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 XFS_IOC_FSGETXATTRA
91 XFS_IOC_FSSETXATTR
92 See ioctl_xfs_fsgetxattr(2) for more information.
93 XFS_IOC_GETBMAP
95 XFS_IOC_GETBMAPA
96 XFS_IOC_GETBMAPX
97 See ioctl_getbmap(2) for more information.
98 XFS_IOC_RESVSP
100 XFS_IOC_RESVSP64
101 This command is used to allocate space to a file. A range of
102 bytes is specified using a pointer to a variable of type
103 xfs_flock64_t in the final argument. The blocks are allocated,
104 but not zeroed, and the file size does not change. If the XFS
105 filesystem is configured to flag unwritten file extents, perfor‐
106 mance will be negatively affected when writing to preallocated
107 space, since extra filesystem transactions are required to con‐
108 vert extent flags on the range of the file written. If
109 xfs_info(8) reports unwritten=1, then the filesystem was made to
110 flag unwritten extents.
111 XFS_IOC_UNRESVSP
113 XFS_IOC_UNRESVSP64
114 This command is used to free space from a file. A range of
115 bytes is specified using a pointer to a variable of type
116 xfs_flock64_t in the final argument. Partial filesystem blocks
117 are zeroed, and whole filesystem blocks are removed from the
118 file. The file size does not change.
119 XFS_IOC_ZERO_RANGE
121 This command is used to convert a range of a file to zeros with‐
122 out issuing data IO. A range of bytes is specified using a
123 pointer to a variable of type xfs_flock64_t in the final argu‐
124 ment. Blocks are preallocated for regions that span holes in
125 the file, and the entire range is converted to unwritten
126 extents. This operation is a fast method of overwriting any
127 from the range specified with zeros without removing any blocks
128 or having to write zeros to disk. Any subsequent read in the
129 given range will return zeros until new data is written. This
130 functionality requires filesystems to support unwritten extents.
131 If xfs_info(8) reports unwritten=1, then the filesystem was made
132 to flag unwritten extents.
133 XFS_IOC_PATH_TO_HANDLE
136 XFS_IOC_PATH_TO_FSHANDLE
137 XFS_IOC_FD_TO_HANDLE
138 XFS_IOC_OPEN_BY_HANDLE
139 XFS_IOC_READLINK_BY_HANDLE
140 XFS_IOC_ATTR_LIST_BY_HANDLE
141 XFS_IOC_ATTR_MULTI_BY_HANDLE
142 XFS_IOC_FSSETDM_BY_HANDLE
143 These are all interfaces that are used to implement various lib‐
144 handle functions (see open_by_handle(3)). They are all subject
145 to change and should not be called directly by applications.
146 Filesystem Operations
148 In order to effect one of the following operations, the pathname and
149 descriptor arguments passed to xfsctl() can be any open file in the XFS
150 filesystem in question.
151 XFS_IOC_FSINUMBERS
153 See ioctl_xfs_fsinumbers(2) for more information.
154 XFS_IOC_FSGEOMETRY
156 See ioctl_xfs_fsop_geometry(2) for more information.
157 XFS_IOC_AG_GEOMETRY
159 See ioctl_xfs_ag_geometry(2) for more information.
160 XFS_IOC_FSBULKSTAT or XFS_IOC_FSBULKSTAT_SINGLE
162 See ioctl_xfs_fsbulkstat(2) for more information.
163 XFS_IOC_SCRUB_METADATA
165 See ioctl_xfs_scrub_metadata(2) for more information.
166 XFS_IOC_FSCOUNTS
168 See ioctl_xfs_fscounts(2) for more information.
169 XFS_IOC_GET_RESBLKS
171 XFS_IOC_SET_RESBLKS
172 See ioctl_xfs_getresblks(2) for more information. Save yourself
173 a lot of frustration and avoid these ioctls.
174 XFS_IOC_GOINGDOWN
176 See ioctl_xfs_goingdown(2) for more information.
177 XFS_IOC_THAW
179 XFS_IOC_FREEZE
180 XFS_IOC_FSGROWFSDATA
181 XFS_IOC_FSGROWFSLOG
182 XFS_IOC_FSGROWFSRT
183 These interfaces are used to implement various filesystem inter‐
184 nal operations on XFS filesystems. The remainder of these oper‐
185 ations will not be described further as they are not of general
186 use to applications.
187
189 ioctl_xfs_fsgetxattr(2), ioctl_xfs_fsop_geometry(2), ioctl_xfs_fsbulk‐
190 stat(2), ioctl_xfs_scrub_metadata(2), ioctl_xfs_fsinumbers(2),
191 ioctl_xfs_fscounts(2), ioctl_xfs_getresblks(2), ioctl_xfs_getbmap(2),
192 ioctl_xfs_goingdown(2), fstatfs(2), statfs(2), xfs(5), xfs_info(8).
193 XFSCTL(3)