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 static void bch_bi_idx_hack_endio(struct bio *bio, int error)
  13 {
  14         struct bio *p = bio->bi_private;
  15
  16         bio_endio(p, error);
  17         bio_put(bio);
  18 }
  19
  20 static void bch_generic_make_request_hack(struct bio *bio)
  21 {
  22         if (bio->bi_idx) {
  23                 struct bio *clone = bio_alloc(GFP_NOIO, bio_segments(bio));
  24
  25                 memcpy(clone->bi_io_vec,
  26                        bio_iovec(bio),
  27                        bio_segments(bio) * sizeof(struct bio_vec));
  28
  29                 clone->bi_sector        = bio->bi_sector;
  30                 clone->bi_bdev          = bio->bi_bdev;
  31                 clone->bi_rw            = bio->bi_rw;
  32                 clone->bi_vcnt          = bio_segments(bio);
  33                 clone->bi_size          = bio->bi_size;
  34
  35                 clone->bi_private       = bio;
  36                 clone->bi_end_io        = bch_bi_idx_hack_endio;
  37
  38                 bio = clone;
  39         }
  40
  41         /*
  42          * Hack, since drivers that clone bios clone up to bi_max_vecs, but our
  43          * bios might have had more than that (before we split them per device
  44          * limitations).
  45          *
  46          * To be taken out once immutable bvec stuff is in.
  47          */
  48         bio->bi_max_vecs = bio->bi_vcnt;
  49
  50         generic_make_request(bio);
  51 }
  52
  53 /**
  54  * bch_bio_split - split a bio
  55  * @bio:        bio to split
  56  * @sectors:    number of sectors to split from the front of @bio
  57  * @gfp:        gfp mask
  58  * @bs:         bio set to allocate from
  59  *
  60  * Allocates and returns a new bio which represents @sectors from the start of
  61  * @bio, and updates @bio to represent the remaining sectors.
  62  *
  63  * If bio_sectors(@bio) was less than or equal to @sectors, returns @bio
  64  * unchanged.
  65  *
  66  * The newly allocated bio will point to @bio's bi_io_vec, if the split was on a
  67  * bvec boundry; it is the caller's responsibility to ensure that @bio is not
  68  * freed before the split.
  69  *
  70  * If bch_bio_split() is running under generic_make_request(), it's not safe to
  71  * allocate more than one bio from the same bio set. Therefore, if it is running
  72  * under generic_make_request() it masks out __GFP_WAIT when doing the
  73  * allocation. The caller must check for failure if there's any possibility of
  74  * it being called from under generic_make_request(); it is then the caller's
  75  * responsibility to retry from a safe context (by e.g. punting to workqueue).
  76  */
  77 struct bio *bch_bio_split(struct bio *bio, int sectors,
  78                           gfp_t gfp, struct bio_set *bs)
  79 {
  80         unsigned idx = bio->bi_idx, vcnt = 0, nbytes = sectors << 9;
  81         struct bio_vec *bv;
  82         struct bio *ret = NULL;
  83
  84         BUG_ON(sectors <= 0);
  85
  86         /*
  87          * If we're being called from underneath generic_make_request() and we
  88          * already allocated any bios from this bio set, we risk deadlock if we
  89          * use the mempool. So instead, we possibly fail and let the caller punt
  90          * to workqueue or somesuch and retry in a safe context.
  91          */
  92         if (current->bio_list)
  93                 gfp &= ~__GFP_WAIT;
  94
  95         if (sectors >= bio_sectors(bio))
  96                 return bio;
  97
  98         if (bio->bi_rw & REQ_DISCARD) {
  99                 ret = bio_alloc_bioset(gfp, 1, bs);
 100                 idx = 0;
 101                 goto out;
 102         }
 103
 104         bio_for_each_segment(bv, bio, idx) {
 105                 vcnt = idx - bio->bi_idx;
 106
 107                 if (!nbytes) {
 108                         ret = bio_alloc_bioset(gfp, vcnt, bs);
 109                         if (!ret)
 110                                 return NULL;
 111
 112                         memcpy(ret->bi_io_vec, bio_iovec(bio),
 113                                sizeof(struct bio_vec) * vcnt);
 114
 115                         break;
 116                 } else if (nbytes < bv->bv_len) {
 117                         ret = bio_alloc_bioset(gfp, ++vcnt, bs);
 118                         if (!ret)
 119                                 return NULL;
 120
 121                         memcpy(ret->bi_io_vec, bio_iovec(bio),
 122                                sizeof(struct bio_vec) * vcnt);
 123
 124                         ret->bi_io_vec[vcnt - 1].bv_len = nbytes;
 125                         bv->bv_offset   += nbytes;
 126                         bv->bv_len      -= nbytes;
 127                         break;
 128                 }
 129
 130                 nbytes -= bv->bv_len;
 131         }
 132 out:
