linux/drivers/md/dm-bufio.c
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   1/*
   2 * Copyright (C) 2009-2011 Red Hat, Inc.
   3 *
   4 * Author: Mikulas Patocka <mpatocka@redhat.com>
   5 *
   6 * This file is released under the GPL.
   7 */
   8
   9#include "dm-bufio.h"
  10
  11#include <linux/device-mapper.h>
  12#include <linux/dm-io.h>
  13#include <linux/slab.h>
  14#include <linux/vmalloc.h>
  15#include <linux/shrinker.h>
  16#include <linux/module.h>
  17
  18#define DM_MSG_PREFIX "bufio"
  19
  20/*
  21 * Memory management policy:
  22 *      Limit the number of buffers to DM_BUFIO_MEMORY_PERCENT of main memory
  23 *      or DM_BUFIO_VMALLOC_PERCENT of vmalloc memory (whichever is lower).
  24 *      Always allocate at least DM_BUFIO_MIN_BUFFERS buffers.
  25 *      Start background writeback when there are DM_BUFIO_WRITEBACK_PERCENT
  26 *      dirty buffers.
  27 */
  28#define DM_BUFIO_MIN_BUFFERS            8
  29
  30#define DM_BUFIO_MEMORY_PERCENT         2
  31#define DM_BUFIO_VMALLOC_PERCENT        25
  32#define DM_BUFIO_WRITEBACK_PERCENT      75
  33
  34/*
  35 * Check buffer ages in this interval (seconds)
  36 */
  37#define DM_BUFIO_WORK_TIMER_SECS        10
  38
  39/*
  40 * Free buffers when they are older than this (seconds)
  41 */
  42#define DM_BUFIO_DEFAULT_AGE_SECS       60
  43
  44/*
  45 * The number of bvec entries that are embedded directly in the buffer.
  46 * If the chunk size is larger, dm-io is used to do the io.
  47 */
  48#define DM_BUFIO_INLINE_VECS            16
  49
  50/*
  51 * Buffer hash
  52 */
  53#define DM_BUFIO_HASH_BITS      20
  54#define DM_BUFIO_HASH(block) \
  55        ((((block) >> DM_BUFIO_HASH_BITS) ^ (block)) & \
  56         ((1 << DM_BUFIO_HASH_BITS) - 1))
  57
  58/*
  59 * Don't try to use kmem_cache_alloc for blocks larger than this.
  60 * For explanation, see alloc_buffer_data below.
  61 */
  62#define DM_BUFIO_BLOCK_SIZE_SLAB_LIMIT  (PAGE_SIZE >> 1)
  63#define DM_BUFIO_BLOCK_SIZE_GFP_LIMIT   (PAGE_SIZE << (MAX_ORDER - 1))
  64
  65/*
  66 * dm_buffer->list_mode
  67 */
  68#define LIST_CLEAN      0
  69#define LIST_DIRTY      1
  70#define LIST_SIZE       2
  71
  72/*
  73 * Linking of buffers:
  74 *      All buffers are linked to cache_hash with their hash_list field.
  75 *
  76 *      Clean buffers that are not being written (B_WRITING not set)
  77 *      are linked to lru[LIST_CLEAN] with their lru_list field.
  78 *
  79 *      Dirty and clean buffers that are being written are linked to
  80 *      lru[LIST_DIRTY] with their lru_list field. When the write
  81 *      finishes, the buffer cannot be relinked immediately (because we
  82 *      are in an interrupt context and relinking requires process
  83 *      context), so some clean-not-writing buffers can be held on
  84 *      dirty_lru too.  They are later added to lru in the process
  85 *      context.
  86 */
  87struct dm_bufio_client {
  88        struct mutex lock;
  89
  90        struct list_head lru[LIST_SIZE];
  91        unsigned long n_buffers[LIST_SIZE];
  92
  93        struct block_device *bdev;
  94        unsigned block_size;
  95        unsigned char sectors_per_block_bits;
  96        unsigned char pages_per_block_bits;
  97        unsigned char blocks_per_page_bits;
  98        unsigned aux_size;
  99        void (*alloc_callback)(struct dm_buffer *);
 100        void (*write_callback)(struct dm_buffer *);
 101
 102        struct dm_io_client *dm_io;
 103
 104        struct list_head reserved_buffers;
 105        unsigned need_reserved_buffers;
 106
 107        struct hlist_head *cache_hash;
 108        wait_queue_head_t free_buffer_wait;
 109
 110        int async_write_error;
 111
 112        struct list_head client_list;
 113        struct shrinker shrinker;
 114};
 115
 116/*
 117 * Buffer state bits.
 118 */
 119#define B_READING       0
 120#define B_WRITING       1
 121#define B_DIRTY         2
 122
 123/*
 124 * Describes how the block was allocated:
 125 * kmem_cache_alloc(), __get_free_pages() or vmalloc().
 126 * See the comment at alloc_buffer_data.
 127 */
 128enum data_mode {
 129        DATA_MODE_SLAB = 0,
 130        DATA_MODE_GET_FREE_PAGES = 1,
 131        DATA_MODE_VMALLOC = 2,
 132        DATA_MODE_LIMIT = 3
 133};
 134
 135struct dm_buffer {
 136        struct hlist_node hash_list;
 137        struct list_head lru_list;
 138        sector_t block;
 139        void *data;
 140        enum data_mode data_mode;
 141        unsigned char list_mode;                /* LIST_* */
 142        unsigned hold_count;
 143        int read_error;
 144        int write_error;
 145        unsigned long state;
 146        unsigned long last_accessed;
 147        struct dm_bufio_client *c;
 148        struct bio bio;
 149        struct bio_vec bio_vec[DM_BUFIO_INLINE_VECS];
 150};
 151
 152/*----------------------------------------------------------------*/
 153
 154static struct kmem_cache *dm_bufio_caches[PAGE_SHIFT - SECTOR_SHIFT];
 155static char *dm_bufio_cache_names[PAGE_SHIFT - SECTOR_SHIFT];
 156
 157static inline int dm_bufio_cache_index(struct dm_bufio_client *c)
 158{
 159        unsigned ret = c->blocks_per_page_bits - 1;
 160
 161        BUG_ON(ret >= ARRAY_SIZE(dm_bufio_caches));
 162
 163        return ret;
 164}
 165
 166#define DM_BUFIO_CACHE(c)       (dm_bufio_caches[dm_bufio_cache_index(c)])
 167#define DM_BUFIO_CACHE_NAME(c)  (dm_bufio_cache_names[dm_bufio_cache_index(c)])
 168
 169#define dm_bufio_in_request()   (!!current->bio_list)
 170
 171static void dm_bufio_lock(struct dm_bufio_client *c)
 172{
 173        mutex_lock_nested(&c->lock, dm_bufio_in_request());
 174}
 175
 176static int dm_bufio_trylock(struct dm_bufio_client *c)
 177{
 178        return mutex_trylock(&c->lock);
 179}
 180
 181static void dm_bufio_unlock(struct dm_bufio_client *c)
 182{
 183        mutex_unlock(&c->lock);
 184}
 185
 186/*
 187 * FIXME Move to sched.h?
 188 */
 189#ifdef CONFIG_PREEMPT_VOLUNTARY
 190#  define dm_bufio_cond_resched()               \
 191do {                                            \
 192        if (unlikely(need_resched()))           \
 193                _cond_resched();                \
 194} while (0)
 195#else
 196#  define dm_bufio_cond_resched()                do { } while (0)
 197#endif
 198
 199/*----------------------------------------------------------------*/
 200
 201/*
 202 * Default cache size: available memory divided by the ratio.
 203 */
 204static unsigned long dm_bufio_default_cache_size;
 205
 206/*
 207 * Total cache size set by the user.
 208 */
 209static unsigned long dm_bufio_cache_size;
 210
 211/*
 212 * A copy of dm_bufio_cache_size because dm_bufio_cache_size can change
 213 * at any time.  If it disagrees, the user has changed cache size.
