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         unsigned long eopnotsupp_bits;
  35         atomic_t count;
  36         struct task_struct *sleeper;
  37         struct dm_io_client *client;
  38         io_notify_fn callback;
  39         void *context;
  40 } __attribute__((aligned(DM_IO_MAX_REGIONS)));
  41
  42 static struct kmem_cache *_dm_io_cache;
  43
  44 /*
  45  * io contexts are only dynamically allocated for asynchronous
  46  * io.  Since async io is likely to be the majority of io we'll
  47  * have the same number of io contexts as bios! (FIXME: must reduce this).
  48  */
  49
  50 static unsigned int pages_to_ios(unsigned int pages)
  51 {
  52         return 4 * pages;       /* too many ? */
  53 }
  54
  55 /*
  56  * Create a client with mempool and bioset.
  57  */
  58 struct dm_io_client *dm_io_client_create(unsigned num_pages)
  59 {
  60         unsigned ios = pages_to_ios(num_pages);
  61         struct dm_io_client *client;
  62
  63         client = kmalloc(sizeof(*client), GFP_KERNEL);
  64         if (!client)
  65                 return ERR_PTR(-ENOMEM);
  66
  67         client->pool = mempool_create_slab_pool(ios, _dm_io_cache);
  68         if (!client->pool)
  69                 goto bad;
  70
  71         client->bios = bioset_create(16, 0);
  72         if (!client->bios)
  73                 goto bad;
  74
  75         return client;
  76
  77    bad:
  78         if (client->pool)
  79                 mempool_destroy(client->pool);
  80         kfree(client);
  81         return ERR_PTR(-ENOMEM);
  82 }
  83 EXPORT_SYMBOL(dm_io_client_create);
  84
  85 int dm_io_client_resize(unsigned num_pages, struct dm_io_client *client)
  86 {
  87         return mempool_resize(client->pool, pages_to_ios(num_pages),
  88                               GFP_KERNEL);
  89 }
  90 EXPORT_SYMBOL(dm_io_client_resize);
  91
  92 void dm_io_client_destroy(struct dm_io_client *client)
  93 {
  94         mempool_destroy(client->pool);
  95         bioset_free(client->bios);
  96         kfree(client);
  97 }
  98 EXPORT_SYMBOL(dm_io_client_destroy);
  99
 100 /*-----------------------------------------------------------------
 101  * We need to keep track of which region a bio is doing io for.
 102  * To avoid a memory allocation to store just 5 or 6 bits, we
 103  * ensure the 'struct io' pointer is aligned so enough low bits are
 104  * always zero and then combine it with the region number directly in
 105  * bi_private.
 106  *---------------------------------------------------------------*/
 107 static void store_io_and_region_in_bio(struct bio *bio, struct io *io,
 108                                        unsigned region)
 109 {
 110         if (unlikely(!IS_ALIGNED((unsigned long)io, DM_IO_MAX_REGIONS))) {
 111                 DMCRIT("Unaligned struct io pointer %p", io);
 112                 BUG();
 113         }
 114
 115         bio->bi_private = (void *)((unsigned long)io | region);
 116 }
 117
 118 static void retrieve_io_and_region_from_bio(struct bio *bio, struct io **io,
 119                                        unsigned *region)
 120 {
 121         unsigned long val = (unsigned long)bio->bi_private;
 122
 123         *io = (void *)(val & -(unsigned long)DM_IO_MAX_REGIONS);
 124         *region = val & (DM_IO_MAX_REGIONS - 1);
 125 }
 126
 127 /*-----------------------------------------------------------------
 128  * We need an io object to keep track of the number of bios that
 129  * have been dispatched for a particular io.
