linux/drivers/md/dm-io.c
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   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#define MIN_IOS         16
  23#define MIN_BIOS        16
  24
  25struct dm_io_client {
  26        mempool_t *pool;
  27        struct bio_set *bios;
  28};
  29
  30/*
  31 * Aligning 'struct io' reduces the number of bits required to store
  32 * its address.  Refer to store_io_and_region_in_bio() below.
  33 */
  34struct io {
  35        unsigned long error_bits;
  36        atomic_t count;
  37        struct task_struct *sleeper;
  38        struct dm_io_client *client;
  39        io_notify_fn callback;
  40        void *context;
  41        void *vma_invalidate_address;
  42        unsigned long vma_invalidate_size;
  43} __attribute__((aligned(DM_IO_MAX_REGIONS)));
  44
  45static struct kmem_cache *_dm_io_cache;
  46
  47/*
  48 * Create a client with mempool and bioset.
  49 */
  50struct dm_io_client *dm_io_client_create(void)
  51{
  52        struct dm_io_client *client;
  53
  54        client = kmalloc(sizeof(*client), GFP_KERNEL);
  55        if (!client)
  56                return ERR_PTR(-ENOMEM);
  57
  58        client->pool = mempool_create_slab_pool(MIN_IOS, _dm_io_cache);
  59        if (!client->pool)
  60                goto bad;
  61
  62        client->bios = bioset_create(MIN_BIOS, 0);
  63        if (!client->bios)
  64                goto bad;
  65
  66        return client;
  67
  68   bad:
  69        if (client->pool)
  70                mempool_destroy(client->pool);
  71        kfree(client);
  72        return ERR_PTR(-ENOMEM);
  73}
  74EXPORT_SYMBOL(dm_io_client_create);
  75
  76void dm_io_client_destroy(struct dm_io_client *client)
  77{
  78        mempool_destroy(client->pool);
  79        bioset_free(client->bios);
  80        kfree(client);
  81}
  82EXPORT_SYMBOL(dm_io_client_destroy);
  83
  84/*-----------------------------------------------------------------
  85 * We need to keep track of which region a bio is doing io for.
  86 * To avoid a memory allocation to store just 5 or 6 bits, we
  87 * ensure the 'struct io' pointer is aligned so enough low bits are
  88 * always zero and then combine it with the region number directly in
  89 * bi_private.
  90 *---------------------------------------------------------------*/
  91static void store_io_and_region_in_bio(struct bio *bio, struct io *io,
  92                                       unsigned region)
  93{
  94        if (unlikely(!IS_ALIGNED((unsigned long)io, DM_IO_MAX_REGIONS))) {
  95                DMCRIT("Unaligned struct io pointer %p", io);
  96                BUG();
  97        }
  98
  99        bio->bi_private = (void *)((unsigned long)io | region);
 100}
 101
 102static void retrieve_io_and_region_from_bio(struct bio *bio, struct io **io,
 103                                       unsigned *region)
 104{
 105        unsigned long val = (unsigned long)bio->bi_private;
 106
 107        *io = (void *)(val & -(unsigned long)DM_IO_MAX_REGIONS);
 108        *region = val & (DM_IO_MAX_REGIONS - 1);
 109}
 110
 111/*-----------------------------------------------------------------
 112 * We need an io object to keep track of the number of bios that
 113 * have been dispatched for a particular io.
 114 *---------------------------------------------------------------*/
 115static void dec_count(struct io *io, unsigned int region, int error)
 116{
 117        if (error)
 118                set_bit(region, &io->error_bits);
 119
 120        if (atomic_dec_and_test(&io->count)) {
 121                if (io->vma_invalidate_size)
 122                        invalidate_kernel_vmap_range(io->vma_invalidate_address,
 123                                                     io->vma_invalidate_size);
 124
 125                if (io->sleeper)
 126                        wake_up_process(io->sleeper);
 127
 128                else {
 129                        unsigned long r = io->error_bits;
 130                        io_notify_fn fn = io->callback;
 131                        void *context = io->context;
 132
 133                        mempool_free(io, io->client->pool);
 134                        fn(r, context);
 135                }
 136        }
 137}
 138
 139static void endio(struct bio *bio, int error)
 140{
 141        struct io *io;
 142        unsigned region;
 143
 144        if (error && bio_data_dir(bio) == READ)
 145                zero_fill_bio(bio);
 146
 147        /*
 148         * The bio destructor in bio_put() may use the io object.