 214 */
 215static unsigned long dm_bufio_cache_size_latch;
 216
 217static DEFINE_SPINLOCK(param_spinlock);
 218
 219/*
 220 * Buffers are freed after this timeout
 221 */
 222static unsigned dm_bufio_max_age = DM_BUFIO_DEFAULT_AGE_SECS;
 223
 224static unsigned long dm_bufio_peak_allocated;
 225static unsigned long dm_bufio_allocated_kmem_cache;
 226static unsigned long dm_bufio_allocated_get_free_pages;
 227static unsigned long dm_bufio_allocated_vmalloc;
 228static unsigned long dm_bufio_current_allocated;
 229
 230/*----------------------------------------------------------------*/
 231
 232/*
 233 * Per-client cache: dm_bufio_cache_size / dm_bufio_client_count
 234 */
 235static unsigned long dm_bufio_cache_size_per_client;
 236
 237/*
 238 * The current number of clients.
 239 */
 240static int dm_bufio_client_count;
 241
 242/*
 243 * The list of all clients.
 244 */
 245static LIST_HEAD(dm_bufio_all_clients);
 246
 247/*
 248 * This mutex protects dm_bufio_cache_size_latch,
 249 * dm_bufio_cache_size_per_client and dm_bufio_client_count
 250 */
 251static DEFINE_MUTEX(dm_bufio_clients_lock);
 252
 253/*----------------------------------------------------------------*/
 254
 255static void adjust_total_allocated(enum data_mode data_mode, long diff)
 256{
 257        static unsigned long * const class_ptr[DATA_MODE_LIMIT] = {
 258                &dm_bufio_allocated_kmem_cache,
 259                &dm_bufio_allocated_get_free_pages,
 260                &dm_bufio_allocated_vmalloc,
 261        };
 262
 263        spin_lock(&param_spinlock);
 264
 265        *class_ptr[data_mode] += diff;
 266
 267        dm_bufio_current_allocated += diff;
 268
 269        if (dm_bufio_current_allocated > dm_bufio_peak_allocated)
 270                dm_bufio_peak_allocated = dm_bufio_current_allocated;
 271
 272        spin_unlock(&param_spinlock);
 273}
 274
 275/*
 276 * Change the number of clients and recalculate per-client limit.
 277 */
 278static void __cache_size_refresh(void)
 279{
 280        BUG_ON(!mutex_is_locked(&dm_bufio_clients_lock));
 281        BUG_ON(dm_bufio_client_count < 0);
 282
 283        dm_bufio_cache_size_latch = dm_bufio_cache_size;
 284
 285        barrier();
 286
 287        /*
 288         * Use default if set to 0 and report the actual cache size used.
 289         */
 290        if (!dm_bufio_cache_size_latch) {
 291                (void)cmpxchg(&dm_bufio_cache_size, 0,
 292                              dm_bufio_default_cache_size);
 293                dm_bufio_cache_size_latch = dm_bufio_default_cache_size;
 294        }
 295
 296        dm_bufio_cache_size_per_client = dm_bufio_cache_size_latch /
 297                                         (dm_bufio_client_count ? : 1);
 298}
 299
 300/*
 301 * Allocating buffer data.
 302 *
 303 * Small buffers are allocated with kmem_cache, to use space optimally.
 304 *
 305 * For large buffers, we choose between get_free_pages and vmalloc.
 306 * Each has advantages and disadvantages.
 307 *
 308 * __get_free_pages can randomly fail if the memory is fragmented.
 309 * __vmalloc won't randomly fail, but vmalloc space is limited (it may be
 310 * as low as 128M) so using it for caching is not appropriate.
 311 *
 312 * If the allocation may fail we use __get_free_pages. Memory fragmentation
 313 * won't have a fatal effect here, but it just causes flushes of some other
 314 * buffers and more I/O will be performed. Don't use __get_free_pages if it
 315 * always fails (i.e. order >= MAX_ORDER).
 316 *
 317 * If the allocation shouldn't fail we use __vmalloc. This is only for the
 318 * initial reserve allocation, so there's no risk of wasting all vmalloc
 319 * space.
 320 */
 321static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask,
 322                               enum data_mode *data_mode)
 323{
 324        if (c->block_size <= DM_BUFIO_BLOCK_SIZE_SLAB_LIMIT) {
 325                *data_mode = DATA_MODE_SLAB;
 326                return kmem_cache_alloc(DM_BUFIO_CACHE(c), gfp_mask);
 327        }
 328
 329        if (c->block_size <= DM_BUFIO_BLOCK_SIZE_GFP_LIMIT &&
 330            gfp_mask & __GFP_NORETRY) {
 331                *data_mode = DATA_MODE_GET_FREE_PAGES;
 332                return (void *)__get_free_pages(gfp_mask,
 333                                                c->pages_per_block_bits);
 334        }
 335
 336        *data_mode = DATA_MODE_VMALLOC;
 337        return __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL);
 338}
 339
 340/*
 341 * Free buffer's data.
 342 */
 343static void free_buffer_data(struct dm_bufio_client *c,
 344                             void *data, enum data_mode data_mode)
 345{
 346        switch (data_mode) {
 347        case DATA_MODE_SLAB:
 348                kmem_cache_free(DM_BUFIO_CACHE(c), data);
 349                break;
 350
 351        case DATA_MODE_GET_FREE_PAGES:
 352                free_pages((unsigned long)data, c->pages_per_block_bits);
 353                break;
 354
 355        case DATA_MODE_VMALLOC:
 356                vfree(data);
 357                break;
 358
 359        default:
 360                DMCRIT("dm_bufio_free_buffer_data: bad data mode: %d",
 361                       data_mode);
 362                BUG();
 363        }
 364}
 365
 366/*
 367 * Allocate buffer and its data.
 368 */
 369static struct dm_buffer *alloc_buffer(struct dm_bufio_client *c, gfp_t gfp_mask)
 370{
 371        struct dm_buffer *b = kmalloc(sizeof(struct dm_buffer) + c->aux_size,
 372                                      gfp_mask);
 373
 374        if (!b)
 375                return NULL;
 376
 377        b->c = c;
 378
 379        b->data = alloc_buffer_data(c, gfp_mask, &b->data_mode);
 380        if (!b->data) {
 381                kfree(b);
 382                return NULL;
 383        }
 384
 385        adjust_total_allocated(b->data_mode, (long)c->block_size);
 386
 387        return b;
 388}
 389
 390/*
 391 * Free buffer and its data.
 392 */
 393static void free_buffer(struct dm_buffer *b)
 394{
 395        struct dm_bufio_client *c = b->c;
 396
 397        adjust_total_allocated(b->data_mode, -(long)c->block_size);
 398
 399        free_buffer_data(c, b->data, b->data_mode);
 400        kfree(b);
 401}
 402
 403/*
 404 * Link buffer to the hash list and clean or dirty queue.
 405 */
 406static void __link_buffer(struct dm_buffer *b, sector_t block, int dirty)
 407{
 408        struct dm_bufio_client *c = b->c;
 409
 410        c->n_buffers[dirty]++;
 411        b->block = block;
 412        b->list_mode = dirty;
 413        list_add(&b->lru_list, &c->lru[dirty]);
 414        hlist_add_head(&b->hash_list, &c->cache_hash[DM_BUFIO_HASH(block)]);
 415        b->last_accessed = jiffies;
 416}
 417
 418/*
 419 * Unlink buffer from the hash list and dirty or clean queue.
 420 */
 421static void __unlink_buffer(struct dm_buffer *b)
 422{
 423        struct dm_bufio_client *c = b->c;
 424
 425        BUG_ON(!c->n_buffers[b->list_mode]);
 426
 427        c->n_buffers[b->list_mode]--;
 428        hlist_del(&b->hash_list);
 429        list_del(&b->lru_list);
 430}
 431
 432/*
 433 * Place the buffer to the head of dirty or clean LRU queue.
