The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/kern/bufq_disksort.c

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    1 /*      $NetBSD: bufq_disksort.c,v 1.9 2008/04/30 12:09:02 reinoud Exp $        */
    2 /*      NetBSD: subr_disk.c,v 1.61 2004/09/25 03:30:44 thorpej Exp      */
    3 
    4 /*-
    5  * Copyright (c) 1996, 1997, 1999, 2000 The NetBSD Foundation, Inc.
    6  * All rights reserved.
    7  *
    8  * This code is derived from software contributed to The NetBSD Foundation
    9  * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
   10  * NASA Ames Research Center.
   11  *
   12  * Redistribution and use in source and binary forms, with or without
   13  * modification, are permitted provided that the following conditions
   14  * are met:
   15  * 1. Redistributions of source code must retain the above copyright
   16  *    notice, this list of conditions and the following disclaimer.
   17  * 2. Redistributions in binary form must reproduce the above copyright
   18  *    notice, this list of conditions and the following disclaimer in the
   19  *    documentation and/or other materials provided with the distribution.
   20  *
   21  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
   22  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
   23  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   24  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
   25  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   26  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   27  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   28  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   29  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   30  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   31  * POSSIBILITY OF SUCH DAMAGE.
   32  */
   33 
   34 /*
   35  * Copyright (c) 1982, 1986, 1988, 1993
   36  *      The Regents of the University of California.  All rights reserved.
   37  * (c) UNIX System Laboratories, Inc.
   38  * All or some portions of this file are derived from material licensed
   39  * to the University of California by American Telephone and Telegraph
   40  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
   41  * the permission of UNIX System Laboratories, Inc.
   42  *
   43  * Redistribution and use in source and binary forms, with or without
   44  * modification, are permitted provided that the following conditions
   45  * are met:
   46  * 1. Redistributions of source code must retain the above copyright
   47  *    notice, this list of conditions and the following disclaimer.
   48  * 2. Redistributions in binary form must reproduce the above copyright
   49  *    notice, this list of conditions and the following disclaimer in the
   50  *    documentation and/or other materials provided with the distribution.
   51  * 3. Neither the name of the University nor the names of its contributors
   52  *    may be used to endorse or promote products derived from this software
   53  *    without specific prior written permission.
   54  *
   55  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   56  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   57  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   58  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   59  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   60  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   61  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   62  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   63  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   64  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   65  * SUCH DAMAGE.
   66  *
   67  *      @(#)ufs_disksubr.c      8.5 (Berkeley) 1/21/94
   68  */
   69 
   70 #include <sys/cdefs.h>
   71 __KERNEL_RCSID(0, "$NetBSD: bufq_disksort.c,v 1.9 2008/04/30 12:09:02 reinoud Exp $");
   72 
   73 #include <sys/param.h>
   74 #include <sys/systm.h>
   75 #include <sys/buf.h>
   76 #include <sys/bufq.h>
   77 #include <sys/bufq_impl.h>
   78 #include <sys/malloc.h>
   79 
   80 /*
   81  * Seek sort for disks.
   82  *
   83  * There are actually two queues, sorted in ascendening order.  The first
   84  * queue holds those requests which are positioned after the current block;
   85  * the second holds requests which came in after their position was passed.
   86  * Thus we implement a one-way scan, retracting after reaching the end of
   87  * the drive to the first request on the second queue, at which time it
   88  * becomes the first queue.
   89  *
   90  * A one-way scan is natural because of the way UNIX read-ahead blocks are
   91  * allocated.
   92  */
   93 
   94 struct bufq_disksort {
   95         TAILQ_HEAD(, buf) bq_head;      /* actual list of buffers */
   96 };
   97 
   98 static void bufq_disksort_init(struct bufq_state *);
   99 static void bufq_disksort_put(struct bufq_state *, struct buf *);
  100 static struct buf *bufq_disksort_get(struct bufq_state *, int);
  101 
