drivers/md/dm-io.c

   1 /*
   2  * Copyright (C) 2003 Sistina Software
   3  *
   4  * This file is released under the GPL.
   5  */
   6
   7 #include "dm-io.h"
   8
   9 #include <linux/bio.h>
  10 #include <linux/mempool.h>
  11 #include <linux/module.h>
  12 #include <linux/sched.h>
  13 #include <linux/slab.h>
  14
  15 static struct bio_set *_bios;
  16
  17 /* FIXME: can we shrink this ? */
  18 struct io {
  19         unsigned long error;
  20         atomic_t count;
  21         struct task_struct *sleeper;
  22         io_notify_fn callback;
  23         void *context;
  24 };
  25
  26 /*
  27  * io contexts are only dynamically allocated for asynchronous
  28  * io.  Since async io is likely to be the majority of io we'll
  29  * have the same number of io contexts as buffer heads ! (FIXME:
  30  * must reduce this).
  31  */
  32 static unsigned _num_ios;
  33 static mempool_t *_io_pool;
  34
  35 static void *alloc_io(unsigned int __nocast gfp_mask, void *pool_data)
  36 {
  37         return kmalloc(sizeof(struct io), gfp_mask);
  38 }
  39
  40 static void free_io(void *element, void *pool_data)
  41 {
  42         kfree(element);
  43 }
  44
  45 static unsigned int pages_to_ios(unsigned int pages)
  46 {
  47         return 4 * pages;       /* too many ? */
  48 }
  49
  50 static int resize_pool(unsigned int new_ios)
  51 {
  52         int r = 0;
  53
  54         if (_io_pool) {
  55                 if (new_ios == 0) {
  56                         /* free off the pool */
  57                         mempool_destroy(_io_pool);
  58                         _io_pool = NULL;
  59                         bioset_free(_bios);
  60
  61                 } else {
  62                         /* resize the pool */
  63                         r = mempool_resize(_io_pool, new_ios, GFP_KERNEL);
  64                 }
  65
  66         } else {
  67                 /* create new pool */
  68                 _io_pool = mempool_create(new_ios, alloc_io, free_io, NULL);
  69                 if (!_io_pool)
  70                         return -ENOMEM;
  71
  72                 _bios = bioset_create(16, 16, 4);
  73                 if (!_bios) {
  74                         mempool_destroy(_io_pool);
  75                         _io_pool = NULL;
  76                         return -ENOMEM;
  77                 }
  78         }
  79
  80         if (!r)
  81                 _num_ios = new_ios;
  82
  83         return r;
  84 }
  85
  86 int dm_io_get(unsigned int num_pages)
  87 {
  88         return resize_pool(_num_ios + pages_to_ios(num_pages));
  89 }
  90
  91 void dm_io_put(unsigned int num_pages)
  92 {
  93         resize_pool(_num_ios - pages_to_ios(num_pages));
  94 }
  95
  96 /*-----------------------------------------------------------------
  97  * We need to keep track of which region a bio is doing io for.
  98  * In order to save a memory allocation we store this the last
  99  * bvec which we know is unused (blech).
 100  * XXX This is ugly and can OOPS with some configs... find another way.
 101  *---------------------------------------------------------------*/
 102 static inline void bio_set_region(struct bio *bio, unsigned region)
 103 {
 104         bio->bi_io_vec[bio->bi_max_vecs - 1].bv_len = region;
 105 }
 106
 107 static inline unsigned bio_get_region(struct bio *bio)
 108 {
 109         return bio->bi_io_vec[bio->bi_max_vecs - 1].bv_len;
 110 }
 111
 112 /*-----------------------------------------------------------------
 113  * We need an io object to keep track of the number of bios that
 114  * have been dispatched for a particular io.
 115  *---------------------------------------------------------------*/
 116 static void dec_count(struct io *io, unsigned int region, int error)
 117 {
 118         if (error)
 119                 set_bit(region, &io->error);
 120
 121         if (atomic_dec_and_test(&io->count)) {
 122                 if (io->sleeper)
 123                         wake_up_process(io->sleeper);
 124
 125                 else {
 126                         int r = io->error;
 127                         io_notify_fn fn = io->callback;
 128                         void *context = io->context;
 129
 130                         mempool_free(io, _io_pool);
 131                         fn(r, context);
 132                 }
 133         }
 134 }
 135
 136 static int endio(struct bio *bio, unsigned int done, int error)
 137 {
 138         struct io *io = (struct io *) bio->bi_private;
 139
 140         /* keep going until we've finished */
 141         if (bio->bi_size)
 142                 return 1;
 143
 144         if (error && bio_data_dir(bio) == READ)
 145                 zero_fill_bio(bio);
 146
 147         dec_count(io, bio_get_region(bio), error);
 148         bio_put(bio);
 149
 150         return 0;
 151 }
 152
 153 /*-----------------------------------------------------------------
 154  * These little objects provide an abstraction for getting a new
 155  * destination page for io.
