1 /*-
2 * Copyright (c) 1998 Michael Smith <msmith@freebsd.org>
3 * Copyright 2015 Toomas Soome <tsoome@me.com>
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 */
27
28 #include <sys/cdefs.h>
29 #include <sys/param.h>
30 __FBSDID("$FreeBSD$");
31
32 /*
33 * Simple hashed block cache
34 */
35
36 #include <sys/stdint.h>
37
38 #include <stand.h>
39 #include <string.h>
40 #include <strings.h>
41
42 #include "bootstrap.h"
43
44 /* #define BCACHE_DEBUG */
45
46 #ifdef BCACHE_DEBUG
47 # define DPRINTF(fmt, args...) printf("%s: " fmt "\n" , __func__ , ## args)
48 #else
49 # define DPRINTF(fmt, args...)
50 #endif
51
52 struct bcachectl
53 {
54 daddr_t bc_blkno;
55 int bc_count;
56 };
57
58 /*
59 * bcache per device node. cache is allocated on device first open and freed
60 * on last close, to save memory. The issue there is the size; biosdisk
61 * supports up to 31 (0x1f) devices. Classic setup would use single disk
62 * to boot from, but this has changed with zfs.
63 */
64 struct bcache {
65 struct bcachectl *bcache_ctl;
66 caddr_t bcache_data;
67 size_t bcache_nblks;
68 size_t ra;
69 };
70
71 static u_int bcache_total_nblks; /* set by bcache_init */
72 static u_int bcache_blksize; /* set by bcache_init */
73 static u_int bcache_numdev; /* set by bcache_add_dev */
74 /* statistics */
75 static u_int bcache_units; /* number of devices with cache */
76 static u_int bcache_unit_nblks; /* nblocks per unit */
77 static u_int bcache_hits;
78 static u_int bcache_misses;
79 static u_int bcache_ops;
80 static u_int bcache_bypasses;
81 static u_int bcache_bcount;
82 static u_int bcache_rablks;
83
84 #define BHASH(bc, blkno) ((blkno) & ((bc)->bcache_nblks - 1))
85 #define BCACHE_LOOKUP(bc, blkno) \
86 ((bc)->bcache_ctl[BHASH((bc), (blkno))].bc_blkno != (blkno))
87 #define BCACHE_READAHEAD 256
88 #define BCACHE_MINREADAHEAD 32
89
90 static void bcache_invalidate(struct bcache *bc, daddr_t blkno);
91 static void bcache_insert(struct bcache *bc, daddr_t blkno);
92 static void bcache_free_instance(struct bcache *bc);
93
94 /*
95 * Initialise the cache for (nblks) of (bsize).
96 */
97 void
bcache_init(size_t nblks,size_t bsize)98 bcache_init(size_t nblks, size_t bsize)
99 {
100 /* set up control data */
101 bcache_total_nblks = nblks;
102 bcache_blksize = bsize;
103 }
104
105 /*
106 * add number of devices to bcache. we have to divide cache space
107 * between the devices, so bcache_add_dev() can be used to set up the
108 * number. The issue is, we need to get the number before actual allocations.
109 * bcache_add_dev() is supposed to be called from device init() call, so the
110 * assumption is, devsw dv_init is called for plain devices first, and
111 * for zfs, last.
