96 lines
3.7 KiB
Groff
96 lines
3.7 KiB
Groff
.\" $NetBSD: puffs_suspend.3,v 1.2 2007/01/28 07:58:05 wiz Exp $
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.\"
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.\" Copyright (c) 2007 Antti Kantee. 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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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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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.Dd January 27, 2007
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.Dt PUFFS_SUSPEND 3
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.Os
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.Sh NAME
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.Nm puffs_suspend
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.Nd puffs file system suspension and snapshotting
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.Sh LIBRARY
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.Lb libpuffs
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.Sh SYNOPSIS
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.In puffs.h
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.Ft int
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.Fn puffs_fs_suspend "struct puffs_usermount *pu"
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.Sh DESCRIPTION
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.Em IMPORTANT NOTE!
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This document describes interfaces which are not yet guaranteed to be
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stable.
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In case you update your system sources, please recompile everything
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and fix compilation errors.
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If your sources are out-of-sync, incorrect operation may result.
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The interfaces in this document will most likely be hugely simplified
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in later versions or made transparent to the implementation.
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.Pp
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The function
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.Fn puffs_fs_suspend
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requests the kernel to suspend operations to the file system indicated by
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.Fa pu .
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There are several possible outcomes: nothing, an error or success.
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These will be indicated through the callback of the same name.
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The file system must set this callback if it wants to be notified of
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file system suspension.
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The interface call itself returns 0 on success or \-1 on error and
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sets
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.Va errno .
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In case an error is returned, the callback will never be called.
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However, the converse does not hold and the callback may never be
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called even if the library call is successful.
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.Pp
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In case the kernel is successful to start suspending the file system,
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the callback is called with status
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.Dv PUFFS_SUSPEND START .
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The file system implementation may use this as a hint on how to handle
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following operations.
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Once the file system has successfully been suspended, the status
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.Dv PUFFS_SUSPEND_SUSPENDED
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will be delivered.
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In case there was an error while suspending,
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.Dv PUFFS_SUSPEND_ERROR
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is given.
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This effectively nullifies any
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.Dv PUFFS_SUSPEND_START
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given earlier.
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Operation will automatically resume after suspension and the status
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.Dv PUFFS_SUSPEND_RESUME
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is delivered to the callback.
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Error or success is always provided in case start is given.
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.Pp
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The file system is supposed to do a file system specific snapshotting
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routine when it receives
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.Dv PUFFS_SUSPEND_SUSPENDED .
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.Sh SEE ALSO
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.Xr puffs 3 ,
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.Xr puffs_cc 3
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.Sh BUGS
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Currently the implementation works only for single-threaded file systems
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which do not use
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.Nm puffs_cc .
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.Pp
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File system data and metadata are not always totally correctly
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synchronized at suspend.
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This will be fixed soon.
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