 434 */
 435static void __relink_lru(struct dm_buffer *b, int dirty)
 436{
 437        struct dm_bufio_client *c = b->c;
 438
 439        BUG_ON(!c->n_buffers[b->list_mode]);
 440
 441        c->n_buffers[b->list_mode]--;
 442        c->n_buffers[dirty]++;
 443        b->list_mode = dirty;
 444        list_del(&b->lru_list);
 445        list_add(&b->lru_list, &c->lru[dirty]);
 446}
 447
 448/*----------------------------------------------------------------
 449 * Submit I/O on the buffer.
 450 *
 451 * Bio interface is faster but it has some problems:
 452 *      the vector list is limited (increasing this limit increases
 453 *      memory-consumption per buffer, so it is not viable);
 454 *
 455 *      the memory must be direct-mapped, not vmalloced;
 456 *
 457 *      the I/O driver can reject requests spuriously if it thinks that
 458 *      the requests are too big for the device or if they cross a
 459 *      controller-defined memory boundary.
 460 *
 461 * If the buffer is small enough (up to DM_BUFIO_INLINE_VECS pages) and
 462 * it is not vmalloced, try using the bio interface.
 463 *
 464 * If the buffer is big, if it is vmalloced or if the underlying device
 465 * rejects the bio because it is too large, use dm-io layer to do the I/O.
 466 * The dm-io layer splits the I/O into multiple requests, avoiding the above
 467 * shortcomings.
 468 *--------------------------------------------------------------*/
 469
 470/*
 471 * dm-io completion routine. It just calls b->bio.bi_end_io, pretending
 472 * that the request was handled directly with bio interface.
 473 */
 474static void dmio_complete(unsigned long error, void *context)
 475{
 476        struct dm_buffer *b = context;
 477
 478        b->bio.bi_end_io(&b->bio, error ? -EIO : 0);
 479}
 480
 481static void use_dmio(struct dm_buffer *b, int rw, sector_t block,
 482                     bio_end_io_t *end_io)
 483{
 484        int r;
 485        struct dm_io_request io_req = {
 486                .bi_rw = rw,
 487                .notify.fn = dmio_complete,
 488                .notify.context = b,
 489                .client = b->c->dm_io,
 490        };
 491        struct dm_io_region region = {
 492                .bdev = b->c->bdev,
 493                .sector = block << b->c->sectors_per_block_bits,
 494                .count = b->c->block_size >> SECTOR_SHIFT,
 495        };
 496
 497        if (b->data_mode != DATA_MODE_VMALLOC) {
 498                io_req.mem.type = DM_IO_KMEM;
 499                io_req.mem.ptr.addr = b->data;
 500        } else {
 501                io_req.mem.type = DM_IO_VMA;
 502                io_req.mem.ptr.vma = b->data;
 503        }
 504
 505        b->bio.bi_end_io = end_io;
 506
 507        r = dm_io(&io_req, 1, &region, NULL);
 508        if (r)
 509                end_io(&b->bio, r);
 510}
 511
 512static void use_inline_bio(struct dm_buffer *b, int rw, sector_t block,
 513                           bio_end_io_t *end_io)
 514{
 515        char *ptr;
 516        int len;
 517
 518        bio_init(&b->bio);
 519        b->bio.bi_io_vec = b->bio_vec;
 520        b->bio.bi_max_vecs = DM_BUFIO_INLINE_VECS;
 521        b->bio.bi_sector = block << b->c->sectors_per_block_bits;
 522        b->bio.bi_bdev = b->c->bdev;
 523        b->bio.bi_end_io = end_io;
 524
 525        /*
 526         * We assume that if len >= PAGE_SIZE ptr is page-aligned.
 527         * If len < PAGE_SIZE the buffer doesn't cross page boundary.
 528         */
 529        ptr = b->data;
 530        len = b->c->block_size;
 531
 532        if (len >= PAGE_SIZE)
 533                BUG_ON((unsigned long)ptr & (PAGE_SIZE - 1));
 534        else
 535                BUG_ON((unsigned long)ptr & (len - 1));
 536
 537        do {
 538                if (!bio_add_page(&b->bio, virt_to_page(ptr),
 539                                  len < PAGE_SIZE ? len : PAGE_SIZE,
 540                                  virt_to_phys(ptr) & (PAGE_SIZE - 1))) {
 541                        BUG_ON(b->c->block_size <= PAGE_SIZE);
 542                        use_dmio(b, rw, block, end_io);
 543                        return;
 544                }
 545
 546                len -= PAGE_SIZE;
 547                ptr += PAGE_SIZE;
 548        } while (len > 0);
 549
 550        submit_bio(rw, &b->bio);
 551}
 552
 553static void submit_io(struct dm_buffer *b, int rw, sector_t block,
 554                      bio_end_io_t *end_io)
 555{
 556        if (rw == WRITE && b->c->write_callback)
 557                b->c->write_callback(b);
 558
 559        if (b->c->block_size <= DM_BUFIO_INLINE_VECS * PAGE_SIZE &&
 560            b->data_mode != DATA_MODE_VMALLOC)
 561                use_inline_bio(b, rw, block, end_io);
 562        else
 563                use_dmio(b, rw, block, end_io);
 564}
 565
 566/*----------------------------------------------------------------
 567 * Writing dirty buffers
 568 *--------------------------------------------------------------*/
 569
 570/*
 571 * The endio routine for write.
 572 *
 573 * Set the error, clear B_WRITING bit and wake anyone who was waiting on
 574 * it.
 575 */
 576static void write_endio(struct bio *bio, int error)
 577{
 578        struct dm_buffer *b = container_of(bio, struct dm_buffer, bio);
 579
 580        b->write_error = error;
 581        if (unlikely(error)) {
 582                struct dm_bufio_client *c = b->c;
 583                (void)cmpxchg(&c->async_write_error, 0, error);
 584        }
 585
 586        BUG_ON(!test_bit(B_WRITING, &b->state));
 587
 588        smp_mb__before_clear_bit();
 589        clear_bit(B_WRITING, &b->state);
 590        smp_mb__after_clear_bit();
 591
 592        wake_up_bit(&b->state, B_WRITING);
 593}
 594
 595/*
 596 * This function is called when wait_on_bit is actually waiting.
 597 */
 598static int do_io_schedule(void *word)
 599{
 600        io_schedule();
 601
 602        return 0;
 603}
 604
 605/*
 606 * Initiate a write on a dirty buffer, but don't wait for it.
 607 *
 608 * - If the buffer is not dirty, exit.
 609 * - If there some previous write going on, wait for it to finish (we can't
 610 *   have two writes on the same buffer simultaneously).
 611 * - Submit our write and don't wait on it. We set B_WRITING indicating
 612 *   that there is a write in progress.
 613 */
 614static void __write_dirty_buffer(struct dm_buffer *b)
 615{
 616        if (!test_bit(B_DIRTY, &b->state))
 617                return;
 618
 619        clear_bit(B_DIRTY, &b->state);
 620        wait_on_bit_lock(&b->state, B_WRITING,
 621                         do_io_schedule, TASK_UNINTERRUPTIBLE);
 622
 623        submit_io(b, WRITE, b->block, write_endio);
 624}
 625
 626/*
 627 * Wait until any activity on the buffer finishes.  Possibly write the
 628 * buffer if it is dirty.  When this function finishes, there is no I/O
 629 * running on the buffer and the buffer is not dirty.
 630 */
 631static void __make_buffer_clean(struct dm_buffer *b)
 632{
 633        BUG_ON(b->hold_count);
 634
 635        if (!b->state)  /* fast case */
 636                return;
 637
 638        wait_on_bit(&b->state, B_READING, do_io_schedule, TASK_UNINTERRUPTIBLE);
 639        __write_dirty_buffer(b);
 640        wait_on_bit(&b->state, B_WRITING, do_io_schedule, TASK_UNINTERRUPTIBLE);
 641}
 642
 643/*
 644 * Find some buffer that is not held by anybody, clean it, unlink it and
 645 * return it.
