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
 252static void dm_bio_destructor(struct bio *bio)
 253{
 254        unsigned region;
 255        struct io *io;
 256
 257        retrieve_io_and_region_from_bio(bio, &io, &region);
 258
 259        bio_free(bio, io->client->bios);
 260}
 261
 262/*
 263 * Functions for getting the pages from kernel memory.
 264 */
 265static void km_get_page(struct dpages *dp, struct page **p, unsigned long *len,
 266                        unsigned *offset)
 267{
 268        *p = virt_to_page(dp->context_ptr);
 269        *offset = dp->context_u;
 270        *len = PAGE_SIZE - dp->context_u;
 271}
 272
 273static void km_next_page(struct dpages *dp)
 274{
 275        dp->context_ptr += PAGE_SIZE - dp->context_u;
 276        dp->context_u = 0;
 277}
 278
 279static void km_dp_init(struct dpages *dp, void *data)
 280{
 281        dp->get_page = km_get_page;
 282        dp->next_page = km_next_page;
 283        dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
 284        dp->context_ptr = data;
 285}
 286
 287/*-----------------------------------------------------------------
 288 * IO routines that accept a list of pages.
 289 *---------------------------------------------------------------*/
 290static void do_region(int rw, unsigned region, struct dm_io_region *where,
 291                      struct dpages *dp, struct io *io)
 292{
 293        struct bio *bio;
 294        struct page *page;
 295        unsigned long len;
 296        unsigned offset;
 297        unsigned num_bvecs;
 298        sector_t remaining = where->count;
 299        struct request_queue *q = bdev_get_queue(where->bdev);
 300        sector_t discard_sectors;
 301
 302        /*
 303         * where->count may be zero if rw holds a flush and we need to
 304         * send a zero-sized flush.
 305         */
 306        do {
 307                /*
 308                 * Allocate a suitably sized-bio.
 309                 */
 310                if (rw & REQ_DISCARD)
 311                        num_bvecs = 1;
 312                else
 313                        num_bvecs = min_t(int, bio_get_nr_vecs(where->bdev),
 314                                          dm_sector_div_up(remaining, (PAGE_SIZE >> SECTOR_SHIFT)));
 315
 316                bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
 317                bio->bi_sector = where->sector + (where->count - remaining);
 318                bio->bi_bdev = where->bdev;
 319                bio->bi_end_io = endio;
 320                bio->bi_destructor = dm_bio_destructor;
 321                store_io_and_region_in_bio(bio, io, region);
 322
 323                if (rw & REQ_DISCARD) {
 324                        discard_sectors = min_t(sector_t, q->limits.max_discard_sectors, remaining);
 325                        bio->bi_size = discard_sectors << SECTOR_SHIFT;
 326                        remaining -= discard_sectors;
 327                } else while (remaining) {
 328                        /*
 329                         * Try and add as many pages as possible.
 330                         */
 331                        dp->get_page(dp, &page, &len, &offset);
 332                        len = min(len, to_bytes(remaining));
 333                        if (!bio_add_page(bio, page, len, offset))
 334                                break;
 335
 336                        offset = 0;
 337                        remaining -= to_sector(len);
 338                        dp->next_page(dp);
 339                }
 340
 341                atomic_inc(&io->count);
 342                submit_bio(rw, bio);
 343        } while (remaining);
 344}
 345
 346static void dispatch_io(int rw, unsigned int num_regions,
 347                        struct dm_io_region *where, struct dpages *dp,
 348                        struct io *io, int sync)
 349{
 350        int i;
 351        struct dpages old_pages = *dp;
 352
 353        BUG_ON(num_regions > DM_IO_MAX_REGIONS);
 354
 355        if (sync)
 356                rw |= REQ_SYNC;
 357
 358        /*
 359         * For multiple regions we need to be careful to rewind
 360         * the dp object for each call to do_region.
 361         */
 362        for (i = 0; i < num_regions; i++) {
 363                *dp = old_pages;
 364                if (where[i].count || (rw & REQ_FLUSH))
 365                        do_region(rw, i, where + i, dp, io);
 366        }
 367
 368        /*
 369         * Drop the extra reference that we were holding to avoid
 370         * the io being completed too early.
 371         */
 372        dec_count(io, 0, 0);
 373}
 374
 375static int sync_io(struct dm_io_client *client, unsigned int num_regions,
 376                   struct dm_io_region *where, int rw, struct dpages *dp,
 377                   unsigned long *error_bits)
 378{
 379        /*
 380         * gcc <= 4.3 can't do the alignment for stack variables, so we must
 381         * align it on our own.
 382         * volatile prevents the optimizer from removing or reusing
 383         * "io_" field from the stack frame (allowed in ANSI C).
