drivers/md/dm-io.c

   1 /*
   2  * Copyright (C) 2003 Sistina Software
   3  * Copyright (C) 2006 Red Hat GmbH
   4  *
   5  * This file is released under the GPL.
   6  */
   7
   8 #include "dm-io.h"
   9
  10 #include <linux/bio.h>
  11 #include <linux/mempool.h>
  12 #include <linux/module.h>
  13 #include <linux/sched.h>
  14 #include <linux/slab.h>
  15
  16 struct dm_io_client {
  17         mempool_t *pool;
  18         struct bio_set *bios;
  19 };
  20
  21 /* FIXME: can we shrink this ? */
  22 struct io {
  23         unsigned long error;
  24         atomic_t count;
  25         struct task_struct *sleeper;
  26         struct dm_io_client *client;
  27         io_notify_fn callback;
  28         void *context;
  29 };
  30
  31 /*
  32  * io contexts are only dynamically allocated for asynchronous
  33  * io.  Since async io is likely to be the majority of io we'll
  34  * have the same number of io contexts as bios! (FIXME: must reduce this).
  35  */
  36
  37 static unsigned int pages_to_ios(unsigned int pages)
  38 {
  39         return 4 * pages;       /* too many ? */
  40 }
  41
  42 /*
  43  * Create a client with mempool and bioset.
  44  */
  45 struct dm_io_client *dm_io_client_create(unsigned num_pages)
  46 {
  47         unsigned ios = pages_to_ios(num_pages);
  48         struct dm_io_client *client;
  49
  50         client = kmalloc(sizeof(*client), GFP_KERNEL);
  51         if (!client)
  52                 return ERR_PTR(-ENOMEM);
  53
  54         client->pool = mempool_create_kmalloc_pool(ios, sizeof(struct io));
  55         if (!client->pool)
  56                 goto bad;
  57
  58         client->bios = bioset_create(16, 16);
  59         if (!client->bios)
  60                 goto bad;
  61
  62         return client;
  63
  64    bad:
  65         if (client->pool)
  66                 mempool_destroy(client->pool);
  67         kfree(client);
  68         return ERR_PTR(-ENOMEM);
  69 }
  70 EXPORT_SYMBOL(dm_io_client_create);
  71
  72 int dm_io_client_resize(unsigned num_pages, struct dm_io_client *client)
  73 {
  74         return mempool_resize(client->pool, pages_to_ios(num_pages),
  75                               GFP_KERNEL);
  76 }
  77 EXPORT_SYMBOL(dm_io_client_resize);
  78
  79 void dm_io_client_destroy(struct dm_io_client *client)
  80 {
  81         mempool_destroy(client->pool);
  82         bioset_free(client->bios);
  83         kfree(client);
  84 }
  85 EXPORT_SYMBOL(dm_io_client_destroy);
  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->client->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;
 130         unsigned region;
 131
 132         /* keep going until we've finished */
 133         if (bio->bi_size)
 134                 return 1;
 135
 136         if (error && bio_data_dir(bio) == READ)
 137                 zero_fill_bio(bio);
 138
 139         /*
 140          * The bio destructor in bio_put() may use the io object.
 141          */
 142         io = bio->bi_private;
 143         region = bio_get_region(bio);
 144
 145         bio->bi_max_vecs++;
 146         bio_put(bio);
 147
 148         dec_count(io, region, error);
 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 /*
 221  * Functions for getting the pages from a VMA.
