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 <linux/device-mapper.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 #include <linux/dm-io.h>
  16
  17 struct dm_io_client {
  18         mempool_t *pool;
  19         struct bio_set *bios;
  20 };
  21
  22 /* FIXME: can we shrink this ? */
  23 struct io {
  24         unsigned long error_bits;
  25         atomic_t count;
  26         struct task_struct *sleeper;
  27         struct dm_io_client *client;
  28         io_notify_fn callback;
  29         void *context;
  30 };
  31
  32 /*
  33  * io contexts are only dynamically allocated for asynchronous
  34  * io.  Since async io is likely to be the majority of io we'll
  35  * have the same number of io contexts as bios! (FIXME: must reduce this).
  36  */
  37
  38 static unsigned int pages_to_ios(unsigned int pages)
  39 {
  40         return 4 * pages;       /* too many ? */
  41 }
  42
  43 /*
  44  * Create a client with mempool and bioset.
  45  */
  46 struct dm_io_client *dm_io_client_create(unsigned num_pages)
  47 {
  48         unsigned ios = pages_to_ios(num_pages);
  49         struct dm_io_client *client;
  50
  51         client = kmalloc(sizeof(*client), GFP_KERNEL);
  52         if (!client)
  53                 return ERR_PTR(-ENOMEM);
  54
  55         client->pool = mempool_create_kmalloc_pool(ios, sizeof(struct io));
  56         if (!client->pool)
  57                 goto bad;
  58
  59         client->bios = bioset_create(16, 0);
  60         if (!client->bios)
  61                 goto bad;
  62
  63         return client;
  64
  65    bad:
  66         if (client->pool)
  67                 mempool_destroy(client->pool);
  68         kfree(client);
  69         return ERR_PTR(-ENOMEM);
  70 }
  71 EXPORT_SYMBOL(dm_io_client_create);
  72
  73 int dm_io_client_resize(unsigned num_pages, struct dm_io_client *client)
  74 {
  75         return mempool_resize(client->pool, pages_to_ios(num_pages),
  76                               GFP_KERNEL);
  77 }
  78 EXPORT_SYMBOL(dm_io_client_resize);
  79
  80 void dm_io_client_destroy(struct dm_io_client *client)
  81 {
  82         mempool_destroy(client->pool);
  83         bioset_free(client->bios);
  84         kfree(client);
  85 }
  86 EXPORT_SYMBOL(dm_io_client_destroy);
  87
  88 /*-----------------------------------------------------------------
  89  * We need to keep track of which region a bio is doing io for.
  90  * In order to save a memory allocation we store this the last
  91  * bvec which we know is unused (blech).
  92  * XXX This is ugly and can OOPS with some configs... find another way.
  93  *---------------------------------------------------------------*/
  94 static inline void bio_set_region(struct bio *bio, unsigned region)
  95 {
  96         bio->bi_io_vec[bio->bi_max_vecs].bv_len = region;
  97 }
  98
  99 static inline unsigned bio_get_region(struct bio *bio)
 100 {
 101         return bio->bi_io_vec[bio->bi_max_vecs].bv_len;
 102 }
 103
 104 /*-----------------------------------------------------------------
 105  * We need an io object to keep track of the number of bios that
 106  * have been dispatched for a particular io.
 107  *---------------------------------------------------------------*/
 108 static void dec_count(struct io *io, unsigned int region, int error)
 109 {
 110         if (error)
 111                 set_bit(region, &io->error_bits);
 112
 113         if (atomic_dec_and_test(&io->count)) {
 114                 if (io->sleeper)
 115                         wake_up_process(io->sleeper);
 116
 117                 else {
 118                         unsigned long r = io->error_bits;
 119                         io_notify_fn fn = io->callback;
 120                         void *context = io->context;
 121
 122                         mempool_free(io, io->client->pool);
 123                         fn(r, context);
 124                 }
 125         }
 126 }
 127
 128 static void endio(struct bio *bio, int error)
 129 {
 130         struct io *io;
 131         unsigned region;
 132
 133         if (error && bio_data_dir(bio) == READ)
 134                 zero_fill_bio(bio);
 135
 136         /*
 137          * The bio destructor in bio_put() may use the io object.
 138          */
 139         io = bio->bi_private;
 140         region = bio_get_region(bio);
 141
 142         bio->bi_max_vecs++;
 143         bio_put(bio);
 144
 145         dec_count(io, region, error);
 146 }
 147
 148 /*-----------------------------------------------------------------
 149  * These little objects provide an abstraction for getting a new
 150  * destination page for io.
 151  *---------------------------------------------------------------*/
 152 struct dpages {
 153         void (*get_page)(struct dpages *dp,
 154                          struct page **p, unsigned long *len, unsigned *offset);
 155         void (*next_page)(struct dpages *dp);
 156
 157         unsigned context_u;
 158         void *context_ptr;
 159 };
 160
 161 /*
 162  * Functions for getting the pages from a list.
