On Tue, Jun 12, 2007 at 11:46:52AM +0530, Amit K. Arora wrote: > Did you get time to write the above man page ? It will help to push > further patches in time (eg. for FA_PREALLOCATE mode). First pass is attached. `nroff -man fallocate.2 | less` to view. Cheers, Dave. -- Dave Chinner Principal Engineer SGI Australian Software Group
.TH fallocate 2 .SH NAME fallocate \- allocate or remove file space .SH SYNOPSIS .nf .B #include <sys/syscall.h> .PP .BI "int syscall(int, int fd, int mode, loff_t offset, loff_t len); .Op .SH DESCRIPTION The .BR 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 .IR offset and continuing for .IR len bytes. The .I mode parameter determines the operation to be performed on the given range. Currently there are three modes: .TP .B FA_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 FA_ALLOCATE closely resembles B posix_fallocate(3) and is intended as a method of optimally implementing this function. B FA_ALLOCATE may allocate a larger range that was specified. TP B FA_PREALLOCATE provides the same functionality as B FA_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. TP B FA_DEALLOCATE removes the underlying disk space with the given range. The disk space shall be removed regardless of it's contents so both allocated space from B FA_ALLOCATE and B FA_PREALLOCATE as well as from B write(3) will be removed. B FA_DEALLOCATE shall never remove disk blocks outside the range specified. B FA_DEALLOCATE shall never change the file size. If changing the file size is required when deallocating blocks from an offset to end of file (or beyond end of file) is required, B ftuncate64(3) should be used. SH "RETURN VALUE" BR fallocate() returns zero on success, or an error number on failure. Note that IR 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 I offset+len exceeds the maximum file size. TP B EINVAL I offset or I len was less than 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. B ENOSYS The filesystem underlying the file descriptor does not support this operation. SH AVAILABILITY The BR fallocate () system call is available since 2.6.XX SH "SEE ALSO" BR syscall (2), BR posix_fadvise (3) BR ftruncate (3)