 156  *---------------------------------------------------------------*/
 157 struct dpages {
 158         void (*get_page)(struct dpages *dp,
 159                          struct page **p, unsigned long *len, unsigned *offset);
 160         void (*next_page)(struct dpages *dp);
 161
 162         unsigned context_u;
 163         void *context_ptr;
 164 };
 165
 166 /*
 167  * Functions for getting the pages from a list.
 168  */
 169 static void list_get_page(struct dpages *dp,
 170                   struct page **p, unsigned long *len, unsigned *offset)
 171 {
 172         unsigned o = dp->context_u;
 173         struct page_list *pl = (struct page_list *) dp->context_ptr;
 174
 175         *p = pl->page;
 176         *len = PAGE_SIZE - o;
 177         *offset = o;
 178 }
 179
 180 static void list_next_page(struct dpages *dp)
 181 {
 182         struct page_list *pl = (struct page_list *) dp->context_ptr;
 183         dp->context_ptr = pl->next;
 184         dp->context_u = 0;
 185 }
 186
 187 static void list_dp_init(struct dpages *dp, struct page_list *pl, unsigned offset)
 188 {
 189         dp->get_page = list_get_page;
 190         dp->next_page = list_next_page;
 191         dp->context_u = offset;
 192         dp->context_ptr = pl;
 193 }
 194
 195 /*
 196  * Functions for getting the pages from a bvec.
 197  */
 198 static void bvec_get_page(struct dpages *dp,
 199                   struct page **p, unsigned long *len, unsigned *offset)
 200 {
 201         struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
 202         *p = bvec->bv_page;
 203         *len = bvec->bv_len;
 204         *offset = bvec->bv_offset;
 205 }
 206
 207 static void bvec_next_page(struct dpages *dp)
 208 {
 209         struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
 210         dp->context_ptr = bvec + 1;
 211 }
 212
 213 static void bvec_dp_init(struct dpages *dp, struct bio_vec *bvec)
 214 {
 215         dp->get_page = bvec_get_page;
 216         dp->next_page = bvec_next_page;
 217         dp->context_ptr = bvec;
 218 }
 219
 220 static void vm_get_page(struct dpages *dp,
 221                  struct page **p, unsigned long *len, unsigned *offset)
 222 {
 223         *p = vmalloc_to_page(dp->context_ptr);
 224         *offset = dp->context_u;
 225         *len = PAGE_SIZE - dp->context_u;
 226 }
 227
 228 static void vm_next_page(struct dpages *dp)
 229 {
 230         dp->context_ptr += PAGE_SIZE - dp->context_u;
 231         dp->context_u = 0;
 232 }
 233
 234 static void vm_dp_init(struct dpages *dp, void *data)
 235 {
 236         dp->get_page = vm_get_page;
 237         dp->next_page = vm_next_page;
 238         dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
 239         dp->context_ptr = data;
 240 }
 241
 242 static void dm_bio_destructor(struct bio *bio)
 243 {
 244         bio_free(bio, _bios);
 245 }
 246
 247 /*-----------------------------------------------------------------
 248  * IO routines that accept a list of pages.
 249  *---------------------------------------------------------------*/
 250 static void do_region(int rw, unsigned int region, struct io_region *where,
 251                       struct dpages *dp, struct io *io)
 252 {
 253         struct bio *bio;
 254         struct page *page;
 255         unsigned long len;
 256         unsigned offset;
 257         unsigned num_bvecs;
 258         sector_t remaining = where->count;
 259
 260         while (remaining) {
 261                 /*
 262                  * Allocate a suitably sized bio, we add an extra
 263                  * bvec for bio_get/set_region().
 264                  */
 265                 num_bvecs = (remaining / (PAGE_SIZE >> 9)) + 2;
 266                 bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, _bios);
 267                 bio->bi_sector = where->sector + (where->count - remaining);
 268                 bio->bi_bdev = where->bdev;
 269                 bio->bi_end_io = endio;
 270                 bio->bi_private = io;
 271                 bio->bi_destructor = dm_bio_destructor;
 272                 bio_set_region(bio, region);
 273
 274                 /*
 275                  * Try and add as many pages as possible.
 276                  */
 277                 while (remaining) {
 278                         dp->get_page(dp, &page, &len, &offset);
 279                         len = min(len, to_bytes(remaining));
 280                         if (!bio_add_page(bio, page, len, offset))
 281                                 break;
 282
 283                         offset = 0;
 284                         remaining -= to_sector(len);
 285                         dp->next_page(dp);
 286                 }
 287
 288                 atomic_inc(&io->count);
 289                 submit_bio(rw, bio);
 290         }
 291 }
 292
 293 static void dispatch_io(int rw, unsigned int num_regions,
 294                         struct io_region *where, struct dpages *dp,
 295                         struct io *io, int sync)
 296 {
 297         int i;
 298         struct dpages old_pages = *dp;
 299
 300         if (sync)
 301                 rw |= (1 << BIO_RW_SYNC);
 302
 303         /*
 304          * For multiple regions we need to be careful to rewind
 305          * the dp object for each call to do_region.