 133         ret->bi_bdev    = bio->bi_bdev;
 134         ret->bi_sector  = bio->bi_sector;
 135         ret->bi_size    = sectors << 9;
 136         ret->bi_rw      = bio->bi_rw;
 137         ret->bi_vcnt    = vcnt;
 138         ret->bi_max_vecs = vcnt;
 139
 140         bio->bi_sector  += sectors;
 141         bio->bi_size    -= sectors << 9;
 142         bio->bi_idx      = idx;
 143
 144         if (bio_integrity(bio)) {
 145                 if (bio_integrity_clone(ret, bio, gfp)) {
 146                         bio_put(ret);
 147                         return NULL;
 148                 }
 149
 150                 bio_integrity_trim(ret, 0, bio_sectors(ret));
 151                 bio_integrity_trim(bio, bio_sectors(ret), bio_sectors(bio));
 152         }
 153
 154         return ret;
 155 }
 156
 157 static unsigned bch_bio_max_sectors(struct bio *bio)
 158 {
 159         unsigned ret = bio_sectors(bio);
 160         struct request_queue *q = bdev_get_queue(bio->bi_bdev);
 161         unsigned max_segments = min_t(unsigned, BIO_MAX_PAGES,
 162                                       queue_max_segments(q));
 163         struct bio_vec *bv, *end = bio_iovec(bio) +
 164                 min_t(int, bio_segments(bio), max_segments);
 165
 166         if (bio->bi_rw & REQ_DISCARD)
 167                 return min(ret, q->limits.max_discard_sectors);
 168
 169         if (bio_segments(bio) > max_segments ||
 170             q->merge_bvec_fn) {
 171                 ret = 0;
 172
 173                 for (bv = bio_iovec(bio); bv < end; bv++) {
 174                         struct bvec_merge_data bvm = {
 175                                 .bi_bdev        = bio->bi_bdev,
 176                                 .bi_sector      = bio->bi_sector,
 177                                 .bi_size        = ret << 9,
 178                                 .bi_rw          = bio->bi_rw,
 179                         };
 180
 181                         if (q->merge_bvec_fn &&
 182                             q->merge_bvec_fn(q, &bvm, bv) < (int) bv->bv_len)
 183                                 break;
 184
 185                         ret += bv->bv_len >> 9;
 186                 }
 187         }
 188
 189         ret = min(ret, queue_max_sectors(q));
 190
 191         WARN_ON(!ret);
 192         ret = max_t(int, ret, bio_iovec(bio)->bv_len >> 9);
 193
 194         return ret;
 195 }
 196
 197 static void bch_bio_submit_split_done(struct closure *cl)
 198 {
 199         struct bio_split_hook *s = container_of(cl, struct bio_split_hook, cl);
 200
 201         s->bio->bi_end_io = s->bi_end_io;
 202         s->bio->bi_private = s->bi_private;
 203         bio_endio(s->bio, 0);
 204
 205         closure_debug_destroy(&s->cl);
 206         mempool_free(s, s->p->bio_split_hook);
 207 }
 208
 209 static void bch_bio_submit_split_endio(struct bio *bio, int error)
 210 {
 211         struct closure *cl = bio->bi_private;
 212         struct bio_split_hook *s = container_of(cl, struct bio_split_hook, cl);
 213
 214         if (error)
 215                 clear_bit(BIO_UPTODATE, &s->bio->bi_flags);
 216
 217         bio_put(bio);
 218         closure_put(cl);
 219 }
 220
 221 static void __bch_bio_submit_split(struct closure *cl)
 222 {
 223         struct bio_split_hook *s = container_of(cl, struct bio_split_hook, cl);
 224         struct bio *bio = s->bio, *n;
 225
 226         do {
 227                 n = bch_bio_split(bio, bch_bio_max_sectors(bio),
 228                                   GFP_NOIO, s->p->bio_split);
 229                 if (!n)
 230                         continue_at(cl, __bch_bio_submit_split, system_wq);
 231
 232                 n->bi_end_io    = bch_bio_submit_split_endio;
 233                 n->bi_private   = cl;
 234
 235                 closure_get(cl);
 236                 bch_generic_make_request_hack(n);
 237         } while (n != bio);
 238
 239         continue_at(cl, bch_bio_submit_split_done, NULL);
 240 }
 241
 242 void bch_generic_make_request(struct bio *bio, struct bio_split_pool *p)
 243 {
 244         struct bio_split_hook *s;
 245
 246         if (!bio_has_data(bio) && !(bio->bi_rw & REQ_DISCARD))
 247                 goto submit;
 248
 249         if (bio_sectors(bio) <= bch_bio_max_sectors(bio))
 250                 goto submit;
 251
 252         s = mempool_alloc(p->bio_split_hook, GFP_NOIO);
 253
 254         s->bio          = bio;
 255         s->p            = p;
 256         s->bi_end_io    = bio->bi_end_io;
 257         s->bi_private   = bio->bi_private;
 258         bio_get(bio);
 259
 260         closure_call(&s->cl, __bch_bio_submit_split, NULL, NULL);
 261         return;
 262 submit:
 263         bch_generic_make_request_hack(bio);
 264 }
 265
 266 /* Bios with headers */
 267
 268 void bch_bbio_free(struct bio *bio, struct cache_set *c)
 269 {
 270         struct bbio *b = container_of(bio, struct bbio, bio);
 271         mempool_free(b, c->bio_meta);
