/*-
* Copyright (c) 1998 Michael Smith <msmith@freebsd.org>
* Copyright 2015 Toomas Soome <tsoome@me.com>
* All rights reserved.
*
* 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 AUTHOR 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 AUTHOR 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.
*/
#include <sys/cdefs.h>
#include <sys/param.h>
__FBSDID("$FreeBSD$");
/*
* Simple hashed block cache
*/
#include <sys/stdint.h>
#include <stand.h>
#include <string.h>
#include <strings.h>
#include "bootstrap.h"
/* #define BCACHE_DEBUG */
#ifdef BCACHE_DEBUG
# define DPRINTF(fmt, args...) printf("%s: " fmt "\n" , __func__ , ## args)
#else
# define DPRINTF(fmt, args...) ((void)0)
#endif
struct bcachectl
{
daddr_t bc_blkno;
int bc_count;
};
/*
* bcache per device node. cache is allocated on device first open and freed
* on last close, to save memory. The issue there is the size; biosdisk
* supports up to 31 (0x1f) devices. Classic setup would use single disk
* to boot from, but this has changed with zfs.
*/
struct bcache {
struct bcachectl *bcache_ctl;
caddr_t bcache_data;
size_t bcache_nblks;
size_t ra;
};
static u_int bcache_total_nblks; /* set by bcache_init */
static u_int bcache_blksize; /* set by bcache_init */
static u_int bcache_numdev; /* set by bcache_add_dev */
/* statistics */
static u_int bcache_units; /* number of devices with cache */
static u_int bcache_unit_nblks; /* nblocks per unit */
static u_int bcache_hits;
static u_int bcache_misses;
static u_int bcache_ops;
static u_int bcache_bypasses;
static u_int bcache_bcount;
static u_int bcache_rablks;
#define BHASH(bc, blkno) ((blkno) & ((bc)->bcache_nblks - 1))
#define BCACHE_LOOKUP(bc, blkno) \
((bc)->bcache_ctl[BHASH((bc), (blkno))].bc_blkno != (blkno))
#define BCACHE_READAHEAD 256
#define BCACHE_MINREADAHEAD 32
static void bcache_invalidate(struct bcache *bc, daddr_t blkno);
static void bcache_insert(struct bcache *bc, daddr_t blkno);
static void bcache_free_instance(struct bcache *bc);
/*
* Initialise the cache for (nblks) of (bsize).
*/
void
bcache_init(size_t nblks, size_t bsize)
{
/* set up control data */
bcache_total_nblks = nblks;
bcache_blksize = bsize;
}
/*
* add number of devices to bcache. we have to divide cache space
* between the devices, so bcache_add_dev() can be used to set up the
* number. The issue is, we need to get the number before actual allocations.
* bcache_add_dev() is supposed to be called from device init() call, so the
* assumption is, devsw dv_init is called for plain devices first, and
* for zfs, last.
*/
void
bcache_add_dev(int devices)
{
bcache_numdev += devices;
}
void *
bcache_allocate(void)
{
u_int i;
struct bcache *bc = malloc(sizeof (struct bcache));
int disks = bcache_numdev;
if (disks == 0)
disks = 1; /* safe guard */
if (bc == NULL) {
errno = ENOMEM;
return (bc);
}
/*
* the bcache block count must be power of 2 for hash function
*/
i = fls(disks) - 1; /* highbit - 1 */
if (disks > (1 << i)) /* next power of 2 */
i++;
bc->bcache_nblks = bcache_total_nblks >> i;
bcache_unit_nblks = bc->bcache_nblks;
bc->bcache_data = malloc(bc->bcache_nblks * bcache_blksize);
if (bc->bcache_data == NULL) {
/* dont error out yet. fall back to 32 blocks and try again */
bc->bcache_nblks = 32;
bc->bcache_data = malloc(bc->bcache_nblks * bcache_blksize +
sizeof(uint32_t));
}
bc->bcache_ctl = malloc(bc->bcache_nblks * sizeof(struct bcachectl));
if ((bc->bcache_data == NULL) || (bc->bcache_ctl == NULL)) {
bcache_free_instance(bc);
errno = ENOMEM;
return (NULL);
}
/* Flush the cache */
for (i = 0; i < bc->bcache_nblks; i++) {
bc->bcache_ctl[i].bc_count = -1;
bc->bcache_ctl[i].bc_blkno = -1;
}
bcache_units++;
bc->ra = BCACHE_READAHEAD; /* optimistic read ahead */
return (bc);
}
void
bcache_free(void *cache)
{
struct bcache *bc = cache;
if (bc == NULL)
return;
bcache_free_instance(bc);
bcache_units--;
}
/*
* Handle a write request; write directly to the disk, and populate the
* cache with the new values.
