1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
|
.\"
.\" Copyright (c) 2005 Robert N. M. Watson
.\" All rights reserved.
.\"
.\" 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(s), this list of conditions and the following disclaimer as
.\" the first lines of this file unmodified other than the possible
.\" addition of one or more copyright notices.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice(s), 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 COPYRIGHT HOLDER(S) ``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 COPYRIGHT HOLDER(S) 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.
.\"
.\" $FreeBSD$
.\"
.Dd September 21, 2005
.Dt VFS_LOCK_GIANT 9
.Os
.Sh NAME
.Nm VFS_LOCK_GIANT ,
.Nm VFS_UNLOCK_GIANT
.Nd "conditionally lock and unlock Giant around entry into VFS"
.Sh SYNOPSIS
.In sys/param.h
.In sys/mount.h
.In sys/vnode.h
.Ft int
.Fn VFS_LOCK_GIANT "struct mount *mp"
.Ft void
.Fn VFS_UNLOCK_GIANT "int vfslocked"
.Sh DESCRIPTION
.Fn VFS_LOCK_GIANT
will conditionally acquire the
.Va Giant
lock if the file system referenced by
.Fa mp
is marked as MPSAFE or not, returning a flag indicating whether
.Va Giant
was
set, which may later be passed to
.Fn VFS_UNLOCK_GIANT .
The value of
.Fa mp
will typically be derived from the mount pointer in a
.Vt vnode
on which a VFS operation will be performed.
.Pp
.Fn VFS_UNLOCK_GIANT
conditionally releases the
.Va Giant
lock if the passed
.Fa vfslocked
argument is non-zero.
It is expected that the argument will be derived from the return values of
.Fn VFS_LOCK_GIANT
or
.Xr NDHASGIANT 9 .
.Sh RETURN VALUES
.Fn VFS_LOCK_GIANT
returns a boolean indicating whether or not
.Va Giant
was acquired.
.Sh SEE ALSO
.Xr mutex 9 ,
.Xr NDHASGIANT 9 ,
.Xr vnode 9
.Sh AUTHORS
.An -nosplit
MPSAFE VFS support for
.Fx
was implemented by
.An Jeff Roberson .
.Pp
This manual page was written by
.An Robert Watson .
.Sh BUGS
Non-MPSAFE file systems exist, requiring callers conditional locking and
unlocking of
.Va Giant .
|
