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                 if (unlikely(num_bvecs > BIO_MAX_PAGES))
 296                         num_bvecs = BIO_MAX_PAGES;
 297                 bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
 298                 bio->bi_sector = where->sector + (where->count - remaining);
 299                 bio->bi_bdev = where->bdev;
 300                 bio->bi_end_io = endio;
 301                 bio->bi_private = io;
 302                 bio->bi_destructor = dm_bio_destructor;
 303                 bio->bi_max_vecs--;
 304                 bio_set_region(bio, region);
 305
 306                 /*
 307                  * Try and add as many pages as possible.
 308                  */
 309                 while (remaining) {
 310                         dp->get_page(dp, &page, &len, &offset);
 311                         len = min(len, to_bytes(remaining));
 312                         if (!bio_add_page(bio, page, len, offset))
 313                                 break;
 314
 315                         offset = 0;
 316                         remaining -= to_sector(len);
 317                         dp->next_page(dp);
 318                 }
 319
 320                 atomic_inc(&io->count);
 321                 submit_bio(rw, bio);
 322         }
 323 }
 324
 325 static void dispatch_io(int rw, unsigned int num_regions,
 326                         struct dm_io_region *where, struct dpages *dp,
 327                         struct io *io, int sync)
 328 {
 329         int i;
 330         struct dpages old_pages = *dp;
 331
 332         if (sync)
 333                 rw |= (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_UNPLUG);
 334
 335         /*
 336          * For multiple regions we need to be careful to rewind
 337          * the dp object for each call to do_region.
 338          */
 339         for (i = 0; i < num_regions; i++) {
 340                 *dp = old_pages;
 341                 if (where[i].count)
 342                         do_region(rw, i, where + i, dp, io);
 343         }
 344
 345         /*
 346          * Drop the extra reference that we were holding to avoid
 347          * the io being completed too early.
 348          */
 349         dec_count(io, 0, 0);
 350 }
 351
 352 static int sync_io(struct dm_io_client *client, unsigned int num_regions,
 353                    struct dm_io_region *where, int rw, struct dpages *dp,
 354                    unsigned long *error_bits)
 355 {
 356         struct io io;
 357
 358         if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
 359                 WARN_ON(1);
 360                 return -EIO;
 361         }
 362
 363         io.error_bits = 0;
 364         atomic_set(&io.count, 1); /* see dispatch_io() */
 365         io.sleeper = current;
 366         io.client = client;
 367
 368         dispatch_io(rw, num_regions, where, dp, &io, 1);
 369
 370         while (1) {
 371                 set_current_state(TASK_UNINTERRUPTIBLE);
 372
 373                 if (!atomic_read(&io.count))
 374                         break;
 375
 376                 io_schedule();
 377         }
 378         set_current_state(TASK_RUNNING);
 379
 380         if (error_bits)
 381                 *error_bits = io.error_bits;
 382
 383         return io.error_bits ? -EIO : 0;
 384 }
 385
 386 static int async_io(struct dm_io_client *client, unsigned int num_regions,
 387                     struct dm_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 & RW_MASK) != 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_bits = 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  * If the IO is asynchronous (i.e. it has notify.fn), you must either unplug
 441  * the queue with blk_unplug() some time later or set the BIO_RW_SYNC bit in
 442  * io_req->bi_rw. If you fail to do one of these, the IO will be submitted to
 443  * the disk after q->unplug_delay, which defaults to 3ms in blk-settings.c.
 444  */
 445 int dm_io(struct dm_io_request *io_req, unsigned num_regions,
 446           struct dm_io_region *where, unsigned long *sync_error_bits)
 447 {
 448         int r;
 449         struct dpages dp;
 450
 451         r = dp_init(io_req, &dp);
 452         if (r)
 453                 return r;
 454
 455         if (!io_req->notify.fn)
 456                 return sync_io(io_req->client, num_regions, where,
 457                                io_req->bi_rw, &dp, sync_error_bits);
 458
 459         return async_io(io_req->client, num_regions, where, io_req->bi_rw,
 460                         &dp, io_req->notify.fn, io_req->notify.context);
 461 }
 462 EXPORT_SYMBOL(dm_io);