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-io.h"
   9
  10 #include <linux/bio.h>
  11 #include <linux/mempool.h>
  12 #include <linux/module.h>
  13 #include <linux/sched.h>
  14 #include <linux/slab.h>
  15
  16 struct dm_io_client {
  17         mempool_t *pool;
  18         struct bio_set *bios;
  19 };
  20
  21 /* FIXME: can we shrink this ? */
  22 struct io {
  23         unsigned long error;
  24         atomic_t count;
  25         struct task_struct *sleeper;
  26         struct dm_io_client *client;
  27         io_notify_fn callback;
  28         void *context;
  29 };
  30
  31 /*
  32  * io contexts are only dynamically allocated for asynchronous
  33  * io.  Since async io is likely to be the majority of io we'll
  34  * have the same number of io contexts as bios! (FIXME: must reduce this).
  35  */
  36
  37 static unsigned int pages_to_ios(unsigned int pages)
  38 {
  39         return 4 * pages;       /* too many ? */
  40 }
  41
  42 /*
  43  * Create a client with mempool and bioset.
  44  */
  45 struct dm_io_client *dm_io_client_create(unsigned num_pages)
  46 {
  47         unsigned ios = pages_to_ios(num_pages);
  48         struct dm_io_client *client;
  49
  50         client = kmalloc(sizeof(*client), GFP_KERNEL);
  51         if (!client)
  52                 return ERR_PTR(-ENOMEM);
  53
  54         client->pool = mempool_create_kmalloc_pool(ios, sizeof(struct io));
  55         if (!client->pool)
  56                 goto bad;
  57
  58         client->bios = bioset_create(16, 16);
  59         if (!client->bios)
  60                 goto bad;
  61
  62         return client;
  63
  64    bad:
  65         if (client->pool)
  66                 mempool_destroy(client->pool);
  67         kfree(client);
  68         return ERR_PTR(-ENOMEM);
  69 }
  70 EXPORT_SYMBOL(dm_io_client_create);
  71
  72 int dm_io_client_resize(unsigned num_pages, struct dm_io_client *client)
  73 {
  74         return mempool_resize(client->pool, pages_to_ios(num_pages),
  75                               GFP_KERNEL);
  76 }
  77 EXPORT_SYMBOL(dm_io_client_resize);
  78
  79 void dm_io_client_destroy(struct dm_io_client *client)
  80 {
  81         mempool_destroy(client->pool);
  82         bioset_free(client->bios);
  83         kfree(client);
  84 }
  85 EXPORT_SYMBOL(dm_io_client_destroy);
  86
  87 /*-----------------------------------------------------------------
  88  * We need to keep track of which region a bio is doing io for.
  89  * In order to save a memory allocation we store this the last
  90  * bvec which we know is unused (blech).
  91  * XXX This is ugly and can OOPS with some configs... find another way.
  92  *---------------------------------------------------------------*/
  93 static inline void bio_set_region(struct bio *bio, unsigned region)
  94 {
  95         bio->bi_io_vec[bio->bi_max_vecs].bv_len = region;
  96 }
  97
  98 static inline unsigned bio_get_region(struct bio *bio)
  99 {
 100         return bio->bi_io_vec[bio->bi_max_vecs].bv_len;
 101 }
 102
 103 /*-----------------------------------------------------------------
 104  * We need an io object to keep track of the number of bios that
 105  * have been dispatched for a particular io.
 106  *---------------------------------------------------------------*/
 107 static void dec_count(struct io *io, unsigned int region, int error)
 108 {
 109         if (error)
 110                 set_bit(region, &io->error);
 111
 112         if (atomic_dec_and_test(&io->count)) {
 113                 if (io->sleeper)
 114                         wake_up_process(io->sleeper);
 115
 116                 else {
 117                         unsigned long r = io->error;
 118                         io_notify_fn fn = io->callback;
 119                         void *context = io->context;
 120
 121                         mempool_free(io, io->client->pool);
 122                         fn(r, context);
 123                 }
 124         }
 125 }
 126
 127 static void endio(struct bio *bio, int error)
 128 {
 129         struct io *io;
 130         unsigned region;
 131
 132         if (error && bio_data_dir(bio) == READ)
 133                 zero_fill_bio(bio);
 134
 135         /*
 136          * The bio destructor in bio_put() may use the io object.
 137          */
 138         io = bio->bi_private;
 139         region = bio_get_region(bio);
 140
 141         bio->bi_max_vecs++;
 142         bio_put(bio);
 143
 144         dec_count(io, region, error);
 145 }
 146
 147 /*-----------------------------------------------------------------
 148  * These little objects provide an abstraction for getting a new
 149  * destination page for io.
 150  *---------------------------------------------------------------*/
 151 struct dpages {
 152         void (*get_page)(struct dpages *dp,
 153                          struct page **p, unsigned long *len, unsigned *offset);
 154         void (*next_page)(struct dpages *dp);
 155
 156         unsigned context_u;
 157         void *context_ptr;
 158 };
 159
 160 /*
 161  * Functions for getting the pages from a list.