 646 */
 647static struct dm_buffer *__get_unclaimed_buffer(struct dm_bufio_client *c)
 648{
 649        struct dm_buffer *b;
 650
 651        list_for_each_entry_reverse(b, &c->lru[LIST_CLEAN], lru_list) {
 652                BUG_ON(test_bit(B_WRITING, &b->state));
 653                BUG_ON(test_bit(B_DIRTY, &b->state));
 654
 655                if (!b->hold_count) {
 656                        __make_buffer_clean(b);
 657                        __unlink_buffer(b);
 658                        return b;
 659                }
 660                dm_bufio_cond_resched();
 661        }
 662
 663        list_for_each_entry_reverse(b, &c->lru[LIST_DIRTY], lru_list) {
 664                BUG_ON(test_bit(B_READING, &b->state));
 665
 666                if (!b->hold_count) {
 667                        __make_buffer_clean(b);
 668                        __unlink_buffer(b);
 669                        return b;
 670                }
 671                dm_bufio_cond_resched();
 672        }
 673
 674        return NULL;
 675}
 676
 677/*
 678 * Wait until some other threads free some buffer or release hold count on
 679 * some buffer.
 680 *
 681 * This function is entered with c->lock held, drops it and regains it
 682 * before exiting.
 683 */
 684static void __wait_for_free_buffer(struct dm_bufio_client *c)
 685{
 686        DECLARE_WAITQUEUE(wait, current);
 687
 688        add_wait_queue(&c->free_buffer_wait, &wait);
 689        set_task_state(current, TASK_UNINTERRUPTIBLE);
 690        dm_bufio_unlock(c);
 691
 692        io_schedule();
 693
 694        set_task_state(current, TASK_RUNNING);
 695        remove_wait_queue(&c->free_buffer_wait, &wait);
 696
 697        dm_bufio_lock(c);
 698}
 699
 700enum new_flag {
 701        NF_FRESH = 0,
 702        NF_READ = 1,
 703        NF_GET = 2,
 704        NF_PREFETCH = 3
 705};
 706
 707/*
 708 * Allocate a new buffer. If the allocation is not possible, wait until
 709 * some other thread frees a buffer.
 710 *
 711 * May drop the lock and regain it.
 712 */
 713static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client *c, enum new_flag nf)
 714{
 715        struct dm_buffer *b;
 716
 717        /*
 718         * dm-bufio is resistant to allocation failures (it just keeps
 719         * one buffer reserved in cases all the allocations fail).
 720         * So set flags to not try too hard:
 721         *      GFP_NOIO: don't recurse into the I/O layer
 722         *      __GFP_NORETRY: don't retry and rather return failure
 723         *      __GFP_NOMEMALLOC: don't use emergency reserves
 724         *      __GFP_NOWARN: don't print a warning in case of failure
 725         *
 726         * For debugging, if we set the cache size to 1, no new buffers will
 727         * be allocated.
 728         */
 729        while (1) {
 730                if (dm_bufio_cache_size_latch != 1) {
 731                        b = alloc_buffer(c, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
 732                        if (b)
 733                                return b;
 734                }
 735
 736                if (nf == NF_PREFETCH)
 737                        return NULL;
 738
 739                if (!list_empty(&c->reserved_buffers)) {
 740                        b = list_entry(c->reserved_buffers.next,
 741                                       struct dm_buffer, lru_list);
 742                        list_del(&b->lru_list);
 743                        c->need_reserved_buffers++;
 744
 745                        return b;
 746                }
 747
 748                b = __get_unclaimed_buffer(c);
 749                if (b)
 750                        return b;
 751
 752                __wait_for_free_buffer(c);
 753        }
 754}
 755
 756static struct dm_buffer *__alloc_buffer_wait(struct dm_bufio_client *c, enum new_flag nf)
 757{
 758        struct dm_buffer *b = __alloc_buffer_wait_no_callback(c, nf);
 759
 760        if (!b)
 761                return NULL;
 762
 763        if (c->alloc_callback)
 764                c->alloc_callback(b);
 765
 766        return b;
 767}
 768
 769/*
 770 * Free a buffer and wake other threads waiting for free buffers.
 771 */
 772static void __free_buffer_wake(struct dm_buffer *b)
 773{
 774        struct dm_bufio_client *c = b->c;
 775
 776        if (!c->need_reserved_buffers)
 777                free_buffer(b);
 778        else {
 779                list_add(&b->lru_list, &c->reserved_buffers);
 780                c->need_reserved_buffers--;
 781        }
 782
 783        wake_up(&c->free_buffer_wait);
 784}
 785
 786static void __write_dirty_buffers_async(struct dm_bufio_client *c, int no_wait)
 787{
 788        struct dm_buffer *b, *tmp;
 789
 790        list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) {
 791                BUG_ON(test_bit(B_READING, &b->state));
 792
 793                if (!test_bit(B_DIRTY, &b->state) &&
 794                    !test_bit(B_WRITING, &b->state)) {
 795                        __relink_lru(b, LIST_CLEAN);
 796                        continue;
 797                }
 798
 799                if (no_wait && test_bit(B_WRITING, &b->state))
 800                        return;
 801
 802                __write_dirty_buffer(b);
 803                dm_bufio_cond_resched();
 804        }
 805}
 806
 807/*
 808 * Get writeback threshold and buffer limit for a given client.
 809 */
 810static void __get_memory_limit(struct dm_bufio_client *c,
 811                               unsigned long *threshold_buffers,
 812                               unsigned long *limit_buffers)
 813{
 814        unsigned long buffers;
 815
 816        if (dm_bufio_cache_size != dm_bufio_cache_size_latch) {
 817                mutex_lock(&dm_bufio_clients_lock);
 818                __cache_size_refresh();
 819                mutex_unlock(&dm_bufio_clients_lock);
 820        }
 821
 822        buffers = dm_bufio_cache_size_per_client >>
 823                  (c->sectors_per_block_bits + SECTOR_SHIFT);
 824
 825        if (buffers < DM_BUFIO_MIN_BUFFERS)
 826                buffers = DM_BUFIO_MIN_BUFFERS;
 827
 828        *limit_buffers = buffers;
 829        *threshold_buffers = buffers * DM_BUFIO_WRITEBACK_PERCENT / 100;
 830}
 831
 832/*
 833 * Check if we're over watermark.
 834 * If we are over threshold_buffers, start freeing buffers.
 835 * If we're over "limit_buffers", block until we get under the limit.
 836 */
 837static void __check_watermark(struct dm_bufio_client *c)
 838{
 839        unsigned long threshold_buffers, limit_buffers;
 840
 841        __get_memory_limit(c, &threshold_buffers, &limit_buffers);
 842
 843        while (c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY] >
 844               limit_buffers) {
 845
 846                struct dm_buffer *b = __get_unclaimed_buffer(c);
 847
 848                if (!b)
 849                        return;
 850
 851                __free_buffer_wake(b);
 852                dm_bufio_cond_resched();
 853        }
 854
 855        if (c->n_buffers[LIST_DIRTY] > threshold_buffers)
 856                __write_dirty_buffers_async(c, 1);
 857}
 858
 859/*
 860 * Find a buffer in the hash.
 861 */
 862static struct dm_buffer *__find(struct dm_bufio_client *c, sector_t block)
 863{
 864        struct dm_buffer *b;
 865        struct hlist_node *hn;
 866
 867        hlist_for_each_entry(b, hn, &c->cache_hash[DM_BUFIO_HASH(block)],
 868                             hash_list) {
 869                dm_bufio_cond_resched();
 870                if (b->block == block)
 871                        return b;
 872        }
 873
 874        return NULL;
 875}
 876
 877/*----------------------------------------------------------------
 878 * Getting a buffer
 879 *--------------------------------------------------------------*/
 880
 881static struct dm_buffer *__bufio_new(struct dm_bufio_client *c, sector_t block,
 882                                     enum new_flag nf, int *need_submit)
 883{
 884        struct dm_buffer *b, *new_b = NULL;
 885
 886        *need_submit = 0;
 887
 888        b = __find(c, block);
 889        if (b)
 890                goto found_buffer;
 891
 892        if (nf == NF_GET)
 893                return NULL;
 894
 895        new_b = __alloc_buffer_wait(c, nf);
 896        if (!new_b)
 897                return NULL;
 898
 899        /*
 900         * We've had a period where the mutex was unlocked, so need to
 901         * recheck the hash table.