 130  *---------------------------------------------------------------*/
 131 static void dec_count(struct io *io, unsigned int region, int error)
 132 {
 133         if (error) {
 134                 set_bit(region, &io->error_bits);
 135                 if (error == -EOPNOTSUPP)
 136                         set_bit(region, &io->eopnotsupp_bits);
 137         }
 138
 139         if (atomic_dec_and_test(&io->count)) {
 140                 if (io->sleeper)
 141                         wake_up_process(io->sleeper);
 142
 143                 else {
 144                         unsigned long r = io->error_bits;
 145                         io_notify_fn fn = io->callback;
 146                         void *context = io->context;
 147
 148                         mempool_free(io, io->client->pool);
 149                         fn(r, context);
 150                 }
 151         }
 152 }
 153
 154 static void endio(struct bio *bio, int error)
 155 {
 156         struct io *io;
 157         unsigned region;
 158
 159         if (error && bio_data_dir(bio) == READ)
 160                 zero_fill_bio(bio);
 161
 162         /*
 163          * The bio destructor in bio_put() may use the io object.
 164          */
 165         retrieve_io_and_region_from_bio(bio, &io, &region);
 166
 167         bio_put(bio);
 168
 169         dec_count(io, region, error);
 170 }
 171
 172 /*-----------------------------------------------------------------
 173  * These little objects provide an abstraction for getting a new
 174  * destination page for io.
 175  *---------------------------------------------------------------*/
 176 struct dpages {
 177         void (*get_page)(struct dpages *dp,
 178                          struct page **p, unsigned long *len, unsigned *offset);
 179         void (*next_page)(struct dpages *dp);
 180
 181         unsigned context_u;
 182         void *context_ptr;
 183 };
 184
 185 /*
 186  * Functions for getting the pages from a list.
 187  */
 188 static void list_get_page(struct dpages *dp,
 189                   struct page **p, unsigned long *len, unsigned *offset)
 190 {
 191         unsigned o = dp->context_u;
 192         struct page_list *pl = (struct page_list *) dp->context_ptr;
 193
 194         *p = pl->page;
 195         *len = PAGE_SIZE - o;
 196         *offset = o;
 197 }
 198
 199 static void list_next_page(struct dpages *dp)
 200 {
 201         struct page_list *pl = (struct page_list *) dp->context_ptr;
 202         dp->context_ptr = pl->next;
 203         dp->context_u = 0;
 204 }
 205
 206 static void list_dp_init(struct dpages *dp, struct page_list *pl, unsigned offset)
 207 {
 208         dp->get_page = list_get_page;
 209         dp->next_page = list_next_page;
 210         dp->context_u = offset;
 211         dp->context_ptr = pl;
 212 }
 213
 214 /*
 215  * Functions for getting the pages from a bvec.
 216  */
 217 static void bvec_get_page(struct dpages *dp,
 218                   struct page **p, unsigned long *len, unsigned *offset)
 219 {
 220         struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
 221         *p = bvec->bv_page;
 222         *len = bvec->bv_len;
 223         *offset = bvec->bv_offset;
 224 }
 225
 226 static void bvec_next_page(struct dpages *dp)
 227 {
 228         struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
 229         dp->context_ptr = bvec + 1;
 230 }
 231
 232 static void bvec_dp_init(struct dpages *dp, struct bio_vec *bvec)
 233 {
 234         dp->get_page = bvec_get_page;
 235         dp->next_page = bvec_next_page;
 236         dp->context_ptr = bvec;
 237 }
 238
 239 /*
 240  * Functions for getting the pages from a VMA.
 241  */
 242 static void vm_get_page(struct dpages *dp,
 243                  struct page **p, unsigned long *len, unsigned *offset)
 244 {
 245         *p = vmalloc_to_page(dp->context_ptr);
 246         *offset = dp->context_u;
 247         *len = PAGE_SIZE - dp->context_u;
 248 }
 249
 250 static void vm_next_page(struct dpages *dp)
 251 {
 252         dp->context_ptr += PAGE_SIZE - dp->context_u;
 253         dp->context_u = 0;
 254 }
 255
 256 static void vm_dp_init(struct dpages *dp, void *data)
 257 {
 258         dp->get_page = vm_get_page;
 259         dp->next_page = vm_next_page;
 260         dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
 261         dp->context_ptr = data;
 262 }
 263
 264 static void dm_bio_destructor(struct bio *bio)
 265 {
 266         unsigned region;
 267         struct io *io;
 268
 269         retrieve_io_and_region_from_bio(bio, &io, &region);
 270
 271         bio_free(bio, io->client->bios);
 272 }
 273
 274 /*
 275  * Functions for getting the pages from kernel memory.
