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 #define MIN_IOS         16
  23 #define MIN_BIOS        16
  24
  25 struct dm_io_client {
  26         mempool_t *pool;
  27         struct bio_set *bios;
  28 };
  29
  30 /*
  31  * Aligning 'struct io' reduces the number of bits required to store
  32  * its address.  Refer to store_io_and_region_in_bio() below.
  33  */
  34 struct io {
  35         unsigned long error_bits;
  36         atomic_t count;
  37         struct task_struct *sleeper;
  38         struct dm_io_client *client;
  39         io_notify_fn callback;
  40         void *context;
  41         void *vma_invalidate_address;
  42         unsigned long vma_invalidate_size;
  43 } __attribute__((aligned(DM_IO_MAX_REGIONS)));
  44
  45 static struct kmem_cache *_dm_io_cache;
  46
  47 /*
  48  * Create a client with mempool and bioset.
  49  */
  50 struct dm_io_client *dm_io_client_create(void)
  51 {
  52         struct dm_io_client *client;
  53
  54         client = kmalloc(sizeof(*client), GFP_KERNEL);
  55         if (!client)
  56                 return ERR_PTR(-ENOMEM);
  57
  58         client->pool = mempool_create_slab_pool(MIN_IOS, _dm_io_cache);
  59         if (!client->pool)
  60                 goto bad;
  61
  62         client->bios = bioset_create(MIN_BIOS, 0);
  63         if (!client->bios)
  64                 goto bad;
  65
  66         return client;
  67
  68    bad:
  69         if (client->pool)
  70                 mempool_destroy(client->pool);
  71         kfree(client);
  72         return ERR_PTR(-ENOMEM);
  73 }
  74 EXPORT_SYMBOL(dm_io_client_create);
  75
  76 void dm_io_client_destroy(struct dm_io_client *client)
  77 {
  78         mempool_destroy(client->pool);
  79         bioset_free(client->bios);
  80         kfree(client);
  81 }
  82 EXPORT_SYMBOL(dm_io_client_destroy);
  83
  84 /*-----------------------------------------------------------------
  85  * We need to keep track of which region a bio is doing io for.
  86  * To avoid a memory allocation to store just 5 or 6 bits, we
  87  * ensure the 'struct io' pointer is aligned so enough low bits are
  88  * always zero and then combine it with the region number directly in
  89  * bi_private.
  90  *---------------------------------------------------------------*/
  91 static void store_io_and_region_in_bio(struct bio *bio, struct io *io,
  92                                        unsigned region)
  93 {
  94         if (unlikely(!IS_ALIGNED((unsigned long)io, DM_IO_MAX_REGIONS))) {
  95                 DMCRIT("Unaligned struct io pointer %p", io);
  96                 BUG();
  97         }
  98
  99         bio->bi_private = (void *)((unsigned long)io | region);
 100 }
 101
 102 static void retrieve_io_and_region_from_bio(struct bio *bio, struct io **io,
 103                                        unsigned *region)
 104 {
 105         unsigned long val = (unsigned long)bio->bi_private;
 106
 107         *io = (void *)(val & -(unsigned long)DM_IO_MAX_REGIONS);
 108         *region = val & (DM_IO_MAX_REGIONS - 1);
 109 }
 110
 111 /*-----------------------------------------------------------------
 112  * We need an io object to keep track of the number of bios that
 113  * have been dispatched for a particular io.
 114  *---------------------------------------------------------------*/
 115 static void dec_count(struct io *io, unsigned int region, int error)
 116 {
 117         if (error)
 118                 set_bit(region, &io->error_bits);
 119
 120         if (atomic_dec_and_test(&io->count)) {
 121                 if (io->vma_invalidate_size)
 122                         invalidate_kernel_vmap_range(io->vma_invalidate_address,
 123                                                      io->vma_invalidate_size);
 124
 125                 if (io->sleeper)
 126                         wake_up_process(io->sleeper);
 127
 128                 else {
 129                         unsigned long r = io->error_bits;
 130                         io_notify_fn fn = io->callback;
 131                         void *context = io->context;
 132
 133                         mempool_free(io, io->client->pool);
 134                         fn(r, context);
 135                 }
 136         }
 137 }
 138
 139 static void endio(struct bio *bio, int error)
 140 {
 141         struct io *io;
 142         unsigned region;
 143
 144         if (error && bio_data_dir(bio) == READ)
 145                 zero_fill_bio(bio);
 146
 147         /*
 148          * The bio destructor in bio_put() may use the io object.