 902         */
 903        b = __find(c, block);
 904        if (b) {
 905                __free_buffer_wake(new_b);
 906                goto found_buffer;
 907        }
 908
 909        __check_watermark(c);
 910
 911        b = new_b;
 912        b->hold_count = 1;
 913        b->read_error = 0;
 914        b->write_error = 0;
 915        __link_buffer(b, block, LIST_CLEAN);
 916
 917        if (nf == NF_FRESH) {
 918                b->state = 0;
 919                return b;
 920        }
 921
 922        b->state = 1 << B_READING;
 923        *need_submit = 1;
 924
 925        return b;
 926
 927found_buffer:
 928        if (nf == NF_PREFETCH)
 929                return NULL;
 930        /*
 931         * Note: it is essential that we don't wait for the buffer to be
 932         * read if dm_bufio_get function is used. Both dm_bufio_get and
 933         * dm_bufio_prefetch can be used in the driver request routine.
 934         * If the user called both dm_bufio_prefetch and dm_bufio_get on
 935         * the same buffer, it would deadlock if we waited.
 936         */
 937        if (nf == NF_GET && unlikely(test_bit(B_READING, &b->state)))
 938                return NULL;
 939
 940        b->hold_count++;
 941        __relink_lru(b, test_bit(B_DIRTY, &b->state) ||
 942                     test_bit(B_WRITING, &b->state));
 943        return b;
 944}
 945
 946/*
 947 * The endio routine for reading: set the error, clear the bit and wake up
 948 * anyone waiting on the buffer.
 949 */
 950static void read_endio(struct bio *bio, int error)
 951{
 952        struct dm_buffer *b = container_of(bio, struct dm_buffer, bio);
 953
 954        b->read_error = error;
 955
 956        BUG_ON(!test_bit(B_READING, &b->state));
 957
 958        smp_mb__before_clear_bit();
 959        clear_bit(B_READING, &b->state);
 960        smp_mb__after_clear_bit();
 961
 962        wake_up_bit(&b->state, B_READING);
 963}
 964
 965/*
 966 * A common routine for dm_bufio_new and dm_bufio_read.  Operation of these
 967 * functions is similar except that dm_bufio_new doesn't read the
 968 * buffer from the disk (assuming that the caller overwrites all the data
 969 * and uses dm_bufio_mark_buffer_dirty to write new data back).
 970 */
 971static void *new_read(struct dm_bufio_client *c, sector_t block,
 972                      enum new_flag nf, struct dm_buffer **bp)
 973{
 974        int need_submit;
 975        struct dm_buffer *b;
 976
 977        dm_bufio_lock(c);
 978        b = __bufio_new(c, block, nf, &need_submit);
 979        dm_bufio_unlock(c);
 980
 981        if (!b)
 982                return b;
 983
 984        if (need_submit)
 985                submit_io(b, READ, b->block, read_endio);
 986
 987        wait_on_bit(&b->state, B_READING, do_io_schedule, TASK_UNINTERRUPTIBLE);
 988
 989        if (b->read_error) {
 990                int error = b->read_error;
 991
 992                dm_bufio_release(b);
 993
 994                return ERR_PTR(error);
 995        }
 996
 997        *bp = b;
 998
 999        return b->data;
1000}
1001
1002void *dm_bufio_get(struct dm_bufio_client *c, sector_t block,
1003                   struct dm_buffer **bp)
1004{
1005        return new_read(c, block, NF_GET, bp);
1006}
1007EXPORT_SYMBOL_GPL(dm_bufio_get);
1008
1009void *dm_bufio_read(struct dm_bufio_client *c, sector_t block,
1010                    struct dm_buffer **bp)
1011{
1012        BUG_ON(dm_bufio_in_request());
1013
1014        return new_read(c, block, NF_READ, bp);
1015}
1016EXPORT_SYMBOL_GPL(dm_bufio_read);
1017
1018void *dm_bufio_new(struct dm_bufio_client *c, sector_t block,
1019                   struct dm_buffer **bp)
1020{
1021        BUG_ON(dm_bufio_in_request());
1022
1023        return new_read(c, block, NF_FRESH, bp);
1024}
1025EXPORT_SYMBOL_GPL(dm_bufio_new);
1026
1027void dm_bufio_prefetch(struct dm_bufio_client *c,
1028                       sector_t block, unsigned n_blocks)
1029{
1030        struct blk_plug plug;
1031
1032        blk_start_plug(&plug);
1033        dm_bufio_lock(c);
1034
1035        for (; n_blocks--; block++) {
1036                int need_submit;
1037                struct dm_buffer *b;
1038                b = __bufio_new(c, block, NF_PREFETCH, &need_submit);
1039                if (unlikely(b != NULL)) {
1040                        dm_bufio_unlock(c);
1041
1042                        if (need_submit)
1043                                submit_io(b, READ, b->block, read_endio);
1044                        dm_bufio_release(b);
1045
1046                        dm_bufio_cond_resched();
1047
1048                        if (!n_blocks)
1049                                goto flush_plug;
1050                        dm_bufio_lock(c);
1051                }
1052
1053        }
1054
1055        dm_bufio_unlock(c);
1056
1057flush_plug:
1058        blk_finish_plug(&plug);
1059}
1060EXPORT_SYMBOL_GPL(dm_bufio_prefetch);
1061
1062void dm_bufio_release(struct dm_buffer *b)
1063{
1064        struct dm_bufio_client *c = b->c;
1065
1066        dm_bufio_lock(c);
1067
1068        BUG_ON(!b->hold_count);
1069
1070        b->hold_count--;
1071        if (!b->hold_count) {
1072                wake_up(&c->free_buffer_wait);
1073
1074                /*
1075                 * If there were errors on the buffer, and the buffer is not
1076                 * to be written, free the buffer. There is no point in caching
1077                 * invalid buffer.
1078                 */
1079                if ((b->read_error || b->write_error) &&
1080                    !test_bit(B_READING, &b->state) &&
1081                    !test_bit(B_WRITING, &b->state) &&
1082                    !test_bit(B_DIRTY, &b->state)) {
1083                        __unlink_buffer(b);
1084                        __free_buffer_wake(b);
1085                }
1086        }
1087
1088        dm_bufio_unlock(c);
1089}
1090EXPORT_SYMBOL_GPL(dm_bufio_release);
1091
1092void dm_bufio_mark_buffer_dirty(struct dm_buffer *b)
1093{
1094        struct dm_bufio_client *c = b->c;
1095
1096        dm_bufio_lock(c);
1097
1098        BUG_ON(test_bit(B_READING, &b->state));
1099
1100        if (!test_and_set_bit(B_DIRTY, &b->state))
1101                __relink_lru(b, LIST_DIRTY);
1102
1103        dm_bufio_unlock(c);
1104}
1105EXPORT_SYMBOL_GPL(dm_bufio_mark_buffer_dirty);
1106
1107void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c)
1108{
1109        BUG_ON(dm_bufio_in_request());
1110
1111        dm_bufio_lock(c);
1112        __write_dirty_buffers_async(c, 0);
1113        dm_bufio_unlock(c);
1114}
1115EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers_async);
1116
1117/*
1118 * For performance, it is essential that the buffers are written asynchronously
1119 * and simultaneously (so that the block layer can merge the writes) and then
1120 * waited upon.
1121 *
1122 * Finally, we flush hardware disk cache.
