root/drivers/md/dm-io.c

DEFINITIONS

1. dm_io_client_create
2. dm_io_client_destroy
3. store_io_and_region_in_bio
4. retrieve_io_and_region_from_bio
5. complete_io
6. dec_count
7. endio
8. list_get_page
9. list_next_page
10. list_dp_init
11. bio_get_page
12. bio_next_page
13. bio_dp_init
14. vm_get_page
15. vm_next_page
16. vm_dp_init
17. km_get_page
18. km_next_page
19. km_dp_init
20. do_region
21. dispatch_io
22. sync_io_complete
23. sync_io
24. async_io
25. dp_init
26. dm_io
27. dm_io_init
28. dm_io_exit

   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-core.h"
   9 
  10 #include <linux/device-mapper.h>
  11 
  12 #include <linux/bio.h>
  13 #include <linux/completion.h>
  14 #include <linux/mempool.h>
  15 #include <linux/module.h>
  16 #include <linux/sched.h>
  17 #include <linux/slab.h>
  18 #include <linux/dm-io.h>
  19 
  20 #define DM_MSG_PREFIX "io"
  21 
  22 #define DM_IO_MAX_REGIONS       BITS_PER_LONG
  23 
  24 struct dm_io_client {
  25         mempool_t pool;
  26         struct bio_set bios;
  27 };
  28 
  29 /*
  30  * Aligning 'struct io' reduces the number of bits required to store
  31  * its address.  Refer to store_io_and_region_in_bio() below.
  32  */
  33 struct io {
  34         unsigned long error_bits;
  35         atomic_t count;
  36         struct dm_io_client *client;
  37         io_notify_fn callback;
  38         void *context;
  39         void *vma_invalidate_address;
  40         unsigned long vma_invalidate_size;
  41 } __attribute__((aligned(DM_IO_MAX_REGIONS)));
  42 
  43 static struct kmem_cache *_dm_io_cache;
  44 
  45 /*
  46  * Create a client with mempool and bioset.
  47  */
  48 struct dm_io_client *dm_io_client_create(void)
  49 {
  50         struct dm_io_client *client;
  51         unsigned min_ios = dm_get_reserved_bio_based_ios();
  52         int ret;
  53 
  54         client = kzalloc(sizeof(*client), GFP_KERNEL);
  55         if (!client)
  56                 return ERR_PTR(-ENOMEM);
  57 
  58         ret = mempool_init_slab_pool(&client->pool, min_ios, _dm_io_cache);
  59         if (ret)
  60                 goto bad;
  61 
  62         ret = bioset_init(&client->bios, min_ios, 0, BIOSET_NEED_BVECS);
  63         if (ret)
  64                 goto bad;
  65 
  66         return client;
  67 
  68    bad:
  69         mempool_exit(&client->pool);
  70         kfree(client);
  71         return ERR_PTR(ret);
  72 }
  73 EXPORT_SYMBOL(dm_io_client_create);
  74 
  75 void dm_io_client_destroy(struct dm_io_client *client)
  76 {
  77         mempool_exit(&client->pool);
  78         bioset_exit(&client->bios);
  79         kfree(client);
  80 }
  81 EXPORT_SYMBOL(dm_io_client_destroy);
  82 
  83 /*-----------------------------------------------------------------
  84  * We need to keep track of which region a bio is doing io for.
  85  * To avoid a memory allocation to store just 5 or 6 bits, we
  86  * ensure the 'struct io' pointer is aligned so enough low bits are
  87  * always zero and then combine it with the region number directly in
  88  * bi_private.
  89  *---------------------------------------------------------------*/
  90 static void store_io_and_region_in_bio(struct bio *bio, struct io *io,
  91                                        unsigned region)
  92 {
  93         if (unlikely(!IS_ALIGNED((unsigned long)io, DM_IO_MAX_REGIONS))) {
  94                 DMCRIT("Unaligned struct io pointer %p", io);
  95                 BUG();
  96         }
  97 
  98         bio->bi_private = (void *)((unsigned long)io | region);
  99 }
 100 
 101 static void retrieve_io_and_region_from_bio(struct bio *bio, struct io **io,
 102                                        unsigned *region)
 103 {
 104         unsigned long val = (unsigned long)bio->bi_private;
 105 
 106         *io = (void *)(val & -(unsigned long)DM_IO_MAX_REGIONS);
 107         *region = val & (DM_IO_MAX_REGIONS - 1);
 108 }
 109 
 110 /*-----------------------------------------------------------------
 111  * We need an io object to keep track of the number of bios that
 112  * have been dispatched for a particular io.
