drivers/md/dm-bufio.c

   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/sched/mm.h>
  15 #include <linux/jiffies.h>
  16 #include <linux/vmalloc.h>
  17 #include <linux/shrinker.h>
  18 #include <linux/module.h>
  19 #include <linux/rbtree.h>
  20 #include <linux/stacktrace.h>
  21
  22 #define DM_MSG_PREFIX "bufio"
  23
  24 /*
  25  * Memory management policy:
  26  *      Limit the number of buffers to DM_BUFIO_MEMORY_PERCENT of main memory
  27  *      or DM_BUFIO_VMALLOC_PERCENT of vmalloc memory (whichever is lower).
  28  *      Always allocate at least DM_BUFIO_MIN_BUFFERS buffers.
  29  *      Start background writeback when there are DM_BUFIO_WRITEBACK_PERCENT
  30  *      dirty buffers.
  31  */
  32 #define DM_BUFIO_MIN_BUFFERS            8
  33
  34 #define DM_BUFIO_MEMORY_PERCENT         2
  35 #define DM_BUFIO_VMALLOC_PERCENT        25
  36 #define DM_BUFIO_WRITEBACK_PERCENT      75
  37
  38 /*
  39  * Check buffer ages in this interval (seconds)
  40  */
  41 #define DM_BUFIO_WORK_TIMER_SECS        30
  42
  43 /*
  44  * Free buffers when they are older than this (seconds)
  45  */
  46 #define DM_BUFIO_DEFAULT_AGE_SECS       300
  47
  48 /*
  49  * The nr of bytes of cached data to keep around.
  50  */
  51 #define DM_BUFIO_DEFAULT_RETAIN_BYTES   (256 * 1024)
  52
  53 /*
  54  * The number of bvec entries that are embedded directly in the buffer.
  55  * If the chunk size is larger, dm-io is used to do the io.
  56  */
  57 #define DM_BUFIO_INLINE_VECS            16
  58
  59 /*
  60  * Don't try to use kmem_cache_alloc for blocks larger than this.
  61  * For explanation, see alloc_buffer_data below.
  62  */
  63 #define DM_BUFIO_BLOCK_SIZE_SLAB_LIMIT  (PAGE_SIZE >> 1)
  64 #define DM_BUFIO_BLOCK_SIZE_GFP_LIMIT   (PAGE_SIZE << (MAX_ORDER - 1))
  65
  66 /*
  67  * Align buffer writes to this boundary.
  68  * Tests show that SSDs have the highest IOPS when using 4k writes.
  69  */
  70 #define DM_BUFIO_WRITE_ALIGN            4096
  71
  72 /*
  73  * dm_buffer->list_mode
  74  */
  75 #define LIST_CLEAN      0
  76 #define LIST_DIRTY      1
  77 #define LIST_SIZE       2
  78
  79 /*
  80  * Linking of buffers:
  81  *      All buffers are linked to cache_hash with their hash_list field.
  82  *
  83  *      Clean buffers that are not being written (B_WRITING not set)
  84  *      are linked to lru[LIST_CLEAN] with their lru_list field.
  85  *
  86  *      Dirty and clean buffers that are being written are linked to
  87  *      lru[LIST_DIRTY] with their lru_list field. When the write
  88  *      finishes, the buffer cannot be relinked immediately (because we
  89  *      are in an interrupt context and relinking requires process
  90  *      context), so some clean-not-writing buffers can be held on
  91  *      dirty_lru too.  They are later added to lru in the process
  92  *      context.
  93  */
  94 struct dm_bufio_client {
  95         struct mutex lock;
  96
  97         struct list_head lru[LIST_SIZE];
  98         unsigned long n_buffers[LIST_SIZE];
  99
 100         struct block_device *bdev;
 101         unsigned block_size;
 102         unsigned char sectors_per_block_bits;
 103         unsigned char pages_per_block_bits;
 104         unsigned char blocks_per_page_bits;
 105         unsigned aux_size;
 106         void (*alloc_callback)(struct dm_buffer *);
 107         void (*write_callback)(struct dm_buffer *);
 108
 109         struct dm_io_client *dm_io;
 110
 111         struct list_head reserved_buffers;
 112         unsigned need_reserved_buffers;
 113
 114         unsigned minimum_buffers;
 115
 116         struct rb_root buffer_tree;
 117         wait_queue_head_t free_buffer_wait;
 118
 119         sector_t start;
 120
 121         int async_write_error;
 122
 123         struct list_head client_list;
 124         struct shrinker shrinker;
 125 };
 126
 127 /*
 128  * Buffer state bits.
 129  */
 130 #define B_READING       0
 131 #define B_WRITING       1
 132 #define B_DIRTY         2
 133
 134 /*
 135  * Describes how the block was allocated:
 136  * kmem_cache_alloc(), __get_free_pages() or vmalloc().
 137  * See the comment at alloc_buffer_data.
 138  */
 139 enum data_mode {
 140         DATA_MODE_SLAB = 0,
 141         DATA_MODE_GET_FREE_PAGES = 1,
 142         DATA_MODE_VMALLOC = 2,
 143         DATA_MODE_LIMIT = 3
 144 };
 145
 146 struct dm_buffer {
 147         struct rb_node node;
 148         struct list_head lru_list;
 149         sector_t block;
 150         void *data;
 151         enum data_mode data_mode;
 152         unsigned char list_mode;                /* LIST_* */
 153         unsigned hold_count;
 154         blk_status_t read_error;
 155         blk_status_t write_error;
 156         unsigned long state;
 157         unsigned long last_accessed;
 158         unsigned dirty_start;
 159         unsigned dirty_end;
 160         unsigned write_start;
 161         unsigned write_end;
 162         struct dm_bufio_client *c;
 163         struct list_head write_list;
 164         struct bio bio;
 165         struct bio_vec bio_vec[DM_BUFIO_INLINE_VECS];
 166 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
 167 #define MAX_STACK 10
 168         struct stack_trace stack_trace;
 169         unsigned long stack_entries[MAX_STACK];
 170 #endif
 171 };
 172
 173 /*----------------------------------------------------------------*/
 174
 175 static struct kmem_cache *dm_bufio_caches[PAGE_SHIFT - SECTOR_SHIFT];
 176 static char *dm_bufio_cache_names[PAGE_SHIFT - SECTOR_SHIFT];
 177
 178 static inline int dm_bufio_cache_index(struct dm_bufio_client *c)
 179 {
 180         unsigned ret = c->blocks_per_page_bits - 1;
 181
 182         BUG_ON(ret >= ARRAY_SIZE(dm_bufio_caches));
 183
 184         return ret;
 185 }
 186
 187 #define DM_BUFIO_CACHE(c)       (dm_bufio_caches[dm_bufio_cache_index(c)])
 188 #define DM_BUFIO_CACHE_NAME(c)  (dm_bufio_cache_names[dm_bufio_cache_index(c)])
 189
 190 #define dm_bufio_in_request()   (!!current->bio_list)
 191
 192 static void dm_bufio_lock(struct dm_bufio_client *c)
 193 {
 194         mutex_lock_nested(&c->lock, dm_bufio_in_request());
 195 }
 196
 197 static int dm_bufio_trylock(struct dm_bufio_client *c)
 198 {
 199         return mutex_trylock(&c->lock);
 200 }
 201
 202 static void dm_bufio_unlock(struct dm_bufio_client *c)
 203 {
 204         mutex_unlock(&c->lock);
 205 }
 206
 207 /*----------------------------------------------------------------*/
 208
 209 /*
 210  * Default cache size: available memory divided by the ratio.