1123 */
1124int dm_bufio_write_dirty_buffers(struct dm_bufio_client *c)
1125{
1126        int a, f;
1127        unsigned long buffers_processed = 0;
1128        struct dm_buffer *b, *tmp;
1129
1130        dm_bufio_lock(c);
1131        __write_dirty_buffers_async(c, 0);
1132
1133again:
1134        list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) {
1135                int dropped_lock = 0;
1136
1137                if (buffers_processed < c->n_buffers[LIST_DIRTY])
1138                        buffers_processed++;
1139
1140                BUG_ON(test_bit(B_READING, &b->state));
1141
1142                if (test_bit(B_WRITING, &b->state)) {
1143                        if (buffers_processed < c->n_buffers[LIST_DIRTY]) {
1144                                dropped_lock = 1;
1145                                b->hold_count++;
1146                                dm_bufio_unlock(c);
1147                                wait_on_bit(&b->state, B_WRITING,
1148                                            do_io_schedule,
1149                                            TASK_UNINTERRUPTIBLE);
1150                                dm_bufio_lock(c);
1151                                b->hold_count--;
1152                        } else
1153                                wait_on_bit(&b->state, B_WRITING,
1154                                            do_io_schedule,
1155                                            TASK_UNINTERRUPTIBLE);
1156                }
1157
1158                if (!test_bit(B_DIRTY, &b->state) &&
1159                    !test_bit(B_WRITING, &b->state))
1160                        __relink_lru(b, LIST_CLEAN);
1161
1162                dm_bufio_cond_resched();
1163
1164                /*
1165                 * If we dropped the lock, the list is no longer consistent,
1166                 * so we must restart the search.
1167                 *
1168                 * In the most common case, the buffer just processed is
1169                 * relinked to the clean list, so we won't loop scanning the
1170                 * same buffer again and again.
1171                 *
1172                 * This may livelock if there is another thread simultaneously
1173                 * dirtying buffers, so we count the number of buffers walked
1174                 * and if it exceeds the total number of buffers, it means that
1175                 * someone is doing some writes simultaneously with us.  In
1176                 * this case, stop, dropping the lock.
1177                 */
1178                if (dropped_lock)
1179                        goto again;
1180        }
1181        wake_up(&c->free_buffer_wait);
1182        dm_bufio_unlock(c);
1183
1184        a = xchg(&c->async_write_error, 0);
1185        f = dm_bufio_issue_flush(c);
1186        if (a)
1187                return a;
1188
1189        return f;
1190}
1191EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers);
1192
1193/*
1194 * Use dm-io to send and empty barrier flush the device.
1195 */
1196int dm_bufio_issue_flush(struct dm_bufio_client *c)
1197{
1198        struct dm_io_request io_req = {
1199                .bi_rw = REQ_FLUSH,
1200                .mem.type = DM_IO_KMEM,
1201                .mem.ptr.addr = NULL,
1202                .client = c->dm_io,
1203        };
1204        struct dm_io_region io_reg = {
1205                .bdev = c->bdev,
1206                .sector = 0,
1207                .count = 0,
1208        };
1209
1210        BUG_ON(dm_bufio_in_request());
1211
1212        return dm_io(&io_req, 1, &io_reg, NULL);
1213}
1214EXPORT_SYMBOL_GPL(dm_bufio_issue_flush);
1215
1216/*
1217 * We first delete any other buffer that may be at that new location.
1218 *
1219 * Then, we write the buffer to the original location if it was dirty.
1220 *
1221 * Then, if we are the only one who is holding the buffer, relink the buffer
1222 * in the hash queue for the new location.
1223 *
1224 * If there was someone else holding the buffer, we write it to the new
1225 * location but not relink it, because that other user needs to have the buffer
1226 * at the same place.
1227 */
1228void dm_bufio_release_move(struct dm_buffer *b, sector_t new_block)
1229{
1230        struct dm_bufio_client *c = b->c;
1231        struct dm_buffer *new;
1232
1233        BUG_ON(dm_bufio_in_request());
1234
1235        dm_bufio_lock(c);
1236
1237retry:
1238        new = __find(c, new_block);
1239        if (new) {
1240                if (new->hold_count) {
1241                        __wait_for_free_buffer(c);
1242                        goto retry;
1243                }
1244
1245                /*
1246                 * FIXME: Is there any point waiting for a write that's going
1247                 * to be overwritten in a bit?
1248                 */
1249                __make_buffer_clean(new);
1250                __unlink_buffer(new);
1251                __free_buffer_wake(new);
1252        }
1253
1254        BUG_ON(!b->hold_count);
1255        BUG_ON(test_bit(B_READING, &b->state));
1256
1257        __write_dirty_buffer(b);
1258        if (b->hold_count == 1) {
1259                wait_on_bit(&b->state, B_WRITING,
1260                            do_io_schedule, TASK_UNINTERRUPTIBLE);
1261                set_bit(B_DIRTY, &b->state);
1262                __unlink_buffer(b);
1263                __link_buffer(b, new_block, LIST_DIRTY);
1264        } else {
1265                sector_t old_block;
1266                wait_on_bit_lock(&b->state, B_WRITING,
1267                                 do_io_schedule, TASK_UNINTERRUPTIBLE);
1268                /*
1269                 * Relink buffer to "new_block" so that write_callback
1270                 * sees "new_block" as a block number.
1271                 * After the write, link the buffer back to old_block.
1272                 * All this must be done in bufio lock, so that block number
1273                 * change isn't visible to other threads.
1274                 */
1275                old_block = b->block;
1276                __unlink_buffer(b);
1277                __link_buffer(b, new_block, b->list_mode);
1278                submit_io(b, WRITE, new_block, write_endio);
1279                wait_on_bit(&b->state, B_WRITING,
1280                            do_io_schedule, TASK_UNINTERRUPTIBLE);
1281                __unlink_buffer(b);
1282                __link_buffer(b, old_block, b->list_mode);
1283        }
1284
1285        dm_bufio_unlock(c);
1286        dm_bufio_release(b);
1287}
1288EXPORT_SYMBOL_GPL(dm_bufio_release_move);
1289
1290unsigned dm_bufio_get_block_size(struct dm_bufio_client *c)
1291{
1292        return c->block_size;
1293}
1294EXPORT_SYMBOL_GPL(dm_bufio_get_block_size);
1295
1296sector_t dm_bufio_get_device_size(struct dm_bufio_client *c)
1297{
1298        return i_size_read(c->bdev->bd_inode) >>
1299                           (SECTOR_SHIFT + c->sectors_per_block_bits);
1300}
1301EXPORT_SYMBOL_GPL(dm_bufio_get_device_size);
1302
1303sector_t dm_bufio_get_block_number(struct dm_buffer *b)
1304{
1305        return b->block;
1306}
1307EXPORT_SYMBOL_GPL(dm_bufio_get_block_number);
1308
1309void *dm_bufio_get_block_data(struct dm_buffer *b)
1310{
1311        return b->data;
1312}
1313EXPORT_SYMBOL_GPL(dm_bufio_get_block_data);
1314
1315void *dm_bufio_get_aux_data(struct dm_buffer *b)
1316{
1317        return b + 1;
1318}
1319EXPORT_SYMBOL_GPL(dm_bufio_get_aux_data);
1320
1321struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b)
1322{
1323        return b->c;
1324}
1325EXPORT_SYMBOL_GPL(dm_bufio_get_client);
1326
1327static void drop_buffers(struct dm_bufio_client *c)
1328{
1329        struct dm_buffer *b;
1330        int i;
1331
1332        BUG_ON(dm_bufio_in_request());
1333
1334        /*
1335         * An optimization so that the buffers are not written one-by-one.
1336         */
1337        dm_bufio_write_dirty_buffers_async(c);
1338
1339        dm_bufio_lock(c);
1340
1341        while ((b = __get_unclaimed_buffer(c)))
1342                __free_buffer_wake(b);
1343
1344        for (i = 0; i < LIST_SIZE; i++)
1345                list_for_each_entry(b, &c->lru[i], lru_list)
1346                        DMERR("leaked buffer %llx, hold count %u, list %d",
1347                              (unsigned long long)b->block, b->hold_count, i);
1348
1349        for (i = 0; i < LIST_SIZE; i++)
1350                BUG_ON(!list_empty(&c->lru[i]));
1351
1352        dm_bufio_unlock(c);
1353}
1354
1355/*
1356 * Test if the buffer is unused and too old, and commit it.
1357 * At if noio is set, we must not do any I/O because we hold
1358 * dm_bufio_clients_lock and we would risk deadlock if the I/O gets rerouted to
1359 * different bufio client.