 162  */
 163 static void list_get_page(struct dpages *dp,
 164                   struct page **p, unsigned long *len, unsigned *offset)
 165 {
 166         unsigned o = dp->context_u;
 167         struct page_list *pl = (struct page_list *) dp->context_ptr;
 168
 169         *p = pl->page;
 170         *len = PAGE_SIZE - o;
 171         *offset = o;
 172 }
 173
 174 static void list_next_page(struct dpages *dp)
 175 {
 176         struct page_list *pl = (struct page_list *) dp->context_ptr;
 177         dp->context_ptr = pl->next;
 178         dp->context_u = 0;
 179 }
 180
 181 static void list_dp_init(struct dpages *dp, struct page_list *pl, unsigned offset)
 182 {
 183         dp->get_page = list_get_page;
 184         dp->next_page = list_next_page;
 185         dp->context_u = offset;
 186         dp->context_ptr = pl;
 187 }
 188
 189 /*
 190  * Functions for getting the pages from a bvec.
 191  */
 192 static void bvec_get_page(struct dpages *dp,
 193                   struct page **p, unsigned long *len, unsigned *offset)
 194 {
 195         struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
 196         *p = bvec->bv_page;
 197         *len = bvec->bv_len;
 198         *offset = bvec->bv_offset;
 199 }
 200
 201 static void bvec_next_page(struct dpages *dp)
 202 {
 203         struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
 204         dp->context_ptr = bvec + 1;
 205 }
 206
 207 static void bvec_dp_init(struct dpages *dp, struct bio_vec *bvec)
 208 {
 209         dp->get_page = bvec_get_page;
 210         dp->next_page = bvec_next_page;
 211         dp->context_ptr = bvec;
 212 }
 213
 214 /*
 215  * Functions for getting the pages from a VMA.
 216  */
 217 static void vm_get_page(struct dpages *dp,
 218                  struct page **p, unsigned long *len, unsigned *offset)
 219 {
 220         *p = vmalloc_to_page(dp->context_ptr);
 221         *offset = dp->context_u;
 222         *len = PAGE_SIZE - dp->context_u;
 223 }
 224
 225 static void vm_next_page(struct dpages *dp)
 226 {
 227         dp->context_ptr += PAGE_SIZE - dp->context_u;
 228         dp->context_u = 0;
 229 }
 230
 231 static void vm_dp_init(struct dpages *dp, void *data)
 232 {
 233         dp->get_page = vm_get_page;
 234         dp->next_page = vm_next_page;
 235         dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
 236         dp->context_ptr = data;
 237 }
 238
 239 static void dm_bio_destructor(struct bio *bio)
 240 {
 241         struct io *io = bio->bi_private;
 242
 243         bio_free(bio, io->client->bios);
 244 }
 245
 246 /*
 247  * Functions for getting the pages from kernel memory.
 248  */
 249 static void km_get_page(struct dpages *dp, struct page **p, unsigned long *len,
 250                         unsigned *offset)
 251 {
 252         *p = virt_to_page(dp->context_ptr);
 253         *offset = dp->context_u;
 254         *len = PAGE_SIZE - dp->context_u;
 255 }
 256
 257 static void km_next_page(struct dpages *dp)
 258 {
 259         dp->context_ptr += PAGE_SIZE - dp->context_u;
 260         dp->context_u = 0;
 261 }
 262
 263 static void km_dp_init(struct dpages *dp, void *data)
 264 {
 265         dp->get_page = km_get_page;
 266         dp->next_page = km_next_page;
 267         dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
 268         dp->context_ptr = data;
 269 }
 270
 271 /*-----------------------------------------------------------------
 272  * IO routines that accept a list of pages.
 273  *---------------------------------------------------------------*/
 274 static void do_region(int rw, unsigned int region, struct io_region *where,
 275                       struct dpages *dp, struct io *io)
 276 {
 277         struct bio *bio;
 278         struct page *page;
 279         unsigned long len;
 280         unsigned offset;
 281         unsigned num_bvecs;
 282         sector_t remaining = where->count;
 283
 284         while (remaining) {
 285                 /*
 286                  * Allocate a suitably sized-bio: we add an extra
 287                  * bvec for bio_get/set_region() and decrement bi_max_vecs
 288                  * to hide it from bio_add_page().
 289                  */
 290                 num_bvecs = dm_sector_div_up(remaining,
 291                                              (PAGE_SIZE >> SECTOR_SHIFT));
 292                 num_bvecs = 1 + min_t(int, bio_get_nr_vecs(where->bdev),
 293                                       num_bvecs);
 294                 bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
 295                 bio->bi_sector = where->sector + (where->count - remaining);
 296                 bio->bi_bdev = where->bdev;
 297                 bio->bi_end_io = endio;
 298                 bio->bi_private = io;
 299                 bio->bi_destructor = dm_bio_destructor;
 300                 bio->bi_max_vecs--;
 301                 bio_set_region(bio, region);
 302
 303                 /*
 304                  * Try and add as many pages as possible.