 211  */
 212 static unsigned long dm_bufio_default_cache_size;
 213
 214 /*
 215  * Total cache size set by the user.
 216  */
 217 static unsigned long dm_bufio_cache_size;
 218
 219 /*
 220  * A copy of dm_bufio_cache_size because dm_bufio_cache_size can change
 221  * at any time.  If it disagrees, the user has changed cache size.
 222  */
 223 static unsigned long dm_bufio_cache_size_latch;
 224
 225 static DEFINE_SPINLOCK(param_spinlock);
 226
 227 /*
 228  * Buffers are freed after this timeout
 229  */
 230 static unsigned dm_bufio_max_age = DM_BUFIO_DEFAULT_AGE_SECS;
 231 static unsigned long dm_bufio_retain_bytes = DM_BUFIO_DEFAULT_RETAIN_BYTES;
 232
 233 static unsigned long dm_bufio_peak_allocated;
 234 static unsigned long dm_bufio_allocated_kmem_cache;
 235 static unsigned long dm_bufio_allocated_get_free_pages;
 236 static unsigned long dm_bufio_allocated_vmalloc;
 237 static unsigned long dm_bufio_current_allocated;
 238
 239 /*----------------------------------------------------------------*/
 240
 241 /*
 242  * Per-client cache: dm_bufio_cache_size / dm_bufio_client_count
 243  */
 244 static unsigned long dm_bufio_cache_size_per_client;
 245
 246 /*
 247  * The current number of clients.
 248  */
 249 static int dm_bufio_client_count;
 250
 251 /*
 252  * The list of all clients.
 253  */
 254 static LIST_HEAD(dm_bufio_all_clients);
 255
 256 /*
 257  * This mutex protects dm_bufio_cache_size_latch,
 258  * dm_bufio_cache_size_per_client and dm_bufio_client_count
 259  */
 260 static DEFINE_MUTEX(dm_bufio_clients_lock);
 261
 262 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
 263 static void buffer_record_stack(struct dm_buffer *b)
 264 {
 265         b->stack_trace.nr_entries = 0;
 266         b->stack_trace.max_entries = MAX_STACK;
 267         b->stack_trace.entries = b->stack_entries;
 268         b->stack_trace.skip = 2;
 269         save_stack_trace(&b->stack_trace);
 270 }
 271 #endif
 272
 273 /*----------------------------------------------------------------
 274  * A red/black tree acts as an index for all the buffers.
 275  *--------------------------------------------------------------*/
 276 static struct dm_buffer *__find(struct dm_bufio_client *c, sector_t block)
 277 {
 278         struct rb_node *n = c->buffer_tree.rb_node;
 279         struct dm_buffer *b;
 280
 281         while (n) {
 282                 b = container_of(n, struct dm_buffer, node);
 283
 284                 if (b->block == block)
 285                         return b;
 286
 287                 n = (b->block < block) ? n->rb_left : n->rb_right;
 288         }
 289
 290         return NULL;
 291 }
 292
 293 static void __insert(struct dm_bufio_client *c, struct dm_buffer *b)
 294 {
 295         struct rb_node **new = &c->buffer_tree.rb_node, *parent = NULL;
 296         struct dm_buffer *found;
 297
 298         while (*new) {
 299                 found = container_of(*new, struct dm_buffer, node);
 300
 301                 if (found->block == b->block) {
 302                         BUG_ON(found != b);
 303                         return;
 304                 }
 305
 306                 parent = *new;
 307                 new = (found->block < b->block) ?
 308                         &((*new)->rb_left) : &((*new)->rb_right);
 309         }
 310
 311         rb_link_node(&b->node, parent, new);
 312         rb_insert_color(&b->node, &c->buffer_tree);
 313 }
 314
 315 static void __remove(struct dm_bufio_client *c, struct dm_buffer *b)
 316 {
 317         rb_erase(&b->node, &c->buffer_tree);
 318 }
 319
 320 /*----------------------------------------------------------------*/
 321
 322 static void adjust_total_allocated(enum data_mode data_mode, long diff)
 323 {
 324         static unsigned long * const class_ptr[DATA_MODE_LIMIT] = {
 325                 &dm_bufio_allocated_kmem_cache,
 326                 &dm_bufio_allocated_get_free_pages,
 327                 &dm_bufio_allocated_vmalloc,
 328         };
 329
 330         spin_lock(&param_spinlock);
 331
 332         *class_ptr[data_mode] += diff;
 333
 334         dm_bufio_current_allocated += diff;
 335
 336         if (dm_bufio_current_allocated > dm_bufio_peak_allocated)
 337                 dm_bufio_peak_allocated = dm_bufio_current_allocated;
 338
 339         spin_unlock(&param_spinlock);
 340 }
 341
 342 /*
 343  * Change the number of clients and recalculate per-client limit.
 344  */
 345 static void __cache_size_refresh(void)
 346 {
 347         BUG_ON(!mutex_is_locked(&dm_bufio_clients_lock));
 348         BUG_ON(dm_bufio_client_count < 0);
 349
 350         dm_bufio_cache_size_latch = READ_ONCE(dm_bufio_cache_size);
 351
 352         /*
 353          * Use default if set to 0 and report the actual cache size used.
 354          */
 355         if (!dm_bufio_cache_size_latch) {
 356                 (void)cmpxchg(&dm_bufio_cache_size, 0,
 357                               dm_bufio_default_cache_size);
 358                 dm_bufio_cache_size_latch = dm_bufio_default_cache_size;
 359         }
 360
 361         dm_bufio_cache_size_per_client = dm_bufio_cache_size_latch /
 362                                          (dm_bufio_client_count ? : 1);
 363 }
 364
 365 /*
 366  * Allocating buffer data.
 367  *
 368  * Small buffers are allocated with kmem_cache, to use space optimally.
 369  *
 370  * For large buffers, we choose between get_free_pages and vmalloc.
 371  * Each has advantages and disadvantages.
 372  *
 373  * __get_free_pages can randomly fail if the memory is fragmented.
 374  * __vmalloc won't randomly fail, but vmalloc space is limited (it may be
 375  * as low as 128M) so using it for caching is not appropriate.
 376  *
 377  * If the allocation may fail we use __get_free_pages. Memory fragmentation
 378  * won't have a fatal effect here, but it just causes flushes of some other
 379  * buffers and more I/O will be performed. Don't use __get_free_pages if it
 380  * always fails (i.e. order >= MAX_ORDER).
