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.h"
   9
  10 #include <linux/device-mapper.h>
  11
  12 #include <linux/bio.h>
  13 #include <linux/mempool.h>
  14 #include <linux/module.h>
  15 #include <linux/sched.h>
  16 #include <linux/slab.h>
  17 #include <linux/dm-io.h>
  18
  19 #define DM_MSG_PREFIX "io"
  20
  21 #define DM_IO_MAX_REGIONS       BITS_PER_LONG
  22
  23 struct dm_io_client {
  24         mempool_t *pool;
  25         struct bio_set *bios;
  26 };
  27
  28 /*
  29  * Aligning 'struct io' reduces the number of bits required to store
  30  * its address.  Refer to store_io_and_region_in_bio() below.
  31  */
  32 struct io {
  33         unsigned long error_bits;
  34         atomic_t count;
  35         struct task_struct *sleeper;
  36         struct dm_io_client *client;
  37         io_notify_fn callback;
  38         void *context;
  39 } __attribute__((aligned(DM_IO_MAX_REGIONS)));
  40
  41 static struct kmem_cache *_dm_io_cache;
  42
  43 /*
  44  * io contexts are only dynamically allocated for asynchronous
  45  * io.  Since async io is likely to be the majority of io we'll
  46  * have the same number of io contexts as bios! (FIXME: must reduce this).
  47  */
  48
  49 static unsigned int pages_to_ios(unsigned int pages)
  50 {
  51         return 4 * pages;       /* too many ? */
  52 }
  53
  54 /*
  55  * Create a client with mempool and bioset.
  56  */
  57 struct dm_io_client *dm_io_client_create(unsigned num_pages)
  58 {
  59         unsigned ios = pages_to_ios(num_pages);
  60         struct dm_io_client *client;
  61
  62         client = kmalloc(sizeof(*client), GFP_KERNEL);
  63         if (!client)
  64                 return ERR_PTR(-ENOMEM);
  65
  66         client->pool = mempool_create_slab_pool(ios, _dm_io_cache);
  67         if (!client->pool)
  68                 goto bad;
  69
  70         client->bios = bioset_create(16, 0);
  71         if (!client->bios)
  72                 goto bad;
  73
  74         return client;
  75
  76    bad:
  77         if (client->pool)
  78                 mempool_destroy(client->pool);
  79         kfree(client);
  80         return ERR_PTR(-ENOMEM);
  81 }
  82 EXPORT_SYMBOL(dm_io_client_create);
  83
  84 int dm_io_client_resize(unsigned num_pages, struct dm_io_client *client)
  85 {
  86         return mempool_resize(client->pool, pages_to_ios(num_pages),
  87                               GFP_KERNEL);
  88 }
  89 EXPORT_SYMBOL(dm_io_client_resize);
  90
  91 void dm_io_client_destroy(struct dm_io_client *client)
  92 {
  93         mempool_destroy(client->pool);
  94         bioset_free(client->bios);
  95         kfree(client);
  96 }
  97 EXPORT_SYMBOL(dm_io_client_destroy);
  98
  99 /*-----------------------------------------------------------------
 100  * We need to keep track of which region a bio is doing io for.
 101  * To avoid a memory allocation to store just 5 or 6 bits, we
 102  * ensure the 'struct io' pointer is aligned so enough low bits are
 103  * always zero and then combine it with the region number directly in
 104  * bi_private.
 105  *---------------------------------------------------------------*/
 106 static void store_io_and_region_in_bio(struct bio *bio, struct io *io,
 107                                        unsigned region)
 108 {
 109         if (unlikely(!IS_ALIGNED((unsigned long)io, DM_IO_MAX_REGIONS))) {
 110                 DMCRIT("Unaligned struct io pointer %p", io);
 111                 BUG();
 112         }
 113
 114         bio->bi_private = (void *)((unsigned long)io | region);
 115 }
 116
 117 static void retrieve_io_and_region_from_bio(struct bio *bio, struct io **io,
 118                                        unsigned *region)
 119 {
 120         unsigned long val = (unsigned long)bio->bi_private;
 121
 122         *io = (void *)(val & -(unsigned long)DM_IO_MAX_REGIONS);
 123         *region = val & (DM_IO_MAX_REGIONS - 1);
 124 }
 125
 126 /*-----------------------------------------------------------------
 127  * We need an io object to keep track of the number of bios that
 128  * have been dispatched for a particular io.