*/
static int
write_strategy(void *devdata, int rw, daddr_t blk, size_t size,
char *buf, size_t *rsize)
{
struct bcache_devdata *dd = (struct bcache_devdata *)devdata;
struct bcache *bc = dd->dv_cache;
daddr_t i, nblk;
nblk = size / bcache_blksize;
/* Invalidate the blocks being written */
for (i = 0; i < nblk; i++) {
bcache_invalidate(bc, blk + i);
}
/* Write the blocks */
return (dd->dv_strategy(dd->dv_devdata, rw, blk, size, buf, rsize));
}
/*
* Handle a read request; fill in parts of the request that can
* be satisfied by the cache, use the supplied strategy routine to do
* device I/O and then use the I/O results to populate the cache.
*/
static int
read_strategy(void *devdata, int rw, daddr_t blk, size_t size,
char *buf, size_t *rsize)
{
struct bcache_devdata *dd = (struct bcache_devdata *)devdata;
struct bcache *bc = dd->dv_cache;
size_t i, nblk, p_size, r_size, complete, ra;
int result;
daddr_t p_blk;
caddr_t p_buf;
if (bc == NULL) {
errno = ENODEV;
return (-1);
}
if (rsize != NULL)
*rsize = 0;
nblk = size / bcache_blksize;
if (nblk == 0 && size != 0)
nblk++;
result = 0;
complete = 1;
/* Satisfy any cache hits up front, break on first miss */
for (i = 0; i < nblk; i++) {
if (BCACHE_LOOKUP(bc, (daddr_t)(blk + i))) {
bcache_misses += (nblk - i);
complete = 0;
if (nblk - i > BCACHE_MINREADAHEAD && bc->ra > BCACHE_MINREADAHEAD)
bc->ra >>= 1; /* reduce read ahead */
break;
} else {
bcache_hits++;
}
}
if (complete) { /* whole set was in cache, return it */
if (bc->ra < BCACHE_READAHEAD)
bc->ra <<= 1; /* increase read ahead */
bcopy(bc->bcache_data + (bcache_blksize * BHASH(bc, blk)), buf, size);
goto done;
}
/*
* Fill in any misses. From check we have i pointing to first missing
* block, read in all remaining blocks + readahead.
* We have space at least for nblk - i before bcache wraps.
*/
p_blk = blk + i;
p_buf = bc->bcache_data + (bcache_blksize * BHASH(bc, p_blk));
r_size = bc->bcache_nblks - BHASH(bc, p_blk); /* remaining blocks */
p_size = MIN(r_size, nblk - i); /* read at least those blocks */
/*
* The read ahead size setup.
* While the read ahead can save us IO, it also can complicate things:
* 1. We do not want to read ahead by wrapping around the
* bcache end - this would complicate the cache management.
* 2. We are using bc->ra as dynamic hint for read ahead size,
* detected cache hits will increase the read-ahead block count, and
* misses will decrease, see the code above.
* 3. The bcache is sized by 512B blocks, however, the underlying device
* may have a larger sector size, and we should perform the IO by
* taking into account these larger sector sizes. We could solve this by
* passing the sector size to bcache_allocate(), or by using ioctl(), but
* in this version we are using the constant, 16 blocks, and are rounding
* read ahead block count down to multiple of 16.
* Using the constant has two reasons, we are not entirely sure if the
* BIOS disk interface is providing the correct value for sector size.
* And secondly, this way we get the most conservative setup for the ra.
*
* The selection of multiple of 16 blocks (8KB) is quite arbitrary, however,
* we want to cover CDs (2K) and 4K disks.
* bcache_allocate() will always fall back to a minimum of 32 blocks.
* Our choice of 16 read ahead blocks will always fit inside the bcache.
*/
if ((rw & F_NORA) == F_NORA)
ra = 0;
else
ra = bc->bcache_nblks - BHASH(bc, p_blk + p_size);
if (ra != 0 && ra != bc->bcache_nblks) { /* do we have RA space? */
ra = MIN(bc->ra, ra - 1);
ra = rounddown(ra, 16); /* multiple of 16 blocks */
p_size += ra;
}
/* invalidate bcache */
for (i = 0; i < p_size; i++) {
bcache_invalidate(bc, p_blk + i);
}
r_size = 0;
/*
* with read-ahead, it may happen we are attempting to read past
* disk end, as bcache has no information about disk size.
* in such case we should get partial read if some blocks can be
* read or error, if no blocks can be read.
* in either case we should return the data in bcache and only
* return error if there is no data.