 149         */
 150        retrieve_io_and_region_from_bio(bio, &io, &region);
 151
 152        bio_put(bio);
 153
 154        dec_count(io, region, error);
 155}
 156
 157/*-----------------------------------------------------------------
 158 * These little objects provide an abstraction for getting a new
 159 * destination page for io.
 160 *---------------------------------------------------------------*/
 161struct dpages {
 162        void (*get_page)(struct dpages *dp,
 163                         struct page **p, unsigned long *len, unsigned *offset);
 164        void (*next_page)(struct dpages *dp);
 165
 166        unsigned context_u;
 167        void *context_ptr;
 168
 169        void *vma_invalidate_address;
 170        unsigned long vma_invalidate_size;
 171};
 172
 173/*
 174 * Functions for getting the pages from a list.
 175 */
 176static void list_get_page(struct dpages *dp,
 177                  struct page **p, unsigned long *len, unsigned *offset)
 178{
 179        unsigned o = dp->context_u;
 180        struct page_list *pl = (struct page_list *) dp->context_ptr;
 181
 182        *p = pl->page;
 183        *len = PAGE_SIZE - o;
 184        *offset = o;
 185}
 186
 187static void list_next_page(struct dpages *dp)
 188{
 189        struct page_list *pl = (struct page_list *) dp->context_ptr;
 190        dp->context_ptr = pl->next;
 191        dp->context_u = 0;
 192}
 193
 194static void list_dp_init(struct dpages *dp, struct page_list *pl, unsigned offset)
 195{
 196        dp->get_page = list_get_page;
 197        dp->next_page = list_next_page;
 198        dp->context_u = offset;
 199        dp->context_ptr = pl;
 200}
 201
 202/*
 203 * Functions for getting the pages from a bvec.
 204 */
 205static void bvec_get_page(struct dpages *dp,
 206                  struct page **p, unsigned long *len, unsigned *offset)
 207{
 208        struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
 209        *p = bvec->bv_page;
 210        *len = bvec->bv_len;
 211        *offset = bvec->bv_offset;
 212}
 213
 214static void bvec_next_page(struct dpages *dp)
 215{
 216        struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
 217        dp->context_ptr = bvec + 1;
 218}
 219
 220static void bvec_dp_init(struct dpages *dp, struct bio_vec *bvec)
 221{
 222        dp->get_page = bvec_get_page;
 223        dp->next_page = bvec_next_page;
 224        dp->context_ptr = bvec;
 225}
 226
 227/*
 228 * Functions for getting the pages from a VMA.
 229 */
 230static void vm_get_page(struct dpages *dp,
 231                 struct page **p, unsigned long *len, unsigned *offset)
 232{
 233        *p = vmalloc_to_page(dp->context_ptr);
 234        *offset = dp->context_u;
 235        *len = PAGE_SIZE - dp->context_u;
 236}
 237
 238static void vm_next_page(struct dpages *dp)
 239{
 240        dp->context_ptr += PAGE_SIZE - dp->context_u;
 241        dp->context_u = 0;
 242}
 243
 244static void vm_dp_init(struct dpages *dp, void *data)
 245{
 246        dp->get_page = vm_get_page;
 247        dp->next_page = vm_next_page;
 248        dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
 249        dp->context_ptr = data;
 250}
 251
 252/*
 253 * Functions for getting the pages from kernel memory.
 254 */
 255static void km_get_page(struct dpages *dp, struct page **p, unsigned long *len,
 256                        unsigned *offset)
 257{
 258        *p = virt_to_page(dp->context_ptr);
 259        *offset = dp->context_u;
 260        *len = PAGE_SIZE - dp->context_u;
 261}
 262
 263static void km_next_page(struct dpages *dp)
 264{
 265        dp->context_ptr += PAGE_SIZE - dp->context_u;
 266        dp->context_u = 0;
 267}
 268
 269static void km_dp_init(struct dpages *dp, void *data)
 270{
 271        dp->get_page = km_get_page;
 272        dp->next_page = km_next_page;
 273        dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
 274        dp->context_ptr = data;
 275}
 276
 277/*-----------------------------------------------------------------
 278 * IO routines that accept a list of pages.