 113  *---------------------------------------------------------------*/
 114 static void complete_io(struct io *io)
 115 {
 116         unsigned long error_bits = io->error_bits;
 117         io_notify_fn fn = io->callback;
 118         void *context = io->context;
 119 
 120         if (io->vma_invalidate_size)
 121                 invalidate_kernel_vmap_range(io->vma_invalidate_address,
 122                                              io->vma_invalidate_size);
 123 
 124         mempool_free(io, &io->client->pool);
 125         fn(error_bits, context);
 126 }
 127 
 128 static void dec_count(struct io *io, unsigned int region, blk_status_t error)
 129 {
 130         if (error)
 131                 set_bit(region, &io->error_bits);
 132 
 133         if (atomic_dec_and_test(&io->count))
 134                 complete_io(io);
 135 }
 136 
 137 static void endio(struct bio *bio)
 138 {
 139         struct io *io;
 140         unsigned region;
 141         blk_status_t error;
 142 
 143         if (bio->bi_status && bio_data_dir(bio) == READ)
 144                 zero_fill_bio(bio);
 145 
 146         /*
 147          * The bio destructor in bio_put() may use the io object.
 148          */
 149         retrieve_io_and_region_from_bio(bio, &io, &region);
 150 
 151         error = bio->bi_status;
 152         bio_put(bio);
 153 
 154         dec_count(io, region, error);
 155 }
 156 
 157 /*-----------------------------------------------------------------
 158  * These little objects provide an abstraction for getting a new
 159  * destination page for io.
 160  *---------------------------------------------------------------*/
 161 struct dpages {
 162         void (*get_page)(struct dpages *dp,
 163                          struct page **p, unsigned long *len, unsigned *offset);
 164         void (*next_page)(struct dpages *dp);
 165 
 166         union {
 167                 unsigned context_u;
 168                 struct bvec_iter context_bi;
 169         };
 170         void *context_ptr;
 171 
 172         void *vma_invalidate_address;
 173         unsigned long vma_invalidate_size;
 174 };
 175 
 176 /*
 177  * Functions for getting the pages from a list.
 178  */
 179 static void list_get_page(struct dpages *dp,
 180                   struct page **p, unsigned long *len, unsigned *offset)
 181 {
 182         unsigned o = dp->context_u;
 183         struct page_list *pl = (struct page_list *) dp->context_ptr;
 184 
 185         *p = pl->page;
 186         *len = PAGE_SIZE - o;
 187         *offset = o;
 188 }
 189 
 190 static void list_next_page(struct dpages *dp)
 191 {
 192         struct page_list *pl = (struct page_list *) dp->context_ptr;
 193         dp->context_ptr = pl->next;
 194         dp->context_u = 0;
 195 }
 196 
 197 static void list_dp_init(struct dpages *dp, struct page_list *pl, unsigned offset)
 198 {
 199         dp->get_page = list_get_page;
 200         dp->next_page = list_next_page;
 201         dp->context_u = offset;
 202         dp->context_ptr = pl;
 203 }
 204 
 205 /*
 206  * Functions for getting the pages from a bvec.
 207  */
 208 static void bio_get_page(struct dpages *dp, struct page **p,
 209                          unsigned long *len, unsigned *offset)
 210 {
 211         struct bio_vec bvec = bvec_iter_bvec((struct bio_vec *)dp->context_ptr,
 212                                              dp->context_bi);
 213 
 214         *p = bvec.bv_page;
 215         *len = bvec.bv_len;
 216         *offset = bvec.bv_offset;
 217 
 218         /* avoid figuring it out again in bio_next_page() */
 219         dp->context_bi.bi_sector = (sector_t)bvec.bv_len;
 220 }
 221 
 222 static void bio_next_page(struct dpages *dp)
 223 {
 224         unsigned int len = (unsigned int)dp->context_bi.bi_sector;
 225 
 226         bvec_iter_advance((struct bio_vec *)dp->context_ptr,
 227                           &dp->context_bi, len);
 228 }
 229 
 230 static void bio_dp_init(struct dpages *dp, struct bio *bio)
 231 {
 232         dp->get_page = bio_get_page;
 233         dp->next_page = bio_next_page;
 234 
 235         /*
 236          * We just use bvec iterator to retrieve pages, so it is ok to
 237          * access the bvec table directly here
 238          */
 239         dp->context_ptr = bio->bi_io_vec;
 240         dp->context_bi = bio->bi_iter;
 241 }
 242 
 243 /*
 244  * Functions for getting the pages from a VMA.
