233 lines
6.2 KiB
Groff
233 lines
6.2 KiB
Groff
.\" $NetBSD: fstrans.9,v 1.15 2010/04/12 21:28:55 jruoho Exp $
|
|
.\"
|
|
.\" Copyright (c) 2007 The NetBSD Foundation, Inc.
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" This code is derived from software contributed to The NetBSD Foundation
|
|
.\" by Juergen Hannken-Illjes.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
|
|
.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
|
|
.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
|
|
.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
|
|
.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
|
|
.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
|
|
.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
|
|
.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
|
|
.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
|
|
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
.\" POSSIBILITY OF SUCH DAMAGE.
|
|
.\"
|
|
.Dd April 13, 2010
|
|
.Dt FSTRANS 9
|
|
.Os
|
|
.Sh NAME
|
|
.Nm fstrans ,
|
|
.Nm fstrans_setstate ,
|
|
.Nm fstrans_getstate ,
|
|
.Nm fstrans_start ,
|
|
.Nm fstrans_start_nowait ,
|
|
.Nm fstrans_done ,
|
|
.Nm fstrans_is_owner ,
|
|
.Nm fscow_establish ,
|
|
.Nm fscow_disestablish ,
|
|
.Nm fscow_run
|
|
.Nd file system suspension helper subsystem
|
|
.Sh SYNOPSIS
|
|
.In sys/mount.h
|
|
.In sys/fstrans.h
|
|
.Ft int
|
|
.Fn fstrans_setstate "struct mount *mp" "enum fstrans_state new_state"
|
|
.Ft "enum fstrans_state"
|
|
.Fn fstrans_getstate "struct mount *mp"
|
|
.Ft void
|
|
.Fn fstrans_start "struct mount *mp" "enum fstrans_lock_type lock_type"
|
|
.Ft int
|
|
.Fn fstrans_start_nowait "struct mount *mp" "enum fstrans_lock_type lock_type"
|
|
.Ft void
|
|
.Fn fstrans_done "struct mount *mp"
|
|
.Ft int
|
|
.Fn fstrans_is_owner "struct mount *mp"
|
|
.Ft int
|
|
.Fn fscow_establish "struct mount *mp" \
|
|
"int (*func)(void *, struct buf *, bool)" "void *cookie"
|
|
.Ft int
|
|
.Fn fscow_disestablish "struct mount *mp" \
|
|
"int (*func)(void *, struct buf *, bool)" "void *cookie"
|
|
.Ft int
|
|
.Fn fscow_run "struct buf *bp" "bool data_valid"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
subsystem is a set of operations to assist file system suspension.
|
|
These operations must not be used outside of file systems.
|
|
.Pp
|
|
File systems supporting this subsystem must set the flag
|
|
.Dv IMNT_HAS_TRANS
|
|
in
|
|
.Dv "mnt_iflag" .
|
|
.Pp
|
|
File systems are always in one of these states:
|
|
.Pp
|
|
.Bl -tag -offset indent -width FSTRANS_SUSPENDING -compact
|
|
.It Dv FSTRANS_NORMAL
|
|
Normal operations.
|
|
.It Dv FSTRANS_SUSPENDING
|
|
Preparing a suspension.
|
|
.It Dv FSTRANS_SUSPENDED
|
|
Suspended.
|
|
.El
|
|
.Pp
|
|
This state is represented by
|
|
.Vt "enum fstrans_state" .
|
|
.Pp
|
|
All file system operations use a
|
|
.Em "fstrans lock" .
|
|
This lock is recursive.
|
|
A thread already owning a lock will always get another lock.
|
|
The lock has two variants:
|
|
.Bl -tag -offset indent -width FSTRANS_SHARED
|
|
.It Dv FSTRANS_SHARED
|
|
A lock that will be granted if the file system is in state
|
|
.Dv FSTRANS_NORMAL .
|
|
.It Dv FSTRANS_LAZY
|
|
A lock that will be granted if the file system is in state
|
|
.Dv FSTRANS_NORMAL
|
|
or
|
|
.Dv FSTRANS_SUSPENDING .
|
|
It needs special care because operations using this variant will not block
|
|
while the file system prepares suspension.
|
|
.El
|
|
.Pp
|
|
The lock variant is represented by
|
|
.Vt "enum fstrans_lock_type" .