112 */
113 void
bcache_add_dev(int devices)114 bcache_add_dev(int devices)
115 {
116 bcache_numdev += devices;
117 }
118
119 void *
bcache_allocate(void)120 bcache_allocate(void)
121 {
122 u_int i;
123 struct bcache *bc = malloc(sizeof (struct bcache));
124 int disks = bcache_numdev;
125
126 if (disks == 0)
127 disks = 1; /* safe guard */
128
129 if (bc == NULL) {
130 errno = ENOMEM;
131 return (bc);
132 }
133
134 /*
135 * the bcache block count must be power of 2 for hash function
136 */
137 i = fls(disks) - 1; /* highbit - 1 */
138 if (disks > (1 << i)) /* next power of 2 */
139 i++;
140
141 bc->bcache_nblks = bcache_total_nblks >> i;
142 bcache_unit_nblks = bc->bcache_nblks;
143 bc->bcache_data = malloc(bc->bcache_nblks * bcache_blksize);
144 if (bc->bcache_data == NULL) {
145 /* dont error out yet. fall back to 32 blocks and try again */
146 bc->bcache_nblks = 32;
147 bc->bcache_data = malloc(bc->bcache_nblks * bcache_blksize +
148 sizeof(uint32_t));
149 }
150
151 bc->bcache_ctl = malloc(bc->bcache_nblks * sizeof(struct bcachectl));
152
153 if ((bc->bcache_data == NULL) || (bc->bcache_ctl == NULL)) {
154 bcache_free_instance(bc);
155 errno = ENOMEM;
156 return (NULL);
157 }
158
159 /* Flush the cache */
160 for (i = 0; i < bc->bcache_nblks; i++) {
161 bc->bcache_ctl[i].bc_count = -1;
162 bc->bcache_ctl[i].bc_blkno = -1;
163 }
164 bcache_units++;
165 bc->ra = BCACHE_READAHEAD; /* optimistic read ahead */
166 return (bc);
167 }
168
169 void
bcache_free(void * cache)170 bcache_free(void *cache)
171 {
172 struct bcache *bc = cache;
173
174 if (bc == NULL)
175 return;
176
177 bcache_free_instance(bc);
178 bcache_units--;
179 }
180
181 /*
182 * Handle a write request; write directly to the disk, and populate the
183 * cache with the new values.
184 */
185 static int
write_strategy(void * devdata,int rw,daddr_t blk,size_t size,char * buf,size_t * rsize)186 write_strategy(void *devdata, int rw, daddr_t blk, size_t size,
187 char *buf, size_t *rsize)
188 {
189 struct bcache_devdata *dd = (struct bcache_devdata *)devdata;
190 struct bcache *bc = dd->dv_cache;
191 daddr_t i, nblk;
192
193 nblk = size / bcache_blksize;
194
195 /* Invalidate the blocks being written */
196 for (i = 0; i < nblk; i++) {
197 bcache_invalidate(bc, blk + i);
198 }
199
200 /* Write the blocks */
201 return (dd->dv_strategy(dd->dv_devdata, rw, blk, size, buf, rsize));
202 }
203
204 /*
205 * Handle a read request; fill in parts of the request that can
206 * be satisfied by the cache, use the supplied strategy routine to do
207 * device I/O and then use the I/O results to populate the cache.
208 */
209 static int
read_strategy(void * devdata,int rw,daddr_t blk,size_t size,char * buf,size_t * rsize)210 read_strategy(void *devdata, int rw, daddr_t blk, size_t size,
211 char *buf, size_t *rsize)
212 {
213 struct bcache_devdata *dd = (struct bcache_devdata *)devdata;
214 struct bcache *bc = dd->dv_cache;
215 size_t i, nblk, p_size, r_size, complete, ra;
216 int result;
217 daddr_t p_blk;
218 caddr_t p_buf;
219
220 if (bc == NULL) {
221 errno = ENODEV;
222 return (-1);
223 }
224
225 if (rsize != NULL)
226 *rsize = 0;
227
228 nblk = size / bcache_blksize;
229 if (nblk == 0 && size != 0)
230 nblk++;
231 result = 0;
232 complete = 1;
233
234 /* Satisfy any cache hits up front, break on first miss */
235 for (i = 0; i < nblk; i++) {
236 if (BCACHE_LOOKUP(bc, (daddr_t)(blk + i))) {
237 bcache_misses += (nblk - i);
238 complete = 0;
239 if (nblk - i > BCACHE_MINREADAHEAD && bc->ra > BCACHE_MINREADAHEAD)
240 bc->ra >>= 1; /* reduce read ahead */
241 break;
242 } else {
243 bcache_hits++;
244 }
245 }
246
247 if (complete) { /* whole set was in cache, return it */
248 if (bc->ra < BCACHE_READAHEAD)
249 bc->ra <<= 1; /* increase read ahead */
250 bcopy(bc->bcache_data + (bcache_blksize * BHASH(bc, blk)), buf, size);
251 goto done;
252 }
253
254 /*
255 * Fill in any misses. From check we have i pointing to first missing
256 * block, read in all remaining blocks + readahead.
257 * We have space at least for nblk - i before bcache wraps.
