1.\"	$OpenBSD: swapctl.2,v 1.14 2003/06/02 20:18:39 millert Exp $
2.\"	$NetBSD: swapctl.2,v 1.10 1998/08/29 17:11:09 mrg Exp $
3.\"
4.\" Copyright (c) 1997 Matthew R. Green
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32.Dd June 20, 1997
33.Dt SWAPCTL 2
34.Os
35.Sh NAME
36.Nm swapctl
37.Nd modify swap configuration
38.Sh SYNOPSIS
39.Fd #include <unistd.h>
40.Fd #include <sys/swap.h>
41.Ft int
42.Fn swapctl "int cmd" "const void *arg" "int misc"
43.Sh DESCRIPTION
44The
45.Fn swapctl
46function is used to add and delete swap devices, and modify their
47configuration.
48.Pp
49The
50.Fa cmd
51parameter specifies the operation to be performed.
52The
53.Fa arg
54and
55.Fa misc
56parameters have different meanings, depending on the
57.Fa cmd
58parameter.
59.Bl -item -offset indent
60.It
61If
62.Fa cmd
63is
64.Dv SWAP_NSWAP ,
65the current number of swap devices in the system is returned.
66The
67.Fa arg
68and
69.Fa misc
70parameters are ignored.
71.It
72If
73.Fa cmd
74is
75.Dv SWAP_STATS ,
76the current statistics for swap devices are returned in the
77.Fa arg
78parameter.
79No more than
80.Fa misc
81swap devices are returned.
82The
83.Fa arg
84parameter should point to an array of at least
85.Fa misc
86struct swapent structures:
87.Bd -literal
88struct swapent {
89	dev_t	se_dev;			/* device id */
90	int	se_flags;		/* entry flags */
91	int	se_nblks;		/* total blocks */
92	int	se_inuse;		/* blocks in use */
93	int	se_priority;		/* priority */
94	char	se_path[MAXPATHLEN];	/* path to entry */
95};
96.Ed
97.Pp
98The flags are defined as
99.Bd -literal
100	SWF_INUSE       in use: we have swapped here
101	SWF_ENABLE      enabled: we can swap here
102	SWF_BUSY        busy: I/O happening here
103	SWF_FAKE        fake: still being built
104.Ed
105.It
106If
107.Fa cmd
108is
109.Dv SWAP_ON ,
110the
111.Fa arg
112parameter is used as a pathname of a file to enable swapping to.
113The
114.Fa misc
115parameter is used to set the priority of this swap device.
116.It
117If
118.Fa cmd
119is
120.Dv SWAP_OFF ,
121the
122.Fa arg
123parameter is used as the pathname of a file to disable swapping from.
124The
125.Fa misc
126parameter is ignored.
127.It
128If
129.Fa cmd
130is
131.Dv SWAP_CTL ,
132the
133.Fa arg
134and
135.Fa misc
136parameters have the same function as for the
137.Dv SWAP_ON
138case, except that they change the priority of a currently enabled swap device.
139.El
140.Pp
141When swapping is enabled on a block device, the first portion of the disk is
142left unused to prevent any disklabel present from being overwritten.
143This space is allocated from the swap device when the
144.Dv SWAP_ON
145command is used.
146.Sh RETURN VALUES
147If the
148.Fa cmd
149parameter is
150.Dv SWAP_NSWAP
151or
152.Dv SWAP_STATS ,
153.Fn swapctl
154returns the number of swap devices, if successful.
155The
156.Dv SWAP_NSWAP
157command is always successful.
158Otherwise it returns 0 on success and \-1 on failure,
159setting the global variable
160.Va errno
161to indicate the error.
162.Sh ERRORS
163.Fn swapctl
164succeeds unless:
165.Bl -tag -width Er
166.It Bq Er ENOTDIR
167A component of the path prefix is not a directory.
168.It Bq Er ENAMETOOLONG
169A component of a pathname exceeded
170.Dv NAME_MAX
171characters, or an entire path name exceeded
172.Dv PATH_MAX
173characters.
174.It Bq Er ENOENT
175The named device does not exist.
176For the
177.Dv SWAP_CTL
178command, the named device is not currently enabled for swapping.
179.It Bq Er EACCES
180Search permission is denied for a component of the path prefix.
181.It Bq Er ELOOP
182Too many symbolic links were encountered in translating the pathname.
183.It Bq Er EPERM
184The caller is not the superuser.
185.It Bq Er EBUSY
186The device specified by
187.Fa arg
188has already been made available for swapping.
189.It Bq Er EINVAL
190The device configured by
191.Fa arg
192has no associated size, or the
193.Fa cmd
194was unknown.
195.It Bq Er ENXIO
196The major device number of
197.Fa arg
198is out of range (this indicates no device driver exists
199for the associated hardware).
200.It Bq Er EIO
201An I/O error occurred while opening the swap device.
202.It Bq Er EFAULT
203.Fa arg
204points outside the process' allocated address space.
205.El
206.Sh SEE ALSO
207.Xr config 8 ,
208.Xr swapctl 8
209.Sh HISTORY
210The
211.Fn swapctl
212function call appeared in
213.Nx 1.3 .
214The
215.Fa se_path
216member was added to
217.Li struct swapent
218in
219.Nx 1.4 ,
220when the header file was also moved from
221.Aq Pa vm/vm_swap.h .
222.Sh AUTHORS
223The current swap system was designed and implemented by
224.An Matthew Green Aq mrg@eterna.com.au ,
225with help from Paul Kranenburg
226.Aq pk@NetBSD.ORG
227and Leo Weppelman
228.Aq leo@NetBSD.ORG ,
229and insights from Jason R. Thorpe
230.Aq thorpej@NetBSD.ORG .
231