 222  */
 223 static void vm_get_page(struct dpages *dp,
 224                  struct page **p, unsigned long *len, unsigned *offset)
 225 {
 226         *p = vmalloc_to_page(dp->context_ptr);
 227         *offset = dp->context_u;
 228         *len = PAGE_SIZE - dp->context_u;
 229 }
 230
 231 static void vm_next_page(struct dpages *dp)
 232 {
 233         dp->context_ptr += PAGE_SIZE - dp->context_u;
 234         dp->context_u = 0;
 235 }
 236
 237 static void vm_dp_init(struct dpages *dp, void *data)
 238 {
 239         dp->get_page = vm_get_page;
 240         dp->next_page = vm_next_page;
 241         dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
 242         dp->context_ptr = data;
 243 }
 244
 245 static void dm_bio_destructor(struct bio *bio)
 246 {
 247         struct io *io = bio->bi_private;
 248
 249         bio_free(bio, io->client->bios);
 250 }
 251
 252 /*
 253  * Functions for getting the pages from kernel memory.
 254  */
 255 static void km_get_page(struct dpages *dp, struct page **p, unsigned long *len,
 256                         unsigned *offset)
 257 {
 258         *p = virt_to_page(dp->context_ptr);
 259         *offset = dp->context_u;
 260         *len = PAGE_SIZE - dp->context_u;
 261 }
 262
 263 static void km_next_page(struct dpages *dp)
 264 {
 265         dp->context_ptr += PAGE_SIZE - dp->context_u;
 266         dp->context_u = 0;
 267 }
 268
 269 static void km_dp_init(struct dpages *dp, void *data)
 270 {
 271         dp->get_page = km_get_page;
 272         dp->next_page = km_next_page;
 273         dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
 274         dp->context_ptr = data;
 275 }
 276
 277 /*-----------------------------------------------------------------
 278  * IO routines that accept a list of pages.
 279  *---------------------------------------------------------------*/
 280 static void do_region(int rw, unsigned int region, struct io_region *where,
 281                       struct dpages *dp, struct io *io)
 282 {
 283         struct bio *bio;
 284         struct page *page;
 285         unsigned long len;
 286         unsigned offset;
 287         unsigned num_bvecs;
 288         sector_t remaining = where->count;
 289
 290         while (remaining) {
 291                 /*
 292                  * Allocate a suitably sized-bio: we add an extra
 293                  * bvec for bio_get/set_region() and decrement bi_max_vecs
 294                  * to hide it from bio_add_page().
 295                  */
 296                 num_bvecs = dm_sector_div_up(remaining,
 297                                              (PAGE_SIZE >> SECTOR_SHIFT));
 298                 num_bvecs = 1 + min_t(int, bio_get_nr_vecs(where->bdev),
 299                                       num_bvecs);
 300                 bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
 301                 bio->bi_sector = where->sector + (where->count - remaining);
 302                 bio->bi_bdev = where->bdev;
 303                 bio->bi_end_io = endio;
 304                 bio->bi_private = io;
 305                 bio->bi_destructor = dm_bio_destructor;
 306                 bio->bi_max_vecs--;
 307                 bio_set_region(bio, region);
 308
 309                 /*
 310                  * Try and add as many pages as possible.
 311                  */
 312                 while (remaining) {
 313                         dp->get_page(dp, &page, &len, &offset);
 314                         len = min(len, to_bytes(remaining));
 315                         if (!bio_add_page(bio, page, len, offset))
 316                                 break;
 317
 318                         offset = 0;
 319                         remaining -= to_sector(len);
 320                         dp->next_page(dp);
 321                 }
 322
 323                 atomic_inc(&io->count);
 324                 submit_bio(rw, bio);
 325         }
 326 }
 327
 328 static void dispatch_io(int rw, unsigned int num_regions,
 329                         struct io_region *where, struct dpages *dp,
 330                         struct io *io, int sync)
 331 {
 332         int i;
 333         struct dpages old_pages = *dp;
 334
 335         if (sync)
 336                 rw |= (1 << BIO_RW_SYNC);
 337
 338         /*
 339          * For multiple regions we need to be careful to rewind
 340          * the dp object for each call to do_region.