 384         */
 385        volatile char io_[sizeof(struct io) + __alignof__(struct io) - 1];
 386        struct io *io = (struct io *)PTR_ALIGN(&io_, __alignof__(struct io));
 387
 388        if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
 389                WARN_ON(1);
 390                return -EIO;
 391        }
 392
 393        io->error_bits = 0;
 394        atomic_set(&io->count, 1); /* see dispatch_io() */
 395        io->sleeper = current;
 396        io->client = client;
 397
 398        io->vma_invalidate_address = dp->vma_invalidate_address;
 399        io->vma_invalidate_size = dp->vma_invalidate_size;
 400
 401        dispatch_io(rw, num_regions, where, dp, io, 1);
 402
 403        while (1) {
 404                set_current_state(TASK_UNINTERRUPTIBLE);
 405
 406                if (!atomic_read(&io->count))
 407                        break;
 408
 409                io_schedule();
 410        }
 411        set_current_state(TASK_RUNNING);
 412
 413        if (error_bits)
 414                *error_bits = io->error_bits;
 415
 416        return io->error_bits ? -EIO : 0;
 417}
 418
 419static int async_io(struct dm_io_client *client, unsigned int num_regions,
 420                    struct dm_io_region *where, int rw, struct dpages *dp,
 421                    io_notify_fn fn, void *context)
 422{
 423        struct io *io;
 424
 425        if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
 426                WARN_ON(1);
 427                fn(1, context);
 428                return -EIO;
 429        }
 430
 431        io = mempool_alloc(client->pool, GFP_NOIO);
 432        io->error_bits = 0;
 433        atomic_set(&io->count, 1); /* see dispatch_io() */
 434        io->sleeper = NULL;
 435        io->client = client;
 436        io->callback = fn;
 437        io->context = context;
 438
 439        io->vma_invalidate_address = dp->vma_invalidate_address;
 440        io->vma_invalidate_size = dp->vma_invalidate_size;
 441
 442        dispatch_io(rw, num_regions, where, dp, io, 0);
 443        return 0;
 444}
 445
 446static int dp_init(struct dm_io_request *io_req, struct dpages *dp,
 447                   unsigned long size)
 448{
 449        /* Set up dpages based on memory type */
 450
 451        dp->vma_invalidate_address = NULL;
 452        dp->vma_invalidate_size = 0;
 453
 454        switch (io_req->mem.type) {
 455        case DM_IO_PAGE_LIST:
 456                list_dp_init(dp, io_req->mem.ptr.pl, io_req->mem.offset);
 457                break;
 458
 459        case DM_IO_BVEC:
 460                bvec_dp_init(dp, io_req->mem.ptr.bvec);
 461                break;
 462
 463        case DM_IO_VMA:
 464                flush_kernel_vmap_range(io_req->mem.ptr.vma, size);
 465                if ((io_req->bi_rw & RW_MASK) == READ) {
 466                        dp->vma_invalidate_address = io_req->mem.ptr.vma;
 467                        dp->vma_invalidate_size = size;
 468                }
 469                vm_dp_init(dp, io_req->mem.ptr.vma);
 470                break;
 471
 472        case DM_IO_KMEM:
 473                km_dp_init(dp, io_req->mem.ptr.addr);
 474                break;
 475
 476        default:
 477                return -EINVAL;
 478        }
 479
 480        return 0;
 481}
 482
 483/*
 484 * New collapsed (a)synchronous interface.
 485 *
 486 * If the IO is asynchronous (i.e. it has notify.fn), you must either unplug
 487 * the queue with blk_unplug() some time later or set REQ_SYNC in
 488io_req->bi_rw. If you fail to do one of these, the IO will be submitted to
 489 * the disk after q->unplug_delay, which defaults to 3ms in blk-settings.c.
 490 */
 491int dm_io(struct dm_io_request *io_req, unsigned num_regions,
 492          struct dm_io_region *where, unsigned long *sync_error_bits)
 493{
 494        int r;
 495        struct dpages dp;
 496
 497        r = dp_init(io_req, &dp, (unsigned long)where->count << SECTOR_SHIFT);
 498        if (r)
 499                return r;
 500
 501        if (!io_req->notify.fn)
 502                return sync_io(io_req->client, num_regions, where,
 503                               io_req->bi_rw, &dp, sync_error_bits);
 504
 505        return async_io(io_req->client, num_regions, where, io_req->bi_rw,
 506                        &dp, io_req->notify.fn, io_req->notify.context);
 507}
 508EXPORT_SYMBOL(dm_io);
 509
 510int __init dm_io_init(void)
 511{
 512        _dm_io_cache = KMEM_CACHE(io, 0);
 513        if (!_dm_io_cache)
 514                return -ENOMEM;
 515
 516        return 0;
 517}
 518
 519void dm_io_exit(void)
 520{
 521        kmem_cache_destroy(_dm_io_cache);
 522        _dm_io_cache = NULL;
 523}
 524
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