 245  */
 246 static void vm_get_page(struct dpages *dp,
 247                  struct page **p, unsigned long *len, unsigned *offset)
 248 {
 249         *p = vmalloc_to_page(dp->context_ptr);
 250         *offset = dp->context_u;
 251         *len = PAGE_SIZE - dp->context_u;
 252 }
 253 
 254 static void vm_next_page(struct dpages *dp)
 255 {
 256         dp->context_ptr += PAGE_SIZE - dp->context_u;
 257         dp->context_u = 0;
 258 }
 259 
 260 static void vm_dp_init(struct dpages *dp, void *data)
 261 {
 262         dp->get_page = vm_get_page;
 263         dp->next_page = vm_next_page;
 264         dp->context_u = offset_in_page(data);
 265         dp->context_ptr = data;
 266 }
 267 
 268 /*
 269  * Functions for getting the pages from kernel memory.
 270  */
 271 static void km_get_page(struct dpages *dp, struct page **p, unsigned long *len,
 272                         unsigned *offset)
 273 {
 274         *p = virt_to_page(dp->context_ptr);
 275         *offset = dp->context_u;
 276         *len = PAGE_SIZE - dp->context_u;
 277 }
 278 
 279 static void km_next_page(struct dpages *dp)
 280 {
 281         dp->context_ptr += PAGE_SIZE - dp->context_u;
 282         dp->context_u = 0;
 283 }
 284 
 285 static void km_dp_init(struct dpages *dp, void *data)
 286 {
 287         dp->get_page = km_get_page;
 288         dp->next_page = km_next_page;
 289         dp->context_u = offset_in_page(data);
 290         dp->context_ptr = data;
 291 }
 292 
 293 /*-----------------------------------------------------------------
 294  * IO routines that accept a list of pages.
 295  *---------------------------------------------------------------*/
 296 static void do_region(int op, int op_flags, unsigned region,
 297                       struct dm_io_region *where, struct dpages *dp,
 298                       struct io *io)
 299 {
 300         struct bio *bio;
 301         struct page *page;
 302         unsigned long len;
 303         unsigned offset;
 304         unsigned num_bvecs;
 305         sector_t remaining = where->count;
 306         struct request_queue *q = bdev_get_queue(where->bdev);
 307         unsigned short logical_block_size = queue_logical_block_size(q);
 308         sector_t num_sectors;
 309         unsigned int uninitialized_var(special_cmd_max_sectors);
 310 
 311         /*
 312          * Reject unsupported discard and write same requests.
 313          */
 314         if (op == REQ_OP_DISCARD)
 315                 special_cmd_max_sectors = q->limits.max_discard_sectors;
 316         else if (op == REQ_OP_WRITE_ZEROES)
 317                 special_cmd_max_sectors = q->limits.max_write_zeroes_sectors;
 318         else if (op == REQ_OP_WRITE_SAME)
 319                 special_cmd_max_sectors = q->limits.max_write_same_sectors;
 320         if ((op == REQ_OP_DISCARD || op == REQ_OP_WRITE_ZEROES ||
 321              op == REQ_OP_WRITE_SAME) && special_cmd_max_sectors == 0) {
 322                 atomic_inc(&io->count);
 323                 dec_count(io, region, BLK_STS_NOTSUPP);
 324                 return;
 325         }
 326 
 327         /*
 328          * where->count may be zero if op holds a flush and we need to
 329          * send a zero-sized flush.
 330          */
 331         do {
 332                 /*
 333                  * Allocate a suitably sized-bio.