 129  *---------------------------------------------------------------*/
 130 static void dec_count(struct io *io, unsigned int region, int error)
 131 {
 132         if (error)
 133                 set_bit(region, &io->error_bits);
 134
 135         if (atomic_dec_and_test(&io->count)) {
 136                 if (io->sleeper)
 137                         wake_up_process(io->sleeper);
 138
 139                 else {
 140                         unsigned long r = io->error_bits;
 141                         io_notify_fn fn = io->callback;
 142                         void *context = io->context;
 143
 144                         mempool_free(io, io->client->pool);
 145                         fn(r, context);
 146                 }
 147         }
 148 }
 149
 150 static void endio(struct bio *bio, int error)
 151 {
 152         struct io *io;
 153         unsigned region;
 154
 155         if (error && bio_data_dir(bio) == READ)
 156                 zero_fill_bio(bio);
 157
 158         /*
 159          * The bio destructor in bio_put() may use the io object.
 160          */
 161         retrieve_io_and_region_from_bio(bio, &io, &region);
 162
 163         bio_put(bio);
 164
 165         dec_count(io, region, error);
 166 }
 167
 168 /*-----------------------------------------------------------------
 169  * These little objects provide an abstraction for getting a new
 170  * destination page for io.
 171  *---------------------------------------------------------------*/
 172 struct dpages {
 173         void (*get_page)(struct dpages *dp,
 174                          struct page **p, unsigned long *len, unsigned *offset);
 175         void (*next_page)(struct dpages *dp);
 176
 177         unsigned context_u;
 178         void *context_ptr;
 179 };
 180
 181 /*
 182  * Functions for getting the pages from a list.
 183  */
 184 static void list_get_page(struct dpages *dp,
 185                   struct page **p, unsigned long *len, unsigned *offset)
 186 {
 187         unsigned o = dp->context_u;
 188         struct page_list *pl = (struct page_list *) dp->context_ptr;
 189
 190         *p = pl->page;
 191         *len = PAGE_SIZE - o;
 192         *offset = o;
 193 }
 194
 195 static void list_next_page(struct dpages *dp)
 196 {
 197         struct page_list *pl = (struct page_list *) dp->context_ptr;
 198         dp->context_ptr = pl->next;
 199         dp->context_u = 0;
 200 }
 201
 202 static void list_dp_init(struct dpages *dp, struct page_list *pl, unsigned offset)
 203 {
 204         dp->get_page = list_get_page;
 205         dp->next_page = list_next_page;
 206         dp->context_u = offset;
 207         dp->context_ptr = pl;
 208 }
 209
 210 /*
 211  * Functions for getting the pages from a bvec.
 212  */
 213 static void bvec_get_page(struct dpages *dp,
 214                   struct page **p, unsigned long *len, unsigned *offset)
 215 {
 216         struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
 217         *p = bvec->bv_page;
 218         *len = bvec->bv_len;
 219         *offset = bvec->bv_offset;
 220 }
 221
 222 static void bvec_next_page(struct dpages *dp)
 223 {
 224         struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
 225         dp->context_ptr = bvec + 1;
 226 }
 227
 228 static void bvec_dp_init(struct dpages *dp, struct bio_vec *bvec)
 229 {
 230         dp->get_page = bvec_get_page;
 231         dp->next_page = bvec_next_page;
 232         dp->context_ptr = bvec;
 233 }
 234
 235 /*
 236  * Functions for getting the pages from a VMA.
 237  */
 238 static void vm_get_page(struct dpages *dp,
 239                  struct page **p, unsigned long *len, unsigned *offset)
 240 {
 241         *p = vmalloc_to_page(dp->context_ptr);
 242         *offset = dp->context_u;
 243         *len = PAGE_SIZE - dp->context_u;
 244 }
 245
 246 static void vm_next_page(struct dpages *dp)
 247 {
 248         dp->context_ptr += PAGE_SIZE - dp->context_u;
 249         dp->context_u = 0;
 250 }
 251
 252 static void vm_dp_init(struct dpages *dp, void *data)
 253 {
 254         dp->get_page = vm_get_page;
 255         dp->next_page = vm_next_page;
 256         dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
 257         dp->context_ptr = data;
 258 }
 259
 260 static void dm_bio_destructor(struct bio *bio)
 261 {
 262         unsigned region;
 263         struct io *io;
 264
 265         retrieve_io_and_region_from_bio(bio, &io, &region);
 266
 267         bio_free(bio, io->client->bios);
 268 }
 269
 270 /*
 271  * Functions for getting the pages from kernel memory.
