fallocate — manipulate file space
#include <linux/falloc.h>
long
fallocate( |
int | fd, |
| int | mode, | |
| loff_t | offset, | |
| loff_t | len); |
fallocate() allows the
caller to directly manipulate the allocated disk space for
the file referred to by fd for the byte range starting
at offset and
continuing for len
bytes.
The mode argument
determines the operation to be performed on the given range.
Currently only one flag is supported for mode:
FALLOC_FL_KEEP_SIZEThis flag allocates and initializes to zero the disk
space within the range specified by offset and len. After a successful
call, subsequent writes into this range are guaranteed
not to fail because of lack of disk space.
Preallocating zeroed blocks beyond the end of the file
is useful for optimizing append workloads.
Preallocating blocks does not change the file size (as
reported by stat(2)) even if it
is less than offset+len.
If FALLOC_FL_KEEP_SIZE flag
is not specified in mode, the default behavior is
almost same as when this flag is specified. The only
difference is that on success, the file size will be changed
if offset + len is
greater than the file size. This default behavior closely
resembles the behavior of the posix_fallocate(3) library
function, and is intended as a method of optimally
implementing that function.
Because allocation is done in block size chunks,
fallocate() may allocate a
larger range than that which was specified.
fallocate() returns zero on
success, or an error number on failure. Note that
errno is not set.
fd is not a
valid file descriptor, or is not opened for
writing.
offset+len exceeds the maximum
file size.
A signal was caught during execution.
offset was
less than 0, or len was less than or
equal to 0.
An I/O error occurred while reading from or writing to a file system.
fd does not
refer to a regular file or a directory. (If fd is a pipe or FIFO, a
different error results.)
There is not enough space left on the device
containing the file referred to by fd.
The file system containing the file referred to by
fd does not
support this operation.
The mode is
not supported by the file system containing the file
referred to by fd.
This page is part of release 2.79 of the Linux man-pages project. A
description of the project, and information about reporting
bugs, can be found at
http://www.kernel.org/doc/man-pages/.
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Copyright (c) 2007 Silicon Graphics, Inc. All Rights Reserved Written by Dave Chinner <dgcsgi.com> May be distributed as per GNU General Public License version 2. |