2fe8fb192f
There is important information about booting non-ack images in docs/UPDATING. ack/aout-format images can't be built any more, and booting clang/ELF-format ones is a little different. Updating to the new boot monitor is recommended. Changes in this commit: . drop boot monitor -> allowing dropping ack support . facility to copy ELF boot files to /boot so that old boot monitor can still boot fairly easily, see UPDATING . no more ack-format libraries -> single-case libraries . some cleanup of OBJECT_FMT, COMPILER_TYPE, etc cases . drop several ack toolchain commands, but not all support commands (e.g. aal is gone but acksize is not yet). . a few libc files moved to netbsd libc dir . new /bin/date as minix date used code in libc/ . test compile fix . harmonize includes . /usr/lib is no longer special: without ack, /usr/lib plays no kind of special bootstrapping role any more and bootstrapping is done exclusively through packages, so releases depend even less on the state of the machine making them now. . rename nbsd_lib* to lib* . reduce mtree
155 lines
4.3 KiB
Groff
155 lines
4.3 KiB
Groff
.\" $NetBSD: fsync.2,v 1.17 2010/05/17 12:38:04 jruoho Exp $
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.\"
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.\" Copyright (c) 1983, 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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.\" 3. 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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.\" @(#)fsync.2 8.1 (Berkeley) 6/4/93
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.\"
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.Dd May 17, 2010
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.Dt FSYNC 2
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.Os
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.Sh NAME
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.Nm fsync ,
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.Nm fsync_range
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.Nd "synchronize a file's in-core state with that on disk"
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In unistd.h
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.Ft int
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.Fn fsync "int fd"
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.Ft int
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.Fn fsync_range "int fd" "int how" "off_t start" "off_t length"
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.Sh DESCRIPTION
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.Fn fsync
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causes all modified data and attributes of
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.Fa fd
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to be moved to a permanent storage device.
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This normally results in all in-core modified copies
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of buffers for the associated file to be written to a disk.
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.Pp
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.Fn fsync
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should be used by programs that require a file to be
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in a known state, for example, in building a simple transaction
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facility.
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.Pp
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.Fn fsync_range
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causes all modified data starting at
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.Fa start
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for length
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.Fa length
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of
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.Fa fd
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to be written to permanent storage.
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Note that
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.Fn fsync_range
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requires that the file
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.Fa fd
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must be open for writing.
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.Pp
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.Fn fsync_range
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may flush the file data in one of two manners:
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.Bl -tag -width FDATASYNC -offset indent
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.It Dv FDATASYNC
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Synchronize the file data and sufficient meta-data to retrieve the
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data for the specified range.
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.It Dv FFILESYNC
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Synchronize all modified file data and meta-data for the specified range.
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.El
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.Pp
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By default,
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.Fn fsync_range
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does not flush disk caches, assuming that storage media are able to ensure
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completed writes are transfered to media.
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The
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.Dv FDISKSYNC
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flag may be included in the
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.Fa how
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parameter to trigger flushing of all disk caches for the file.
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.Pp
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If the
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.Fa length
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parameter is zero,
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.Fn fsync_range
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will synchronize all of the file data.
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.Sh RETURN VALUES
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A 0 value is returned on success.
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A \-1 value indicates an error.
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.Sh ERRORS
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.Fn fsync
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or
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.Fn fsync_range
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fail if:
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.Bl -tag -width Er
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.It Bq Er EBADF
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.Fa fd
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is not a valid descriptor.
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.It Bq Er EINVAL
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.Fa fd
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refers to a socket, not to a file.
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.It Bq Er EIO
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An I/O error occurred while reading from or writing to the file system.
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.El
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.Pp
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Additionally,
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.Fn fsync_range
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fails if:
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.Bl -tag -width Er
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.It Bq Er EBADF
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.Fa fd
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is not open for writing.
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.It Bq Er EINVAL
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.Fa start
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+
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.Fa length
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is less than
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.Fa start .
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.El
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.Sh NOTES
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For optimal efficiency, the
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.Fn fsync_range
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call requires that the file system containing the file referenced by
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.Fa fd
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support partial synchronization of file data.
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For file systems which do
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not support partial synchronization, the entire file will be synchronized
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and the call will be the equivalent of calling
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.Fn fsync .
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.Sh SEE ALSO
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.Xr sync 2 ,
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.Xr sync 8
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.Sh HISTORY
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The
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.Fn fsync
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function call appeared in
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.Bx 4.2 .
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.Pp
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The
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.Fn fsync_range
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function call first appeared in
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.Nx 2.0
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and is modeled after the function available in AIX.
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