release/src-rt-6.x.4708/linux/linux-2.6.36/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 static unsigned int pages_to_ios(unsigned int pages)
  46 {
  47         return 4 * pages;       /* too many ? */
  48 }
  49
  50 /*
  51  * Create a client with mempool and bioset.
  52  */
  53 struct dm_io_client *dm_io_client_create(unsigned num_pages)
  54 {
  55         unsigned ios = pages_to_ios(num_pages);
  56         struct dm_io_client *client;
  57
  58         client = kmalloc(sizeof(*client), GFP_KERNEL);
  59         if (!client)
  60                 return ERR_PTR(-ENOMEM);
  61
  62         client->pool = mempool_create_slab_pool(ios, _dm_io_cache);
  63         if (!client->pool)
  64                 goto bad;
  65
  66         client->bios = bioset_create(16, 0);
  67         if (!client->bios)
  68                 goto bad;
  69
  70         return client;
  71
  72    bad:
  73         if (client->pool)
  74                 mempool_destroy(client->pool);
  75         kfree(client);
  76         return ERR_PTR(-ENOMEM);
  77 }
  78 EXPORT_SYMBOL(dm_io_client_create);
  79
  80 int dm_io_client_resize(unsigned num_pages, struct dm_io_client *client)
  81 {
  82         return mempool_resize(client->pool, pages_to_ios(num_pages),
  83                               GFP_KERNEL);
  84 }
  85 EXPORT_SYMBOL(dm_io_client_resize);
  86
  87 void dm_io_client_destroy(struct dm_io_client *client)
  88 {
  89         mempool_destroy(client->pool);
  90         bioset_free(client->bios);
  91         kfree(client);
  92 }
  93 EXPORT_SYMBOL(dm_io_client_destroy);
  94
  95 /*-----------------------------------------------------------------
  96  * We need to keep track of which region a bio is doing io for.
  97  * To avoid a memory allocation to store just 5 or 6 bits, we
  98  * ensure the 'struct io' pointer is aligned so enough low bits are
  99  * always zero and then combine it with the region number directly in
 100  * bi_private.
 101  *---------------------------------------------------------------*/
 102 static void store_io_and_region_in_bio(struct bio *bio, struct io *io,
 103                                        unsigned region)
 104 {
 105         if (unlikely(!IS_ALIGNED((unsigned long)io, DM_IO_MAX_REGIONS))) {
 106                 DMCRIT("Unaligned struct io pointer %p", io);
 107                 BUG();
 108         }
 109
 110         bio->bi_private = (void *)((unsigned long)io | region);
 111 }
 112
 113 static void retrieve_io_and_region_from_bio(struct bio *bio, struct io **io,
 114                                        unsigned *region)
 115 {
 116         unsigned long val = (unsigned long)bio->bi_private;
 117
 118         *io = (void *)(val & -(unsigned long)DM_IO_MAX_REGIONS);
 119         *region = val & (DM_IO_MAX_REGIONS - 1);
 120 }
 121
 122 /*-----------------------------------------------------------------
 123  * We need an io object to keep track of the number of bios that
 124  * have been dispatched for a particular io.
 125  *---------------------------------------------------------------*/
 126 static void dec_count(struct io *io, unsigned int region, int error)
 127 {
 128         if (error) {
 129                 set_bit(region, &io->error_bits);
 130                 if (error == -EOPNOTSUPP)
 131                         set_bit(region, &io->eopnotsupp_bits);
 132         }
 133
 134         if (atomic_dec_and_test(&io->count)) {
 135                 if (io->sleeper)
 136                         wake_up_process(io->sleeper);
 137
 138                 else {
 139                         unsigned long r = io->error_bits;
 140                         io_notify_fn fn = io->callback;
 141                         void *context = io->context;
 142
 143                         mempool_free(io, io->client->pool);
 144                         fn(r, context);
 145                 }
 146         }
 147 }
 148
 149 static void endio(struct bio *bio, int error)
 150 {
 151         struct io *io;
 152         unsigned region;
 153
 154         if (error && bio_data_dir(bio) == READ)
 155                 zero_fill_bio(bio);
 156
 157         /*
 158          * The bio destructor in bio_put() may use the io object.