 305                  */
 306                 while (remaining) {
 307                         dp->get_page(dp, &page, &len, &offset);
 308                         len = min(len, to_bytes(remaining));
 309                         if (!bio_add_page(bio, page, len, offset))
 310                                 break;
 311
 312                         offset = 0;
 313                         remaining -= to_sector(len);
 314                         dp->next_page(dp);
 315                 }
 316
 317                 atomic_inc(&io->count);
 318                 submit_bio(rw, bio);
 319         }
 320 }
 321
 322 static void dispatch_io(int rw, unsigned int num_regions,
 323                         struct io_region *where, struct dpages *dp,
 324                         struct io *io, int sync)
 325 {
 326         int i;
 327         struct dpages old_pages = *dp;
 328
 329         if (sync)
 330                 rw |= (1 << BIO_RW_SYNC);
 331
 332         /*
 333          * For multiple regions we need to be careful to rewind
 334          * the dp object for each call to do_region.
 335          */
 336         for (i = 0; i < num_regions; i++) {
 337                 *dp = old_pages;
 338                 if (where[i].count)
 339                         do_region(rw, i, where + i, dp, io);
 340         }
 341
 342         /*
 343          * Drop the extra reference that we were holding to avoid
 344          * the io being completed too early.
 345          */
 346         dec_count(io, 0, 0);
 347 }
 348
 349 static int sync_io(struct dm_io_client *client, unsigned int num_regions,
 350                    struct io_region *where, int rw, struct dpages *dp,
 351                    unsigned long *error_bits)
 352 {
 353         struct io io;
 354
 355         if (num_regions > 1 && rw != WRITE) {
 356                 WARN_ON(1);
 357                 return -EIO;
 358         }
 359
 360         io.error = 0;
 361         atomic_set(&io.count, 1); /* see dispatch_io() */
 362         io.sleeper = current;
 363         io.client = client;
 364
 365         dispatch_io(rw, num_regions, where, dp, &io, 1);
 366
 367         while (1) {
 368                 set_current_state(TASK_UNINTERRUPTIBLE);
 369
 370                 if (!atomic_read(&io.count) || signal_pending(current))
 371                         break;
 372
 373                 io_schedule();
 374         }
 375         set_current_state(TASK_RUNNING);
 376
 377         if (atomic_read(&io.count))
 378                 return -EINTR;
 379
 380         if (error_bits)
 381                 *error_bits = io.error;
 382
 383         return io.error ? -EIO : 0;
 384 }
 385
 386 static int async_io(struct dm_io_client *client, unsigned int num_regions,
 387                     struct io_region *where, int rw, struct dpages *dp,
 388                     io_notify_fn fn, void *context)
 389 {
 390         struct io *io;
 391
 392         if (num_regions > 1 && rw != WRITE) {
 393                 WARN_ON(1);
 394                 fn(1, context);
 395                 return -EIO;
 396         }
 397
 398         io = mempool_alloc(client->pool, GFP_NOIO);
 399         io->error = 0;
 400         atomic_set(&io->count, 1); /* see dispatch_io() */
 401         io->sleeper = NULL;
 402         io->client = client;
 403         io->callback = fn;
 404         io->context = context;
 405
 406         dispatch_io(rw, num_regions, where, dp, io, 0);
 407         return 0;
 408 }
 409
 410 static int dp_init(struct dm_io_request *io_req, struct dpages *dp)
 411 {
 412         /* Set up dpages based on memory type */
 413         switch (io_req->mem.type) {
 414         case DM_IO_PAGE_LIST:
 415                 list_dp_init(dp, io_req->mem.ptr.pl, io_req->mem.offset);
 416                 break;
 417
 418         case DM_IO_BVEC:
 419                 bvec_dp_init(dp, io_req->mem.ptr.bvec);
 420                 break;
 421
 422         case DM_IO_VMA:
 423                 vm_dp_init(dp, io_req->mem.ptr.vma);
 424                 break;
 425
 426         case DM_IO_KMEM:
 427                 km_dp_init(dp, io_req->mem.ptr.addr);
 428                 break;
 429
 430         default:
 431                 return -EINVAL;
 432         }
 433
 434         return 0;
 435 }
 436
 437 /*
 438  * New collapsed (a)synchronous interface
 439  */
 440 int dm_io(struct dm_io_request *io_req, unsigned num_regions,
 441           struct io_region *where, unsigned long *sync_error_bits)
 442 {
 443         int r;
 444         struct dpages dp;
 445
 446         r = dp_init(io_req, &dp);
 447         if (r)
 448                 return r;
 449
 450         if (!io_req->notify.fn)
 451                 return sync_io(io_req->client, num_regions, where,
 452                                io_req->bi_rw, &dp, sync_error_bits);
 453
 454         return async_io(io_req->client, num_regions, where, io_req->bi_rw,
 455                         &dp, io_req->notify.fn, io_req->notify.context);
 456 }
 457 EXPORT_SYMBOL(dm_io);