 163  */
 164 static void list_get_page(struct dpages *dp,
 165                   struct page **p, unsigned long *len, unsigned *offset)
 166 {
 167         unsigned o = dp->context_u;
 168         struct page_list *pl = (struct page_list *) dp->context_ptr;
 169
 170         *p = pl->page;
 171         *len = PAGE_SIZE - o;
 172         *offset = o;
 173 }
 174
 175 static void list_next_page(struct dpages *dp)
 176 {
 177         struct page_list *pl = (struct page_list *) dp->context_ptr;
 178         dp->context_ptr = pl->next;
 179         dp->context_u = 0;
 180 }
 181
 182 static void list_dp_init(struct dpages *dp, struct page_list *pl, unsigned offset)
 183 {
 184         dp->get_page = list_get_page;
 185         dp->next_page = list_next_page;
 186         dp->context_u = offset;
 187         dp->context_ptr = pl;
 188 }
 189
 190 /*
 191  * Functions for getting the pages from a bvec.
 192  */
 193 static void bvec_get_page(struct dpages *dp,
 194                   struct page **p, unsigned long *len, unsigned *offset)
 195 {
 196         struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
 197         *p = bvec->bv_page;
 198         *len = bvec->bv_len;
 199         *offset = bvec->bv_offset;
 200 }
 201
 202 static void bvec_next_page(struct dpages *dp)
 203 {
 204         struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
 205         dp->context_ptr = bvec + 1;
 206 }
 207
 208 static void bvec_dp_init(struct dpages *dp, struct bio_vec *bvec)
 209 {
 210         dp->get_page = bvec_get_page;
 211         dp->next_page = bvec_next_page;
 212         dp->context_ptr = bvec;
 213 }
 214
 215 /*
 216  * Functions for getting the pages from a VMA.
 217  */
 218 static void vm_get_page(struct dpages *dp,
 219                  struct page **p, unsigned long *len, unsigned *offset)
 220 {
 221         *p = vmalloc_to_page(dp->context_ptr);
 222         *offset = dp->context_u;
 223         *len = PAGE_SIZE - dp->context_u;
 224 }
 225
 226 static void vm_next_page(struct dpages *dp)
 227 {
 228         dp->context_ptr += PAGE_SIZE - dp->context_u;
 229         dp->context_u = 0;
 230 }
 231
 232 static void vm_dp_init(struct dpages *dp, void *data)
 233 {
 234         dp->get_page = vm_get_page;
 235         dp->next_page = vm_next_page;
 236         dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
 237         dp->context_ptr = data;
 238 }
 239
 240 static void dm_bio_destructor(struct bio *bio)
 241 {
 242         struct io *io = bio->bi_private;
 243
 244         bio_free(bio, io->client->bios);
 245 }
 246
 247 /*
 248  * Functions for getting the pages from kernel memory.
 249  */
 250 static void km_get_page(struct dpages *dp, struct page **p, unsigned long *len,
 251                         unsigned *offset)
 252 {
 253         *p = virt_to_page(dp->context_ptr);
 254         *offset = dp->context_u;
 255         *len = PAGE_SIZE - dp->context_u;
 256 }
 257
 258 static void km_next_page(struct dpages *dp)
 259 {
 260         dp->context_ptr += PAGE_SIZE - dp->context_u;
 261         dp->context_u = 0;
 262 }
 263
 264 static void km_dp_init(struct dpages *dp, void *data)
 265 {
 266         dp->get_page = km_get_page;
 267         dp->next_page = km_next_page;
 268         dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
 269         dp->context_ptr = data;
 270 }
 271
 272 /*-----------------------------------------------------------------
 273  * IO routines that accept a list of pages.
 274  *---------------------------------------------------------------*/
 275 static void do_region(int rw, unsigned region, struct dm_io_region *where,
 276                       struct dpages *dp, struct io *io)
 277 {
 278         struct bio *bio;
 279         struct page *page;
 280         unsigned long len;
 281         unsigned offset;
 282         unsigned num_bvecs;
 283         sector_t remaining = where->count;
 284
 285         while (remaining) {
 286                 /*
 287                  * Allocate a suitably sized-bio: we add an extra
 288                  * bvec for bio_get/set_region() and decrement bi_max_vecs
 289                  * to hide it from bio_add_page().
 290                  */
 291                 num_bvecs = dm_sector_div_up(remaining,
 292                                              (PAGE_SIZE >> SECTOR_SHIFT));
 293                 num_bvecs = 1 + min_t(int, bio_get_nr_vecs(where->bdev),
 294                                       num_bvecs);
 295                 bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
 296                 bio->bi_sector = where->sector + (where->count - remaining);
 297                 bio->bi_bdev = where->bdev;
 298                 bio->bi_end_io = endio;
 299                 bio->bi_private = io;
 300                 bio->bi_destructor = dm_bio_destructor;
 301                 bio->bi_max_vecs--;
 302                 bio_set_region(bio, region);
 303
 304                 /*
 305                  * Try and add as many pages as possible.
