| /* Copyright (C) 2000-2018 Free Software Foundation, Inc. |
| This file is part of the GNU C Library. |
| |
| The GNU C Library is free software; you can redistribute it and/or |
| modify it under the terms of the GNU Lesser General Public |
| License as published by the Free Software Foundation; either |
| version 2.1 of the License, or (at your option) any later version. |
| |
| The GNU C Library is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| Lesser General Public License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public |
| License along with the GNU C Library; if not, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include <errno.h> |
| #include <fcntl.h> |
| #include <unistd.h> |
| #include <stdint.h> |
| #include <sys/fcntl.h> |
| #include <sys/stat.h> |
| #include <sys/statfs.h> |
| |
| /* Reserve storage for the data of the file associated with FD. This |
| emulation is far from perfect, but the kernel cannot do not much |
| better for network file systems, either. */ |
| |
| int |
| posix_fallocate (int fd, __off_t offset, __off_t len) |
| { |
| struct stat64 st; |
| |
| if (offset < 0 || len < 0) |
| return EINVAL; |
| |
| /* Perform overflow check. The outer cast relies on a GCC |
| extension. */ |
| if ((__off_t) ((uint64_t) offset + (uint64_t) len) < 0) |
| return EFBIG; |
| |
| /* pwrite below will not do the right thing in O_APPEND mode. */ |
| { |
| int flags = __fcntl (fd, F_GETFL, 0); |
| if (flags < 0 || (flags & O_APPEND) != 0) |
| return EBADF; |
| } |
| |
| /* We have to make sure that this is really a regular file. */ |
| if (__fxstat64 (_STAT_VER, fd, &st) != 0) |
| return EBADF; |
| if (S_ISFIFO (st.st_mode)) |
| return ESPIPE; |
| if (! S_ISREG (st.st_mode)) |
| return ENODEV; |
| |
| if (len == 0) |
| { |
| /* This is racy, but there is no good way to satisfy a |
| zero-length allocation request. */ |
| if (st.st_size < offset) |
| { |
| int ret = __ftruncate (fd, offset); |
| |
| if (ret != 0) |
| ret = errno; |
| return ret; |
| } |
| return 0; |
| } |
| |
| /* Minimize data transfer for network file systems, by issuing |
| single-byte write requests spaced by the file system block size. |
| (Most local file systems have fallocate support, so this fallback |
| code is not used there.) */ |
| |
| unsigned increment; |
| { |
| struct statfs64 f; |
| |
| if (__fstatfs64 (fd, &f) != 0) |
| return errno; |
| if (f.f_bsize == 0) |
| increment = 512; |
| else if (f.f_bsize < 4096) |
| increment = f.f_bsize; |
| else |
| /* NFS does not propagate the block size of the underlying |
| storage and may report a much larger value which would still |
| leave holes after the loop below, so we cap the increment at |
| 4096. */ |
| increment = 4096; |
| } |
| |
| /* Write a null byte to every block. This is racy; we currently |
| lack a better option. Compare-and-swap against a file mapping |
| might additional local races, but requires interposition of a |
| signal handler to catch SIGBUS. */ |
| for (offset += (len - 1) % increment; len > 0; offset += increment) |
| { |
| len -= increment; |
| |
| if (offset < st.st_size) |
| { |
| unsigned char c; |
| ssize_t rsize = __pread (fd, &c, 1, offset); |
| |
| if (rsize < 0) |
| return errno; |
| /* If there is a non-zero byte, the block must have been |
| allocated already. */ |
| else if (rsize == 1 && c != 0) |
| continue; |
| } |
| |
| if (__pwrite (fd, "", 1, offset) != 1) |
| return errno; |
| } |
| |
| return 0; |
| } |