 149          */
 150         retrieve_io_and_region_from_bio(bio, &io, &region);
 151
 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         unsigned context_u;
 167         void *context_ptr;
 168
 169         void *vma_invalidate_address;
 170         unsigned long vma_invalidate_size;
 171 };
 172
 173 /*
 174  * Functions for getting the pages from a list.
 175  */
 176 static void list_get_page(struct dpages *dp,
 177                   struct page **p, unsigned long *len, unsigned *offset)
 178 {
 179         unsigned o = dp->context_u;
 180         struct page_list *pl = (struct page_list *) dp->context_ptr;
 181
 182         *p = pl->page;
 183         *len = PAGE_SIZE - o;
 184         *offset = o;
 185 }
 186
 187 static void list_next_page(struct dpages *dp)
 188 {
 189         struct page_list *pl = (struct page_list *) dp->context_ptr;
 190         dp->context_ptr = pl->next;
 191         dp->context_u = 0;
 192 }
 193
 194 static void list_dp_init(struct dpages *dp, struct page_list *pl, unsigned offset)
 195 {
 196         dp->get_page = list_get_page;
 197         dp->next_page = list_next_page;
 198         dp->context_u = offset;
 199         dp->context_ptr = pl;
 200 }
 201
 202 /*
 203  * Functions for getting the pages from a bvec.
 204  */
 205 static void bvec_get_page(struct dpages *dp,
 206                   struct page **p, unsigned long *len, unsigned *offset)
 207 {
 208         struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
 209         *p = bvec->bv_page;
 210         *len = bvec->bv_len;
 211         *offset = bvec->bv_offset;
 212 }
 213
 214 static void bvec_next_page(struct dpages *dp)
 215 {
 216         struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
 217         dp->context_ptr = bvec + 1;
 218 }
 219
 220 static void bvec_dp_init(struct dpages *dp, struct bio_vec *bvec)
 221 {
 222         dp->get_page = bvec_get_page;
 223         dp->next_page = bvec_next_page;
 224         dp->context_ptr = bvec;
 225 }
 226
 227 /*
 228  * Functions for getting the pages from a VMA.
 229  */
 230 static void vm_get_page(struct dpages *dp,
 231                  struct page **p, unsigned long *len, unsigned *offset)
 232 {
 233         *p = vmalloc_to_page(dp->context_ptr);
 234         *offset = dp->context_u;
 235         *len = PAGE_SIZE - dp->context_u;
 236 }
 237
 238 static void vm_next_page(struct dpages *dp)
 239 {
 240         dp->context_ptr += PAGE_SIZE - dp->context_u;
 241         dp->context_u = 0;
 242 }
 243
 244 static void vm_dp_init(struct dpages *dp, void *data)
 245 {
 246         dp->get_page = vm_get_page;
 247         dp->next_page = vm_next_page;
 248         dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
 249         dp->context_ptr = data;
 250 }
 251
 252 static void dm_bio_destructor(struct bio *bio)
 253 {
 254         unsigned region;
 255         struct io *io;
 256
 257         retrieve_io_and_region_from_bio(bio, &io, &region);
 258
 259         bio_free(bio, io->client->bios);
 260 }
 261
 262 /*
 263  * Functions for getting the pages from kernel memory.
 264  */
 265 static void km_get_page(struct dpages *dp, struct page **p, unsigned long *len,
 266                         unsigned *offset)
 267 {
 268         *p = virt_to_page(dp->context_ptr);
 269         *offset = dp->context_u;
 270         *len = PAGE_SIZE - dp->context_u;
 271 }
 272
 273 static void km_next_page(struct dpages *dp)
 274 {
 275         dp->context_ptr += PAGE_SIZE - dp->context_u;
 276         dp->context_u = 0;
 277 }
 278
 279 static void km_dp_init(struct dpages *dp, void *data)
 280 {
 281         dp->get_page = km_get_page;
 282         dp->next_page = km_next_page;
 283         dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
 284         dp->context_ptr = data;
 285 }
 286
 287 /*-----------------------------------------------------------------
 288  * IO routines that accept a list of pages.
