Following is the modified version of the manpage originally submitted by David Chinner. Please use `nroff -man fallocate.2 | less` to view. This includes changes suggested by Heikki Orsila and Barry Naujok. .TH fallocate 2 .SH NAME fallocate \- allocate or remove file space .SH SYNOPSIS .nf .B #include <fcntl.h> .PP .BI "long fallocate(int " fd ", int " mode ", loff_t " offset ", loff_t " len); .SH DESCRIPTION The .B fallocate syscall allows a user to directly manipulate the allocated disk space for the file referred to by .I fd for the byte range starting at .I offset and continuing for .I len bytes. The .I mode parameter determines the operation to be performed on the given range. Currently there are two modes: .TP .B FALLOC_ALLOCATE allocates and initialises to zero the disk space within the given range. After a successful call, subsequent writes are guaranteed not to fail because of lack of disk space. If the size of the file is less than .IR offset + len , then the file is increased to this size; otherwise the file size is left unchanged. .B FALLOC_ALLOCATE closely resembles .BR posix_fallocate (3) and is intended as a method of optimally implementing this function. .B FALLOC_ALLOCATE may allocate a larger range than that was specified. .TP .B FALLOC_RESV_SPACE provides the same functionality as .B FALLOC_ALLOCATE except it does not ever change the file size. This allows allocation of zero blocks beyond the end of file and is useful for optimising append workloads. .SH RETURN VALUE .B fallocate returns zero on success, or an error number on failure. Note that .I errno is not set. .SH ERRORS .TP .B EBADF .I fd is not a valid file descriptor, or is not opened for writing. .TP .B EFBIG .IR offset + len exceeds the maximum file size. .TP .B EINVAL .I offset was less than 0, or .I len was less than or equal to 0. .TP .B ENODEV .I fd does not refer to a regular file or a directory. .TP .B ENOSPC There is not enough space left on the device containing the file referred to by .IR fd . .TP .B ESPIPE .I fd refers to a pipe of file descriptor. .TP .B ENOSYS The filesystem underlying the file descriptor does not support this operation. .TP .B EINTR A signal was caught during execution .TP .B EIO An I/O error occurred while reading from or writing to a file system. .TP .B EOPNOTSUPP The mode is not supported on the file descriptor. .SH AVAILABILITY The .B fallocate system call is available since 2.6.XX .SH SEE ALSO .BR syscall (2), .BR posix_fadvise (3), .BR ftruncate (3). - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