 306          */
 307         for (i = 0; i < num_regions; i++) {
 308                 *dp = old_pages;
 309                 if (where[i].count)
 310                         do_region(rw, i, where + i, dp, io);
 311         }
 312
 313         /*
 314          * Drop the extra refence that we were holding to avoid
 315          * the io being completed too early.
 316          */
 317         dec_count(io, 0, 0);
 318 }
 319
 320 static int sync_io(unsigned int num_regions, struct io_region *where,
 321             int rw, struct dpages *dp, unsigned long *error_bits)
 322 {
 323         struct io io;
 324
 325         if (num_regions > 1 && rw != WRITE) {
 326                 WARN_ON(1);
 327                 return -EIO;
 328         }
 329
 330         io.error = 0;
 331         atomic_set(&io.count, 1); /* see dispatch_io() */
 332         io.sleeper = current;
 333
 334         dispatch_io(rw, num_regions, where, dp, &io, 1);
 335
 336         while (1) {
 337                 set_current_state(TASK_UNINTERRUPTIBLE);
 338
 339                 if (!atomic_read(&io.count) || signal_pending(current))
 340                         break;
 341
 342                 io_schedule();
 343         }
 344         set_current_state(TASK_RUNNING);
 345
 346         if (atomic_read(&io.count))
 347                 return -EINTR;
 348
 349         *error_bits = io.error;
 350         return io.error ? -EIO : 0;
 351 }
 352
 353 static int async_io(unsigned int num_regions, struct io_region *where, int rw,
 354              struct dpages *dp, io_notify_fn fn, void *context)
 355 {
 356         struct io *io;
 357
 358         if (num_regions > 1 && rw != WRITE) {
 359                 WARN_ON(1);
 360                 fn(1, context);
 361                 return -EIO;
 362         }
 363
 364         io = mempool_alloc(_io_pool, GFP_NOIO);
 365         io->error = 0;
 366         atomic_set(&io->count, 1); /* see dispatch_io() */
 367         io->sleeper = NULL;
 368         io->callback = fn;
 369         io->context = context;
 370
 371         dispatch_io(rw, num_regions, where, dp, io, 0);
 372         return 0;
 373 }
 374
 375 int dm_io_sync(unsigned int num_regions, struct io_region *where, int rw,
 376                struct page_list *pl, unsigned int offset,
 377                unsigned long *error_bits)
 378 {
 379         struct dpages dp;
 380         list_dp_init(&dp, pl, offset);
 381         return sync_io(num_regions, where, rw, &dp, error_bits);
 382 }
 383
 384 int dm_io_sync_bvec(unsigned int num_regions, struct io_region *where, int rw,
 385                     struct bio_vec *bvec, unsigned long *error_bits)
 386 {
 387         struct dpages dp;
 388         bvec_dp_init(&dp, bvec);
 389         return sync_io(num_regions, where, rw, &dp, error_bits);
 390 }
 391
 392 int dm_io_sync_vm(unsigned int num_regions, struct io_region *where, int rw,
 393                   void *data, unsigned long *error_bits)
 394 {
 395         struct dpages dp;
 396         vm_dp_init(&dp, data);
 397         return sync_io(num_regions, where, rw, &dp, error_bits);
 398 }
 399
 400 int dm_io_async(unsigned int num_regions, struct io_region *where, int rw,
 401                 struct page_list *pl, unsigned int offset,
 402                 io_notify_fn fn, void *context)
 403 {
 404         struct dpages dp;
 405         list_dp_init(&dp, pl, offset);
 406         return async_io(num_regions, where, rw, &dp, fn, context);
 407 }
 408
 409 int dm_io_async_bvec(unsigned int num_regions, struct io_region *where, int rw,
 410                      struct bio_vec *bvec, io_notify_fn fn, void *context)
 411 {
 412         struct dpages dp;
 413         bvec_dp_init(&dp, bvec);
 414         return async_io(num_regions, where, rw, &dp, fn, context);
 415 }
 416
 417 int dm_io_async_vm(unsigned int num_regions, struct io_region *where, int rw,
 418                    void *data, io_notify_fn fn, void *context)
 419 {
 420         struct dpages dp;
 421         vm_dp_init(&dp, data);
 422         return async_io(num_regions, where, rw, &dp, fn, context);
 423 }
 424
 425 EXPORT_SYMBOL(dm_io_get);
 426 EXPORT_SYMBOL(dm_io_put);
 427 EXPORT_SYMBOL(dm_io_sync);
 428 EXPORT_SYMBOL(dm_io_async);
 429 EXPORT_SYMBOL(dm_io_sync_bvec);
 430 EXPORT_SYMBOL(dm_io_async_bvec);
 431 EXPORT_SYMBOL(dm_io_sync_vm);
 432 EXPORT_SYMBOL(dm_io_async_vm);