9abd5d84ac
the first time block 0 is read. This fix initialises the block numbers to -1 which isn't the most correct thing for a daddr_t but it isn't likely to cause a problem in the boot blocks and it could do with a more thought out fix later. The bug is probably benign on the i386 but on the alpha it can cause initial file opens to fail. This is the cause of the "can't open /boot/boot.conf" errors. It appears on the alpha because of a number of combining factors. On the alpha the LABELSECTOR is 0 so block 0 needs to be read in from the media. The first time this happens you get a false hit because the bc_blkno field is zero initially. Also, the timestamp check against this cache hit succeeds because on the alpha a hacked getsecs() function can return 0 when it starts counting so that the zero initial timestamp + BCACHE_TIMEOUT is greater than the current time until getsecs() has counted passed BCACHE_TIMEOUT. The overall effect is that the first open() that occurs gets a false cache hit and returns garbage to the bd_strategy() function which then fails the open() call. This false hit then stays in the cache until BCACHE_TIMEOUT getsecs() ticks have passed; all open() calls during this time fail. This explains why you can generally access the media by the time you get to interp() and start issuing commands but the earlier attempts to run the boot scripts are failing. It's possible that this is causing the problem switching to the mfsroot floppy as well but I haven't confirmed that.
263 lines
7.4 KiB
C
263 lines
7.4 KiB
C
/*-
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* Copyright (c) 1998 Michael Smith <msmith@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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* $Id: bcache.c,v 1.3 1998/11/04 00:29:01 msmith Exp $
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*/
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/*
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* Simple LRU block cache
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*/
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#include <stand.h>
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#include <string.h>
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#include <bitstring.h>
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#include "bootstrap.h"
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/* #define BCACHE_DEBUG */
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#ifdef BCACHE_DEBUG
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#define BCACHE_TIMEOUT 10
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# define DEBUG(fmt, args...) printf("%s: " fmt "\n" , __FUNCTION__ , ## args)
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#else
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#define BCACHE_TIMEOUT 2
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# define DEBUG(fmt, args...)
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#endif
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struct bcachectl
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{
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daddr_t bc_blkno;
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time_t bc_stamp;
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int bc_count;
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};
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static struct bcachectl *bcache_ctl;
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static caddr_t bcache_data;
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static bitstr_t *bcache_miss;
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static int bcache_nblks;
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static int bcache_blksize;
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static int bcache_hits, bcache_misses, bcache_ops, bcache_bypasses;
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static int bcache_bcount;
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static void bcache_insert(caddr_t buf, daddr_t blkno);
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static int bcache_lookup(caddr_t buf, daddr_t blkno);
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/*
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* Initialise the cache for (nblks) of (bsize).
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*/
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int
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bcache_init(int nblks, size_t bsize)
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{
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int i;
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/* discard any old contents */
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if (bcache_data != NULL) {
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free(bcache_data);
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bcache_data = NULL;
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free(bcache_ctl);
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}
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/* Allocate control structures */
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bcache_nblks = nblks;
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bcache_blksize = bsize;
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bcache_data = malloc(bcache_nblks * bcache_blksize);
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bcache_ctl = (struct bcachectl *)malloc(bcache_nblks * sizeof(struct bcachectl));
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bcache_miss = bit_alloc((bcache_nblks + 1) / 2);
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if ((bcache_data == NULL) || (bcache_ctl == NULL) || (bcache_miss == NULL)) {
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if (bcache_miss)
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free(bcache_miss);
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if (bcache_ctl)
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free(bcache_ctl);
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if (bcache_data)
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free(bcache_data);
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bcache_data = NULL;
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return(ENOMEM);
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}
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/* Invalidate the cache */
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for (i = 0; i < bcache_nblks; i++) {
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bcache_ctl[i].bc_count = -1;
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bcache_ctl[i].bc_blkno = -1;
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}
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return(0);
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}
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/*
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* Handle a transfer request; fill in parts of the request that can
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* be satisfied by the cache, use the supplied strategy routine to do
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* device I/O and then use the I/O results to populate the cache.
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*
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* Requests larger than 1/2 the cache size will be bypassed and go
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* directly to the disk. XXX tune this.