 272  */
 273 static void km_get_page(struct dpages *dp, struct page **p, unsigned long *len,
 274                         unsigned *offset)
 275 {
 276         *p = virt_to_page(dp->context_ptr);
 277         *offset = dp->context_u;
 278         *len = PAGE_SIZE - dp->context_u;
 279 }
 280
 281 static void km_next_page(struct dpages *dp)
 282 {
 283         dp->context_ptr += PAGE_SIZE - dp->context_u;
 284         dp->context_u = 0;
 285 }
 286
 287 static void km_dp_init(struct dpages *dp, void *data)
 288 {
 289         dp->get_page = km_get_page;
 290         dp->next_page = km_next_page;
 291         dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
 292         dp->context_ptr = data;
 293 }
 294
 295 /*-----------------------------------------------------------------
 296  * IO routines that accept a list of pages.
 297  *---------------------------------------------------------------*/
 298 static void do_region(int rw, unsigned region, struct dm_io_region *where,
 299                       struct dpages *dp, struct io *io)
 300 {
 301         struct bio *bio;
 302         struct page *page;
 303         unsigned long len;
 304         unsigned offset;
 305         unsigned num_bvecs;
 306         sector_t remaining = where->count;
 307
 308         /*
 309          * where->count may be zero if rw holds a flush and we need to
 310          * send a zero-sized flush.
 311          */
 312         do {
 313                 /*
 314                  * Allocate a suitably sized-bio.
 315                  */
 316                 num_bvecs = dm_sector_div_up(remaining,
 317                                              (PAGE_SIZE >> SECTOR_SHIFT));
 318                 num_bvecs = min_t(int, bio_get_nr_vecs(where->bdev), num_bvecs);
 319                 bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
 320                 bio->bi_sector = where->sector + (where->count - remaining);
 321                 bio->bi_bdev = where->bdev;
 322                 bio->bi_end_io = endio;
 323                 bio->bi_destructor = dm_bio_destructor;
 324                 store_io_and_region_in_bio(bio, io, region);
 325
 326                 /*
 327                  * Try and add as many pages as possible.
 328                  */
 329                 while (remaining) {
 330                         dp->get_page(dp, &page, &len, &offset);
 331                         len = min(len, to_bytes(remaining));
 332                         if (!bio_add_page(bio, page, len, offset))
 333                                 break;
 334
 335                         offset = 0;
 336                         remaining -= to_sector(len);
 337                         dp->next_page(dp);
 338                 }
 339
 340                 atomic_inc(&io->count);
 341                 submit_bio(rw, bio);
 342         } while (remaining);
 343 }
 344
 345 static void dispatch_io(int rw, unsigned int num_regions,
 346                         struct dm_io_region *where, struct dpages *dp,
 347                         struct io *io, int sync)
 348 {
 349         int i;
 350         struct dpages old_pages = *dp;
 351
 352         BUG_ON(num_regions > DM_IO_MAX_REGIONS);
 353
 354         if (sync)
 355                 rw |= REQ_SYNC | REQ_UNPLUG;
 356
 357         /*
 358          * For multiple regions we need to be careful to rewind
 359          * the dp object for each call to do_region.
 360          */
 361         for (i = 0; i < num_regions; i++) {
 362                 *dp = old_pages;
 363                 if (where[i].count || (rw & REQ_FLUSH))
 364                         do_region(rw, i, where + i, dp, io);
 365         }
 366
 367         /*
 368          * Drop the extra reference that we were holding to avoid
 369          * the io being completed too early.
 370          */
 371         dec_count(io, 0, 0);
 372 }
 373
 374 static int sync_io(struct dm_io_client *client, unsigned int num_regions,
 375                    struct dm_io_region *where, int rw, struct dpages *dp,
 376                    unsigned long *error_bits)
 377 {
 378         /*
 379          * gcc <= 4.3 can't do the alignment for stack variables, so we must
 380          * align it on our own.