 276  */
 277 static void km_get_page(struct dpages *dp, struct page **p, unsigned long *len,
 278                         unsigned *offset)
 279 {
 280         *p = virt_to_page(dp->context_ptr);
 281         *offset = dp->context_u;
 282         *len = PAGE_SIZE - dp->context_u;
 283 }
 284
 285 static void km_next_page(struct dpages *dp)
 286 {
 287         dp->context_ptr += PAGE_SIZE - dp->context_u;
 288         dp->context_u = 0;
 289 }
 290
 291 static void km_dp_init(struct dpages *dp, void *data)
 292 {
 293         dp->get_page = km_get_page;
 294         dp->next_page = km_next_page;
 295         dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
 296         dp->context_ptr = data;
 297 }
 298
 299 /*-----------------------------------------------------------------
 300  * IO routines that accept a list of pages.
 301  *---------------------------------------------------------------*/
 302 static void do_region(int rw, unsigned region, struct dm_io_region *where,
 303                       struct dpages *dp, struct io *io)
 304 {
 305         struct bio *bio;
 306         struct page *page;
 307         unsigned long len;
 308         unsigned offset;
 309         unsigned num_bvecs;
 310         sector_t remaining = where->count;
 311
 312         /*
 313          * where->count may be zero if rw holds a write barrier and we
 314          * need to send a zero-sized barrier.
 315          */
 316         do {
 317                 /*
 318                  * Allocate a suitably sized-bio.
 319                  */
 320                 num_bvecs = dm_sector_div_up(remaining,
 321                                              (PAGE_SIZE >> SECTOR_SHIFT));
 322                 num_bvecs = min_t(int, bio_get_nr_vecs(where->bdev), num_bvecs);
 323                 bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
 324                 bio->bi_sector = where->sector + (where->count - remaining);
 325                 bio->bi_bdev = where->bdev;
 326                 bio->bi_end_io = endio;
 327                 bio->bi_destructor = dm_bio_destructor;
 328                 store_io_and_region_in_bio(bio, io, region);
 329
 330                 /*
 331                  * Try and add as many pages as possible.
 332                  */
 333                 while (remaining) {
 334                         dp->get_page(dp, &page, &len, &offset);
 335                         len = min(len, to_bytes(remaining));
 336                         if (!bio_add_page(bio, page, len, offset))
 337                                 break;
 338
 339                         offset = 0;
 340                         remaining -= to_sector(len);
 341                         dp->next_page(dp);
 342                 }
 343
 344                 atomic_inc(&io->count);
 345                 submit_bio(rw, bio);
 346         } while (remaining);
 347 }
 348
 349 static void dispatch_io(int rw, unsigned int num_regions,
 350                         struct dm_io_region *where, struct dpages *dp,
 351                         struct io *io, int sync)
 352 {
 353         int i;
 354         struct dpages old_pages = *dp;
 355
 356         BUG_ON(num_regions > DM_IO_MAX_REGIONS);
 357
 358         if (sync)
 359                 rw |= (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_UNPLUG);
 360
 361         /*
 362          * For multiple regions we need to be careful to rewind
 363          * the dp object for each call to do_region.
 364          */
 365         for (i = 0; i < num_regions; i++) {
 366                 *dp = old_pages;
 367                 if (where[i].count || (rw & (1 << BIO_RW_BARRIER)))
 368                         do_region(rw, i, where + i, dp, io);
 369         }
 370
 371         /*
 372          * Drop the extra reference that we were holding to avoid
 373          * the io being completed too early.
 374          */
 375         dec_count(io, 0, 0);
 376 }
 377
 378 static int sync_io(struct dm_io_client *client, unsigned int num_regions,
 379                    struct dm_io_region *where, int rw, struct dpages *dp,
 380                    unsigned long *error_bits)
 381 {
 382         /*
 383          * gcc <= 4.3 can't do the alignment for stack variables, so we must
 384          * align it on our own.
 385          * volatile prevents the optimizer from removing or reusing
 386          * "io_" field from the stack frame (allowed in ANSI C).