1360 */
1361static int __cleanup_old_buffer(struct dm_buffer *b, gfp_t gfp,
1362                                unsigned long max_jiffies)
1363{
1364        if (jiffies - b->last_accessed < max_jiffies)
1365                return 1;
1366
1367        if (!(gfp & __GFP_IO)) {
1368                if (test_bit(B_READING, &b->state) ||
1369                    test_bit(B_WRITING, &b->state) ||
1370                    test_bit(B_DIRTY, &b->state))
1371                        return 1;
1372        }
1373
1374        if (b->hold_count)
1375                return 1;
1376
1377        __make_buffer_clean(b);
1378        __unlink_buffer(b);
1379        __free_buffer_wake(b);
1380
1381        return 0;
1382}
1383
1384static void __scan(struct dm_bufio_client *c, unsigned long nr_to_scan,
1385                   struct shrink_control *sc)
1386{
1387        int l;
1388        struct dm_buffer *b, *tmp;
1389
1390        for (l = 0; l < LIST_SIZE; l++) {
1391                list_for_each_entry_safe_reverse(b, tmp, &c->lru[l], lru_list)
1392                        if (!__cleanup_old_buffer(b, sc->gfp_mask, 0) &&
1393                            !--nr_to_scan)
1394                                return;
1395                dm_bufio_cond_resched();
1396        }
1397}
1398
1399static int shrink(struct shrinker *shrinker, struct shrink_control *sc)
1400{
1401        struct dm_bufio_client *c =
1402            container_of(shrinker, struct dm_bufio_client, shrinker);
1403        unsigned long r;
1404        unsigned long nr_to_scan = sc->nr_to_scan;
1405
1406        if (sc->gfp_mask & __GFP_IO)
1407                dm_bufio_lock(c);
1408        else if (!dm_bufio_trylock(c))
1409                return !nr_to_scan ? 0 : -1;
1410
1411        if (nr_to_scan)
1412                __scan(c, nr_to_scan, sc);
1413
1414        r = c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY];
1415        if (r > INT_MAX)
1416                r = INT_MAX;
1417
1418        dm_bufio_unlock(c);
1419
1420        return r;
1421}
1422
1423/*
1424 * Create the buffering interface
1425 */
1426struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsigned block_size,
1427                                               unsigned reserved_buffers, unsigned aux_size,
1428                                               void (*alloc_callback)(struct dm_buffer *),
1429                                               void (*write_callback)(struct dm_buffer *))
1430{
1431        int r;
1432        struct dm_bufio_client *c;
1433        unsigned i;
1434
1435        BUG_ON(block_size < 1 << SECTOR_SHIFT ||
1436               (block_size & (block_size - 1)));
1437
1438        c = kmalloc(sizeof(*c), GFP_KERNEL);
1439        if (!c) {
1440                r = -ENOMEM;
1441                goto bad_client;
1442        }
1443        c->cache_hash = vmalloc(sizeof(struct hlist_head) << DM_BUFIO_HASH_BITS);
1444        if (!c->cache_hash) {
1445                r = -ENOMEM;
1446                goto bad_hash;
1447        }
1448
1449        c->bdev = bdev;
1450        c->block_size = block_size;
1451        c->sectors_per_block_bits = ffs(block_size) - 1 - SECTOR_SHIFT;
1452        c->pages_per_block_bits = (ffs(block_size) - 1 >= PAGE_SHIFT) ?
1453                                  ffs(block_size) - 1 - PAGE_SHIFT : 0;
1454        c->blocks_per_page_bits = (ffs(block_size) - 1 < PAGE_SHIFT ?
1455                                  PAGE_SHIFT - (ffs(block_size) - 1) : 0);
1456
1457        c->aux_size = aux_size;
1458        c->alloc_callback = alloc_callback;
1459        c->write_callback = write_callback;
1460
1461        for (i = 0; i < LIST_SIZE; i++) {
1462                INIT_LIST_HEAD(&c->lru[i]);
1463                c->n_buffers[i] = 0;
1464        }
1465
1466        for (i = 0; i < 1 << DM_BUFIO_HASH_BITS; i++)
1467                INIT_HLIST_HEAD(&c->cache_hash[i]);
1468
1469        mutex_init(&c->lock);
1470        INIT_LIST_HEAD(&c->reserved_buffers);
1471        c->need_reserved_buffers = reserved_buffers;
1472
1473        init_waitqueue_head(&c->free_buffer_wait);
1474        c->async_write_error = 0;
1475
1476        c->dm_io = dm_io_client_create();
1477        if (IS_ERR(c->dm_io)) {
1478                r = PTR_ERR(c->dm_io);
1479                goto bad_dm_io;
1480        }
1481
1482        mutex_lock(&dm_bufio_clients_lock);
1483        if (c->blocks_per_page_bits) {
1484                if (!DM_BUFIO_CACHE_NAME(c)) {
1485                        DM_BUFIO_CACHE_NAME(c) = kasprintf(GFP_KERNEL, "dm_bufio_cache-%u", c->block_size);
1486                        if (!DM_BUFIO_CACHE_NAME(c)) {
1487                                r = -ENOMEM;
1488                                mutex_unlock(&dm_bufio_clients_lock);
1489                                goto bad_cache;
1490                        }
1491                }
1492
1493                if (!DM_BUFIO_CACHE(c)) {
1494                        DM_BUFIO_CACHE(c) = kmem_cache_create(DM_BUFIO_CACHE_NAME(c),
1495                                                              c->block_size,
1496                                                              c->block_size, 0, NULL);
1497                        if (!DM_BUFIO_CACHE(c)) {
1498                                r = -ENOMEM;
1499                                mutex_unlock(&dm_bufio_clients_lock);
1500                                goto bad_cache;
1501                        }
1502                }
1503        }
1504        mutex_unlock(&dm_bufio_clients_lock);
1505
1506        while (c->need_reserved_buffers) {
1507                struct dm_buffer *b = alloc_buffer(c, GFP_KERNEL);
1508
1509                if (!b) {
1510                        r = -ENOMEM;
1511                        goto bad_buffer;
1512                }
1513                __free_buffer_wake(b);
1514        }
1515
1516        mutex_lock(&dm_bufio_clients_lock);
1517        dm_bufio_client_count++;
1518        list_add(&c->client_list, &dm_bufio_all_clients);
1519        __cache_size_refresh();
1520        mutex_unlock(&dm_bufio_clients_lock);
1521
1522        c->shrinker.shrink = shrink;
1523        c->shrinker.seeks = 1;
1524        c->shrinker.batch = 0;
1525        register_shrinker(&c->shrinker);
1526
1527        return c;
1528
1529bad_buffer:
1530bad_cache:
1531        while (!list_empty(&c->reserved_buffers)) {
1532                struct dm_buffer *b = list_entry(c->reserved_buffers.next,
1533                                                 struct dm_buffer, lru_list);
1534                list_del(&b->lru_list);
1535                free_buffer(b);
1536        }
1537        dm_io_client_destroy(c->dm_io);
1538bad_dm_io:
1539        vfree(c->cache_hash);
1540bad_hash:
1541        kfree(c);
1542bad_client:
1543        return ERR_PTR(r);
1544}
1545EXPORT_SYMBOL_GPL(dm_bufio_client_create);
1546
1547/*
1548 * Free the buffering interface.
1549 * It is required that there are no references on any buffers.