 289  *---------------------------------------------------------------*/
 290 static void do_region(int rw, unsigned region, struct dm_io_region *where,
 291                       struct dpages *dp, struct io *io)
 292 {
 293         struct bio *bio;
 294         struct page *page;
 295         unsigned long len;
 296         unsigned offset;
 297         unsigned num_bvecs;
 298         sector_t remaining = where->count;
 299
 300         /*
 301          * where->count may be zero if rw holds a flush and we need to
 302          * send a zero-sized flush.
 303          */
 304         do {
 305                 /*
 306                  * Allocate a suitably sized-bio.
 307                  */
 308                 num_bvecs = dm_sector_div_up(remaining,
 309                                              (PAGE_SIZE >> SECTOR_SHIFT));
 310                 num_bvecs = min_t(int, bio_get_nr_vecs(where->bdev), num_bvecs);
 311                 bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
 312                 bio->bi_sector = where->sector + (where->count - remaining);
 313                 bio->bi_bdev = where->bdev;
 314                 bio->bi_end_io = endio;
 315                 bio->bi_destructor = dm_bio_destructor;
 316                 store_io_and_region_in_bio(bio, io, region);
 317
 318                 /*
 319                  * Try and add as many pages as possible.
 320                  */
 321                 while (remaining) {
 322                         dp->get_page(dp, &page, &len, &offset);
 323                         len = min(len, to_bytes(remaining));
 324                         if (!bio_add_page(bio, page, len, offset))
 325                                 break;
 326
 327                         offset = 0;
 328                         remaining -= to_sector(len);
 329                         dp->next_page(dp);
 330                 }
 331
 332                 atomic_inc(&io->count);
 333                 submit_bio(rw, bio);
 334         } while (remaining);
 335 }
 336
 337 static void dispatch_io(int rw, unsigned int num_regions,
 338                         struct dm_io_region *where, struct dpages *dp,
 339                         struct io *io, int sync)
 340 {
 341         int i;
 342         struct dpages old_pages = *dp;
 343
 344         BUG_ON(num_regions > DM_IO_MAX_REGIONS);
 345
 346         if (sync)
 347                 rw |= REQ_SYNC;
 348
 349         /*
 350          * For multiple regions we need to be careful to rewind
 351          * the dp object for each call to do_region.
 352          */
 353         for (i = 0; i < num_regions; i++) {
 354                 *dp = old_pages;
 355                 if (where[i].count || (rw & REQ_FLUSH))
 356                         do_region(rw, i, where + i, dp, io);
 357         }
 358
 359         /*
 360          * Drop the extra reference that we were holding to avoid
 361          * the io being completed too early.
 362          */
 363         dec_count(io, 0, 0);
 364 }
 365
 366 static int sync_io(struct dm_io_client *client, unsigned int num_regions,
 367                    struct dm_io_region *where, int rw, struct dpages *dp,
 368                    unsigned long *error_bits)
 369 {
 370         /*
 371          * gcc <= 4.3 can't do the alignment for stack variables, so we must
 372          * align it on our own.
 373          * volatile prevents the optimizer from removing or reusing
 374          * "io_" field from the stack frame (allowed in ANSI C).