 387          */
 388         volatile char io_[sizeof(struct io) + __alignof__(struct io) - 1];
 389         struct io *io = (struct io *)PTR_ALIGN(&io_, __alignof__(struct io));
 390
 391         if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
 392                 WARN_ON(1);
 393                 return -EIO;
 394         }
 395
 396 retry:
 397         io->error_bits = 0;
 398         io->eopnotsupp_bits = 0;
 399         atomic_set(&io->count, 1); /* see dispatch_io() */
 400         io->sleeper = current;
 401         io->client = client;
 402
 403         dispatch_io(rw, num_regions, where, dp, io, 1);
 404
 405         while (1) {
 406                 set_current_state(TASK_UNINTERRUPTIBLE);
 407
 408                 if (!atomic_read(&io->count))
 409                         break;
 410
 411                 io_schedule();
 412         }
 413         set_current_state(TASK_RUNNING);
 414
 415         if (io->eopnotsupp_bits && (rw & (1 << BIO_RW_BARRIER))) {
 416                 rw &= ~(1 << BIO_RW_BARRIER);
 417                 goto retry;
 418         }
 419
 420         if (error_bits)
 421                 *error_bits = io->error_bits;
 422
 423         return io->error_bits ? -EIO : 0;
 424 }
 425
 426 static int async_io(struct dm_io_client *client, unsigned int num_regions,
 427                     struct dm_io_region *where, int rw, struct dpages *dp,
 428                     io_notify_fn fn, void *context)
 429 {
 430         struct io *io;
 431
 432         if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
 433                 WARN_ON(1);
 434                 fn(1, context);
 435                 return -EIO;
 436         }
 437
 438         io = mempool_alloc(client->pool, GFP_NOIO);
 439         io->error_bits = 0;
 440         io->eopnotsupp_bits = 0;
 441         atomic_set(&io->count, 1); /* see dispatch_io() */
 442         io->sleeper = NULL;
 443         io->client = client;
 444         io->callback = fn;
 445         io->context = context;
 446
 447         dispatch_io(rw, num_regions, where, dp, io, 0);
 448         return 0;
 449 }
 450
 451 static int dp_init(struct dm_io_request *io_req, struct dpages *dp)
 452 {
 453         /* Set up dpages based on memory type */
 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                 vm_dp_init(dp, io_req->mem.ptr.vma);
 465                 break;
 466
 467         case DM_IO_KMEM:
 468                 km_dp_init(dp, io_req->mem.ptr.addr);
 469                 break;
 470
 471         default:
 472                 return -EINVAL;
 473         }
 474
 475         return 0;
 476 }
 477
 478 /*
 479  * New collapsed (a)synchronous interface.
 480  *
 481  * If the IO is asynchronous (i.e. it has notify.fn), you must either unplug
 482  * the queue with blk_unplug() some time later or set the BIO_RW_SYNC bit in
 483  * io_req->bi_rw. If you fail to do one of these, the IO will be submitted to
 484  * the disk after q->unplug_delay, which defaults to 3ms in blk-settings.c.
 485  */
 486 int dm_io(struct dm_io_request *io_req, unsigned num_regions,
 487           struct dm_io_region *where, unsigned long *sync_error_bits)
 488 {
 489         int r;
 490         struct dpages dp;
 491
 492         r = dp_init(io_req, &dp);
 493         if (r)
 494                 return r;
 495
 496         if (!io_req->notify.fn)
 497                 return sync_io(io_req->client, num_regions, where,
 498                                io_req->bi_rw, &dp, sync_error_bits);
 499
 500         return async_io(io_req->client, num_regions, where, io_req->bi_rw,
 501                         &dp, io_req->notify.fn, io_req->notify.context);
 502 }
 503 EXPORT_SYMBOL(dm_io);
 504
 505 int __init dm_io_init(void)
 506 {
 507         _dm_io_cache = KMEM_CACHE(io, 0);
 508         if (!_dm_io_cache)
 509                 return -ENOMEM;
 510
 511         return 0;
 512 }
 513
 514 void dm_io_exit(void)
 515 {
 516         kmem_cache_destroy(_dm_io_cache);
 517         _dm_io_cache = NULL;
 518 }