 159          */
 160         retrieve_io_and_region_from_bio(bio, &io, &region);
 161
 162         bio_put(bio);
 163
 164         dec_count(io, region, error);
 165 }
 166
 167 /*-----------------------------------------------------------------
 168  * These little objects provide an abstraction for getting a new
 169  * destination page for io.
 170  *---------------------------------------------------------------*/
 171 struct dpages {
 172         void (*get_page)(struct dpages *dp,
 173                          struct page **p, unsigned long *len, unsigned *offset);
 174         void (*next_page)(struct dpages *dp);
 175
 176         unsigned context_u;
 177         void *context_ptr;
 178 };
 179
 180 /*
 181  * Functions for getting the pages from a list.
 182  */
 183 static void list_get_page(struct dpages *dp,
 184                   struct page **p, unsigned long *len, unsigned *offset)
 185 {
 186         unsigned o = dp->context_u;
 187         struct page_list *pl = (struct page_list *) dp->context_ptr;
 188
 189         *p = pl->page;
 190         *len = PAGE_SIZE - o;
 191         *offset = o;
 192 }
 193
 194 static void list_next_page(struct dpages *dp)
 195 {
 196         struct page_list *pl = (struct page_list *) dp->context_ptr;
 197         dp->context_ptr = pl->next;
 198         dp->context_u = 0;
 199 }
 200
 201 static void list_dp_init(struct dpages *dp, struct page_list *pl, unsigned offset)
 202 {
 203         dp->get_page = list_get_page;
 204         dp->next_page = list_next_page;
 205         dp->context_u = offset;
 206         dp->context_ptr = pl;
 207 }
 208
 209 /*
 210  * Functions for getting the pages from a bvec.
 211  */
 212 static void bvec_get_page(struct dpages *dp,
 213                   struct page **p, unsigned long *len, unsigned *offset)
 214 {
 215         struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
 216         *p = bvec->bv_page;
 217         *len = bvec->bv_len;
 218         *offset = bvec->bv_offset;
 219 }
 220
 221 static void bvec_next_page(struct dpages *dp)
 222 {
 223         struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
 224         dp->context_ptr = bvec + 1;
 225 }
 226
 227 static void bvec_dp_init(struct dpages *dp, struct bio_vec *bvec)
 228 {
 229         dp->get_page = bvec_get_page;
 230         dp->next_page = bvec_next_page;
 231         dp->context_ptr = bvec;
 232 }
 233
 234 /*
 235  * Functions for getting the pages from a VMA.
 236  */
 237 static void vm_get_page(struct dpages *dp,
 238                  struct page **p, unsigned long *len, unsigned *offset)
 239 {
 240         *p = vmalloc_to_page(dp->context_ptr);
 241         *offset = dp->context_u;
 242         *len = PAGE_SIZE - dp->context_u;
 243 }
 244
 245 static void vm_next_page(struct dpages *dp)
 246 {
 247         dp->context_ptr += PAGE_SIZE - dp->context_u;
 248         dp->context_u = 0;
 249 }
 250
 251 static void vm_dp_init(struct dpages *dp, void *data)
 252 {
 253         dp->get_page = vm_get_page;
 254         dp->next_page = vm_next_page;
 255         dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
 256         dp->context_ptr = data;
 257 }
 258
 259 static void dm_bio_destructor(struct bio *bio)
 260 {
 261         unsigned region;
 262         struct io *io;
 263
 264         retrieve_io_and_region_from_bio(bio, &io, &region);
 265
 266         bio_free(bio, io->client->bios);
 267 }
 268
 269 /*
 270  * Functions for getting the pages from kernel memory.
