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         struct request_queue *q = bdev_get_queue(where->bdev);
 300         sector_t discard_sectors;
 301
 302         /*
 303          * where->count may be zero if rw holds a flush and we need to
 304          * send a zero-sized flush.
 305          */
 306         do {
 307                 /*
 308                  * Allocate a suitably sized-bio.
 309                  */
 310                 if (rw & REQ_DISCARD)
 311                         num_bvecs = 1;
 312                 else
 313                         num_bvecs = min_t(int, bio_get_nr_vecs(where->bdev),
 314                                           dm_sector_div_up(remaining, (PAGE_SIZE >> SECTOR_SHIFT)));
 315
 316                 bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
 317                 bio->bi_sector = where->sector + (where->count - remaining);
 318                 bio->bi_bdev = where->bdev;
 319                 bio->bi_end_io = endio;
 320                 bio->bi_destructor = dm_bio_destructor;
 321                 store_io_and_region_in_bio(bio, io, region);
 322
 323                 if (rw & REQ_DISCARD) {
 324                         discard_sectors = min_t(sector_t, q->limits.max_discard_sectors, remaining);
 325                         bio->bi_size = discard_sectors << SECTOR_SHIFT;
 326                         remaining -= discard_sectors;
 327                 } else while (remaining) {
 328                         /*
 329                          * Try and add as many pages as possible.
 330                          */
 331                         dp->get_page(dp, &page, &len, &offset);
 332                         len = min(len, to_bytes(remaining));
 333                         if (!bio_add_page(bio, page, len, offset))
 334                                 break;
 335
 336                         offset = 0;
 337                         remaining -= to_sector(len);
 338                         dp->next_page(dp);
 339                 }
 340
 341                 atomic_inc(&io->count);
 342                 submit_bio(rw, bio);
 343         } while (remaining);
 344 }
 345
 346 static void dispatch_io(int rw, unsigned int num_regions,
 347                         struct dm_io_region *where, struct dpages *dp,
 348                         struct io *io, int sync)
 349 {
 350         int i;
 351         struct dpages old_pages = *dp;
 352
 353         BUG_ON(num_regions > DM_IO_MAX_REGIONS);
 354
 355         if (sync)
 356                 rw |= REQ_SYNC;
 357
 358         /*
 359          * For multiple regions we need to be careful to rewind
 360          * the dp object for each call to do_region.
 361          */
 362         for (i = 0; i < num_regions; i++) {
 363                 *dp = old_pages;
 364                 if (where[i].count || (rw & REQ_FLUSH))
 365                         do_region(rw, i, where + i, dp, io);
 366         }
 367
 368         /*
 369          * Drop the extra reference that we were holding to avoid
 370          * the io being completed too early.
 371          */
 372         dec_count(io, 0, 0);
 373 }
 374
 375 static int sync_io(struct dm_io_client *client, unsigned int num_regions,
 376                    struct dm_io_region *where, int rw, struct dpages *dp,
 377                    unsigned long *error_bits)
 378 {
 379         /*
 380          * gcc <= 4.3 can't do the alignment for stack variables, so we must
 381          * align it on our own.
 382          * volatile prevents the optimizer from removing or reusing
 383          * "io_" field from the stack frame (allowed in ANSI C).
