9bf7a991c5
when there is no memory available to do so. Use the uvnode's strategy routine to retrieve data from the device, rather than always using pread(). Add a buffer header flag that specifies external management of the buffer's data area. All of this in support of a new cleaner, which is not included in this commit.
409 lines
9.9 KiB
C
409 lines
9.9 KiB
C
/* $NetBSD: bufcache.c,v 1.7 2005/05/20 18:59:36 perseant Exp $ */
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/*-
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* Copyright (c) 2003 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by Konrad E. Schroder <perseant@hhhh.org>.
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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. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the NetBSD
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* Foundation, Inc. and its contributors.
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* 4. Neither the name of The NetBSD Foundation nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/types.h>
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#include <sys/param.h>
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#include <sys/time.h>
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#include <sys/buf.h>
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#include <sys/queue.h>
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#include <sys/mount.h>
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#include <assert.h>
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#include <err.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include "bufcache.h"
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#include "vnode.h"
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/*
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* Definitions for the buffer free lists.
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*/
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#define BQUEUES 3 /* number of free buffer queues */
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#define BQ_LOCKED 0 /* super-blocks &c */
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#define BQ_LRU 1 /* lru, useful buffers */
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#define BQ_AGE 2 /* rubbish */
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TAILQ_HEAD(bqueues, ubuf) bufqueues[BQUEUES];
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struct bufhash_struct *bufhash;
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#define HASH_MAX 1024
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int hashmax = HASH_MAX;
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int hashmask = (HASH_MAX - 1);
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int maxbufs = BUF_CACHE_SIZE;
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int nbufs = 0;
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int cachehits = 0;
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int cachemisses = 0;
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int max_depth = 0;
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off_t locked_queue_bytes = 0;
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int locked_queue_count = 0;
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/* Simple buffer hash function */
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static int
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vl_hash(struct uvnode * vp, daddr_t lbn)
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{
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return (int)((unsigned long) vp + lbn) & hashmask;
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}
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/* Initialize buffer cache */
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void
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bufinit(int max)
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{
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int i;
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if (max) {
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for (hashmax = 1; hashmax < max; hashmax <<= 1)
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;
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hashmask = hashmax - 1;
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}
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for (i = 0; i < BQUEUES; i++) {
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TAILQ_INIT(&bufqueues[i]);
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}
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bufhash = (struct bufhash_struct *)malloc(hashmax * sizeof(*bufhash));
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for (i = 0; i < hashmax; i++)
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LIST_INIT(&bufhash[i]);
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}
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/* Widen the hash table. */
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void bufrehash(int max)
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{
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int i, newhashmax, newhashmask;
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struct ubuf *bp, *nbp;
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struct bufhash_struct *np;
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if (max < 0 || max < hashmax)
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return;
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/* Round up to a power of two */
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for (newhashmax = 1; newhashmax < max; newhashmax <<= 1)
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;
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newhashmask = newhashmax - 1;
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/* Allocate new empty hash table, if we can */
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np = (struct bufhash_struct *)malloc(newhashmax * sizeof(*bufhash));
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if (np == NULL)
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return;
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for (i = 0; i < newhashmax; i++)
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LIST_INIT(&np[i]);
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/* Now reassign all existing buffers to their new hash chains. */
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for (i = 0; i < hashmax; i++) {
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bp = LIST_FIRST(&bufhash[i]);
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while(bp) {
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nbp = LIST_NEXT(bp, b_hash);
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LIST_REMOVE(bp, b_hash);
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bp->b_hashval = vl_hash(bp->b_vp, bp->b_lblkno);
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LIST_INSERT_HEAD(&np[bp->b_hashval], bp, b_hash);
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bp = nbp;
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}
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}
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/* Switch over and clean up */
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free(bufhash);
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bufhash = np;
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hashmax = newhashmax;
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hashmask = newhashmask;
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}
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/* Print statistics of buffer cache usage */
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void
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bufstats(void)
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{
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printf("buffer cache: %d hits %d misses (%2.2f%%); hash width %d, depth %d\n",
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cachehits, cachemisses,
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(cachehits * 100.0) / (cachehits + cachemisses),
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hashmax, max_depth);
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}
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/*
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* Remove a buffer from the cache.