 381  *
 382  * If the allocation shouldn't fail we use __vmalloc. This is only for the
 383  * initial reserve allocation, so there's no risk of wasting all vmalloc
 384  * space.
 385  */
 386 static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask,
 387                                enum data_mode *data_mode)
 388 {
 389         unsigned noio_flag;
 390         void *ptr;
 391
 392         if (c->block_size <= DM_BUFIO_BLOCK_SIZE_SLAB_LIMIT) {
 393                 *data_mode = DATA_MODE_SLAB;
 394                 return kmem_cache_alloc(DM_BUFIO_CACHE(c), gfp_mask);
 395         }
 396
 397         if (c->block_size <= DM_BUFIO_BLOCK_SIZE_GFP_LIMIT &&
 398             gfp_mask & __GFP_NORETRY) {
 399                 *data_mode = DATA_MODE_GET_FREE_PAGES;
 400                 return (void *)__get_free_pages(gfp_mask,
 401                                                 c->pages_per_block_bits);
 402         }
 403
 404         *data_mode = DATA_MODE_VMALLOC;
 405
 406         /*
 407          * __vmalloc allocates the data pages and auxiliary structures with
 408          * gfp_flags that were specified, but pagetables are always allocated
 409          * with GFP_KERNEL, no matter what was specified as gfp_mask.
 410          *
 411          * Consequently, we must set per-process flag PF_MEMALLOC_NOIO so that
 412          * all allocations done by this process (including pagetables) are done
 413          * as if GFP_NOIO was specified.
 414          */
 415
 416         if (gfp_mask & __GFP_NORETRY)
 417                 noio_flag = memalloc_noio_save();
 418
 419         ptr = __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL);
 420
 421         if (gfp_mask & __GFP_NORETRY)
 422                 memalloc_noio_restore(noio_flag);
 423
 424         return ptr;
 425 }
 426
 427 /*
 428  * Free buffer's data.
 429  */
 430 static void free_buffer_data(struct dm_bufio_client *c,
 431                              void *data, enum data_mode data_mode)
 432 {
 433         switch (data_mode) {
 434         case DATA_MODE_SLAB:
 435                 kmem_cache_free(DM_BUFIO_CACHE(c), data);
 436                 break;
 437
 438         case DATA_MODE_GET_FREE_PAGES:
 439                 free_pages((unsigned long)data, c->pages_per_block_bits);
 440                 break;
 441
 442         case DATA_MODE_VMALLOC:
 443                 vfree(data);
 444                 break;
 445
 446         default:
 447                 DMCRIT("dm_bufio_free_buffer_data: bad data mode: %d",
 448                        data_mode);
 449                 BUG();
 450         }
 451 }
 452
 453 /*
 454  * Allocate buffer and its data.
 455  */
 456 static struct dm_buffer *alloc_buffer(struct dm_bufio_client *c, gfp_t gfp_mask)
 457 {
 458         struct dm_buffer *b = kmalloc(sizeof(struct dm_buffer) + c->aux_size,
 459                                       gfp_mask);
 460
 461         if (!b)
 462                 return NULL;
 463
 464         b->c = c;
 465
 466         b->data = alloc_buffer_data(c, gfp_mask, &b->data_mode);
 467         if (!b->data) {
 468                 kfree(b);
 469                 return NULL;
 470         }
 471
 472         adjust_total_allocated(b->data_mode, (long)c->block_size);
 473
 474 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
 475         memset(&b->stack_trace, 0, sizeof(b->stack_trace));
 476 #endif
 477         return b;
 478 }
 479
 480 /*
 481  * Free buffer and its data.
 482  */
 483 static void free_buffer(struct dm_buffer *b)
 484 {
 485         struct dm_bufio_client *c = b->c;
 486
 487         adjust_total_allocated(b->data_mode, -(long)c->block_size);
 488
 489         free_buffer_data(c, b->data, b->data_mode);
 490         kfree(b);
 491 }
 492
 493 /*
 494  * Link buffer to the hash list and clean or dirty queue.
 495  */
 496 static void __link_buffer(struct dm_buffer *b, sector_t block, int dirty)
 497 {
 498         struct dm_bufio_client *c = b->c;
 499
 500         c->n_buffers[dirty]++;
 501         b->block = block;
 502         b->list_mode = dirty;
 503         list_add(&b->lru_list, &c->lru[dirty]);
 504         __insert(b->c, b);
 505         b->last_accessed = jiffies;
 506 }
 507
 508 /*
 509  * Unlink buffer from the hash list and dirty or clean queue.
 510  */
 511 static void __unlink_buffer(struct dm_buffer *b)
 512 {
 513         struct dm_bufio_client *c = b->c;
 514
 515         BUG_ON(!c->n_buffers[b->list_mode]);
 516
 517         c->n_buffers[b->list_mode]--;
 518         __remove(b->c, b);
 519         list_del(&b->lru_list);
 520 }
 521
 522 /*
 523  * Place the buffer to the head of dirty or clean LRU queue.
 524  */
 525 static void __relink_lru(struct dm_buffer *b, int dirty)
 526 {
 527         struct dm_bufio_client *c = b->c;
 528
 529         BUG_ON(!c->n_buffers[b->list_mode]);
 530
 531         c->n_buffers[b->list_mode]--;
 532         c->n_buffers[dirty]++;
 533         b->list_mode = dirty;
 534         list_move(&b->lru_list, &c->lru[dirty]);
 535         b->last_accessed = jiffies;
 536 }
 537
 538 /*----------------------------------------------------------------
 539  * Submit I/O on the buffer.
 540  *
 541  * Bio interface is faster but it has some problems:
 542  *      the vector list is limited (increasing this limit increases
 543  *      memory-consumption per buffer, so it is not viable);
 544  *
 545  *      the memory must be direct-mapped, not vmalloced;
 546  *
 547  *      the I/O driver can reject requests spuriously if it thinks that
 548  *      the requests are too big for the device or if they cross a
 549  *      controller-defined memory boundary.
 550  *
 551  * If the buffer is small enough (up to DM_BUFIO_INLINE_VECS pages) and
 552  * it is not vmalloced, try using the bio interface.
 553  *
 554  * If the buffer is big, if it is vmalloced or if the underlying device
 555  * rejects the bio because it is too large, use dm-io layer to do the I/O.
 556  * The dm-io layer splits the I/O into multiple requests, avoiding the above
 557  * shortcomings.
 558  *--------------------------------------------------------------*/
 559
 560 /*
 561  * dm-io completion routine. It just calls b->bio.bi_end_io, pretending
 562  * that the request was handled directly with bio interface.