 306                  */
 307                 while (remaining) {
 308                         dp->get_page(dp, &page, &len, &offset);
 309                         len = min(len, to_bytes(remaining));
 310                         if (!bio_add_page(bio, page, len, offset))
 311                                 break;
 312
 313                         offset = 0;
 314                         remaining -= to_sector(len);
 315                         dp->next_page(dp);
 316                 }
 317
 318                 atomic_inc(&io->count);
 319                 submit_bio(rw, bio);
 320         }
 321 }
 322
 323 static void dispatch_io(int rw, unsigned int num_regions,
 324                         struct dm_io_region *where, struct dpages *dp,
 325                         struct io *io, int sync)
 326 {
 327         int i;
 328         struct dpages old_pages = *dp;
 329
 330         if (sync)
 331                 rw |= (1 << BIO_RW_SYNC);
 332
 333         /*
 334          * For multiple regions we need to be careful to rewind
 335          * the dp object for each call to do_region.
 336          */
 337         for (i = 0; i < num_regions; i++) {
 338                 *dp = old_pages;
 339                 if (where[i].count)
 340                         do_region(rw, i, where + i, dp, io);
 341         }
 342
 343         /*
 344          * Drop the extra reference that we were holding to avoid
 345          * the io being completed too early.
 346          */
 347         dec_count(io, 0, 0);
 348 }
 349
 350 static int sync_io(struct dm_io_client *client, unsigned int num_regions,
 351                    struct dm_io_region *where, int rw, struct dpages *dp,
 352                    unsigned long *error_bits)
 353 {
 354         struct io io;
 355
 356         if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
 357                 WARN_ON(1);
 358                 return -EIO;
 359         }
 360
 361         io.error_bits = 0;
 362         atomic_set(&io.count, 1); /* see dispatch_io() */
 363         io.sleeper = current;
 364         io.client = client;
 365
 366         dispatch_io(rw, num_regions, where, dp, &io, 1);
 367
 368         while (1) {
 369                 set_current_state(TASK_UNINTERRUPTIBLE);
 370
 371                 if (!atomic_read(&io.count) || signal_pending(current))
 372                         break;
 373
 374                 io_schedule();
 375         }
 376         set_current_state(TASK_RUNNING);
 377
 378         if (atomic_read(&io.count))
 379                 return -EINTR;
 380
 381         if (error_bits)
 382                 *error_bits = io.error_bits;
 383
 384         return io.error_bits ? -EIO : 0;
 385 }
 386
 387 static int async_io(struct dm_io_client *client, unsigned int num_regions,
 388                     struct dm_io_region *where, int rw, struct dpages *dp,
 389                     io_notify_fn fn, void *context)
 390 {
 391         struct io *io;
 392
 393         if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
 394                 WARN_ON(1);
 395                 fn(1, context);
 396                 return -EIO;
 397         }
 398
 399         io = mempool_alloc(client->pool, GFP_NOIO);
 400         io->error_bits = 0;
 401         atomic_set(&io->count, 1); /* see dispatch_io() */
 402         io->sleeper = NULL;
 403         io->client = client;
 404         io->callback = fn;
 405         io->context = context;
 406
 407         dispatch_io(rw, num_regions, where, dp, io, 0);
 408         return 0;
 409 }
 410
 411 static int dp_init(struct dm_io_request *io_req, struct dpages *dp)
 412 {
 413         /* Set up dpages based on memory type */
 414         switch (io_req->mem.type) {
 415         case DM_IO_PAGE_LIST:
 416                 list_dp_init(dp, io_req->mem.ptr.pl, io_req->mem.offset);
 417                 break;
 418
 419         case DM_IO_BVEC:
 420                 bvec_dp_init(dp, io_req->mem.ptr.bvec);
 421                 break;
 422
 423         case DM_IO_VMA:
 424                 vm_dp_init(dp, io_req->mem.ptr.vma);
 425                 break;
 426
 427         case DM_IO_KMEM:
 428                 km_dp_init(dp, io_req->mem.ptr.addr);
 429                 break;
 430
 431         default:
 432                 return -EINVAL;
 433         }
 434
 435         return 0;
 436 }
 437
 438 /*
 439  * New collapsed (a)synchronous interface.
 440  *
 441  * If the IO is asynchronous (i.e. it has notify.fn), you must either unplug
 442  * the queue with blk_unplug() some time later or set the BIO_RW_SYNC bit in
 443  * io_req->bi_rw. If you fail to do one of these, the IO will be submitted to
 444  * the disk after q->unplug_delay, which defaults to 3ms in blk-settings.c.
 445  */
 446 int dm_io(struct dm_io_request *io_req, unsigned num_regions,
 447           struct dm_io_region *where, unsigned long *sync_error_bits)
 448 {
 449         int r;
 450         struct dpages dp;
 451
 452         r = dp_init(io_req, &dp);
 453         if (r)
 454                 return r;
 455
 456         if (!io_req->notify.fn)
 457                 return sync_io(io_req->client, num_regions, where,
 458                                io_req->bi_rw, &dp, sync_error_bits);
 459
 460         return async_io(io_req->client, num_regions, where, io_req->bi_rw,
 461                         &dp, io_req->notify.fn, io_req->notify.context);
 462 }
 463 EXPORT_SYMBOL(dm_io);