.\" $NetBSD: swapctl.2,v 1.10 1998/08/29 17:11:09 mrg Exp $ .\" .\" Copyright (c) 1997 Matthew R. Green .\" Copyright (c) 1980, 1991, 1993 .\" The Regents of the University of California. 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, 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. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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 June 20, 1997 .Dt SWAPCTL 2 .Os NetBSD .Sh NAME .Nm swapctl .Nd modify swap configuration .Sh SYNOPSIS .Fd #include .Fd #include .Ft int .Fn swapctl "int cmd" "const void *arg" "int misc" .Sh DESCRIPTION The .Nm function is used to add and delete swap devices, and modify their configuration. .Pp The .Fa cmd parameter specifies the operation to be performed. The .Fa arg and .Fa misc parameters have different meanings, depending on the .Fa cmd parameter. .Bl -item -offset indent .It If .Fa cmd is .Dv SWAP_NSWAP , the current number of swap devices in the system is returned. The .Fa arg and .Fa misc parameters are ignored. .It If .Fa cmd is .Dv SWAP_STATS , the current statistics for swap devices are returned in the .Fa arg parameter. No more than .Fa misc swap devices are returned. The .Fa arg parameter should point to an array of at least .Fa misc struct swapent structures: .Bd -literal struct swapent { dev_t se_dev; /* device id */ int se_flags; /* entry flags */ int se_nblks; /* total blocks */ int se_inuse; /* blocks in use */ int se_priority; /* priority */ char se_path[PATH_MAX+1]; /* path to entry */ }; .Ed .Pp The flags are defined as .Bd -literal SWF_INUSE in use: we have swapped here SWF_ENABLE enabled: we can swap here SWF_BUSY busy: I/O happening here SWF_FAKE fake: still being built .Ed .It If .Fa cmd is .Dv SWAP_ON , the .Fa arg parameter is used as a pathname of a file to enable swapping to. The .Fa misc parameter is used to set the priority of this swap device. .It If .Fa cmd is .Dv SWAP_OFF , the .Fa arg parameter is used as the pathname of a file to disable swapping from. The .Fa misc parameter is ignored. .It If .Fa cmd is .Dv SWAP_CTL , the .Fa arg and .Fa misc parameters have the same function as for the .Dv SWAP_ON case, except that they change the priority of a currently enabled swap device. .El .Pp When swapping is enabled on a block device, the first portion of the disk is left unused to prevent any disklable present from being overwritten. This space is allocated from the swap device when the .Dv SWAP_ON command is used. .Sh RETURN VALUES If the .Fa cmd parameter is .Dv SWAP_NSWAP or .Dv SWAP_STATS , .Fn swapctl returns the number of swap devices, if successful. The .Dv SWAP_NSWAP command is always successful. Otherwise it returns 0 on success and -1 on failure, setting the global variable .Va errno to indicate the error. .Sh ERRORS .Fn swapctl succeeds unless: .Bl -tag -width Er .It Bq Er ENOTDIR A component of the path prefix is not a directory. .It Bq Er ENAMETOOLONG A component of a pathname exceeded .Dv NAME_MAX characters, or an entire path name exceeded .Dv PATH_MAX characters. .It Bq Er ENOENT The named device does not exist. For the .Dv SWAP_CTL command, the named device is not currently enabled for swapping. .It Bq Er EACCES Search permission is denied for a component of the path prefix. .It Bq Er ELOOP Too many symbolic links were encountered in translating the pathname. .It Bq Er EPERM The caller is not the super-user. .It Bq Er EBUSY The device specified by .Fa arg has already been made available for swapping. .It Bq Er EINVAL The device configured by .Fa arg has no associated size, or the .Fa cmd was unknown. .It Bq Er ENXIO The major device number of .Fa arg is out of range (this indicates no device driver exists for the associated hardware). .It Bq Er EIO An I/O error occurred while opening the swap device. .It Bq Er EFAULT .Fa arg points outside the process' allocated address space. .El .Sh SEE ALSO .Xr config 8 , .Xr swapctl 8 .Sh BUGS The .Dv SWAP_OFF command is currently unimplemented by the .Nx kernel. .Sh AUTHOR The current swap system was designed and implemented by Matthew Green , with help from Paul Kranenburg and Leo Weppelman , and insights from Jason R. Thorpe . .Sh HISTORY The .Fn swapctl function call appeared in .Nx 1.3 . The .Fa se_path member was added to .Va struct swapent in .Nx 1.4 , when the header file was also moved from .Pa .