 341          */
 342         for (i = 0; i < num_regions; i++) {
 343                 *dp = old_pages;
 344                 if (where[i].count)
 345                         do_region(rw, i, where + i, dp, io);
 346         }
 347
 348         /*
 349          * Drop the extra reference that we were holding to avoid
 350          * the io being completed too early.
 351          */
 352         dec_count(io, 0, 0);
 353 }
 354
 355 static int sync_io(struct dm_io_client *client, unsigned int num_regions,
 356                    struct io_region *where, int rw, struct dpages *dp,
 357                    unsigned long *error_bits)
 358 {
 359         struct io io;
 360
 361         if (num_regions > 1 && rw != WRITE) {
 362                 WARN_ON(1);
 363                 return -EIO;
 364         }
 365
 366         io.error = 0;
 367         atomic_set(&io.count, 1); /* see dispatch_io() */
 368         io.sleeper = current;
 369         io.client = client;
 370
 371         dispatch_io(rw, num_regions, where, dp, &io, 1);
 372
 373         while (1) {
 374                 set_current_state(TASK_UNINTERRUPTIBLE);
 375
 376                 if (!atomic_read(&io.count) || signal_pending(current))
 377                         break;
 378
 379                 io_schedule();
 380         }
 381         set_current_state(TASK_RUNNING);
 382
 383         if (atomic_read(&io.count))
 384                 return -EINTR;
 385
 386         if (error_bits)
 387                 *error_bits = io.error;
 388
 389         return io.error ? -EIO : 0;
 390 }
 391
 392 static int async_io(struct dm_io_client *client, unsigned int num_regions,
 393                     struct io_region *where, int rw, struct dpages *dp,
 394                     io_notify_fn fn, void *context)
 395 {
 396         struct io *io;
 397
 398         if (num_regions > 1 && rw != WRITE) {
 399                 WARN_ON(1);
 400                 fn(1, context);
 401                 return -EIO;
 402         }
 403
 404         io = mempool_alloc(client->pool, GFP_NOIO);
 405         io->error = 0;
 406         atomic_set(&io->count, 1); /* see dispatch_io() */
 407         io->sleeper = NULL;
 408         io->client = client;
 409         io->callback = fn;
 410         io->context = context;
 411
 412         dispatch_io(rw, num_regions, where, dp, io, 0);
 413         return 0;
 414 }
 415
 416 static int dp_init(struct dm_io_request *io_req, struct dpages *dp)
 417 {
 418         /* Set up dpages based on memory type */
 419         switch (io_req->mem.type) {
 420         case DM_IO_PAGE_LIST:
 421                 list_dp_init(dp, io_req->mem.ptr.pl, io_req->mem.offset);
 422                 break;
 423
 424         case DM_IO_BVEC:
 425                 bvec_dp_init(dp, io_req->mem.ptr.bvec);
 426                 break;
 427
 428         case DM_IO_VMA:
 429                 vm_dp_init(dp, io_req->mem.ptr.vma);
 430                 break;
 431
 432         case DM_IO_KMEM:
 433                 km_dp_init(dp, io_req->mem.ptr.addr);
 434                 break;
 435
 436         default:
 437                 return -EINVAL;
 438         }
 439
 440         return 0;
 441 }
 442
 443 /*
 444  * New collapsed (a)synchronous interface
 445  */
 446 int dm_io(struct dm_io_request *io_req, unsigned num_regions,
 447           struct io_region *where, unsigned long *sync_error_bits)
 448 {
 449         int r;
 450         struct dpages dp;
 451
 452         r = dp_init(io_req, &dp);
 453         if (r)
 454                 return r;
 455
 456         if (!io_req->notify.fn)
 457                 return sync_io(io_req->client, num_regions, where,
 458                                io_req->bi_rw, &dp, sync_error_bits);
 459
 460         return async_io(io_req->client, num_regions, where, io_req->bi_rw,
 461                         &dp, io_req->notify.fn, io_req->notify.context);
 462 }
 463 EXPORT_SYMBOL(dm_io);