333dcaa498
Previously before you could call unrhdr_delete you needed to individually free every allocated unit. It is useful to be able to tear down the unr without having to go through this process, as it is significantly faster than freeing the individual units. Reviewed by: cem, lidl Approved by: rstone (mentor) Sponsored by: Dell EMC Isilon Differential Revision: https://reviews.freebsd.org/D12591
122 lines
3.9 KiB
Groff
122 lines
3.9 KiB
Groff
.\" Copyright (c) 2005 Gleb Smirnoff <glebius@FreeBSD.org>
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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, 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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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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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.\" $FreeBSD$
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.\"
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.Dd October 4, 2017
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.Dt UNR 9
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.Os
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.Sh NAME
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.Nm new_unrhdr ,
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.Nm clear_unrhdr ,
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.Nm delete_unrhdr ,
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.Nm alloc_unr ,
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.Nm alloc_unr_specific ,
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.Nm free_unr
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.Nd "kernel unit number allocator"
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.Sh SYNOPSIS
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.In sys/systm.h
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.Ft "struct unrhdr *"
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.Fn new_unrhdr "int low" "int high" "struct mtx *mutex"
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.Ft void
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.Fn clear_unrhdr "struct unrhdr *uh"
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.Ft void
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.Fn delete_unrhdr "struct unrhdr *uh"
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.Ft int
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.Fn alloc_unr "struct unrhdr *uh"
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.Ft int
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.Fn alloc_unrl "struct unrhdr *uh"
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.Ft int
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.Fn alloc_unr_specific "struct unrhdr *uh" "u_int item"
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.Ft void
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.Fn free_unr "struct unrhdr *uh" "u_int item"
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.Sh DESCRIPTION
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The kernel unit number allocator is a generic facility, which allows to allocate
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unit numbers within a specified range.
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.Bl -tag -width indent
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.It Fn new_unrhdr low high mutex
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Initialize a new unit number allocator entity.
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The
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.Fa low
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and
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.Fa high
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arguments
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specify minimum and maximum number of unit numbers.
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There is no cost associated with the range of unit numbers, so unless the resource
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really is finite,
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.Dv INT_MAX
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can be used.
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If
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.Fa mutex
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is not
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.Dv NULL ,
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it is used for locking when allocating and freeing units.
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Otherwise, internal mutex is used.
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.It Fn clear_unrhdr uh
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Clear all units from the specified unit number allocator entity.
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This function resets the entity as if it were just initialized with
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.Fn new_unrhdr .
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.It Fn delete_unrhdr uh
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Delete specified unit number allocator entity.
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This function frees the memory associated with the entity, it does not free
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any units.
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To free all units use
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.Fn clear_unrhdr .
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.It Fn alloc_unr uh
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Return a new unit number.
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The lowest free number is always allocated.
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This function does not allocate memory and never sleeps, however it may
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block on a mutex.
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If no free unit numbers are left,
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.Li \-1
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is returned.
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.It Fn alloc_unrl uh
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Same as
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.Fn alloc_unr
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except that mutex is assumed to be already locked and thus is not used.
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.It Fn alloc_unr_specific uh item
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Allocate a specific unit number.
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This function allocates memory and thus may sleep.
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The allocated unit number is returned on success.
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If the specified number is already allocated or out of the range,
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.Li \-1
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is returned.
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.It Fn free_unr uh item
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Free a previously allocated unit number.
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This function may require allocating memory, and thus it can sleep.
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There is no pre-locked variant.
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.El
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.Sh CODE REFERENCES
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The above functions are implemented in
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.Pa sys/kern/subr_unit.c .
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.Sh HISTORY
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Kernel unit number allocator first appeared in
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.Fx 6.0 .
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.Sh AUTHORS
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.An -nosplit
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Kernel unit number allocator was written by
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.An Poul-Henning Kamp .
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This manpage was written by
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.An Gleb Smirnoff .
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