 375          */
 376         volatile char io_[sizeof(struct io) + __alignof__(struct io) - 1];
 377         struct io *io = (struct io *)PTR_ALIGN(&io_, __alignof__(struct io));
 378
 379         if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
 380                 WARN_ON(1);
 381                 return -EIO;
 382         }
 383
 384         io->error_bits = 0;
 385         atomic_set(&io->count, 1); /* see dispatch_io() */
 386         io->sleeper = current;
 387         io->client = client;
 388
 389         io->vma_invalidate_address = dp->vma_invalidate_address;
 390         io->vma_invalidate_size = dp->vma_invalidate_size;
 391
 392         dispatch_io(rw, num_regions, where, dp, io, 1);
 393
 394         while (1) {
 395                 set_current_state(TASK_UNINTERRUPTIBLE);
 396
 397                 if (!atomic_read(&io->count))
 398                         break;
 399
 400                 io_schedule();
 401         }
 402         set_current_state(TASK_RUNNING);
 403
 404         if (error_bits)
 405                 *error_bits = io->error_bits;
 406
 407         return io->error_bits ? -EIO : 0;
 408 }
 409
 410 static int async_io(struct dm_io_client *client, unsigned int num_regions,
 411                     struct dm_io_region *where, int rw, struct dpages *dp,
 412                     io_notify_fn fn, void *context)
 413 {
 414         struct io *io;
 415
 416         if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
 417                 WARN_ON(1);
 418                 fn(1, context);
 419                 return -EIO;
 420         }
 421
 422         io = mempool_alloc(client->pool, GFP_NOIO);
 423         io->error_bits = 0;
 424         atomic_set(&io->count, 1); /* see dispatch_io() */
 425         io->sleeper = NULL;
 426         io->client = client;
 427         io->callback = fn;
 428         io->context = context;
 429
 430         io->vma_invalidate_address = dp->vma_invalidate_address;
 431         io->vma_invalidate_size = dp->vma_invalidate_size;
 432
 433         dispatch_io(rw, num_regions, where, dp, io, 0);
 434         return 0;
 435 }
 436
 437 static int dp_init(struct dm_io_request *io_req, struct dpages *dp,
 438                    unsigned long size)
 439 {
 440         /* Set up dpages based on memory type */
 441
 442         dp->vma_invalidate_address = NULL;
 443         dp->vma_invalidate_size = 0;
 444
 445         switch (io_req->mem.type) {
 446         case DM_IO_PAGE_LIST:
 447                 list_dp_init(dp, io_req->mem.ptr.pl, io_req->mem.offset);
 448                 break;
 449
 450         case DM_IO_BVEC:
 451                 bvec_dp_init(dp, io_req->mem.ptr.bvec);
 452                 break;
 453
 454         case DM_IO_VMA:
 455                 flush_kernel_vmap_range(io_req->mem.ptr.vma, size);
 456                 if ((io_req->bi_rw & RW_MASK) == READ) {
 457                         dp->vma_invalidate_address = io_req->mem.ptr.vma;
 458                         dp->vma_invalidate_size = size;
 459                 }
 460                 vm_dp_init(dp, io_req->mem.ptr.vma);
 461                 break;
 462
 463         case DM_IO_KMEM:
 464                 km_dp_init(dp, io_req->mem.ptr.addr);
 465                 break;
 466
 467         default:
 468                 return -EINVAL;
 469         }
 470
 471         return 0;
 472 }
 473
 474 /*
 475  * New collapsed (a)synchronous interface.
 476  *
 477  * If the IO is asynchronous (i.e. it has notify.fn), you must either unplug
 478  * the queue with blk_unplug() some time later or set REQ_SYNC in
 479 io_req->bi_rw. If you fail to do one of these, the IO will be submitted to
 480  * the disk after q->unplug_delay, which defaults to 3ms in blk-settings.c.
 481  */
 482 int dm_io(struct dm_io_request *io_req, unsigned num_regions,
 483           struct dm_io_region *where, unsigned long *sync_error_bits)
 484 {
 485         int r;
 486         struct dpages dp;
 487
 488         r = dp_init(io_req, &dp, (unsigned long)where->count << SECTOR_SHIFT);
 489         if (r)
 490                 return r;
 491
 492         if (!io_req->notify.fn)
 493                 return sync_io(io_req->client, num_regions, where,
 494                                io_req->bi_rw, &dp, sync_error_bits);
 495
 496         return async_io(io_req->client, num_regions, where, io_req->bi_rw,
 497                         &dp, io_req->notify.fn, io_req->notify.context);
 498 }
 499 EXPORT_SYMBOL(dm_io);
 500
 501 int __init dm_io_init(void)
 502 {
 503         _dm_io_cache = KMEM_CACHE(io, 0);
 504         if (!_dm_io_cache)
 505                 return -ENOMEM;
 506
 507         return 0;
 508 }
 509
 510 void dm_io_exit(void)
 511 {
 512         kmem_cache_destroy(_dm_io_cache);
 513         _dm_io_cache = NULL;
 514 }