 563  */
 564 static void dmio_complete(unsigned long error, void *context)
 565 {
 566         struct dm_buffer *b = context;
 567
 568         b->bio.bi_status = error ? BLK_STS_IOERR : 0;
 569         b->bio.bi_end_io(&b->bio);
 570 }
 571
 572 static void use_dmio(struct dm_buffer *b, int rw, sector_t sector,
 573                      unsigned n_sectors, unsigned offset, bio_end_io_t *end_io)
 574 {
 575         int r;
 576         struct dm_io_request io_req = {
 577                 .bi_op = rw,
 578                 .bi_op_flags = 0,
 579                 .notify.fn = dmio_complete,
 580                 .notify.context = b,
 581                 .client = b->c->dm_io,
 582         };
 583         struct dm_io_region region = {
 584                 .bdev = b->c->bdev,
 585                 .sector = sector,
 586                 .count = n_sectors,
 587         };
 588
 589         if (b->data_mode != DATA_MODE_VMALLOC) {
 590                 io_req.mem.type = DM_IO_KMEM;
 591                 io_req.mem.ptr.addr = (char *)b->data + offset;
 592         } else {
 593                 io_req.mem.type = DM_IO_VMA;
 594                 io_req.mem.ptr.vma = (char *)b->data + offset;
 595         }
 596
 597         b->bio.bi_end_io = end_io;
 598
 599         r = dm_io(&io_req, 1, &region, NULL);
 600         if (r) {
 601                 b->bio.bi_status = errno_to_blk_status(r);
 602                 end_io(&b->bio);
 603         }
 604 }
 605
 606 static void inline_endio(struct bio *bio)
 607 {
 608         bio_end_io_t *end_fn = bio->bi_private;
 609         blk_status_t status = bio->bi_status;
 610
 611         /*
 612          * Reset the bio to free any attached resources
 613          * (e.g. bio integrity profiles).
 614          */
 615         bio_reset(bio);
 616
 617         bio->bi_status = status;
 618         end_fn(bio);
 619 }
 620
 621 static void use_inline_bio(struct dm_buffer *b, int rw, sector_t sector,
 622                            unsigned n_sectors, unsigned offset, bio_end_io_t *end_io)
 623 {
 624         char *ptr;
 625         unsigned len;
 626
 627         bio_init(&b->bio, b->bio_vec, DM_BUFIO_INLINE_VECS);
 628         b->bio.bi_iter.bi_sector = sector;
 629         bio_set_dev(&b->bio, b->c->bdev);
 630         b->bio.bi_end_io = inline_endio;
 631         /*
 632          * Use of .bi_private isn't a problem here because
 633          * the dm_buffer's inline bio is local to bufio.
 634          */
 635         b->bio.bi_private = end_io;
 636         bio_set_op_attrs(&b->bio, rw, 0);
 637
 638         ptr = (char *)b->data + offset;
 639         len = n_sectors << SECTOR_SHIFT;
 640
 641         do {
 642                 unsigned this_step = min((unsigned)(PAGE_SIZE - offset_in_page(ptr)), len);
 643                 if (!bio_add_page(&b->bio, virt_to_page(ptr), this_step,
 644                                   offset_in_page(ptr))) {
 645                         BUG_ON(b->c->block_size <= PAGE_SIZE);
 646                         use_dmio(b, rw, sector, n_sectors, offset, end_io);
 647                         return;
 648                 }
 649
 650                 len -= this_step;
 651                 ptr += this_step;
 652         } while (len > 0);
 653
 654         submit_bio(&b->bio);
 655 }
 656
 657 static void submit_io(struct dm_buffer *b, int rw, bio_end_io_t *end_io)
 658 {
 659         unsigned n_sectors;
 660         sector_t sector;
 661         unsigned offset, end;
 662
 663         sector = (b->block << b->c->sectors_per_block_bits) + b->c->start;
 664
 665         if (rw != WRITE) {
 666                 n_sectors = 1 << b->c->sectors_per_block_bits;
 667                 offset = 0;
 668         } else {
 669                 if (b->c->write_callback)
 670                         b->c->write_callback(b);
 671                 offset = b->write_start;
 672                 end = b->write_end;
 673                 offset &= -DM_BUFIO_WRITE_ALIGN;
 674                 end += DM_BUFIO_WRITE_ALIGN - 1;
 675                 end &= -DM_BUFIO_WRITE_ALIGN;
 676                 if (unlikely(end > b->c->block_size))
 677                         end = b->c->block_size;
 678
 679                 sector += offset >> SECTOR_SHIFT;
 680                 n_sectors = (end - offset) >> SECTOR_SHIFT;
 681         }
 682
 683         if (n_sectors <= ((DM_BUFIO_INLINE_VECS * PAGE_SIZE) >> SECTOR_SHIFT) &&
 684             b->data_mode != DATA_MODE_VMALLOC)
 685                 use_inline_bio(b, rw, sector, n_sectors, offset, end_io);
 686         else
 687                 use_dmio(b, rw, sector, n_sectors, offset, end_io);
 688 }
 689
 690 /*----------------------------------------------------------------
 691  * Writing dirty buffers
 692  *--------------------------------------------------------------*/
 693
 694 /*
 695  * The endio routine for write.
 696  *
 697  * Set the error, clear B_WRITING bit and wake anyone who was waiting on
 698  * it.
 699  */
 700 static void write_endio(struct bio *bio)
 701 {
 702         struct dm_buffer *b = container_of(bio, struct dm_buffer, bio);
 703
 704         b->write_error = bio->bi_status;
 705         if (unlikely(bio->bi_status)) {
 706                 struct dm_bufio_client *c = b->c;
 707
 708                 (void)cmpxchg(&c->async_write_error, 0,
 709                                 blk_status_to_errno(bio->bi_status));
 710         }
 711
 712         BUG_ON(!test_bit(B_WRITING, &b->state));
 713
 714         smp_mb__before_atomic();
 715         clear_bit(B_WRITING, &b->state);
 716         smp_mb__after_atomic();
 717
 718         wake_up_bit(&b->state, B_WRITING);
 719 }
 720
 721 /*
 722  * Initiate a write on a dirty buffer, but don't wait for it.
 723  *
 724  * - If the buffer is not dirty, exit.
 725  * - If there some previous write going on, wait for it to finish (we can't
 726  *   have two writes on the same buffer simultaneously).
 727  * - Submit our write and don't wait on it. We set B_WRITING indicating
 728  *   that there is a write in progress.
 729  */
 730 static void __write_dirty_buffer(struct dm_buffer *b,
 731                                  struct list_head *write_list)
 732 {
 733         if (!test_bit(B_DIRTY, &b->state))
 734                 return;
 735
 736         clear_bit(B_DIRTY, &b->state);
 737         wait_on_bit_lock_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
 738
 739         b->write_start = b->dirty_start;
 740         b->write_end = b->dirty_end;
 741
 742         if (!write_list)
 743                 submit_io(b, WRITE, write_endio);
 744         else
 745                 list_add_tail(&b->write_list, write_list);
 746 }
 747
 748 static void __flush_write_list(struct list_head *write_list)
 749 {
 750         struct blk_plug plug;
 751         blk_start_plug(&plug);
 752         while (!list_empty(write_list)) {
 753                 struct dm_buffer *b =
 754                         list_entry(write_list->next, struct dm_buffer, write_list);
 755                 list_del(&b->write_list);
 756                 submit_io(b, WRITE, write_endio);
 757                 cond_resched();
 758         }
 759         blk_finish_plug(&plug);
 760 }
 761
 762 /*
 763  * Wait until any activity on the buffer finishes.  Possibly write the
 764  * buffer if it is dirty.  When this function finishes, there is no I/O
 765  * running on the buffer and the buffer is not dirty.