 334                  */
 335                 switch (op) {
 336                 case REQ_OP_DISCARD:
 337                 case REQ_OP_WRITE_ZEROES:
 338                         num_bvecs = 0;
 339                         break;
 340                 case REQ_OP_WRITE_SAME:
 341                         num_bvecs = 1;
 342                         break;
 343                 default:
 344                         num_bvecs = min_t(int, BIO_MAX_PAGES,
 345                                           dm_sector_div_up(remaining, (PAGE_SIZE >> SECTOR_SHIFT)));
 346                 }
 347 
 348                 bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, &io->client->bios);
 349                 bio->bi_iter.bi_sector = where->sector + (where->count - remaining);
 350                 bio_set_dev(bio, where->bdev);
 351                 bio->bi_end_io = endio;
 352                 bio_set_op_attrs(bio, op, op_flags);
 353                 store_io_and_region_in_bio(bio, io, region);
 354 
 355                 if (op == REQ_OP_DISCARD || op == REQ_OP_WRITE_ZEROES) {
 356                         num_sectors = min_t(sector_t, special_cmd_max_sectors, remaining);
 357                         bio->bi_iter.bi_size = num_sectors << SECTOR_SHIFT;
 358                         remaining -= num_sectors;
 359                 } else if (op == REQ_OP_WRITE_SAME) {
 360                         /*
 361                          * WRITE SAME only uses a single page.
 362                          */
 363                         dp->get_page(dp, &page, &len, &offset);
 364                         bio_add_page(bio, page, logical_block_size, offset);
 365                         num_sectors = min_t(sector_t, special_cmd_max_sectors, remaining);
 366                         bio->bi_iter.bi_size = num_sectors << SECTOR_SHIFT;
 367 
 368                         offset = 0;
 369                         remaining -= num_sectors;
 370                         dp->next_page(dp);
 371                 } else while (remaining) {
 372                         /*
 373                          * Try and add as many pages as possible.
 374                          */
 375                         dp->get_page(dp, &page, &len, &offset);
 376                         len = min(len, to_bytes(remaining));
 377                         if (!bio_add_page(bio, page, len, offset))
 378                                 break;
 379 
 380                         offset = 0;
 381                         remaining -= to_sector(len);
 382                         dp->next_page(dp);
 383                 }
 384 
 385                 atomic_inc(&io->count);
 386                 submit_bio(bio);
 387         } while (remaining);
 388 }
 389 
 390 static void dispatch_io(int op, int op_flags, unsigned int num_regions,
 391                         struct dm_io_region *where, struct dpages *dp,
 392                         struct io *io, int sync)
 393 {
 394         int i;
 395         struct dpages old_pages = *dp;
 396 
 397         BUG_ON(num_regions > DM_IO_MAX_REGIONS);
 398 
 399         if (sync)
 400                 op_flags |= REQ_SYNC;
 401 
 402         /*
 403          * For multiple regions we need to be careful to rewind
 404          * the dp object for each call to do_region.
 405          */
 406         for (i = 0; i < num_regions; i++) {
 407                 *dp = old_pages;
 408                 if (where[i].count || (op_flags & REQ_PREFLUSH))
 409                         do_region(op, op_flags, i, where + i, dp, io);
 410         }
 411 
 412         /*
 413          * Drop the extra reference that we were holding to avoid
 414          * the io being completed too early.
 415          */
 416         dec_count(io, 0, 0);
 417 }
 418 
 419 struct sync_io {
 420         unsigned long error_bits;
 421         struct completion wait;
 422 };
 423 
 424 static void sync_io_complete(unsigned long error, void *context)
 425 {
 426         struct sync_io *sio = context;
 427 
 428         sio->error_bits = error;
 429         complete(&sio->wait);
 430 }
 431 
 432 static int sync_io(struct dm_io_client *client, unsigned int num_regions,
 433                    struct dm_io_region *where, int op, int op_flags,
 434                    struct dpages *dp, unsigned long *error_bits)
 435 {
 436         struct io *io;
 437         struct sync_io sio;
 438 
 439         if (num_regions > 1 && !op_is_write(op)) {
 440                 WARN_ON(1);
 441                 return -EIO;