 381          * volatile prevents the optimizer from removing or reusing
 382          * "io_" field from the stack frame (allowed in ANSI C).
 383          */
 384         volatile char io_[sizeof(struct io) + __alignof__(struct io) - 1];
 385         struct io *io = (struct io *)PTR_ALIGN(&io_, __alignof__(struct io));
 386
 387         if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
 388                 WARN_ON(1);
 389                 return -EIO;
 390         }
 391
 392         io->error_bits = 0;
 393         atomic_set(&io->count, 1); /* see dispatch_io() */
 394         io->sleeper = current;
 395         io->client = client;
 396
 397         dispatch_io(rw, num_regions, where, dp, io, 1);
 398
 399         while (1) {
 400                 set_current_state(TASK_UNINTERRUPTIBLE);
 401
 402                 if (!atomic_read(&io->count))
 403                         break;
 404
 405                 io_schedule();
 406         }
 407         set_current_state(TASK_RUNNING);
 408
 409         if (error_bits)
 410                 *error_bits = io->error_bits;
 411
 412         return io->error_bits ? -EIO : 0;
 413 }
 414
 415 static int async_io(struct dm_io_client *client, unsigned int num_regions,
 416                     struct dm_io_region *where, int rw, struct dpages *dp,
 417                     io_notify_fn fn, void *context)
 418 {
 419         struct io *io;
 420
 421         if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
 422                 WARN_ON(1);
 423                 fn(1, context);
 424                 return -EIO;
 425         }
 426
 427         io = mempool_alloc(client->pool, GFP_NOIO);
 428         io->error_bits = 0;
 429         atomic_set(&io->count, 1); /* see dispatch_io() */
 430         io->sleeper = NULL;
 431         io->client = client;
 432         io->callback = fn;
 433         io->context = context;
 434
 435         dispatch_io(rw, num_regions, where, dp, io, 0);
 436         return 0;
 437 }
 438
 439 static int dp_init(struct dm_io_request *io_req, struct dpages *dp)
 440 {
 441         /* Set up dpages based on memory type */
 442         switch (io_req->mem.type) {
 443         case DM_IO_PAGE_LIST:
 444                 list_dp_init(dp, io_req->mem.ptr.pl, io_req->mem.offset);
 445                 break;
 446
 447         case DM_IO_BVEC:
 448                 bvec_dp_init(dp, io_req->mem.ptr.bvec);
 449                 break;
 450
 451         case DM_IO_VMA:
 452                 vm_dp_init(dp, io_req->mem.ptr.vma);
 453                 break;
 454
 455         case DM_IO_KMEM:
 456                 km_dp_init(dp, io_req->mem.ptr.addr);
 457                 break;
 458
 459         default:
 460                 return -EINVAL;
 461         }
 462
 463         return 0;
 464 }
 465
 466 /*
 467  * New collapsed (a)synchronous interface.
 468  *
 469  * If the IO is asynchronous (i.e. it has notify.fn), you must either unplug
 470  * the queue with blk_unplug() some time later or set REQ_SYNC in
 471 io_req->bi_rw. If you fail to do one of these, the IO will be submitted to
 472  * the disk after q->unplug_delay, which defaults to 3ms in blk-settings.c.
 473  */
 474 int dm_io(struct dm_io_request *io_req, unsigned num_regions,
 475           struct dm_io_region *where, unsigned long *sync_error_bits)
 476 {
 477         int r;
 478         struct dpages dp;
 479
 480         r = dp_init(io_req, &dp);
 481         if (r)
 482                 return r;
 483
 484         if (!io_req->notify.fn)
 485                 return sync_io(io_req->client, num_regions, where,
 486                                io_req->bi_rw, &dp, sync_error_bits);
 487
 488         return async_io(io_req->client, num_regions, where, io_req->bi_rw,
 489                         &dp, io_req->notify.fn, io_req->notify.context);
 490 }
 491 EXPORT_SYMBOL(dm_io);
 492
 493 int __init dm_io_init(void)
 494 {
 495         _dm_io_cache = KMEM_CACHE(io, 0);
 496         if (!_dm_io_cache)
 497                 return -ENOMEM;
 498
 499         return 0;
 500 }
 501
 502 void dm_io_exit(void)
 503 {
 504         kmem_cache_destroy(_dm_io_cache);
 505         _dm_io_cache = NULL;
 506 }