 384          */
 385         volatile char io_[sizeof(struct io) + __alignof__(struct io) - 1];
 386         struct io *io = (struct io *)PTR_ALIGN(&io_, __alignof__(struct io));
 387
 388         if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
 389                 WARN_ON(1);
 390                 return -EIO;
 391         }
 392
 393         io->error_bits = 0;
 394         atomic_set(&io->count, 1); /* see dispatch_io() */
 395         io->sleeper = current;
 396         io->client = client;
 397
 398         io->vma_invalidate_address = dp->vma_invalidate_address;
 399         io->vma_invalidate_size = dp->vma_invalidate_size;
 400
 401         dispatch_io(rw, num_regions, where, dp, io, 1);
 402
 403         while (1) {
 404                 set_current_state(TASK_UNINTERRUPTIBLE);
 405
 406                 if (!atomic_read(&io->count))
 407                         break;
 408
 409                 io_schedule();
 410         }
 411         set_current_state(TASK_RUNNING);
 412
 413         if (error_bits)
 414                 *error_bits = io->error_bits;
 415
 416         return io->error_bits ? -EIO : 0;
 417 }
 418
 419 static int async_io(struct dm_io_client *client, unsigned int num_regions,
 420                     struct dm_io_region *where, int rw, struct dpages *dp,
 421                     io_notify_fn fn, void *context)
 422 {
 423         struct io *io;
 424
 425         if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
 426                 WARN_ON(1);
 427                 fn(1, context);
 428                 return -EIO;
 429         }
 430
 431         io = mempool_alloc(client->pool, GFP_NOIO);
 432         io->error_bits = 0;
 433         atomic_set(&io->count, 1); /* see dispatch_io() */
 434         io->sleeper = NULL;
 435         io->client = client;
 436         io->callback = fn;
 437         io->context = context;
 438
 439         io->vma_invalidate_address = dp->vma_invalidate_address;
 440         io->vma_invalidate_size = dp->vma_invalidate_size;
 441
 442         dispatch_io(rw, num_regions, where, dp, io, 0);
 443         return 0;
 444 }
 445
 446 static int dp_init(struct dm_io_request *io_req, struct dpages *dp,
 447                    unsigned long size)
 448 {
 449         /* Set up dpages based on memory type */
 450
 451         dp->vma_invalidate_address = NULL;
 452         dp->vma_invalidate_size = 0;
 453
 454         switch (io_req->mem.type) {
 455         case DM_IO_PAGE_LIST:
 456                 list_dp_init(dp, io_req->mem.ptr.pl, io_req->mem.offset);
 457                 break;
 458
 459         case DM_IO_BVEC:
 460                 bvec_dp_init(dp, io_req->mem.ptr.bvec);
 461                 break;
 462
 463         case DM_IO_VMA:
 464                 flush_kernel_vmap_range(io_req->mem.ptr.vma, size);
 465                 if ((io_req->bi_rw & RW_MASK) == READ) {
 466                         dp->vma_invalidate_address = io_req->mem.ptr.vma;
 467                         dp->vma_invalidate_size = size;
 468                 }
 469                 vm_dp_init(dp, io_req->mem.ptr.vma);
 470                 break;
 471
 472         case DM_IO_KMEM:
 473                 km_dp_init(dp, io_req->mem.ptr.addr);
 474                 break;
 475
 476         default:
 477                 return -EINVAL;
 478         }
 479
 480         return 0;
 481 }
 482
 483 /*
 484  * New collapsed (a)synchronous interface.
 485  *
 486  * If the IO is asynchronous (i.e. it has notify.fn), you must either unplug
 487  * the queue with blk_unplug() some time later or set REQ_SYNC in
 488 io_req->bi_rw. If you fail to do one of these, the IO will be submitted to
 489  * the disk after q->unplug_delay, which defaults to 3ms in blk-settings.c.
 490  */
 491 int dm_io(struct dm_io_request *io_req, unsigned num_regions,
 492           struct dm_io_region *where, unsigned long *sync_error_bits)
 493 {
 494         int r;
 495         struct dpages dp;
 496
 497         r = dp_init(io_req, &dp, (unsigned long)where->count << SECTOR_SHIFT);
 498         if (r)
 499                 return r;
 500
 501         if (!io_req->notify.fn)
 502                 return sync_io(io_req->client, num_regions, where,
 503                                io_req->bi_rw, &dp, sync_error_bits);
 504
 505         return async_io(io_req->client, num_regions, where, io_req->bi_rw,
 506                         &dp, io_req->notify.fn, io_req->notify.context);
 507 }
 508 EXPORT_SYMBOL(dm_io);
 509
 510 int __init dm_io_init(void)
 511 {
 512         _dm_io_cache = KMEM_CACHE(io, 0);
 513         if (!_dm_io_cache)
 514                 return -ENOMEM;
 515
 516         return 0;
 517 }
 518
 519 void dm_io_exit(void)
 520 {
 521         kmem_cache_destroy(_dm_io_cache);
 522         _dm_io_cache = NULL;
 523 }