 279 *---------------------------------------------------------------*/
 280static void do_region(int rw, unsigned region, struct dm_io_region *where,
 281                      struct dpages *dp, struct io *io)
 282{
 283        struct bio *bio;
 284        struct page *page;
 285        unsigned long len;
 286        unsigned offset;
 287        unsigned num_bvecs;
 288        sector_t remaining = where->count;
 289        struct request_queue *q = bdev_get_queue(where->bdev);
 290        sector_t discard_sectors;
 291
 292        /*
 293         * where->count may be zero if rw holds a flush and we need to
 294         * send a zero-sized flush.
 295         */
 296        do {
 297                /*
 298                 * Allocate a suitably sized-bio.
 299                 */
 300                if (rw & REQ_DISCARD)
 301                        num_bvecs = 1;
 302                else
 303                        num_bvecs = min_t(int, bio_get_nr_vecs(where->bdev),
 304                                          dm_sector_div_up(remaining, (PAGE_SIZE >> SECTOR_SHIFT)));
 305
 306                bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
 307                bio->bi_sector = where->sector + (where->count - remaining);
 308                bio->bi_bdev = where->bdev;
 309                bio->bi_end_io = endio;
 310                store_io_and_region_in_bio(bio, io, region);
 311
 312                if (rw & REQ_DISCARD) {
 313                        discard_sectors = min_t(sector_t, q->limits.max_discard_sectors, remaining);
 314                        bio->bi_size = discard_sectors << SECTOR_SHIFT;
 315                        remaining -= discard_sectors;
 316                } else while (remaining) {
 317                        /*
 318                         * Try and add as many pages as possible.
 319                         */
 320                        dp->get_page(dp, &page, &len, &offset);
 321                        len = min(len, to_bytes(remaining));
 322                        if (!bio_add_page(bio, page, len, offset))
 323                                break;
 324
 325                        offset = 0;
 326                        remaining -= to_sector(len);
 327                        dp->next_page(dp);
 328                }
 329
 330                atomic_inc(&io->count);
 331                submit_bio(rw, bio);
 332        } while (remaining);
 333}
 334
 335static void dispatch_io(int rw, unsigned int num_regions,
 336                        struct dm_io_region *where, struct dpages *dp,
 337                        struct io *io, int sync)
 338{
 339        int i;
 340        struct dpages old_pages = *dp;
 341
 342        BUG_ON(num_regions > DM_IO_MAX_REGIONS);
 343
 344        if (sync)
 345                rw |= REQ_SYNC;
 346
 347        /*
 348         * For multiple regions we need to be careful to rewind
 349         * the dp object for each call to do_region.
 350         */
 351        for (i = 0; i < num_regions; i++) {
 352                *dp = old_pages;
 353                if (where[i].count || (rw & REQ_FLUSH))
 354                        do_region(rw, i, where + i, dp, io);
 355        }
 356
 357        /*
 358         * Drop the extra reference that we were holding to avoid
 359         * the io being completed too early.
 360         */
 361        dec_count(io, 0, 0);
 362}
 363
 364static int sync_io(struct dm_io_client *client, unsigned int num_regions,
 365                   struct dm_io_region *where, int rw, struct dpages *dp,
 366                   unsigned long *error_bits)
 367{
 368        /*
 369         * gcc <= 4.3 can't do the alignment for stack variables, so we must
 370         * align it on our own.
 371         * volatile prevents the optimizer from removing or reusing
 372         * "io_" field from the stack frame (allowed in ANSI C).