1550 */
1551void dm_bufio_client_destroy(struct dm_bufio_client *c)
1552{
1553        unsigned i;
1554
1555        drop_buffers(c);
1556
1557        unregister_shrinker(&c->shrinker);
1558
1559        mutex_lock(&dm_bufio_clients_lock);
1560
1561        list_del(&c->client_list);
1562        dm_bufio_client_count--;
1563        __cache_size_refresh();
1564
1565        mutex_unlock(&dm_bufio_clients_lock);
1566
1567        for (i = 0; i < 1 << DM_BUFIO_HASH_BITS; i++)
1568                BUG_ON(!hlist_empty(&c->cache_hash[i]));
1569
1570        BUG_ON(c->need_reserved_buffers);
1571
1572        while (!list_empty(&c->reserved_buffers)) {
1573                struct dm_buffer *b = list_entry(c->reserved_buffers.next,
1574                                                 struct dm_buffer, lru_list);
1575                list_del(&b->lru_list);
1576                free_buffer(b);
1577        }
1578
1579        for (i = 0; i < LIST_SIZE; i++)
1580                if (c->n_buffers[i])
1581                        DMERR("leaked buffer count %d: %ld", i, c->n_buffers[i]);
1582
1583        for (i = 0; i < LIST_SIZE; i++)
1584                BUG_ON(c->n_buffers[i]);
1585
1586        dm_io_client_destroy(c->dm_io);
1587        vfree(c->cache_hash);
1588        kfree(c);
1589}
1590EXPORT_SYMBOL_GPL(dm_bufio_client_destroy);
1591
1592static void cleanup_old_buffers(void)
1593{
1594        unsigned long max_age = dm_bufio_max_age;
1595        struct dm_bufio_client *c;
1596
1597        barrier();
1598
1599        if (max_age > ULONG_MAX / HZ)
1600                max_age = ULONG_MAX / HZ;
1601
1602        mutex_lock(&dm_bufio_clients_lock);
1603        list_for_each_entry(c, &dm_bufio_all_clients, client_list) {
1604                if (!dm_bufio_trylock(c))
1605                        continue;
1606
1607                while (!list_empty(&c->lru[LIST_CLEAN])) {
1608                        struct dm_buffer *b;
1609                        b = list_entry(c->lru[LIST_CLEAN].prev,
1610                                       struct dm_buffer, lru_list);
1611                        if (__cleanup_old_buffer(b, 0, max_age * HZ))
1612                                break;
1613                        dm_bufio_cond_resched();
1614                }
1615
1616                dm_bufio_unlock(c);
1617                dm_bufio_cond_resched();
1618        }
1619        mutex_unlock(&dm_bufio_clients_lock);
1620}
1621
1622static struct workqueue_struct *dm_bufio_wq;
1623static struct delayed_work dm_bufio_work;
1624
1625static void work_fn(struct work_struct *w)
1626{
1627        cleanup_old_buffers();
1628
1629        queue_delayed_work(dm_bufio_wq, &dm_bufio_work,
1630                           DM_BUFIO_WORK_TIMER_SECS * HZ);
1631}
1632
1633/*----------------------------------------------------------------
1634 * Module setup
1635 *--------------------------------------------------------------*/
1636
1637/*
1638 * This is called only once for the whole dm_bufio module.
1639 * It initializes memory limit.
1640 */
1641static int __init dm_bufio_init(void)
1642{
1643        __u64 mem;
1644
1645        memset(&dm_bufio_caches, 0, sizeof dm_bufio_caches);
1646        memset(&dm_bufio_cache_names, 0, sizeof dm_bufio_cache_names);
1647
1648        mem = (__u64)((totalram_pages - totalhigh_pages) *
1649                      DM_BUFIO_MEMORY_PERCENT / 100) << PAGE_SHIFT;
1650
1651        if (mem > ULONG_MAX)
1652                mem = ULONG_MAX;
1653
1654#ifdef CONFIG_MMU
1655        /*
1656         * Get the size of vmalloc space the same way as VMALLOC_TOTAL
1657         * in fs/proc/internal.h
1658         */
1659        if (mem > (VMALLOC_END - VMALLOC_START) * DM_BUFIO_VMALLOC_PERCENT / 100)
1660                mem = (VMALLOC_END - VMALLOC_START) * DM_BUFIO_VMALLOC_PERCENT / 100;
1661#endif
1662
1663        dm_bufio_default_cache_size = mem;
1664
1665        mutex_lock(&dm_bufio_clients_lock);
1666        __cache_size_refresh();
1667        mutex_unlock(&dm_bufio_clients_lock);
1668
1669        dm_bufio_wq = create_singlethread_workqueue("dm_bufio_cache");
1670        if (!dm_bufio_wq)
1671                return -ENOMEM;
1672
1673        INIT_DELAYED_WORK(&dm_bufio_work, work_fn);
1674        queue_delayed_work(dm_bufio_wq, &dm_bufio_work,
1675                           DM_BUFIO_WORK_TIMER_SECS * HZ);
1676
1677        return 0;
1678}
1679
1680/*
1681 * This is called once when unloading the dm_bufio module.
1682 */
1683static void __exit dm_bufio_exit(void)
1684{
1685        int bug = 0;
1686        int i;
1687
1688        cancel_delayed_work_sync(&dm_bufio_work);
1689        destroy_workqueue(dm_bufio_wq);
1690
1691        for (i = 0; i < ARRAY_SIZE(dm_bufio_caches); i++) {
1692                struct kmem_cache *kc = dm_bufio_caches[i];
1693
1694                if (kc)
1695                        kmem_cache_destroy(kc);
1696        }
1697
1698        for (i = 0; i < ARRAY_SIZE(dm_bufio_cache_names); i++)
1699                kfree(dm_bufio_cache_names[i]);
1700
1701        if (dm_bufio_client_count) {
1702                DMCRIT("%s: dm_bufio_client_count leaked: %d",
1703                        __func__, dm_bufio_client_count);
1704                bug = 1;
1705        }
1706
1707        if (dm_bufio_current_allocated) {
1708                DMCRIT("%s: dm_bufio_current_allocated leaked: %lu",
1709                        __func__, dm_bufio_current_allocated);
1710                bug = 1;
1711        }
1712
1713        if (dm_bufio_allocated_get_free_pages) {
1714                DMCRIT("%s: dm_bufio_allocated_get_free_pages leaked: %lu",
1715                       __func__, dm_bufio_allocated_get_free_pages);
1716                bug = 1;
1717        }
1718
1719        if (dm_bufio_allocated_vmalloc) {
1720                DMCRIT("%s: dm_bufio_vmalloc leaked: %lu",
1721                       __func__, dm_bufio_allocated_vmalloc);
1722                bug = 1;
1723        }
1724
1725        if (bug)
1726                BUG();
1727}
1728
1729module_init(dm_bufio_init)
1730module_exit(dm_bufio_exit)
1731
1732module_param_named(max_cache_size_bytes, dm_bufio_cache_size, ulong, S_IRUGO | S_IWUSR);
1733MODULE_PARM_DESC(max_cache_size_bytes, "Size of metadata cache");
1734
1735module_param_named(max_age_seconds, dm_bufio_max_age, uint, S_IRUGO | S_IWUSR);
1736MODULE_PARM_DESC(max_age_seconds, "Max age of a buffer in seconds");
1737
1738module_param_named(peak_allocated_bytes, dm_bufio_peak_allocated, ulong, S_IRUGO | S_IWUSR);
1739MODULE_PARM_DESC(peak_allocated_bytes, "Tracks the maximum allocated memory");
1740
1741module_param_named(allocated_kmem_cache_bytes, dm_bufio_allocated_kmem_cache, ulong, S_IRUGO);
1742MODULE_PARM_DESC(allocated_kmem_cache_bytes, "Memory allocated with kmem_cache_alloc");
1743
1744module_param_named(allocated_get_free_pages_bytes, dm_bufio_allocated_get_free_pages, ulong, S_IRUGO);
1745MODULE_PARM_DESC(allocated_get_free_pages_bytes, "Memory allocated with get_free_pages");
1746
1747module_param_named(allocated_vmalloc_bytes, dm_bufio_allocated_vmalloc, ulong, S_IRUGO);
1748MODULE_PARM_DESC(allocated_vmalloc_bytes, "Memory allocated with vmalloc");
1749
1750module_param_named(current_allocated_bytes, dm_bufio_current_allocated, ulong, S_IRUGO);
1751MODULE_PARM_DESC(current_allocated_bytes, "Memory currently used by the cache");
1752
1753MODULE_AUTHOR("Mikulas Patocka <dm-devel@redhat.com>");
1754MODULE_DESCRIPTION(DM_NAME " buffered I/O library");
1755MODULE_LICENSE("GPL");
1756
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