 271  */
 272 static void km_get_page(struct dpages *dp, struct page **p, unsigned long *len,
 273                         unsigned *offset)
 274 {
 275         *p = virt_to_page(dp->context_ptr);
 276         *offset = dp->context_u;
 277         *len = PAGE_SIZE - dp->context_u;
 278 }
 279
 280 static void km_next_page(struct dpages *dp)
 281 {
 282         dp->context_ptr += PAGE_SIZE - dp->context_u;
 283         dp->context_u = 0;
 284 }
 285
 286 static void km_dp_init(struct dpages *dp, void *data)
 287 {
 288         dp->get_page = km_get_page;
 289         dp->next_page = km_next_page;
 290         dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
 291         dp->context_ptr = data;
 292 }
 293
 294 /*-----------------------------------------------------------------
 295  * IO routines that accept a list of pages.
 296  *---------------------------------------------------------------*/
 297 static void do_region(int rw, unsigned region, struct dm_io_region *where,
 298                       struct dpages *dp, 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
 307         /*
 308          * where->count may be zero if rw holds a write barrier and we
 309          * need to send a zero-sized barrier.
 310          */
 311         do {
 312                 /*
 313                  * Allocate a suitably sized-bio.
 314                  */
 315                 num_bvecs = dm_sector_div_up(remaining,
 316                                              (PAGE_SIZE >> SECTOR_SHIFT));
 317                 num_bvecs = min_t(int, bio_get_nr_vecs(where->bdev), num_bvecs);
 318                 bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
 319                 bio->bi_sector = where->sector + (where->count - remaining);
 320                 bio->bi_bdev = where->bdev;
 321                 bio->bi_end_io = endio;
 322                 bio->bi_destructor = dm_bio_destructor;
 323                 store_io_and_region_in_bio(bio, io, region);
 324
 325                 /*
 326                  * Try and add as many pages as possible.
 327                  */
 328                 while (remaining) {
 329                         dp->get_page(dp, &page, &len, &offset);
 330                         len = min(len, to_bytes(remaining));
 331                         if (!bio_add_page(bio, page, len, offset))
 332                                 break;
 333
 334                         offset = 0;
 335                         remaining -= to_sector(len);
 336                         dp->next_page(dp);
 337                 }
 338
 339                 atomic_inc(&io->count);
 340                 submit_bio(rw, bio);
 341         } while (remaining);
 342 }
 343
 344 static void dispatch_io(int rw, unsigned int num_regions,
 345                         struct dm_io_region *where, struct dpages *dp,
 346                         struct io *io, int sync)
 347 {
 348         int i;
 349         struct dpages old_pages = *dp;
 350
 351         BUG_ON(num_regions > DM_IO_MAX_REGIONS);
 352
 353         if (sync)
 354                 rw |= REQ_SYNC | REQ_UNPLUG;
 355
 356         /*
 357          * For multiple regions we need to be careful to rewind
 358          * the dp object for each call to do_region.
 359          */
 360         for (i = 0; i < num_regions; i++) {
 361                 *dp = old_pages;
 362                 if (where[i].count || (rw & REQ_HARDBARRIER))
 363                         do_region(rw, i, where + i, dp, io);
 364         }
 365
 366         /*
 367          * Drop the extra reference that we were holding to avoid
 368          * the io being completed too early.
 369          */
 370         dec_count(io, 0, 0);
 371 }
 372
 373 static int sync_io(struct dm_io_client *client, unsigned int num_regions,
 374                    struct dm_io_region *where, int rw, struct dpages *dp,
 375                    unsigned long *error_bits)
 376 {
 377         /*
 378          * gcc <= 4.3 can't do the alignment for stack variables, so we must
 379          * align it on our own.
 380          * volatile prevents the optimizer from removing or reusing
 381          * "io_" field from the stack frame (allowed in ANSI C).