|
|
.Sh FUNCTIONS
|
|
The following functions comprise the
|
|
.Tn API
|
|
provided by
|
|
.Nm .
|
|
.Bl -tag -width compact
|
|
.It Fn fstrans_getstate "mp"
|
|
Returns the current state of the file system
|
|
.Fa mp .
|
|
.It Fn fstrans_setstate "mp" "new_state"
|
|
Changes the state of the file system
|
|
.Fa mp
|
|
to
|
|
.Fa new_state .
|
|
.It Fn fstrans_start "mp" "lock_type"
|
|
Sets a lock of type
|
|
.Fa lock_type
|
|
on the file system
|
|
.Fa mp .
|
|
.It Fn fstrans_start_nowait "mp" "lock_type"
|
|
Like
|
|
.Fn fstrans_start ,
|
|
but will not wait for a state change of the file system when attempting to
|
|
acquire the lock.
|
|
The thread may still sleep while attempting to acquire the lock.
|
|
.It Fn fstrans_done "mp"
|
|
Releases a lock on the file system
|
|
.Fa mp .
|
|
.It Fn fstrans_is_owner "mp"
|
|
Returns
|
|
.Dv true
|
|
if this thread is currently suspending the file system
|
|
.Fa mp .
|
|
.It Fn fscow_establish "mp" "func" "cookie"
|
|
Establish a copy-on-write callback for the file system
|
|
.Fa mp .
|
|
The function
|
|
.Fa func
|
|
will be called for every buffer written through this file system.
|
|
.It Fn fscow_disestablish "mp" "func" "cookie"
|
|
Disestablish a copy-on-write callback registered with
|
|
.Fn fscow_establish .
|
|
.It Fn fscow_run "bp" "data_valid"
|
|
Run all copy-on-write callbacks established for the file system this buffer
|
|
belongs to.
|
|
If
|
|
.Fa data_valid
|
|
is
|
|
.Dv true
|
|
the buffer data has not yet been modified.
|
|
.El
|
|
.Sh RETURN VALUES
|
|
The functions
|
|
.Fn fstrans_setstate
|
|
and
|
|
.Fn fstrans_start_nowait
|
|
return zero on success and an error value on failure.
|
|
.Sh EXAMPLES
|
|
The following is an example of a file system suspend operation.
|
|
.Bd -literal
|
|
int
|
|
xxx_suspendctl(struct mount *mp, int cmd)
|
|
{
|
|
int error;
|
|
|
|
switch (cmd) {
|
|
case SUSPEND_SUSPEND:
|
|
error = fstrans_setstate(mp, FSTRANS_SUSPENDING);
|
|
if (error != 0)
|
|
return error;
|
|
|
|
/* Sync file system state to disk. */
|
|
|
|
return fstrans_setstate(mp, FSTRANS_SUSPENDED);
|
|
|
|
case SUSPEND_RESUME:
|
|
return fstrans_setstate(mp, FSTRANS_NORMAL);
|
|
|
|
default:
|
|
return EINVAL;
|
|
}
|
|
}
|
|
.Ed
|
|
.Pp
|
|
This is an example of a file system operation.
|
|
.Bd -literal
|
|
int
|
|
xxx_create(void *v)
|
|
{
|
|
struct vop_create_args *ap = v;
|
|
struct mount *mp = ap-\*[Gt]a_dvp-\*[Gt]v_mount;
|
|
int error;
|
|
|
|
if ((error = fstrans_start(mp, FSTRANS_SHARED)) != 0)
|
|
return error;
|
|
|
|
/* Actually create the node. */
|
|
|
|
fstrans_done(mp);
|
|
|
|
return 0;
|
|
}
|
|
.Ed
|
|
.Sh SEE ALSO
|
|
.Xr vfs_resume 9 ,
|
|
.Xr vfs_suspend 9
|
|
.Sh CODE REFERENCES
|
|
The actual code implementing this subsystem can be found in the file
|
|
.Pa sys/kern/vfs_trans.c .
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
subsystem appeared in
|
|
.Nx 5.0 .
|
|
.Sh AUTHORS
|
|
The
|
|
.Nm
|
|
subsystem was written by
|
|
.An J\(:urgen Hannken-Illjes
|
|
.Aq hannken@NetBSD.org .
|