 442         }
 443 
 444         init_completion(&sio.wait);
 445 
 446         io = mempool_alloc(&client->pool, GFP_NOIO);
 447         io->error_bits = 0;
 448         atomic_set(&io->count, 1); /* see dispatch_io() */
 449         io->client = client;
 450         io->callback = sync_io_complete;
 451         io->context = &sio;
 452 
 453         io->vma_invalidate_address = dp->vma_invalidate_address;
 454         io->vma_invalidate_size = dp->vma_invalidate_size;
 455 
 456         dispatch_io(op, op_flags, num_regions, where, dp, io, 1);
 457 
 458         wait_for_completion_io(&sio.wait);
 459 
 460         if (error_bits)
 461                 *error_bits = sio.error_bits;
 462 
 463         return sio.error_bits ? -EIO : 0;
 464 }
 465 
 466 static int async_io(struct dm_io_client *client, unsigned int num_regions,
 467                     struct dm_io_region *where, int op, int op_flags,
 468                     struct dpages *dp, io_notify_fn fn, void *context)
 469 {
 470         struct io *io;
 471 
 472         if (num_regions > 1 && !op_is_write(op)) {
 473                 WARN_ON(1);
 474                 fn(1, context);
 475                 return -EIO;
 476         }
 477 
 478         io = mempool_alloc(&client->pool, GFP_NOIO);
 479         io->error_bits = 0;
 480         atomic_set(&io->count, 1); /* see dispatch_io() */
 481         io->client = client;
 482         io->callback = fn;
 483         io->context = context;
 484 
 485         io->vma_invalidate_address = dp->vma_invalidate_address;
 486         io->vma_invalidate_size = dp->vma_invalidate_size;
 487 
 488         dispatch_io(op, op_flags, num_regions, where, dp, io, 0);
 489         return 0;
 490 }
 491 
 492 static int dp_init(struct dm_io_request *io_req, struct dpages *dp,
 493                    unsigned long size)
 494 {
 495         /* Set up dpages based on memory type */
 496 
 497         dp->vma_invalidate_address = NULL;
 498         dp->vma_invalidate_size = 0;
 499 
 500         switch (io_req->mem.type) {
 501         case DM_IO_PAGE_LIST:
 502                 list_dp_init(dp, io_req->mem.ptr.pl, io_req->mem.offset);
 503                 break;
 504 
 505         case DM_IO_BIO:
 506                 bio_dp_init(dp, io_req->mem.ptr.bio);
 507                 break;
 508 
 509         case DM_IO_VMA:
 510                 flush_kernel_vmap_range(io_req->mem.ptr.vma, size);
 511                 if (io_req->bi_op == REQ_OP_READ) {
 512                         dp->vma_invalidate_address = io_req->mem.ptr.vma;
 513                         dp->vma_invalidate_size = size;
 514                 }
 515                 vm_dp_init(dp, io_req->mem.ptr.vma);
 516                 break;
 517 
 518         case DM_IO_KMEM:
 519                 km_dp_init(dp, io_req->mem.ptr.addr);
 520                 break;
 521 
 522         default:
 523                 return -EINVAL;
 524         }
 525 
 526         return 0;
 527 }
 528 
 529 /*
 530  * New collapsed (a)synchronous interface.
 531  *
 532  * If the IO is asynchronous (i.e. it has notify.fn), you must either unplug
 533  * the queue with blk_unplug() some time later or set REQ_SYNC in
 534  * io_req->bi_opf. If you fail to do one of these, the IO will be submitted to
 535  * the disk after q->unplug_delay, which defaults to 3ms in blk-settings.c.
 536  */
 537 int dm_io(struct dm_io_request *io_req, unsigned num_regions,
 538           struct dm_io_region *where, unsigned long *sync_error_bits)
 539 {
 540         int r;
 541         struct dpages dp;
 542 
 543         r = dp_init(io_req, &dp, (unsigned long)where->count << SECTOR_SHIFT);
 544         if (r)
 545                 return r;
 546 
 547         if (!io_req->notify.fn)
 548                 return sync_io(io_req->client, num_regions, where,
 549                                io_req->bi_op, io_req->bi_op_flags, &dp,
 550                                sync_error_bits);
 551 
 552         return async_io(io_req->client, num_regions, where, io_req->bi_op,
 553                         io_req->bi_op_flags, &dp, io_req->notify.fn,
 554                         io_req->notify.context);
 555 }
 556 EXPORT_SYMBOL(dm_io);
 557 
 558 int __init dm_io_init(void)
 559 {
 560         _dm_io_cache = KMEM_CACHE(io, 0);
 561         if (!_dm_io_cache)
 562                 return -ENOMEM;
 563 
 564         return 0;
 565 }
 566 
 567 void dm_io_exit(void)
 568 {
 569         kmem_cache_destroy(_dm_io_cache);
 570         _dm_io_cache = NULL;
 571 }