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https://github.com/freebsd/freebsd-src
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8269e7673c
Remove core system call implementations and documentation to lib/libsys and lib/libsys/<arch> from lib/libc/sys and lib/libc/<arch>/<sys>. Update paths to allow libc to find them in their new home. Reviewed by: kib, emaste, imp Pull Request: https://github.com/freebsd/freebsd-src/pull/908
160 lines
4.5 KiB
Groff
160 lines
4.5 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993
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.\" The Regents of the University of California. 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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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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 December 8, 2021
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.Dt SWAPON 2
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.Os
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.Sh NAME
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.Nm swapon , swapoff
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.Nd control devices for interleaved paging/swapping
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.It vm/vm_param.h
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.It vm/swap_pager.h
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.In unistd.h
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.Ft int
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.Fn swapon "const char *special"
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.Ft int
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.Fn swapoff "const char *special" "u_int flags"
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.Sh DESCRIPTION
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The
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.Fn swapon
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system call
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makes the block device
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.Fa special
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available to the system for
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allocation for paging and swapping.
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The names of potentially
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available devices are known to the system and defined at system
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configuration time.
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The size of the swap area on
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.Fa special
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is calculated at the time the device is first made available
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for swapping.
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.Pp
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The
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.Fn swapoff
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system call disables paging and swapping on the given device.
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All associated swap metadata are deallocated, and the device
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is made available for other purposes.
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.Pp
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The
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.Fa special
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argument points to the name of the device or file used for swapping.
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.The
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.Va flags
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argument takes the following flags:
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.Bl -tag -width SWAPOFF_FORCE
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.It Dv SWAPOFF_FORCE
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Overrides a very conservative check that prevents swapoff
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if the total amount of free memory and remaining swap
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devices space might be unsufficient for the system to continue
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operating.
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.El
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.Sh RETURN VALUES
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If an error has occurred, a value of -1 is returned and
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.Va errno
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is set to indicate the error.
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.Sh ERRORS
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Both
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.Fn swapon
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and
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.Fn swapoff
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can fail if:
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.Bl -tag -width Er
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.It Bq Er ENOTDIR
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A component of the path prefix is not a directory.
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.It Bq Er ENAMETOOLONG
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A component of a pathname exceeded 255 characters,
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or an entire path name exceeded 1023 characters.
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.It Bq Er ENOENT
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The named device does not exist.
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.It Bq Er EACCES
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Search permission is denied for a component of the path prefix.
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.It Bq Er ELOOP
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Too many symbolic links were encountered in translating the pathname.
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.It Bq Er EPERM
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The caller is not the super-user.
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.It Bq Er EFAULT
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The
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.Fa special
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argument
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points outside the process's allocated address space.
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.El
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.Pp
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Additionally,
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.Fn swapon
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can fail for the following reasons:
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.Bl -tag -width Er
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.It Bq Er ENOTBLK
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The
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.Fa special
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argument
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is not a block device.
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.It Bq Er EBUSY
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The device specified by
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.Fa special
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has already
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been made available for swapping
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.It Bq Er ENXIO
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The major device number of
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.Fa special
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is out of range (this indicates no device driver exists
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for the associated hardware).
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.It Bq Er EIO
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An I/O error occurred while opening the swap device.
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.It Bq Er EINTEGRITY
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Corrupted data was detected while reading from the file system to open the
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swap device.
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.El
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.Pp
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Lastly,
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.Fn swapoff
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can fail if:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The system is not currently swapping to
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.Fa special .
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.It Bq Er ENOMEM
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Not enough virtual memory is available to safely disable
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paging and swapping to the given device.
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.El
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.Sh SEE ALSO
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.Xr config 8 ,
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.Xr swapon 8 ,
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.Xr sysctl 8
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.Sh HISTORY
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The
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.Fn swapon
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system call appeared in
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.Bx 4.0 .
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The
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.Fn swapoff
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system call appeared in
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.Fx 5.1 .
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