1/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
2#ifndef _FALLOC_H_
3#define _FALLOC_H_
4
5#define FALLOC_FL_ALLOCATE_RANGE 0x00 /* allocate range */
6#define FALLOC_FL_KEEP_SIZE 0x01 /* default is extend size */
7#define FALLOC_FL_PUNCH_HOLE 0x02 /* de-allocates range */
8#define FALLOC_FL_NO_HIDE_STALE 0x04 /* reserved codepoint */
9
10/*
11 * FALLOC_FL_COLLAPSE_RANGE is used to remove a range of a file
12 * without leaving a hole in the file. The contents of the file beyond
13 * the range being removed is appended to the start offset of the range
14 * being removed (i.e. the hole that was punched is "collapsed"),
15 * resulting in a file layout that looks like the range that was
16 * removed never existed. As such collapsing a range of a file changes
17 * the size of the file, reducing it by the same length of the range
18 * that has been removed by the operation.
19 *
20 * Different filesystems may implement different limitations on the
21 * granularity of the operation. Most will limit operations to
22 * filesystem block size boundaries, but this boundary may be larger or
23 * smaller depending on the filesystem and/or the configuration of the
24 * filesystem or file.
25 *
26 * Attempting to collapse a range that crosses the end of the file is
27 * considered an illegal operation - just use ftruncate(2) if you need
28 * to collapse a range that crosses EOF.
29 */
30#define FALLOC_FL_COLLAPSE_RANGE 0x08
31
32/*
33 * FALLOC_FL_ZERO_RANGE is used to convert a range of file to zeros preferably
34 * without issuing data IO. Blocks should be preallocated for the regions that
35 * span holes in the file, and the entire range is preferable converted to
36 * unwritten extents - even though file system may choose to zero out the
37 * extent or do whatever which will result in reading zeros from the range
38 * while the range remains allocated for the file.
39 *
40 * This can be also used to preallocate blocks past EOF in the same way as
41 * with fallocate. Flag FALLOC_FL_KEEP_SIZE should cause the inode
42 * size to remain the same.
43 */
44#define FALLOC_FL_ZERO_RANGE 0x10
45
46/*
47 * FALLOC_FL_INSERT_RANGE is use to insert space within the file size without
48 * overwriting any existing data. The contents of the file beyond offset are
49 * shifted towards right by len bytes to create a hole. As such, this
50 * operation will increase the size of the file by len bytes.
51 *
52 * Different filesystems may implement different limitations on the granularity
53 * of the operation. Most will limit operations to filesystem block size
54 * boundaries, but this boundary may be larger or smaller depending on
55 * the filesystem and/or the configuration of the filesystem or file.
56 *
57 * Attempting to insert space using this flag at OR beyond the end of
58 * the file is considered an illegal operation - just use ftruncate(2) or
59 * fallocate(2) with mode 0 for such type of operations.
60 */
61#define FALLOC_FL_INSERT_RANGE 0x20
62
63/*
64 * FALLOC_FL_UNSHARE_RANGE is used to unshare shared blocks within the
65 * file size without overwriting any existing data. The purpose of this
66 * call is to preemptively reallocate any blocks that are subject to
67 * copy-on-write.
68 *
69 * Different filesystems may implement different limitations on the
70 * granularity of the operation. Most will limit operations to filesystem
71 * block size boundaries, but this boundary may be larger or smaller
72 * depending on the filesystem and/or the configuration of the filesystem
73 * or file.
74 *
75 * This flag can only be used with allocate-mode fallocate, which is
76 * to say that it cannot be used with the punch, zero, collapse, or
77 * insert range modes.
78 */
79#define FALLOC_FL_UNSHARE_RANGE 0x40
80
81/*
82 * FALLOC_FL_WRITE_ZEROES zeroes a specified file range in such a way that
83 * subsequent writes to that range do not require further changes to the file
84 * mapping metadata. This flag is beneficial for subsequent pure overwriting
85 * within this range, as it can save on block allocation and, consequently,
86 * significant metadata changes. Therefore, filesystems that always require
87 * out-of-place writes should not support this flag.
88 *
89 * Different filesystems may implement different limitations on the
90 * granularity of the zeroing operation. Most will preferably be accelerated
91 * by submitting write zeroes command if the backing storage supports, which
92 * may not physically write zeros to the media.
93 *
94 * This flag cannot be specified in conjunction with the FALLOC_FL_KEEP_SIZE.
95 */
96#define FALLOC_FL_WRITE_ZEROES 0x80
97
98#endif /* _FALLOC_H_ */
99