258 */
259 p_blk = blk + i;
260 p_buf = bc->bcache_data + (bcache_blksize * BHASH(bc, p_blk));
261 r_size = bc->bcache_nblks - BHASH(bc, p_blk); /* remaining blocks */
262
263 p_size = MIN(r_size, nblk - i); /* read at least those blocks */
264
265 /*
266 * The read ahead size setup.
267 * While the read ahead can save us IO, it also can complicate things:
268 * 1. We do not want to read ahead by wrapping around the
269 * bcache end - this would complicate the cache management.
270 * 2. We are using bc->ra as dynamic hint for read ahead size,
271 * detected cache hits will increase the read-ahead block count, and
272 * misses will decrease, see the code above.
273 * 3. The bcache is sized by 512B blocks, however, the underlying device
274 * may have a larger sector size, and we should perform the IO by
275 * taking into account these larger sector sizes. We could solve this by
276 * passing the sector size to bcache_allocate(), or by using ioctl(), but
277 * in this version we are using the constant, 16 blocks, and are rounding
278 * read ahead block count down to multiple of 16.
279 * Using the constant has two reasons, we are not entirely sure if the
280 * BIOS disk interface is providing the correct value for sector size.
281 * And secondly, this way we get the most conservative setup for the ra.
282 *
283 * The selection of multiple of 16 blocks (8KB) is quite arbitrary, however,
284 * we want to cover CDs (2K) and 4K disks.
285 * bcache_allocate() will always fall back to a minimum of 32 blocks.
286 * Our choice of 16 read ahead blocks will always fit inside the bcache.
287 */
288
289 if ((rw & F_NORA) == F_NORA)
290 ra = 0;
291 else
292 ra = bc->bcache_nblks - BHASH(bc, p_blk + p_size);
293
294 if (ra != 0 && ra != bc->bcache_nblks) { /* do we have RA space? */
295 ra = MIN(bc->ra, ra - 1);
296 ra = rounddown(ra, 16); /* multiple of 16 blocks */
297 p_size += ra;
298 }
299
300 /* invalidate bcache */
301 for (i = 0; i < p_size; i++) {
302 bcache_invalidate(bc, p_blk + i);
303 }
304
305 r_size = 0;
306 /*
307 * with read-ahead, it may happen we are attempting to read past
308 * disk end, as bcache has no information about disk size.
309 * in such case we should get partial read if some blocks can be
310 * read or error, if no blocks can be read.
311 * in either case we should return the data in bcache and only
312 * return error if there is no data.
313 */
314 rw &= F_MASK;
315 result = dd->dv_strategy(dd->dv_devdata, rw, p_blk,
316 p_size * bcache_blksize, p_buf, &r_size);
317
318 r_size /= bcache_blksize;
319 for (i = 0; i < r_size; i++)
320 bcache_insert(bc, p_blk + i);
321
322 /* update ra statistics */
323 if (r_size != 0) {
324 if (r_size < p_size)
325 bcache_rablks += (p_size - r_size);
326 else
327 bcache_rablks += ra;
328 }
329
330 /* check how much data can we copy */
331 for (i = 0; i < nblk; i++) {
332 if (BCACHE_LOOKUP(bc, (daddr_t)(blk + i)))
333 break;
334 }
335
336 if (size > i * bcache_blksize)
337 size = i * bcache_blksize;
338
339 if (size != 0) {
340 bcopy(bc->bcache_data + (bcache_blksize * BHASH(bc, blk)), buf, size);
341 result = 0;
342 }
343
344 done:
345 if ((result == 0) && (rsize != NULL))
346 *rsize = size;
347 return(result);
348 }
349
350 /*
351 * Requests larger than 1/2 cache size will be bypassed and go
352 * directly to the disk. XXX tune this.
