91 lines
2.8 KiB
Groff
91 lines
2.8 KiB
Groff
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.\"
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.\" Copyright (c) 2005 Robert N. M. Watson
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.\" 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(s), this list of conditions and the following disclaimer as
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.\" the first lines of this file unmodified other than the possible
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.\" addition of one or more copyright notices.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice(s), 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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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
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.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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.\" DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
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.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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.\" 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 SUCH
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.\" DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd September 21, 2005
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.Dt VFS_LOCK_GIANT 9
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.Os
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.Sh NAME
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.Nm VFS_LOCK_GIANT ,
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.Nm VFS_UNLOCK_GIANT
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.Nd "Conditionally lock and unlock Giant around entry into VFS"
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.Sh SYNOPSIS
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.In sys/param.h
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.In sys/vnode.h
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.Ft int
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.Fn VFS_LOCK_GIANT "struct mount *mp"
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.Ft void
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.Fn VFS_UNLOCK_GIANT "int vfslocked"
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.Sh DESCRIPTION
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.Fn VFS_LOCK_GIANT
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will conditionally acquire the
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.Dv Giant
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lock if the file system referenced by
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.Fa mp
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is marked as MPSAFE or not, returning a flag indicating whether Giant was
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set, which may later be passed to
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.Fn VFS_UNLOCK_GIANT .
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The value of
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.Fa mp
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will typically be derived from the mount pointer in a
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.Xr vnode
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on which a VFS operation will be performed.
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.Pp
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.Fn VFS_UNLOCK_GIANT
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conditionally releases the
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.Va Giant
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lock if the passed
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.Fa vfslocked
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argument is non-zero.
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It is expected that the argument will be derived from the return values of
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.Vn VFS_LOCK_GIANT
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or
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.Xr NDHASGIANT 9 .
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.Sh RETURN VALUES
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.Fn VFS_LOCK_GIANT
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returns a boolean indicating whether or not
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.Va Giant
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was acquired.
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.Sh SEE ALSO
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.Xr mutex 9 ,
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.Xr NDHASGIANT 9 ,
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.Xr vnode 9
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.Sh AUTHORS
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MPSAFE VFS support for
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.Fx
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was implemented by
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.An Jeff Roberson .
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.Pp
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This manual page was written by
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.An Robert Watson .
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.Sh BUGS
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.Pp
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Non-MPSAFE file systems exist, requiring callers conditional locking and
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unlocking of
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.Va Giant .
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