/*-
* Copyright (c) 1996, 1997, 1999, 2000 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
* NASA Ames Research Center.
*
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
*/
/*
* Copyright (c) 1982, 1986, 1988, 1993
* The Regents of the University of California. All rights reserved.
* (c) UNIX System Laboratories, Inc.
* All or some portions of this file are derived from material licensed
* to the University of California by American Telephone and Telegraph
* Co. or Unix System Laboratories, Inc. and are reproduced herein with
* the permission of UNIX System Laboratories, Inc.
*
* 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. 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.
*
* @(#)ufs_disksubr.c 8.5 (Berkeley) 1/21/94
*/
/*
* Seek sort for disks.
*
* There are actually two queues, sorted in ascendening order. The first
* queue holds those requests which are positioned after the current block;
* the second holds requests which came in after their position was passed.
* Thus we implement a one-way scan, retracting after reaching the end of
* the drive to the first request on the second queue, at which time it
* becomes the first queue.
*
* A one-way scan is natural because of the way UNIX read-ahead blocks are
* allocated.
*/
struct bufq_disksort {
TAILQ_HEAD(, buf) bq_head; /* actual list of buffers */
};
/*
* If the queue is empty it's easy; we just go on the end.
*/
if (bq == NULL) {
TAILQ_INSERT_TAIL(&disksort->bq_head, bp, b_actq);
return;
}
/*
* If we lie before the currently active request, then we
* must locate the second request list and add ourselves to it.
*/
if (buf_inorder(bp, bq, sortby)) {
while ((nbq = TAILQ_NEXT(bq, b_actq)) != NULL) {
/*
* Check for an ``inversion'' in the normally ascending
* block numbers, indicating the start of the second
* request list.
*/
if (buf_inorder(nbq, bq, sortby)) {
/*
* Search the second request list for the first
* request at a larger block number. We go
* after that; if there is no such request, we
* go at the end.
*/
do {
if (buf_inorder(bp, nbq, sortby))
goto insert;
bq = nbq;
} while ((nbq =
TAILQ_NEXT(bq, b_actq)) != NULL);
goto insert; /* after last */
}
bq = nbq;
}
/*
* No inversions... we will go after the last, and
* be the first request in the second request list.
*/
goto insert;
}
/*
* Request is at/after the current request...
* sort in the first request list.
*/
while ((nbq = TAILQ_NEXT(bq, b_actq)) != NULL) {
/*
* We want to go after the current request if there is an
* inversion after it (i.e. it is the end of the first
* request list), or if the next request is a larger cylinder
* than our request.
*/
if (buf_inorder(nbq, bq, sortby) ||
buf_inorder(bp, nbq, sortby))
goto insert;
bq = nbq;
}
/*
* Neither a second list nor a larger request... we go at the end of
* the first list, which is the same as the end of the whole schebang.
*/
insert: TAILQ_INSERT_AFTER(&disksort->bq_head, bq, bp, b_actq);
}