 766  */
 767 static void __make_buffer_clean(struct dm_buffer *b)
 768 {
 769         BUG_ON(b->hold_count);
 770
 771         if (!b->state)  /* fast case */
 772                 return;
 773
 774         wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
 775         __write_dirty_buffer(b, NULL);
 776         wait_on_bit_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
 777 }
 778
 779 /*
 780  * Find some buffer that is not held by anybody, clean it, unlink it and
 781  * return it.
 782  */
 783 static struct dm_buffer *__get_unclaimed_buffer(struct dm_bufio_client *c)
 784 {
 785         struct dm_buffer *b;
 786
 787         list_for_each_entry_reverse(b, &c->lru[LIST_CLEAN], lru_list) {
 788                 BUG_ON(test_bit(B_WRITING, &b->state));
 789                 BUG_ON(test_bit(B_DIRTY, &b->state));
 790
 791                 if (!b->hold_count) {
 792                         __make_buffer_clean(b);
 793                         __unlink_buffer(b);
 794                         return b;
 795                 }
 796                 cond_resched();
 797         }
 798
 799         list_for_each_entry_reverse(b, &c->lru[LIST_DIRTY], lru_list) {
 800                 BUG_ON(test_bit(B_READING, &b->state));
 801
 802                 if (!b->hold_count) {
 803                         __make_buffer_clean(b);
 804                         __unlink_buffer(b);
 805                         return b;
 806                 }
 807                 cond_resched();
 808         }
 809
 810         return NULL;
 811 }
 812
 813 /*
 814  * Wait until some other threads free some buffer or release hold count on
 815  * some buffer.
 816  *
 817  * This function is entered with c->lock held, drops it and regains it
 818  * before exiting.
 819  */
 820 static void __wait_for_free_buffer(struct dm_bufio_client *c)
 821 {
 822         DECLARE_WAITQUEUE(wait, current);
 823
 824         add_wait_queue(&c->free_buffer_wait, &wait);
 825         set_current_state(TASK_UNINTERRUPTIBLE);
 826         dm_bufio_unlock(c);
 827
 828         io_schedule();
 829
 830         remove_wait_queue(&c->free_buffer_wait, &wait);
 831
 832         dm_bufio_lock(c);
 833 }
 834
 835 enum new_flag {
 836         NF_FRESH = 0,
 837         NF_READ = 1,
 838         NF_GET = 2,
 839         NF_PREFETCH = 3
 840 };
 841
 842 /*
 843  * Allocate a new buffer. If the allocation is not possible, wait until
 844  * some other thread frees a buffer.
 845  *
 846  * May drop the lock and regain it.
 847  */
 848 static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client *c, enum new_flag nf)
 849 {
 850         struct dm_buffer *b;
 851         bool tried_noio_alloc = false;
 852
 853         /*
 854          * dm-bufio is resistant to allocation failures (it just keeps
 855          * one buffer reserved in cases all the allocations fail).
 856          * So set flags to not try too hard:
 857          *      GFP_NOWAIT: don't wait; if we need to sleep we'll release our
 858          *                  mutex and wait ourselves.
 859          *      __GFP_NORETRY: don't retry and rather return failure
 860          *      __GFP_NOMEMALLOC: don't use emergency reserves
 861          *      __GFP_NOWARN: don't print a warning in case of failure
 862          *
 863          * For debugging, if we set the cache size to 1, no new buffers will
 864          * be allocated.
 865          */
 866         while (1) {
 867                 if (dm_bufio_cache_size_latch != 1) {
 868                         b = alloc_buffer(c, GFP_NOWAIT | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
 869                         if (b)
 870                                 return b;
 871                 }
 872
 873                 if (nf == NF_PREFETCH)
 874                         return NULL;
 875
 876                 if (dm_bufio_cache_size_latch != 1 && !tried_noio_alloc) {
 877                         dm_bufio_unlock(c);
 878                         b = alloc_buffer(c, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
 879                         dm_bufio_lock(c);
 880                         if (b)
 881                                 return b;
 882                         tried_noio_alloc = true;
 883                 }
 884
 885                 if (!list_empty(&c->reserved_buffers)) {
 886                         b = list_entry(c->reserved_buffers.next,
 887                                        struct dm_buffer, lru_list);
 888                         list_del(&b->lru_list);
 889                         c->need_reserved_buffers++;
 890
 891                         return b;
 892                 }
 893
 894                 b = __get_unclaimed_buffer(c);
 895                 if (b)
 896                         return b;
 897
 898                 __wait_for_free_buffer(c);
 899         }
 900 }
 901
 902 static struct dm_buffer *__alloc_buffer_wait(struct dm_bufio_client *c, enum new_flag nf)
 903 {
 904         struct dm_buffer *b = __alloc_buffer_wait_no_callback(c, nf);
 905
 906         if (!b)
 907                 return NULL;
 908
 909         if (c->alloc_callback)
 910                 c->alloc_callback(b);
 911
 912         return b;
 913 }
 914
 915 /*
 916  * Free a buffer and wake other threads waiting for free buffers.
 917  */
 918 static void __free_buffer_wake(struct dm_buffer *b)
 919 {
 920         struct dm_bufio_client *c = b->c;
 921
 922         if (!c->need_reserved_buffers)
 923                 free_buffer(b);
 924         else {
 925                 list_add(&b->lru_list, &c->reserved_buffers);
 926                 c->need_reserved_buffers--;
 927         }
 928
 929         wake_up(&c->free_buffer_wait);
 930 }
 931
 932 static void __write_dirty_buffers_async(struct dm_bufio_client *c, int no_wait,
 933                                         struct list_head *write_list)
 934 {
 935         struct dm_buffer *b, *tmp;
 936
 937         list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) {
 938                 BUG_ON(test_bit(B_READING, &b->state));
 939
 940                 if (!test_bit(B_DIRTY, &b->state) &&
 941                     !test_bit(B_WRITING, &b->state)) {
 942                         __relink_lru(b, LIST_CLEAN);
 943                         continue;
 944                 }
 945
 946                 if (no_wait && test_bit(B_WRITING, &b->state))
 947                         return;
 948
 949                 __write_dirty_buffer(b, write_list);
 950                 cond_resched();
 951         }
 952 }
 953
 954 /*
 955  * Get writeback threshold and buffer limit for a given client.