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*/
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int
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bcache_strategy(void *devdata, int rw, daddr_t blk, size_t size, void *buf, size_t *rsize)
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{
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struct bcache_devdata *dd = (struct bcache_devdata *)devdata;
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int nblk, p_size;
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daddr_t p_blk;
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caddr_t p_buf;
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int i, j, result;
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bcache_ops++;
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/* bypass large requests, or when the cache is inactive */
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if ((bcache_data == NULL) || ((size * 2 / bcache_blksize) > bcache_nblks)) {
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DEBUG("bypass %d from %d", size / bcache_blksize, blk);
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bcache_bypasses++;
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return(dd->dv_strategy(dd->dv_devdata, rw, blk, size, buf, rsize));
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}
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nblk = size / bcache_blksize;
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result = 0;
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/* Satisfy any cache hits up front */
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for (i = 0; i < nblk; i++) {
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if (bcache_lookup(buf + (bcache_blksize * i), blk + i)) {
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bit_set(bcache_miss, i); /* cache miss */
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bcache_misses++;
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} else {
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bit_clear(bcache_miss, i); /* cache hit */
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bcache_hits++;
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}
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}
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/* Go back and fill in any misses XXX optimise */
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p_blk = -1;
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p_buf = NULL;
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p_size = 0;
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for (i = 0; i < nblk; i++) {
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if (bit_test(bcache_miss, i)) {
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/* miss, add to pending transfer */
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if (p_blk == -1) {
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p_blk = blk + i;
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p_buf = buf + (bcache_blksize * i);
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p_size = 1;
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} else {
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p_size++;
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}
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} else if (p_blk != -1) {
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/* hit, complete pending transfer */
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result = dd->dv_strategy(dd->dv_devdata, rw, p_blk, p_size * bcache_blksize, p_buf, NULL);
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if (result != 0)
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goto done;
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for (j = 0; j < p_size; j++)
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bcache_insert(p_buf + (j * bcache_blksize), p_blk + j);
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p_blk = -1;
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}
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}
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if (p_blk != -1) {
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/* pending transfer left */
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result = dd->dv_strategy(dd->dv_devdata, rw, p_blk, p_size * bcache_blksize, p_buf, NULL);
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if (result != 0)
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goto done;
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for (j = 0; j < p_size; j++)
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bcache_insert(p_buf + (j * bcache_blksize), p_blk + j);
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}
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done:
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if ((result == 0) && (rsize != NULL))
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*rsize = size;
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return(result);
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}
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/*
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* Insert a block into the cache. Retire the oldest block to do so, if required.
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*
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* XXX the LRU algorithm will fail after 2^31 blocks have been transferred.
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*/
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static void
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bcache_insert(caddr_t buf, daddr_t blkno)
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{
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time_t now;
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int i, cand, ocount;
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time(&now);
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cand = 0; /* assume the first block */
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ocount = bcache_ctl[0].bc_count;
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/* find the oldest block */
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for (i = 1; i < bcache_nblks; i++) {
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if (bcache_ctl[i].bc_blkno == blkno) {
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/* reuse old entry */
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cand = i;
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break;
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}
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if (bcache_ctl[i].bc_count < ocount) {
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ocount = bcache_ctl[i].bc_count;
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cand = i;
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}
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}
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DEBUG("insert blk %d -> %d @ %d # %d", blkno, cand, now, bcache_bcount);
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bcopy(buf, bcache_data + (bcache_blksize * cand), bcache_blksize);
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bcache_ctl[cand].bc_blkno = blkno;
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bcache_ctl[cand].bc_stamp = now;
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bcache_ctl[cand].bc_count = bcache_bcount++;
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}
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/*
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* Look for a block in the cache. Blocks more than BCACHE_TIMEOUT seconds old
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* may be stale (removable media) and thus are discarded. Copy the block out
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* if successful and return zero, or return nonzero on failure.
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*/
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static int
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bcache_lookup(caddr_t buf, daddr_t blkno)
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{
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time_t now;
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int i;
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time(&now);
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for (i = 0; i < bcache_nblks; i++)
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/* cache hit? */
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if ((bcache_ctl[i].bc_blkno == blkno) && ((bcache_ctl[i].bc_stamp + BCACHE_TIMEOUT) >= now)) {
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bcopy(bcache_data + (bcache_blksize * i), buf, bcache_blksize);
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DEBUG("hit blk %d <- %d (now %d then %d)", blkno, i, now, bcache_ctl[i].bc_stamp);
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return(0);
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}
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return(ENOENT);
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}
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COMMAND_SET(bcachestat, "bcachestat", "get disk block cache stats", command_bcache);
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static int
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command_bcache(int argc, char *argv[])
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{
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int i;
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for (i = 0; i < bcache_nblks; i++) {
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printf("%08x %04x %04x|", bcache_ctl[i].bc_blkno, bcache_ctl[i].bc_stamp & 0xffff, bcache_ctl[i].bc_count & 0xffff);
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if (((i + 1) % 4) == 0)
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printf("\n");
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}
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printf("\n%d ops %d bypasses %d hits %d misses\n", bcache_ops, bcache_bypasses, bcache_hits, bcache_misses);
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return(CMD_OK);
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}
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