d91f88f7f3
vop_stdallocate() is filesystem agnostic and will run as slow as a read/write loop in userspace; however, it serves to correctly implement the functionality for filesystems that do not implement a VOP_ALLOCATE. Note that __FreeBSD_version was already bumped today to 900036 for any ports which would like to use this function. Also reserve space in the syscall table for posix_fadvise(2). Reviewed by: -arch (previous version)
147 lines
4.0 KiB
Groff
147 lines
4.0 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)open.2 8.2 (Berkeley) 11/16/93
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.\" $FreeBSD$
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.\"
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.Dd April 13, 2011
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.Dt POSIX_FALLOCATE 2
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.Os
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.Sh NAME
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.Nm posix_fallocate
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.Nd pre-allocate storage for a range in a file
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In fcntl.h
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.Ft int
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.Fn posix_fallocate "int fd" "off_t offset" "off_t len"
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.Sh DESCRIPTION
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Required storage for the range
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.Fa offset
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to
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.Fa offset +
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.Fa len
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in the file referenced by
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.Fa fd
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is guarateed to be allocated upon successful return.
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That is, if
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.Fn posix_fallocate
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returns successfully, subsequent writes to the specified file data
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will not fail due to lack of free space on the file system storage
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media.
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Any existing file data in the specified range is unmodified.
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If
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.Fa offset +
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.Fa len
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is beyond the current file size, then
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.Fn posix_fallocate
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will adjust the file size to
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.Fa offset +
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.Fa len .
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Otherwise, the file size will not be changed.
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.Pp
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Space allocated by
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.Fn posix_fallocate
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will be freed by a successful call to
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.Xr creat 2
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or
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.Xr open 2
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that truncates the size of the file.
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Space allocated via
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.Fn posix_fallocate
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may be freed by a successful call to
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.Xr ftruncate 2
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that reduces the file size to a size smaller than
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.Fa offset +
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.Fa len .
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.Pp
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.Sh RETURN VALUES
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If successful,
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.Fn posix_fallocate
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returns zero.
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It returns -1 on failure, and sets
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.Va errno
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to indicate the error.
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.Sh ERRORS
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Possible failure conditions:
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.Bl -tag -width Er
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.It Bq Er EBADF
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The
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.Fa fd
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argument is not a valid file descriptor.
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.It Bq Er EBADF
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The
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.Fa fd
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argument references a file that was opened without write permission.
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.It Bq Er EFBIG
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The value of
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.Fa offset +
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.Fa len
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is greater than the maximum file size.
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.It Bq Er EINTR
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A signal was caught during execution.
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.It Bq Er EINVAL
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The
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.Fa len
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argument was zero or the
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.Fa offset
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argument was less than zero.
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.It Bq Er EIO
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An I/O error occurred while reading from or writing to a file system.
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.It Bq Er ENODEV
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The
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.Fa fd
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argument does not refer to a regular file.
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.It Bq Er ENOSPC
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There is insufficient free space remaining on the file system storage
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media.
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.It Bq Er ESPIPE
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The
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.Fa fd
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argument is associated with a pipe or FIFO.
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.El
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.Sh SEE ALSO
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.Xr creat 2 ,
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.Xr ftruncate 2 ,
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.Xr open 2 ,
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.Xr unlink 2
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.Sh STANDARDS
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The
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.Fn posix_fallocate
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system call conforms to
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.St -p1003.1-2004 .
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.Sh HISTORY
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The
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.Fn posix_fallocate
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function appeared in
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.Fx 9.0 .
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.Sh AUTHORS
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.Fn posix_fallocate
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and this manual page were initially written by
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.An Matthew Fleming Aq mdf@FreeBSD.org .
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