353 */
354 int
bcache_strategy(void * devdata,int rw,daddr_t blk,size_t size,char * buf,size_t * rsize)355 bcache_strategy(void *devdata, int rw, daddr_t blk, size_t size,
356 char *buf, size_t *rsize)
357 {
358 struct bcache_devdata *dd = (struct bcache_devdata *)devdata;
359 struct bcache *bc = dd->dv_cache;
360 u_int bcache_nblks = 0;
361 int nblk, cblk, ret;
362 size_t csize, isize, total;
363
364 bcache_ops++;
365
366 if (bc != NULL)
367 bcache_nblks = bc->bcache_nblks;
368
369 /* bypass large requests, or when the cache is inactive */
370 if (bc == NULL ||
371 ((size * 2 / bcache_blksize) > bcache_nblks)) {
372 DPRINTF("bypass %zu from %qu", size / bcache_blksize, blk);
373 bcache_bypasses++;
374 rw &= F_MASK;
375 return (dd->dv_strategy(dd->dv_devdata, rw, blk, size, buf, rsize));
376 }
377
378 switch (rw & F_MASK) {
379 case F_READ:
380 nblk = size / bcache_blksize;
381 if (size != 0 && nblk == 0)
382 nblk++; /* read at least one block */
383
384 ret = 0;
385 total = 0;
386 while(size) {
387 cblk = bcache_nblks - BHASH(bc, blk); /* # of blocks left */
388 cblk = MIN(cblk, nblk);
389
390 if (size <= bcache_blksize)
391 csize = size;
392 else
393 csize = cblk * bcache_blksize;
394
395 ret = read_strategy(devdata, rw, blk, csize, buf+total, &isize);
396
397 /*
398 * we may have error from read ahead, if we have read some data
399 * return partial read.
400 */
401 if (ret != 0 || isize == 0) {
402 if (total != 0)
403 ret = 0;
404 break;
405 }
406 blk += isize / bcache_blksize;
407 total += isize;
408 size -= isize;
409 nblk = size / bcache_blksize;
410 }
411
412 if (rsize)
413 *rsize = total;
414
415 return (ret);
416 case F_WRITE:
417 return write_strategy(devdata, F_WRITE, blk, size, buf, rsize);
418 }
419 return -1;
420 }
421
422 /*
423 * Free allocated bcache instance
424 */
425 static void
bcache_free_instance(struct bcache * bc)426 bcache_free_instance(struct bcache *bc)
427 {
428 if (bc != NULL) {
429 if (bc->bcache_ctl)
430 free(bc->bcache_ctl);
431 if (bc->bcache_data)
432 free(bc->bcache_data);
433 free(bc);
434 }
435 }
436
437 /*
438 * Insert a block into the cache.
439 */
440 static void
bcache_insert(struct bcache * bc,daddr_t blkno)441 bcache_insert(struct bcache *bc, daddr_t blkno)
442 {
443 u_int cand;
444
445 cand = BHASH(bc, blkno);
446
447 DPRINTF("insert blk %llu -> %u # %d", blkno, cand, bcache_bcount);
448 bc->bcache_ctl[cand].bc_blkno = blkno;
449 bc->bcache_ctl[cand].bc_count = bcache_bcount++;
450 }
451
452 /*
453 * Invalidate a block from the cache.
454 */
455 static void
bcache_invalidate(struct bcache * bc,daddr_t blkno)456 bcache_invalidate(struct bcache *bc, daddr_t blkno)
457 {
458 u_int i;
459
460 i = BHASH(bc, blkno);
461 if (bc->bcache_ctl[i].bc_blkno == blkno) {
462 bc->bcache_ctl[i].bc_count = -1;
463 bc->bcache_ctl[i].bc_blkno = -1;
464 DPRINTF("invalidate blk %llu", blkno);
465 }
466 }
467
468 #ifndef BOOT2
469 COMMAND_SET(bcachestat, "bcachestat", "get disk block cache stats", command_bcache);
470
471 static int
command_bcache(int argc,char * argv[])472 command_bcache(int argc, char *argv[])
473 {
474 if (argc != 1) {
475 command_errmsg = "wrong number of arguments";
476 return(CMD_ERROR);
477 }
478
479 printf("\ncache blocks: %u\n", bcache_total_nblks);
480 printf("cache blocksz: %u\n", bcache_blksize);
481 printf("cache readahead: %u\n", bcache_rablks);
482 printf("unit cache blocks: %u\n", bcache_unit_nblks);
483 printf("cached units: %u\n", bcache_units);
484 printf("%u ops %d bypasses %u hits %u misses\n", bcache_ops,
485 bcache_bypasses, bcache_hits, bcache_misses);
486 return(CMD_OK);
487 }
488 #endif
489