 272 }
 273
 274 struct bio *bch_bbio_alloc(struct cache_set *c)
 275 {
 276         struct bbio *b = mempool_alloc(c->bio_meta, GFP_NOIO);
 277         struct bio *bio = &b->bio;
 278
 279         bio_init(bio);
 280         bio->bi_flags           |= BIO_POOL_NONE << BIO_POOL_OFFSET;
 281         bio->bi_max_vecs         = bucket_pages(c);
 282         bio->bi_io_vec           = bio->bi_inline_vecs;
 283
 284         return bio;
 285 }
 286
 287 void __bch_submit_bbio(struct bio *bio, struct cache_set *c)
 288 {
 289         struct bbio *b = container_of(bio, struct bbio, bio);
 290
 291         bio->bi_sector  = PTR_OFFSET(&b->key, 0);
 292         bio->bi_bdev    = PTR_CACHE(c, &b->key, 0)->bdev;
 293
 294         b->submit_time_us = local_clock_us();
 295         closure_bio_submit(bio, bio->bi_private, PTR_CACHE(c, &b->key, 0));
 296 }
 297
 298 void bch_submit_bbio(struct bio *bio, struct cache_set *c,
 299                      struct bkey *k, unsigned ptr)
 300 {
 301         struct bbio *b = container_of(bio, struct bbio, bio);
 302         bch_bkey_copy_single_ptr(&b->key, k, ptr);
 303         __bch_submit_bbio(bio, c);
 304 }
 305
 306 /* IO errors */
 307
 308 void bch_count_io_errors(struct cache *ca, int error, const char *m)
 309 {
 310         /*
 311          * The halflife of an error is:
 312          * log2(1/2)/log2(127/128) * refresh ~= 88 * refresh
 313          */
 314
 315         if (ca->set->error_decay) {
 316                 unsigned count = atomic_inc_return(&ca->io_count);
 317
 318                 while (count > ca->set->error_decay) {
 319                         unsigned errors;
 320                         unsigned old = count;
 321                         unsigned new = count - ca->set->error_decay;
 322
 323                         /*
 324                          * First we subtract refresh from count; each time we
 325                          * succesfully do so, we rescale the errors once:
 326                          */
 327
 328                         count = atomic_cmpxchg(&ca->io_count, old, new);
 329
 330                         if (count == old) {
 331                                 count = new;
 332
 333                                 errors = atomic_read(&ca->io_errors);
 334                                 do {
 335                                         old = errors;
 336                                         new = ((uint64_t) errors * 127) / 128;
 337                                         errors = atomic_cmpxchg(&ca->io_errors,
 338                                                                 old, new);
 339                                 } while (old != errors);
 340                         }
 341                 }
 342         }
 343
 344         if (error) {
 345                 char buf[BDEVNAME_SIZE];
 346                 unsigned errors = atomic_add_return(1 << IO_ERROR_SHIFT,
 347                                                     &ca->io_errors);
 348                 errors >>= IO_ERROR_SHIFT;
 349
 350                 if (errors < ca->set->error_limit)
 351                         pr_err("%s: IO error on %s, recovering",
 352                                bdevname(ca->bdev, buf), m);
 353                 else
 354                         bch_cache_set_error(ca->set,
 355                                             "%s: too many IO errors %s",
 356                                             bdevname(ca->bdev, buf), m);
 357         }
 358 }
 359
 360 void bch_bbio_count_io_errors(struct cache_set *c, struct bio *bio,
 361                               int error, const char *m)
 362 {
 363         struct bbio *b = container_of(bio, struct bbio, bio);
 364         struct cache *ca = PTR_CACHE(c, &b->key, 0);
 365
 366         unsigned threshold = bio->bi_rw & REQ_WRITE
 367                 ? c->congested_write_threshold_us
 368                 : c->congested_read_threshold_us;
 369
 370         if (threshold) {
 371                 unsigned t = local_clock_us();
 372
 373                 int us = t - b->submit_time_us;
 374                 int congested = atomic_read(&c->congested);
 375
 376                 if (us > (int) threshold) {
 377                         int ms = us / 1024;
 378                         c->congested_last_us = t;
 379
 380                         ms = min(ms, CONGESTED_MAX + congested);
 381                         atomic_sub(ms, &c->congested);
 382                 } else if (congested < 0)
 383                         atomic_inc(&c->congested);
 384         }
 385
 386         bch_count_io_errors(ca, error, m);
 387 }
 388
 389 void bch_bbio_endio(struct cache_set *c, struct bio *bio,
 390                     int error, const char *m)
 391 {
 392         struct closure *cl = bio->bi_private;
 393
 394         bch_bbio_count_io_errors(c, bio, error, m);
 395         bio_put(bio);
 396         closure_put(cl);
 397 }