drivers/md/bcache/io.c

   1 /*
   2  * Some low level IO code, and hacks for various block layer limitations
   3  *
   4  * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
   5  * Copyright 2012 Google, Inc.
   6  */
   7
   8 #include "bcache.h"
   9 #include "bset.h"
  10 #include "debug.h"
  11
  12 #include <linux/blkdev.h>
  13
  14 static void bch_bi_idx_hack_endio(struct bio *bio, int error)
  15 {
  16         struct bio *p = bio->bi_private;
  17
  18         bio_endio(p, error);
  19         bio_put(bio);
  20 }
  21
  22 static void bch_generic_make_request_hack(struct bio *bio)
  23 {
  24         if (bio->bi_idx) {
  25                 struct bio *clone = bio_alloc(GFP_NOIO, bio_segments(bio));
  26
  27                 memcpy(clone->bi_io_vec,
  28                        bio_iovec(bio),
  29                        bio_segments(bio) * sizeof(struct bio_vec));
  30
  31                 clone->bi_sector        = bio->bi_sector;
  32                 clone->bi_bdev          = bio->bi_bdev;
  33                 clone->bi_rw            = bio->bi_rw;
  34                 clone->bi_vcnt          = bio_segments(bio);
  35                 clone->bi_size          = bio->bi_size;
  36
  37                 clone->bi_private       = bio;
  38                 clone->bi_end_io        = bch_bi_idx_hack_endio;
  39
  40                 bio = clone;
  41         }
  42
  43         /*
  44          * Hack, since drivers that clone bios clone up to bi_max_vecs, but our
  45          * bios might have had more than that (before we split them per device
  46          * limitations).
  47          *
  48          * To be taken out once immutable bvec stuff is in.
  49          */
  50         bio->bi_max_vecs = bio->bi_vcnt;
  51
  52         generic_make_request(bio);
  53 }
  54
  55 /**
  56  * bch_bio_split - split a bio
  57  * @bio:        bio to split
  58  * @sectors:    number of sectors to split from the front of @bio
  59  * @gfp:        gfp mask
  60  * @bs:         bio set to allocate from
  61  *
  62  * Allocates and returns a new bio which represents @sectors from the start of
  63  * @bio, and updates @bio to represent the remaining sectors.
  64  *
  65  * If bio_sectors(@bio) was less than or equal to @sectors, returns @bio
  66  * unchanged.
  67  *
  68  * The newly allocated bio will point to @bio's bi_io_vec, if the split was on a
  69  * bvec boundry; it is the caller's responsibility to ensure that @bio is not
  70  * freed before the split.
  71  */
  72 struct bio *bch_bio_split(struct bio *bio, int sectors,
  73                           gfp_t gfp, struct bio_set *bs)
  74 {
  75         unsigned idx = bio->bi_idx, vcnt = 0, nbytes = sectors << 9;
  76         struct bio_vec *bv;
  77         struct bio *ret = NULL;
  78
  79         BUG_ON(sectors <= 0);
  80
  81         if (sectors >= bio_sectors(bio))
  82                 return bio;
  83
  84         if (bio->bi_rw & REQ_DISCARD) {
  85                 ret = bio_alloc_bioset(gfp, 1, bs);
  86                 if (!ret)
  87                         return NULL;
  88                 idx = 0;
  89                 goto out;
  90         }
  91
  92         bio_for_each_segment(bv, bio, idx) {
  93                 vcnt = idx - bio->bi_idx;
  94
  95                 if (!nbytes) {
  96                         ret = bio_alloc_bioset(gfp, vcnt, bs);
  97                         if (!ret)
  98                                 return NULL;
  99
 100                         memcpy(ret->bi_io_vec, bio_iovec(bio),
 101                                sizeof(struct bio_vec) * vcnt);
 102
 103                         break;
 104                 } else if (nbytes < bv->bv_len) {
 105                         ret = bio_alloc_bioset(gfp, ++vcnt, bs);
 106                         if (!ret)
 107                                 return NULL;
 108
 109                         memcpy(ret->bi_io_vec, bio_iovec(bio),
 110                                sizeof(struct bio_vec) * vcnt);
 111
 112                         ret->bi_io_vec[vcnt - 1].bv_len = nbytes;
 113                         bv->bv_offset   += nbytes;
 114                         bv->bv_len      -= nbytes;
 115                         break;
 116                 }
 117
 118                 nbytes -= bv->bv_len;
 119         }
 120 out:
 121         ret->bi_bdev    = bio->bi_bdev;
 122         ret->bi_sector  = bio->bi_sector;
 123         ret->bi_size    = sectors << 9;
 124         ret->bi_rw      = bio->bi_rw;
 125         ret->bi_vcnt    = vcnt;
 126         ret->bi_max_vecs = vcnt;
 127
 128         bio->bi_sector  += sectors;