 956  */
 957 static void __get_memory_limit(struct dm_bufio_client *c,
 958                                unsigned long *threshold_buffers,
 959                                unsigned long *limit_buffers)
 960 {
 961         unsigned long buffers;
 962
 963         if (unlikely(READ_ONCE(dm_bufio_cache_size) != dm_bufio_cache_size_latch)) {
 964                 if (mutex_trylock(&dm_bufio_clients_lock)) {
 965                         __cache_size_refresh();
 966                         mutex_unlock(&dm_bufio_clients_lock);
 967                 }
 968         }
 969
 970         buffers = dm_bufio_cache_size_per_client >>
 971                   (c->sectors_per_block_bits + SECTOR_SHIFT);
 972
 973         if (buffers < c->minimum_buffers)
 974                 buffers = c->minimum_buffers;
 975
 976         *limit_buffers = buffers;
 977         *threshold_buffers = mult_frac(buffers,
 978                                        DM_BUFIO_WRITEBACK_PERCENT, 100);
 979 }
 980
 981 /*
 982  * Check if we're over watermark.
 983  * If we are over threshold_buffers, start freeing buffers.
 984  * If we're over "limit_buffers", block until we get under the limit.
 985  */
 986 static void __check_watermark(struct dm_bufio_client *c,
 987                               struct list_head *write_list)
 988 {
 989         unsigned long threshold_buffers, limit_buffers;
 990
 991         __get_memory_limit(c, &threshold_buffers, &limit_buffers);
 992
 993         while (c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY] >
 994                limit_buffers) {
 995
 996                 struct dm_buffer *b = __get_unclaimed_buffer(c);
 997
 998                 if (!b)
 999                         return;
1000
1001                 __free_buffer_wake(b);
1002                 cond_resched();
1003         }
1004
1005         if (c->n_buffers[LIST_DIRTY] > threshold_buffers)
1006                 __write_dirty_buffers_async(c, 1, write_list);
1007 }
1008
1009 /*----------------------------------------------------------------
1010  * Getting a buffer
1011  *--------------------------------------------------------------*/
1012
1013 static struct dm_buffer *__bufio_new(struct dm_bufio_client *c, sector_t block,
1014                                      enum new_flag nf, int *need_submit,
1015                                      struct list_head *write_list)
1016 {
1017         struct dm_buffer *b, *new_b = NULL;
1018
1019         *need_submit = 0;
1020
1021         b = __find(c, block);
1022         if (b)
1023                 goto found_buffer;
1024
1025         if (nf == NF_GET)
1026                 return NULL;
1027
1028         new_b = __alloc_buffer_wait(c, nf);
1029         if (!new_b)
1030                 return NULL;
1031
1032         /*
1033          * We've had a period where the mutex was unlocked, so need to
1034          * recheck the hash table.
1035          */
1036         b = __find(c, block);
1037         if (b) {
1038                 __free_buffer_wake(new_b);
1039                 goto found_buffer;
1040         }
1041
1042         __check_watermark(c, write_list);
1043
1044         b = new_b;
1045         b->hold_count = 1;
1046         b->read_error = 0;
1047         b->write_error = 0;
1048         __link_buffer(b, block, LIST_CLEAN);
1049
1050         if (nf == NF_FRESH) {
1051                 b->state = 0;
1052                 return b;
1053         }
1054
1055         b->state = 1 << B_READING;
1056         *need_submit = 1;
1057
1058         return b;
1059
1060 found_buffer:
1061         if (nf == NF_PREFETCH)
1062                 return NULL;
1063         /*
1064          * Note: it is essential that we don't wait for the buffer to be
1065          * read if dm_bufio_get function is used. Both dm_bufio_get and
1066          * dm_bufio_prefetch can be used in the driver request routine.
1067          * If the user called both dm_bufio_prefetch and dm_bufio_get on
1068          * the same buffer, it would deadlock if we waited.
1069          */
1070         if (nf == NF_GET && unlikely(test_bit(B_READING, &b->state)))
1071                 return NULL;
1072
1073         b->hold_count++;
1074         __relink_lru(b, test_bit(B_DIRTY, &b->state) ||
1075                      test_bit(B_WRITING, &b->state));
1076         return b;
1077 }
1078
1079 /*
1080  * The endio routine for reading: set the error, clear the bit and wake up
1081  * anyone waiting on the buffer.
1082  */
1083 static void read_endio(struct bio *bio)
1084 {
1085         struct dm_buffer *b = container_of(bio, struct dm_buffer, bio);
1086
1087         b->read_error = bio->bi_status;
1088
1089         BUG_ON(!test_bit(B_READING, &b->state));
1090
1091         smp_mb__before_atomic();
1092         clear_bit(B_READING, &b->state);
1093         smp_mb__after_atomic();
1094
1095         wake_up_bit(&b->state, B_READING);
1096 }
1097
1098 /*
1099  * A common routine for dm_bufio_new and dm_bufio_read.  Operation of these
1100  * functions is similar except that dm_bufio_new doesn't read the
1101  * buffer from the disk (assuming that the caller overwrites all the data
1102  * and uses dm_bufio_mark_buffer_dirty to write new data back).