  102 BUFQ_DEFINE(disksort, 20, bufq_disksort_init);
  103 
  104 static void
  105 bufq_disksort_put(struct bufq_state *bufq, struct buf *bp)
  106 {
  107         struct bufq_disksort *disksort = bufq_private(bufq);
  108         struct buf *bq, *nbq;
  109         int sortby;
  110 
  111         sortby = bufq->bq_flags & BUFQ_SORT_MASK;
  112 
  113         bq = TAILQ_FIRST(&disksort->bq_head);
  114 
  115         /*
  116          * If the queue is empty it's easy; we just go on the end.
  117          */
  118         if (bq == NULL) {
  119                 TAILQ_INSERT_TAIL(&disksort->bq_head, bp, b_actq);
  120                 return;
  121         }
  122 
  123         /*
  124          * If we lie before the currently active request, then we
  125          * must locate the second request list and add ourselves to it.
  126          */
  127         if (buf_inorder(bp, bq, sortby)) {
  128                 while ((nbq = TAILQ_NEXT(bq, b_actq)) != NULL) {
  129                         /*
  130                          * Check for an ``inversion'' in the normally ascending
  131                          * block numbers, indicating the start of the second
  132                          * request list.
  133                          */
  134                         if (buf_inorder(nbq, bq, sortby)) {
  135                                 /*
  136                                  * Search the second request list for the first
  137                                  * request at a larger block number.  We go
  138                                  * after that; if there is no such request, we
  139                                  * go at the end.
  140                                  */
  141                                 do {
  142                                         if (buf_inorder(bp, nbq, sortby))
  143                                                 goto insert;
  144                                         bq = nbq;
  145                                 } while ((nbq =
  146                                     TAILQ_NEXT(bq, b_actq)) != NULL);
  147                                 goto insert;            /* after last */
  148                         }
  149                         bq = nbq;
  150                 }
  151                 /*
  152                  * No inversions... we will go after the last, and
  153                  * be the first request in the second request list.
  154                  */
  155                 goto insert;
  156         }
  157         /*
  158          * Request is at/after the current request...
  159          * sort in the first request list.
  160          */
  161         while ((nbq = TAILQ_NEXT(bq, b_actq)) != NULL) {
  162                 /*
  163                  * We want to go after the current request if there is an
  164                  * inversion after it (i.e. it is the end of the first
  165                  * request list), or if the next request is a larger cylinder
  166                  * than our request.
  167                  */
  168                 if (buf_inorder(nbq, bq, sortby) ||
  169                     buf_inorder(bp, nbq, sortby))
  170                         goto insert;
  171                 bq = nbq;
  172         }
  173         /*
  174          * Neither a second list nor a larger request... we go at the end of
  175          * the first list, which is the same as the end of the whole schebang.
  176          */
  177 insert: TAILQ_INSERT_AFTER(&disksort->bq_head, bq, bp, b_actq);
  178 }
  179 
  180 static struct buf *
  181 bufq_disksort_get(struct bufq_state *bufq, int remove)
  182 {
  183         struct bufq_disksort *disksort = bufq->bq_private;
  184         struct buf *bp;
  185 
  186         bp = TAILQ_FIRST(&disksort->bq_head);
  187 
  188         if (bp != NULL && remove)
  189                 TAILQ_REMOVE(&disksort->bq_head, bp, b_actq);
  190 
  191         return (bp);
  192 }
  193 
  194 static struct buf *
  195 bufq_disksort_cancel(struct bufq_state *bufq, struct buf *buf)
  196 {
  197         struct bufq_disksort *disksort = bufq->bq_private;
  198         struct buf *bq;
  199 
  200         bq = TAILQ_FIRST(&disksort->bq_head);
  201         while (bq) {
  202                 if (bq == buf) {
  203                         TAILQ_REMOVE(&disksort->bq_head, bq, b_actq);
  204                         return buf;
  205                 }
  206                 bq = TAILQ_NEXT(bq, b_actq);
  207         }
  208         return NULL;
  209 }
  210 
  211 static void
  212 bufq_disksort_init(struct bufq_state *bufq)
  213 {
  214         struct bufq_disksort *disksort;
  215 
  216         disksort = malloc(sizeof(*disksort), M_DEVBUF, M_ZERO);
  217         bufq->bq_private = disksort;
  218         bufq->bq_get = bufq_disksort_get;
  219         bufq->bq_put = bufq_disksort_put;
  220         bufq->bq_cancel = bufq_disksort_cancel;
  221         TAILQ_INIT(&disksort->bq_head);
  222 }

Cache object: 5381c4024b4724c7d77a59ef005840a6


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