 129         bio->bi_size    -= sectors << 9;
 130         bio->bi_idx      = idx;
 131
 132         if (bio_integrity(bio)) {
 133                 if (bio_integrity_clone(ret, bio, gfp)) {
 134                         bio_put(ret);
 135                         return NULL;
 136                 }
 137
 138                 bio_integrity_trim(ret, 0, bio_sectors(ret));
 139                 bio_integrity_trim(bio, bio_sectors(ret), bio_sectors(bio));
 140         }
 141
 142         return ret;
 143 }
 144
 145 static unsigned bch_bio_max_sectors(struct bio *bio)
 146 {
 147         unsigned ret = bio_sectors(bio);
 148         struct request_queue *q = bdev_get_queue(bio->bi_bdev);
 149         unsigned max_segments = min_t(unsigned, BIO_MAX_PAGES,
 150                                       queue_max_segments(q));
 151
 152         if (bio->bi_rw & REQ_DISCARD)
 153                 return min(ret, q->limits.max_discard_sectors);
 154
 155         if (bio_segments(bio) > max_segments ||
 156             q->merge_bvec_fn) {
 157                 struct bio_vec *bv;
 158                 int i, seg = 0;
 159
 160                 ret = 0;
 161
 162                 bio_for_each_segment(bv, bio, i) {
 163                         struct bvec_merge_data bvm = {
 164                                 .bi_bdev        = bio->bi_bdev,
 165                                 .bi_sector      = bio->bi_sector,
 166                                 .bi_size        = ret << 9,
 167                                 .bi_rw          = bio->bi_rw,
 168                         };
 169
 170                         if (seg == max_segments)
 171                                 break;
 172
 173                         if (q->merge_bvec_fn &&
 174                             q->merge_bvec_fn(q, &bvm, bv) < (int) bv->bv_len)
 175                                 break;
 176
 177                         seg++;
 178                         ret += bv->bv_len >> 9;
 179                 }
 180         }
 181
 182         ret = min(ret, queue_max_sectors(q));
 183
 184         WARN_ON(!ret);
 185         ret = max_t(int, ret, bio_iovec(bio)->bv_len >> 9);
 186
 187         return ret;
 188 }
 189
 190 static void bch_bio_submit_split_done(struct closure *cl)
 191 {
 192         struct bio_split_hook *s = container_of(cl, struct bio_split_hook, cl);
 193
 194         s->bio->bi_end_io = s->bi_end_io;
 195         s->bio->bi_private = s->bi_private;
 196         bio_endio(s->bio, 0);
 197
 198         closure_debug_destroy(&s->cl);
 199         mempool_free(s, s->p->bio_split_hook);
 200 }
 201
 202 static void bch_bio_submit_split_endio(struct bio *bio, int error)
 203 {
 204         struct closure *cl = bio->bi_private;
 205         struct bio_split_hook *s = container_of(cl, struct bio_split_hook, cl);
 206
 207         if (error)
 208                 clear_bit(BIO_UPTODATE, &s->bio->bi_flags);
 209
 210         bio_put(bio);
 211         closure_put(cl);
 212 }
 213
 214 void bch_generic_make_request(struct bio *bio, struct bio_split_pool *p)
 215 {
 216         struct bio_split_hook *s;
 217         struct bio *n;
 218
 219         if (!bio_has_data(bio) && !(bio->bi_rw & REQ_DISCARD))
 220                 goto submit;
 221
 222         if (bio_sectors(bio) <= bch_bio_max_sectors(bio))
 223                 goto submit;
 224
 225         s = mempool_alloc(p->bio_split_hook, GFP_NOIO);
 226         closure_init(&s->cl, NULL);
 227
 228         s->bio          = bio;
 229         s->p            = p;
 230         s->bi_end_io    = bio->bi_end_io;
 231         s->bi_private   = bio->bi_private;
 232         bio_get(bio);
 233
 234         do {
 235                 n = bch_bio_split(bio, bch_bio_max_sectors(bio),
 236                                   GFP_NOIO, s->p->bio_split);
 237
 238                 n->bi_end_io    = bch_bio_submit_split_endio;
 239                 n->bi_private   = &s->cl;
 240
 241                 closure_get(&s->cl);
 242                 bch_generic_make_request_hack(n);
 243         } while (n != bio);
 244
 245         continue_at(&s->cl, bch_bio_submit_split_done, NULL);
 246 submit:
 247         bch_generic_make_request_hack(bio);
 248 }
 249
 250 /* Bios with headers */
 251
 252 void bch_bbio_free(struct bio *bio, struct cache_set *c)
 253 {
 254         struct bbio *b = container_of(bio, struct bbio, bio);
 255         mempool_free(b, c->bio_meta);
 256 }
 257
 258 struct bio *bch_bbio_alloc(struct cache_set *c)
 259 {
 260         struct bbio *b = mempool_alloc(c->bio_meta, GFP_NOIO);
 261         struct bio *bio = &b->bio;
 262
 263         bio_init(bio);
 264         bio->bi_flags           |= BIO_POOL_NONE << BIO_POOL_OFFSET;