1103  */
1104 static void *new_read(struct dm_bufio_client *c, sector_t block,
1105                       enum new_flag nf, struct dm_buffer **bp)
1106 {
1107         int need_submit;
1108         struct dm_buffer *b;
1109
1110         LIST_HEAD(write_list);
1111
1112         dm_bufio_lock(c);
1113         b = __bufio_new(c, block, nf, &need_submit, &write_list);
1114 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1115         if (b && b->hold_count == 1)
1116                 buffer_record_stack(b);
1117 #endif
1118         dm_bufio_unlock(c);
1119
1120         __flush_write_list(&write_list);
1121
1122         if (!b)
1123                 return NULL;
1124
1125         if (need_submit)
1126                 submit_io(b, READ, read_endio);
1127
1128         wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
1129
1130         if (b->read_error) {
1131                 int error = blk_status_to_errno(b->read_error);
1132
1133                 dm_bufio_release(b);
1134
1135                 return ERR_PTR(error);
1136         }
1137
1138         *bp = b;
1139
1140         return b->data;
1141 }
1142
1143 void *dm_bufio_get(struct dm_bufio_client *c, sector_t block,
1144                    struct dm_buffer **bp)
1145 {
1146         return new_read(c, block, NF_GET, bp);
1147 }
1148 EXPORT_SYMBOL_GPL(dm_bufio_get);
1149
1150 void *dm_bufio_read(struct dm_bufio_client *c, sector_t block,
1151                     struct dm_buffer **bp)
1152 {
1153         BUG_ON(dm_bufio_in_request());
1154
1155         return new_read(c, block, NF_READ, bp);
1156 }
1157 EXPORT_SYMBOL_GPL(dm_bufio_read);
1158
1159 void *dm_bufio_new(struct dm_bufio_client *c, sector_t block,
1160                    struct dm_buffer **bp)
1161 {
1162         BUG_ON(dm_bufio_in_request());
1163
1164         return new_read(c, block, NF_FRESH, bp);
1165 }
1166 EXPORT_SYMBOL_GPL(dm_bufio_new);
1167
1168 void dm_bufio_prefetch(struct dm_bufio_client *c,
1169                        sector_t block, unsigned n_blocks)
1170 {
1171         struct blk_plug plug;
1172
1173         LIST_HEAD(write_list);
1174
1175         BUG_ON(dm_bufio_in_request());
1176
1177         blk_start_plug(&plug);
1178         dm_bufio_lock(c);
1179
1180         for (; n_blocks--; block++) {
1181                 int need_submit;
1182                 struct dm_buffer *b;
1183                 b = __bufio_new(c, block, NF_PREFETCH, &need_submit,
1184                                 &write_list);
1185                 if (unlikely(!list_empty(&write_list))) {
1186                         dm_bufio_unlock(c);
1187                         blk_finish_plug(&plug);
1188                         __flush_write_list(&write_list);
1189                         blk_start_plug(&plug);
1190                         dm_bufio_lock(c);
1191                 }
1192                 if (unlikely(b != NULL)) {
1193                         dm_bufio_unlock(c);
1194
1195                         if (need_submit)
1196                                 submit_io(b, READ, read_endio);
1197                         dm_bufio_release(b);
1198
1199                         cond_resched();
1200
1201                         if (!n_blocks)
1202                                 goto flush_plug;
1203                         dm_bufio_lock(c);
1204                 }
1205         }
1206
1207         dm_bufio_unlock(c);
1208
1209 flush_plug:
1210         blk_finish_plug(&plug);
1211 }
1212 EXPORT_SYMBOL_GPL(dm_bufio_prefetch);
1213
1214 void dm_bufio_release(struct dm_buffer *b)
1215 {
1216         struct dm_bufio_client *c = b->c;
1217
1218         dm_bufio_lock(c);
1219
1220         BUG_ON(!b->hold_count);
1221
1222         b->hold_count--;
1223         if (!b->hold_count) {
1224                 wake_up(&c->free_buffer_wait);
1225
1226                 /*
1227                  * If there were errors on the buffer, and the buffer is not
1228                  * to be written, free the buffer. There is no point in caching
1229                  * invalid buffer.
1230                  */
1231                 if ((b->read_error || b->write_error) &&
1232                     !test_bit(B_READING, &b->state) &&
1233                     !test_bit(B_WRITING, &b->state) &&
1234                     !test_bit(B_DIRTY, &b->state)) {
1235                         __unlink_buffer(b);
1236                         __free_buffer_wake(b);
1237                 }
1238         }
1239
1240         dm_bufio_unlock(c);
1241 }
1242 EXPORT_SYMBOL_GPL(dm_bufio_release);
1243
1244 void dm_bufio_mark_partial_buffer_dirty(struct dm_buffer *b,
1245                                         unsigned start, unsigned end)
1246 {
1247         struct dm_bufio_client *c = b->c;
1248
1249         BUG_ON(start >= end);
1250         BUG_ON(end > b->c->block_size);
1251
1252         dm_bufio_lock(c);
1253
1254         BUG_ON(test_bit(B_READING, &b->state));
1255
1256         if (!test_and_set_bit(B_DIRTY, &b->state)) {
1257                 b->dirty_start = start;
1258                 b->dirty_end = end;
1259                 __relink_lru(b, LIST_DIRTY);
1260         } else {
1261                 if (start < b->dirty_start)
1262                         b->dirty_start = start;
1263                 if (end > b->dirty_end)
1264                         b->dirty_end = end;
1265         }
1266
1267         dm_bufio_unlock(c);
1268 }
1269 EXPORT_SYMBOL_GPL(dm_bufio_mark_partial_buffer_dirty);
1270
1271 void dm_bufio_mark_buffer_dirty(struct dm_buffer *b)
1272 {
1273         dm_bufio_mark_partial_buffer_dirty(b, 0, b->c->block_size);
1274 }
1275 EXPORT_SYMBOL_GPL(dm_bufio_mark_buffer_dirty);
1276
1277 void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c)
1278 {
1279         LIST_HEAD(write_list);
1280
1281         BUG_ON(dm_bufio_in_request());
1282
1283         dm_bufio_lock(c);
1284         __write_dirty_buffers_async(c, 0, &write_list);
1285         dm_bufio_unlock(c);
1286         __flush_write_list(&write_list);
1287 }
1288 EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers_async);
1289
1290 /*
1291  * For performance, it is essential that the buffers are written asynchronously
1292  * and simultaneously (so that the block layer can merge the writes) and then
1293  * waited upon.
1294  *
1295  * Finally, we flush hardware disk cache.
1296  */
1297 int dm_bufio_write_dirty_buffers(struct dm_bufio_client *c)
1298 {
1299         int a, f;
1300         unsigned long buffers_processed = 0;
1301         struct dm_buffer *b, *tmp;
1302
1303         LIST_HEAD(write_list);
1304
1305         dm_bufio_lock(c);
1306         __write_dirty_buffers_async(c, 0, &write_list);
1307         dm_bufio_unlock(c);
1308         __flush_write_list(&write_list);
1309         dm_bufio_lock(c);
1310
1311 again:
1312         list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) {
1313                 int dropped_lock = 0;
1314
1315                 if (buffers_processed < c->n_buffers[LIST_DIRTY])
1316                         buffers_processed++;
1317
1318                 BUG_ON(test_bit(B_READING, &b->state));
1319
1320                 if (test_bit(B_WRITING, &b->state)) {
1321                         if (buffers_processed < c->n_buffers[LIST_DIRTY]) {
1322                                 dropped_lock = 1;
1323                                 b->hold_count++;
1324                                 dm_bufio_unlock(c);
1325                                 wait_on_bit_io(&b->state, B_WRITING,
1326                                                TASK_UNINTERRUPTIBLE);
1327                                 dm_bufio_lock(c);
1328                                 b->hold_count--;
1329                         } else
1330                                 wait_on_bit_io(&b->state, B_WRITING,
1331                                                TASK_UNINTERRUPTIBLE);
1332                 }
1333
1334                 if (!test_bit(B_DIRTY, &b->state) &&
1335                     !test_bit(B_WRITING, &b->state))
1336                         __relink_lru(b, LIST_CLEAN);
1337
1338                 cond_resched();
1339
1340                 /*
1341                  * If we dropped the lock, the list is no longer consistent,
1342                  * so we must restart the search.
1343                  *
1344                  * In the most common case, the buffer just processed is
1345                  * relinked to the clean list, so we won't loop scanning the
1346                  * same buffer again and again.
1347                  *
1348                  * This may livelock if there is another thread simultaneously
1349                  * dirtying buffers, so we count the number of buffers walked
1350                  * and if it exceeds the total number of buffers, it means that
1351                  * someone is doing some writes simultaneously with us.  In
1352                  * this case, stop, dropping the lock.