*/
rw &= F_MASK;
result = dd->dv_strategy(dd->dv_devdata, rw, p_blk,
p_size * bcache_blksize, p_buf, &r_size);
r_size /= bcache_blksize;
for (i = 0; i < r_size; i++)
bcache_insert(bc, p_blk + i);
/* update ra statistics */
if (r_size != 0) {
if (r_size < p_size)
bcache_rablks += (p_size - r_size);
else
bcache_rablks += ra;
}
/* check how much data can we copy */
for (i = 0; i < nblk; i++) {
if (BCACHE_LOOKUP(bc, (daddr_t)(blk + i)))
break;
}
if (size > i * bcache_blksize)
size = i * bcache_blksize;
if (size != 0) {
bcopy(bc->bcache_data + (bcache_blksize * BHASH(bc, blk)), buf, size);
result = 0;
}
done:
if ((result == 0) && (rsize != NULL))
*rsize = size;
return(result);
}
/*
* Requests larger than 1/2 cache size will be bypassed and go
* directly to the disk. XXX tune this.
*/
int
bcache_strategy(void *devdata, int rw, daddr_t blk, size_t size,
char *buf, size_t *rsize)
{
struct bcache_devdata *dd = (struct bcache_devdata *)devdata;
struct bcache *bc = dd->dv_cache;
u_int bcache_nblks = 0;
int nblk, cblk, ret;
size_t csize, isize, total;
bcache_ops++;
if (bc != NULL)
bcache_nblks = bc->bcache_nblks;
/* bypass large requests, or when the cache is inactive */
if (bc == NULL ||
((size * 2 / bcache_blksize) > bcache_nblks)) {
DPRINTF("bypass %zu from %qu", size / bcache_blksize, blk);
bcache_bypasses++;
rw &= F_MASK;
return (dd->dv_strategy(dd->dv_devdata, rw, blk, size, buf, rsize));
}
switch (rw & F_MASK) {
case F_READ:
nblk = size / bcache_blksize;
if (size != 0 && nblk == 0)
nblk++; /* read at least one block */
ret = 0;
total = 0;
while(size) {
cblk = bcache_nblks - BHASH(bc, blk); /* # of blocks left */
cblk = MIN(cblk, nblk);
if (size <= bcache_blksize)
csize = size;
else
csize = cblk * bcache_blksize;
ret = read_strategy(devdata, rw, blk, csize, buf+total, &isize);
/*
* we may have error from read ahead, if we have read some data
* return partial read.
*/
if (ret != 0 || isize == 0) {
if (total != 0)
ret = 0;
break;
}
blk += isize / bcache_blksize;
total += isize;
size -= isize;
nblk = size / bcache_blksize;
}
if (rsize)
*rsize = total;
return (ret);
case F_WRITE:
return write_strategy(devdata, F_WRITE, blk, size, buf, rsize);
}
return -1;
}
/*
* Free allocated bcache instance
*/
static void
bcache_free_instance(struct bcache *bc)
{
if (bc != NULL) {
free(bc->bcache_ctl);
free(bc->bcache_data);
free(bc);
}
}
/*
* Insert a block into the cache.
*/
static void
bcache_insert(struct bcache *bc, daddr_t blkno)
{
u_int cand;
cand = BHASH(bc, blkno);
DPRINTF("insert blk %llu -> %u # %d", blkno, cand, bcache_bcount);
bc->bcache_ctl[cand].bc_blkno = blkno;
bc->bcache_ctl[cand].bc_count = bcache_bcount++;
}
/*
* Invalidate a block from the cache.
*/
static void
bcache_invalidate(struct bcache *bc, daddr_t blkno)
{
u_int i;
i = BHASH(bc, blkno);
if (bc->bcache_ctl[i].bc_blkno == blkno) {
bc->bcache_ctl[i].bc_count = -1;
bc->bcache_ctl[i].bc_blkno = -1;
DPRINTF("invalidate blk %llu", blkno);
}
}
#ifndef BOOT2
COMMAND_SET(bcachestat, "bcachestat", "get disk block cache stats", command_bcache);
static int
command_bcache(int argc, char *argv[] __unused)
{
if (argc != 1) {
command_errmsg = "wrong number of arguments";
return(CMD_ERROR);
}
printf("\ncache blocks: %u\n", bcache_total_nblks);
printf("cache blocksz: %u\n", bcache_blksize);
printf("cache readahead: %u\n", bcache_rablks);
printf("unit cache blocks: %u\n", bcache_unit_nblks);
printf("cached units: %u\n", bcache_units);
printf("%u ops %d bypasses %u hits %u misses\n", bcache_ops,
bcache_bypasses, bcache_hits, bcache_misses);
return(CMD_OK);
}
#endif