 265         bio->bi_max_vecs         = bucket_pages(c);
 266         bio->bi_io_vec           = bio->bi_inline_vecs;
 267
 268         return bio;
 269 }
 270
 271 void __bch_submit_bbio(struct bio *bio, struct cache_set *c)
 272 {
 273         struct bbio *b = container_of(bio, struct bbio, bio);
 274
 275         bio->bi_sector  = PTR_OFFSET(&b->key, 0);
 276         bio->bi_bdev    = PTR_CACHE(c, &b->key, 0)->bdev;
 277
 278         b->submit_time_us = local_clock_us();
 279         closure_bio_submit(bio, bio->bi_private, PTR_CACHE(c, &b->key, 0));
 280 }
 281
 282 void bch_submit_bbio(struct bio *bio, struct cache_set *c,
 283                      struct bkey *k, unsigned ptr)
 284 {
 285         struct bbio *b = container_of(bio, struct bbio, bio);
 286         bch_bkey_copy_single_ptr(&b->key, k, ptr);
 287         __bch_submit_bbio(bio, c);
 288 }
 289
 290 /* IO errors */
 291
 292 void bch_count_io_errors(struct cache *ca, int error, const char *m)
 293 {
 294         /*
 295          * The halflife of an error is:
 296          * log2(1/2)/log2(127/128) * refresh ~= 88 * refresh
 297          */
 298
 299         if (ca->set->error_decay) {
 300                 unsigned count = atomic_inc_return(&ca->io_count);
 301
 302                 while (count > ca->set->error_decay) {
 303                         unsigned errors;
 304                         unsigned old = count;
 305                         unsigned new = count - ca->set->error_decay;
 306
 307                         /*
 308                          * First we subtract refresh from count; each time we
 309                          * succesfully do so, we rescale the errors once:
 310                          */
 311
 312                         count = atomic_cmpxchg(&ca->io_count, old, new);
 313
 314                         if (count == old) {
 315                                 count = new;
 316
 317                                 errors = atomic_read(&ca->io_errors);
 318                                 do {
 319                                         old = errors;
 320                                         new = ((uint64_t) errors * 127) / 128;
 321                                         errors = atomic_cmpxchg(&ca->io_errors,
 322                                                                 old, new);
 323                                 } while (old != errors);
 324                         }
 325                 }
 326         }
 327
 328         if (error) {
 329                 char buf[BDEVNAME_SIZE];
 330                 unsigned errors = atomic_add_return(1 << IO_ERROR_SHIFT,
 331                                                     &ca->io_errors);
 332                 errors >>= IO_ERROR_SHIFT;
 333
 334                 if (errors < ca->set->error_limit)
 335                         pr_err("%s: IO error on %s, recovering",
 336                                bdevname(ca->bdev, buf), m);
 337                 else
 338                         bch_cache_set_error(ca->set,
 339                                             "%s: too many IO errors %s",
 340                                             bdevname(ca->bdev, buf), m);
 341         }
 342 }
 343
 344 void bch_bbio_count_io_errors(struct cache_set *c, struct bio *bio,
 345                               int error, const char *m)
 346 {
 347         struct bbio *b = container_of(bio, struct bbio, bio);
 348         struct cache *ca = PTR_CACHE(c, &b->key, 0);
 349
 350         unsigned threshold = bio->bi_rw & REQ_WRITE
 351                 ? c->congested_write_threshold_us
 352                 : c->congested_read_threshold_us;
 353
 354         if (threshold) {
 355                 unsigned t = local_clock_us();
 356
 357                 int us = t - b->submit_time_us;
 358                 int congested = atomic_read(&c->congested);
 359
 360                 if (us > (int) threshold) {
 361                         int ms = us / 1024;
 362                         c->congested_last_us = t;
 363
 364                         ms = min(ms, CONGESTED_MAX + congested);
 365                         atomic_sub(ms, &c->congested);
 366                 } else if (congested < 0)
 367                         atomic_inc(&c->congested);
 368         }
 369
 370         bch_count_io_errors(ca, error, m);
 371 }
 372
 373 void bch_bbio_endio(struct cache_set *c, struct bio *bio,
 374                     int error, const char *m)
 375 {
 376         struct closure *cl = bio->bi_private;
 377
 378         bch_bbio_count_io_errors(c, bio, error, m);
 379         bio_put(bio);
 380         closure_put(cl);
 381 }