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f7a9f785 | 1 | /* Copyright (C) 2000-2016 Free Software Foundation, Inc. |
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2 | This file is part of the GNU C Library. |
3 | ||
4 | The GNU C Library is free software; you can redistribute it and/or | |
41bdb6e2 AJ |
5 | modify it under the terms of the GNU Lesser General Public |
6 | License as published by the Free Software Foundation; either | |
7 | version 2.1 of the License, or (at your option) any later version. | |
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8 | |
9 | The GNU C Library is distributed in the hope that it will be useful, | |
10 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
41bdb6e2 | 12 | Lesser General Public License for more details. |
bb8e0116 | 13 | |
41bdb6e2 | 14 | You should have received a copy of the GNU Lesser General Public |
59ba27a6 PE |
15 | License along with the GNU C Library; if not, see |
16 | <http://www.gnu.org/licenses/>. */ | |
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17 | |
18 | #include <errno.h> | |
19 | #include <fcntl.h> | |
20 | #include <unistd.h> | |
7fe9e2e0 FW |
21 | #include <stdint.h> |
22 | #include <sys/fcntl.h> | |
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23 | #include <sys/stat.h> |
24 | #include <sys/statfs.h> | |
25 | ||
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26 | /* Reserve storage for the data of the file associated with FD. This |
27 | emulation is far from perfect, but the kernel cannot do not much | |
28 | better for network file systems, either. */ | |
bb8e0116 UD |
29 | |
30 | int | |
089d05d5 | 31 | posix_fallocate (int fd, __off_t offset, __off_t len) |
bb8e0116 | 32 | { |
8edf6e0d | 33 | struct stat64 st; |
bb8e0116 | 34 | |
089d05d5 | 35 | if (offset < 0 || len < 0) |
bb8e0116 | 36 | return EINVAL; |
7fe9e2e0 FW |
37 | |
38 | /* Perform overflow check. The outer cast relies on a GCC | |
39 | extension. */ | |
543ef578 | 40 | if ((__off_t) ((uint64_t) offset + (uint64_t) len) < 0) |
bb8e0116 UD |
41 | return EFBIG; |
42 | ||
7fe9e2e0 FW |
43 | /* pwrite below will not do the right thing in O_APPEND mode. */ |
44 | { | |
45 | int flags = __fcntl (fd, F_GETFL, 0); | |
46 | if (flags < 0 || (flags & O_APPEND) != 0) | |
47 | return EBADF; | |
48 | } | |
49 | ||
50 | /* We have to make sure that this is really a regular file. */ | |
8edf6e0d | 51 | if (__fxstat64 (_STAT_VER, fd, &st) != 0) |
bb8e0116 UD |
52 | return EBADF; |
53 | if (S_ISFIFO (st.st_mode)) | |
54 | return ESPIPE; | |
55 | if (! S_ISREG (st.st_mode)) | |
56 | return ENODEV; | |
57 | ||
fe80efd5 UD |
58 | if (len == 0) |
59 | { | |
7fe9e2e0 FW |
60 | /* This is racy, but there is no good way to satisfy a |
61 | zero-length allocation request. */ | |
fe80efd5 UD |
62 | if (st.st_size < offset) |
63 | { | |
64 | int ret = __ftruncate (fd, offset); | |
65 | ||
66 | if (ret != 0) | |
67 | ret = errno; | |
68 | return ret; | |
69 | } | |
70 | return 0; | |
71 | } | |
72 | ||
7fe9e2e0 FW |
73 | /* Minimize data transfer for network file systems, by issuing |
74 | single-byte write requests spaced by the file system block size. | |
75 | (Most local file systems have fallocate support, so this fallback | |
76 | code is not used there.) */ | |
77 | ||
78 | unsigned increment; | |
79 | { | |
80 | struct statfs64 f; | |
81 | ||
82 | if (__fstatfs64 (fd, &f) != 0) | |
83 | return errno; | |
84 | if (f.f_bsize == 0) | |
85 | increment = 512; | |
86 | else if (f.f_bsize < 4096) | |
87 | increment = f.f_bsize; | |
88 | else | |
89 | /* NFS does not propagate the block size of the underlying | |
90 | storage and may report a much larger value which would still | |
91 | leave holes after the loop below, so we cap the increment at | |
92 | 4096. */ | |
93 | increment = 4096; | |
94 | } | |
95 | ||
96 | /* Write a null byte to every block. This is racy; we currently | |
97 | lack a better option. Compare-and-swap against a file mapping | |
98 | might additional local races, but requires interposition of a | |
99 | signal handler to catch SIGBUS. */ | |
100 | for (offset += (len - 1) % increment; len > 0; offset += increment) | |
bb8e0116 | 101 | { |
7fe9e2e0 | 102 | len -= increment; |
fe80efd5 UD |
103 | |
104 | if (offset < st.st_size) | |
105 | { | |
106 | unsigned char c; | |
107 | ssize_t rsize = __pread (fd, &c, 1, offset); | |
108 | ||
109 | if (rsize < 0) | |
110 | return errno; | |
111 | /* If there is a non-zero byte, the block must have been | |
112 | allocated already. */ | |
113 | else if (rsize == 1 && c != 0) | |
114 | continue; | |
115 | } | |
bb8e0116 | 116 | |
4aebaa6b | 117 | if (__pwrite (fd, "", 1, offset) != 1) |
bb8e0116 | 118 | return errno; |
bb8e0116 UD |
119 | } |
120 | ||
121 | return 0; | |
122 | } |