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* Caller must remove the buffer from its free list.
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*/
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void
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buf_destroy(struct ubuf * bp)
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{
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bp->b_flags |= B_NEEDCOMMIT;
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LIST_REMOVE(bp, b_vnbufs);
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LIST_REMOVE(bp, b_hash);
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if (!(bp->b_flags & B_DONTFREE))
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free(bp->b_data);
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free(bp);
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--nbufs;
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}
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/* Remove a buffer from its free list. */
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void
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bremfree(struct ubuf * bp)
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{
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struct bqueues *dp = NULL;
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/*
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* We only calculate the head of the freelist when removing
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* the last element of the list as that is the only time that
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* it is needed (e.g. to reset the tail pointer).
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*
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* NB: This makes an assumption about how tailq's are implemented.
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*/
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if (bp->b_flags & B_LOCKED) {
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locked_queue_bytes -= bp->b_bcount;
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--locked_queue_count;
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}
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if (TAILQ_NEXT(bp, b_freelist) == NULL) {
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for (dp = bufqueues; dp < &bufqueues[BQUEUES]; dp++)
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if (dp->tqh_last == &bp->b_freelist.tqe_next)
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break;
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if (dp == &bufqueues[BQUEUES])
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errx(1, "bremfree: lost tail");
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}
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++bp->b_vp->v_usecount;
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TAILQ_REMOVE(dp, bp, b_freelist);
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}
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/* Return a buffer if it is in the cache, otherwise return NULL. */
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struct ubuf *
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incore(struct uvnode * vp, int lbn)
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{
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struct ubuf *bp;
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int hash, depth;
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hash = vl_hash(vp, lbn);
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/* XXX use a real hash instead. */
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depth = 0;
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LIST_FOREACH(bp, &bufhash[hash], b_hash) {
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if (++depth > max_depth)
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max_depth = depth;
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assert(depth <= nbufs);
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if (bp->b_vp == vp && bp->b_lblkno == lbn) {
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return bp;
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}
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}
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return NULL;
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}
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/*
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* Return a buffer of the given size, lbn and uvnode.
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* If none is in core, make a new one.
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*/
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struct ubuf *
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getblk(struct uvnode * vp, daddr_t lbn, int size)
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{
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struct ubuf *bp;
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#ifdef DEBUG
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static int warned;
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#endif
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/*
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* First check the buffer cache lists.
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* We might sometimes need to resize a buffer. If we are growing
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* the buffer, its contents are invalid; but shrinking is okay.
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*/
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if ((bp = incore(vp, lbn)) != NULL) {
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assert(!(bp->b_flags & B_NEEDCOMMIT));
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assert(!(bp->b_flags & B_BUSY));
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bp->b_flags |= B_BUSY;
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bremfree(bp);
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if (bp->b_bcount == size)
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return bp;
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else if (bp->b_bcount > size) {
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assert(!(bp->b_flags & B_DELWRI));
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bp->b_bcount = size;
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bp->b_data = realloc(bp->b_data, size);
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return bp;
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}
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buf_destroy(bp);
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bp = NULL;
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}
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/*
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* Not on the list.
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* Get a new block of the appropriate size and use that.
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* If not enough space, free blocks from the AGE and LRU lists
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* to make room.