 373         */
 374        volatile char io_[sizeof(struct io) + __alignof__(struct io) - 1];
 375        struct io *io = (struct io *)PTR_ALIGN(&io_, __alignof__(struct io));
 376
 377        if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
 378                WARN_ON(1);
 379                return -EIO;
 380        }
 381
 382        io->error_bits = 0;
 383        atomic_set(&io->count, 1); /* see dispatch_io() */
 384        io->sleeper = current;
 385        io->client = client;
 386
 387        io->vma_invalidate_address = dp->vma_invalidate_address;
 388        io->vma_invalidate_size = dp->vma_invalidate_size;
 389
 390        dispatch_io(rw, num_regions, where, dp, io, 1);
 391
 392        while (1) {
 393                set_current_state(TASK_UNINTERRUPTIBLE);
 394
 395                if (!atomic_read(&io->count))
 396                        break;
 397
 398                io_schedule();
 399        }
 400        set_current_state(TASK_RUNNING);
 401
 402        if (error_bits)
 403                *error_bits = io->error_bits;
 404
 405        return io->error_bits ? -EIO : 0;
 406}
 407
 408static int async_io(struct dm_io_client *client, unsigned int num_regions,
 409                    struct dm_io_region *where, int rw, struct dpages *dp,
 410                    io_notify_fn fn, void *context)
 411{
 412        struct io *io;
 413
 414        if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
 415                WARN_ON(1);
 416                fn(1, context);
 417                return -EIO;
 418        }
 419
 420        io = mempool_alloc(client->pool, GFP_NOIO);
 421        io->error_bits = 0;
 422        atomic_set(&io->count, 1); /* see dispatch_io() */
 423        io->sleeper = NULL;
 424        io->client = client;
 425        io->callback = fn;
 426        io->context = context;
 427
 428        io->vma_invalidate_address = dp->vma_invalidate_address;
 429        io->vma_invalidate_size = dp->vma_invalidate_size;
 430
 431        dispatch_io(rw, num_regions, where, dp, io, 0);
 432        return 0;
 433}
 434
 435static int dp_init(struct dm_io_request *io_req, struct dpages *dp,
 436                   unsigned long size)
 437{
 438        /* Set up dpages based on memory type */
 439
 440        dp->vma_invalidate_address = NULL;
 441        dp->vma_invalidate_size = 0;
 442
 443        switch (io_req->mem.type) {
 444        case DM_IO_PAGE_LIST:
 445                list_dp_init(dp, io_req->mem.ptr.pl, io_req->mem.offset);
 446                break;
 447
 448        case DM_IO_BVEC:
 449                bvec_dp_init(dp, io_req->mem.ptr.bvec);
 450                break;
 451
 452        case DM_IO_VMA:
 453                flush_kernel_vmap_range(io_req->mem.ptr.vma, size);
 454                if ((io_req->bi_rw & RW_MASK) == READ) {
 455                        dp->vma_invalidate_address = io_req->mem.ptr.vma;
 456                        dp->vma_invalidate_size = size;
 457                }
 458                vm_dp_init(dp, io_req->mem.ptr.vma);
 459                break;
 460
 461        case DM_IO_KMEM:
 462                km_dp_init(dp, io_req->mem.ptr.addr);
 463                break;
 464
 465        default:
 466                return -EINVAL;
 467        }
 468
 469        return 0;
 470}
 471
 472/*
 473 * New collapsed (a)synchronous interface.
 474 *
 475 * If the IO is asynchronous (i.e. it has notify.fn), you must either unplug
 476 * the queue with blk_unplug() some time later or set REQ_SYNC in
 477io_req->bi_rw. If you fail to do one of these, the IO will be submitted to
 478 * the disk after q->unplug_delay, which defaults to 3ms in blk-settings.c.
 479 */
 480int dm_io(struct dm_io_request *io_req, unsigned num_regions,
 481          struct dm_io_region *where, unsigned long *sync_error_bits)
 482{
 483        int r;
 484        struct dpages dp;
 485
 486        r = dp_init(io_req, &dp, (unsigned long)where->count << SECTOR_SHIFT);
 487        if (r)
 488                return r;
 489
 490        if (!io_req->notify.fn)
 491                return sync_io(io_req->client, num_regions, where,
 492                               io_req->bi_rw, &dp, sync_error_bits);
 493
 494        return async_io(io_req->client, num_regions, where, io_req->bi_rw,
 495                        &dp, io_req->notify.fn, io_req->notify.context);
 496}
 497EXPORT_SYMBOL(dm_io);
 498
 499int __init dm_io_init(void)
 500{
 501        _dm_io_cache = KMEM_CACHE(io, 0);
 502        if (!_dm_io_cache)
 503                return -ENOMEM;
 504
 505        return 0;
 506}
 507
 508void dm_io_exit(void)
 509{
 510        kmem_cache_destroy(_dm_io_cache);
 511        _dm_io_cache = NULL;
 512}
 513
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