. It is intended to be called itera‐
269 tively, to obtain the entire set of inodes. The information is
270 passed in and out via a structure of type xfs_fsop_bulkreq_t
271 pointed to by the final argument. lastip is a pointer to a
272 variable containing the last inode number returned, initially it
273 should be zero. icount is the size of the array of structures
274 specified by ubuffer. ubuffer is the address of an array of
275 structures, of type xfs_inogrp_t. This structure has the fol‐
276 lowing elements: xi_startino (starting inode number), xi_alloc‐
277 count (count of bits set in xi_allocmask), and xi_allocmask
278 (mask of allocated inodes in this group). The bitmask is 64
279 bits long, and the least significant bit corresponds to inode
280 xi_startino. Each bit is set if the corresponding inode is in
281 use. ocount is a pointer to a count of returned values, filled
282 in by the call. An output ocount value of zero means that the
283 inode table has been exhausted.
284 XFS_IOC_FSBULKSTAT
286 This interface is used to extract inode information (stat infor‐
287 mation) "in bulk" from a filesystem. It is intended to be
288 called iteratively, to obtain information about the entire set
289 of inodes in a filesystem. The information is passed in and out
290 via a structure of type xfs_fsop_bulkreq_t pointed to by the
291 final argument. lastip is a pointer to a variable containing
292 the last inode number returned, initially it should be zero.
293 icount indicates the size of the array of structures specified
294 by ubuffer. ubuffer is the address of an array of structures of
295 type xfs_bstat_t. Many of the elements in the structure are the
296 same as for the stat structure. The structure has the following
297 elements: bs_ino (inode number), bs_mode (type and mode),
298 bs_nlink (number of links), bs_uid (user id), bs_gid (group id),
299 bs_rdev (device value), bs_blksize (block size of the filesys‐
300 tem), bs_size (file size in bytes), bs_atime (access time),
301 bs_mtime (modify time), bs_ctime (inode change time), bs_blocks
302 (number of blocks used by the file), bs_xflags (extended flags),
303 bs_extsize (extent size), bs_extents (number of extents), bs_gen
304 (generation count), bs_projid_lo (project id - low word),
305 bs_projid_hi (project id - high word, used when projid32bit fea‐
306 ture is enabled), bs_dmevmask (DMIG event mask), bs_dmstate
307 (DMIG state information), and bs_aextents (attribute extent
308 count). ocount is a pointer to a count of returned values,
309 filled in by the call. An output ocount value of zero means
310 that the inode table has been exhausted.
311 XFS_IOC_FSBULKSTAT_SINGLE
313 This interface is a variant of the XFS_IOC_FSBULKSTAT interface,
314 used to obtain information about a single inode. for an open
315 file in the filesystem of interest. The same structure is used
316 to pass information in and out of the kernel, except no output
317 count parameter is used (should be initialized to zero). An
318 error is returned if the inode number is invalid.
319 XFS_IOC_THAW
321 XFS_IOC_FREEZE
322 XFS_IOC_GET_RESBLKS
323 XFS_IOC_SET_RESBLKS
324 XFS_IOC_FSGROWFSDATA
325 XFS_IOC_FSGROWFSLOG
326 XFS_IOC_FSGROWFSRT
327 XFS_IOC_FSCOUNTS
328 These interfaces are used to implement various filesystem inter‐
329 nal operations on XFS filesystems. For XFS_IOC_FSGEOMETRY (get
330 filesystem mkfs time information), the output structure is of
331 type xfs_fsop_geom_t. For XFS_FS_COUNTS (get filesystem dynamic
332 global information), the output structure is of type
333 xfs_fsop_counts_t. The remainder of these operations will not
334 be described further as they are not of general use to applica‐
335 tions.
336
338 fstatfs(2), statfs(2), xfs(5), xfs_info(8).
339 XFSCTL(3)