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*/
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while (nbufs >= maxbufs + locked_queue_count) {
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bp = TAILQ_FIRST(&bufqueues[BQ_AGE]);
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if (bp)
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TAILQ_REMOVE(&bufqueues[BQ_AGE], bp, b_freelist);
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if (bp == NULL) {
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bp = TAILQ_FIRST(&bufqueues[BQ_LRU]);
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if (bp)
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TAILQ_REMOVE(&bufqueues[BQ_LRU], bp,
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b_freelist);
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}
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if (bp) {
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if (bp->b_flags & B_DELWRI)
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VOP_STRATEGY(bp);
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buf_destroy(bp);
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break;
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}
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#ifdef DEBUG
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else if (!warned) {
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warnx("allocating more than %d buffers", maxbufs);
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++warned;
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}
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#endif
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break;
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}
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++nbufs;
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bp = (struct ubuf *) malloc(sizeof(*bp));
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memset(bp, 0, sizeof(*bp));
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bp->b_data = malloc(size);
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memset(bp->b_data, 0, size);
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bp->b_vp = vp;
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bp->b_blkno = bp->b_lblkno = lbn;
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bp->b_bcount = size;
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bp->b_hashval = vl_hash(vp, lbn);
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LIST_INSERT_HEAD(&bufhash[bp->b_hashval], bp, b_hash);
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LIST_INSERT_HEAD(&vp->v_cleanblkhd, bp, b_vnbufs);
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bp->b_flags = B_BUSY;
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return bp;
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}
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/* Write a buffer to disk according to its strategy routine. */
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void
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bwrite(struct ubuf * bp)
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{
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bp->b_flags &= ~(B_READ | B_DONE | B_DELWRI | B_LOCKED);
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VOP_STRATEGY(bp);
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bp->b_flags |= B_DONE;
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reassignbuf(bp, bp->b_vp);
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brelse(bp);
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}
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/* Put a buffer back on its free list, clear B_BUSY. */
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void
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brelse(struct ubuf * bp)
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{
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int age;
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assert(!(bp->b_flags & B_NEEDCOMMIT));
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assert(bp->b_flags & B_BUSY);
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age = bp->b_flags & B_AGE;
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bp->b_flags &= ~(B_BUSY | B_AGE);
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if (bp->b_flags & B_INVAL) {
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buf_destroy(bp);
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return;
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}
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if (bp->b_flags & B_LOCKED) {
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locked_queue_bytes += bp->b_bcount;
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++locked_queue_count;
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TAILQ_INSERT_TAIL(&bufqueues[BQ_LOCKED], bp, b_freelist);
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} else if (age) {
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TAILQ_INSERT_TAIL(&bufqueues[BQ_AGE], bp, b_freelist);
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} else {
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TAILQ_INSERT_TAIL(&bufqueues[BQ_LRU], bp, b_freelist);
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}
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--bp->b_vp->v_usecount;
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/* Move to the front of the hash chain */
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if (LIST_FIRST(&bufhash[bp->b_hashval]) != bp) {
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LIST_REMOVE(bp, b_hash);
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LIST_INSERT_HEAD(&bufhash[bp->b_hashval], bp, b_hash);
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}
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}
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/* Read the given block from disk, return it B_BUSY. */
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int
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bread(struct uvnode * vp, daddr_t lbn, int size, struct ucred * unused,
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struct ubuf ** bpp)
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{
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struct ubuf *bp;
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daddr_t daddr;
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int error;
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bp = getblk(vp, lbn, size);
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*bpp = bp;
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if (bp->b_flags & (B_DELWRI | B_DONE)) {
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++cachehits;
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return 0;
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}
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++cachemisses;
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/*
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* Not found. Need to find that block's location on disk,
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* and load it in.
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*/
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daddr = -1;
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error = VOP_BMAP(vp, lbn, &daddr);
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bp->b_blkno = daddr;
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if (daddr >= 0) {
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bp->b_flags |= B_READ;
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return VOP_STRATEGY(bp);
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}
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memset(bp->b_data, 0, bp->b_bcount);
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return 0;
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}
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/* Move a buffer between dirty and clean block lists. */
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void
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reassignbuf(struct ubuf * bp, struct uvnode * vp)
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{
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LIST_REMOVE(bp, b_vnbufs);
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if (bp->b_flags & B_DELWRI) {
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LIST_INSERT_HEAD(&vp->v_dirtyblkhd, bp, b_vnbufs);
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} else {
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LIST_INSERT_HEAD(&vp->v_cleanblkhd, bp, b_vnbufs);
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}
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}
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#ifdef DEBUG
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void
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dump_free_lists(void)
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{
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struct ubuf *bp;
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int i;
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for (i = 0; i <= BQ_LOCKED; i++) {
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printf("==> free list %d:\n", i);
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TAILQ_FOREACH(bp, &bufqueues[i], b_freelist) {
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printf("vp %p lbn %" PRId64 " flags %lx\n",
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bp->b_vp, bp->b_lblkno, bp->b_flags);
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}
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}
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}
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#endif
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