 382          */
 383         volatile char io_[sizeof(struct io) + __alignof__(struct io) - 1];
 384         struct io *io = (struct io *)PTR_ALIGN(&io_, __alignof__(struct io));
 385
 386         if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
 387                 WARN_ON(1);
 388                 return -EIO;
 389         }
 390
 391 retry:
 392         io->error_bits = 0;
 393         io->eopnotsupp_bits = 0;
 394         atomic_set(&io->count, 1); /* see dispatch_io() */
 395         io->sleeper = current;
 396         io->client = client;
 397
 398         dispatch_io(rw, num_regions, where, dp, io, 1);
 399
 400         while (1) {
 401                 set_current_state(TASK_UNINTERRUPTIBLE);
 402
 403                 if (!atomic_read(&io->count))
 404                         break;
 405
 406                 io_schedule();
 407         }
 408         set_current_state(TASK_RUNNING);
 409
 410         if (io->eopnotsupp_bits && (rw & REQ_HARDBARRIER)) {
 411                 rw &= ~REQ_HARDBARRIER;
 412                 goto retry;
 413         }
 414
 415         if (error_bits)
 416                 *error_bits = io->error_bits;
 417
 418         return io->error_bits ? -EIO : 0;
 419 }
 420
 421 static int async_io(struct dm_io_client *client, unsigned int num_regions,
 422                     struct dm_io_region *where, int rw, struct dpages *dp,
 423                     io_notify_fn fn, void *context)
 424 {
 425         struct io *io;
 426
 427         if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
 428                 WARN_ON(1);
 429                 fn(1, context);
 430                 return -EIO;
 431         }
 432
 433         io = mempool_alloc(client->pool, GFP_NOIO);
 434         io->error_bits = 0;
 435         io->eopnotsupp_bits = 0;
 436         atomic_set(&io->count, 1); /* see dispatch_io() */
 437         io->sleeper = NULL;
 438         io->client = client;
 439         io->callback = fn;
 440         io->context = context;
 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 {
 448         /* Set up dpages based on memory type */
 449         switch (io_req->mem.type) {
 450         case DM_IO_PAGE_LIST:
 451                 list_dp_init(dp, io_req->mem.ptr.pl, io_req->mem.offset);
 452                 break;
 453
 454         case DM_IO_BVEC:
 455                 bvec_dp_init(dp, io_req->mem.ptr.bvec);
 456                 break;
 457
 458         case DM_IO_VMA:
 459                 vm_dp_init(dp, io_req->mem.ptr.vma);
 460                 break;
 461
 462         case DM_IO_KMEM:
 463                 km_dp_init(dp, io_req->mem.ptr.addr);
 464                 break;
 465
 466         default:
 467                 return -EINVAL;
 468         }
 469
 470         return 0;
 471 }
 472
 473 /*
 474  * New collapsed (a)synchronous interface.
 475  *
 476  * If the IO is asynchronous (i.e. it has notify.fn), you must either unplug
 477  * the queue with blk_unplug() some time later or set REQ_SYNC in
 478 io_req->bi_rw. If you fail to do one of these, the IO will be submitted to
 479  * the disk after q->unplug_delay, which defaults to 3ms in blk-settings.c.
 480  */
 481 int dm_io(struct dm_io_request *io_req, unsigned num_regions,
 482           struct dm_io_region *where, unsigned long *sync_error_bits)
 483 {
 484         int r;
 485         struct dpages dp;
 486
 487         r = dp_init(io_req, &dp);
 488         if (r)
 489                 return r;
 490
 491         if (!io_req->notify.fn)
 492                 return sync_io(io_req->client, num_regions, where,
 493                                io_req->bi_rw, &dp, sync_error_bits);
 494
 495         return async_io(io_req->client, num_regions, where, io_req->bi_rw,
 496                         &dp, io_req->notify.fn, io_req->notify.context);
 497 }
 498 EXPORT_SYMBOL(dm_io);
 499
 500 int __init dm_io_init(void)
 501 {
 502         _dm_io_cache = KMEM_CACHE(io, 0);
 503         if (!_dm_io_cache)
 504                 return -ENOMEM;
 505
 506         return 0;
 507 }
 508
 509 void dm_io_exit(void)
 510 {
 511         kmem_cache_destroy(_dm_io_cache);
 512         _dm_io_cache = NULL;
 513 }