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