1353                  */
1354                 if (dropped_lock)
1355                         goto again;
1356         }
1357         wake_up(&c->free_buffer_wait);
1358         dm_bufio_unlock(c);
1359
1360         a = xchg(&c->async_write_error, 0);
1361         f = dm_bufio_issue_flush(c);
1362         if (a)
1363                 return a;
1364
1365         return f;
1366 }
1367 EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers);
1368
1369 /*
1370  * Use dm-io to send and empty barrier flush the device.
1371  */
1372 int dm_bufio_issue_flush(struct dm_bufio_client *c)
1373 {
1374         struct dm_io_request io_req = {
1375                 .bi_op = REQ_OP_WRITE,
1376                 .bi_op_flags = REQ_PREFLUSH | REQ_SYNC,
1377                 .mem.type = DM_IO_KMEM,
1378                 .mem.ptr.addr = NULL,
1379                 .client = c->dm_io,
1380         };
1381         struct dm_io_region io_reg = {
1382                 .bdev = c->bdev,
1383                 .sector = 0,
1384                 .count = 0,
1385         };
1386
1387         BUG_ON(dm_bufio_in_request());
1388
1389         return dm_io(&io_req, 1, &io_reg, NULL);
1390 }
1391 EXPORT_SYMBOL_GPL(dm_bufio_issue_flush);
1392
1393 /*
1394  * We first delete any other buffer that may be at that new location.
1395  *
1396  * Then, we write the buffer to the original location if it was dirty.
1397  *
1398  * Then, if we are the only one who is holding the buffer, relink the buffer
1399  * in the hash queue for the new location.
1400  *
1401  * If there was someone else holding the buffer, we write it to the new
1402  * location but not relink it, because that other user needs to have the buffer
1403  * at the same place.
1404  */
1405 void dm_bufio_release_move(struct dm_buffer *b, sector_t new_block)
1406 {
1407         struct dm_bufio_client *c = b->c;
1408         struct dm_buffer *new;
1409
1410         BUG_ON(dm_bufio_in_request());
1411
1412         dm_bufio_lock(c);
1413
1414 retry:
1415         new = __find(c, new_block);
1416         if (new) {
1417                 if (new->hold_count) {
1418                         __wait_for_free_buffer(c);
1419                         goto retry;
1420                 }
1421
1422                 /*
1423                  * FIXME: Is there any point waiting for a write that's going
1424                  * to be overwritten in a bit?
1425                  */
1426                 __make_buffer_clean(new);
1427                 __unlink_buffer(new);
1428                 __free_buffer_wake(new);
1429         }
1430
1431         BUG_ON(!b->hold_count);
1432         BUG_ON(test_bit(B_READING, &b->state));
1433
1434         __write_dirty_buffer(b, NULL);
1435         if (b->hold_count == 1) {
1436                 wait_on_bit_io(&b->state, B_WRITING,
1437                                TASK_UNINTERRUPTIBLE);
1438                 set_bit(B_DIRTY, &b->state);
1439                 b->dirty_start = 0;
1440                 b->dirty_end = c->block_size;
1441                 __unlink_buffer(b);
1442                 __link_buffer(b, new_block, LIST_DIRTY);
1443         } else {
1444                 sector_t old_block;
1445                 wait_on_bit_lock_io(&b->state, B_WRITING,
1446                                     TASK_UNINTERRUPTIBLE);
1447                 /*
1448                  * Relink buffer to "new_block" so that write_callback
1449                  * sees "new_block" as a block number.
1450                  * After the write, link the buffer back to old_block.
1451                  * All this must be done in bufio lock, so that block number
1452                  * change isn't visible to other threads.
1453                  */
1454                 old_block = b->block;
1455                 __unlink_buffer(b);
1456                 __link_buffer(b, new_block, b->list_mode);
1457                 submit_io(b, WRITE, write_endio);
1458                 wait_on_bit_io(&b->state, B_WRITING,
1459                                TASK_UNINTERRUPTIBLE);
1460                 __unlink_buffer(b);
1461                 __link_buffer(b, old_block, b->list_mode);
1462         }
1463
1464         dm_bufio_unlock(c);
1465         dm_bufio_release(b);
1466 }
1467 EXPORT_SYMBOL_GPL(dm_bufio_release_move);
1468
1469 /*
1470  * Free the given buffer.
1471  *
1472  * This is just a hint, if the buffer is in use or dirty, this function
1473  * does nothing.
1474  */
1475 void dm_bufio_forget(struct dm_bufio_client *c, sector_t block)
1476 {
1477         struct dm_buffer *b;
1478
1479         dm_bufio_lock(c);
1480
1481         b = __find(c, block);
1482         if (b && likely(!b->hold_count) && likely(!b->state)) {
1483                 __unlink_buffer(b);
1484                 __free_buffer_wake(b);
1485         }
1486
1487         dm_bufio_unlock(c);
1488 }
1489 EXPORT_SYMBOL(dm_bufio_forget);
1490
1491 void dm_bufio_set_minimum_buffers(struct dm_bufio_client *c, unsigned n)
1492 {
1493         c->minimum_buffers = n;
1494 }
1495 EXPORT_SYMBOL(dm_bufio_set_minimum_buffers);
1496
1497 unsigned dm_bufio_get_block_size(struct dm_bufio_client *c)
1498 {
1499         return c->block_size;
1500 }
1501 EXPORT_SYMBOL_GPL(dm_bufio_get_block_size);
1502
1503 sector_t dm_bufio_get_device_size(struct dm_bufio_client *c)
1504 {
1505         return i_size_read(c->bdev->bd_inode) >>
1506                            (SECTOR_SHIFT + c->sectors_per_block_bits);
1507 }
1508 EXPORT_SYMBOL_GPL(dm_bufio_get_device_size);
1509
1510 sector_t dm_bufio_get_block_number(struct dm_buffer *b)
1511 {
1512         return b->block;
1513 }
1514 EXPORT_SYMBOL_GPL(dm_bufio_get_block_number);
1515
1516 void *dm_bufio_get_block_data(struct dm_buffer *b)
1517 {
1518         return b->data;
1519 }
1520 EXPORT_SYMBOL_GPL(dm_bufio_get_block_data);
1521
1522 void *dm_bufio_get_aux_data(struct dm_buffer *b)
1523 {
1524         return b + 1;
1525 }
1526 EXPORT_SYMBOL_GPL(dm_bufio_get_aux_data);
1527
1528 struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b)
1529 {
1530         return b->c;
1531 }
1532 EXPORT_SYMBOL_GPL(dm_bufio_get_client);
1533
1534 static void drop_buffers(struct dm_bufio_client *c)
1535 {
1536         struct dm_buffer *b;
1537         int i;
1538         bool warned = false;
1539
1540         BUG_ON(dm_bufio_in_request());
1541
1542         /*
1543          * An optimization so that the buffers are not written one-by-one.
1544          */
1545         dm_bufio_write_dirty_buffers_async(c);
1546
1547         dm_bufio_lock(c);
1548
1549         while ((b = __get_unclaimed_buffer(c)))
1550                 __free_buffer_wake(b);
1551
1552         for (i = 0; i < LIST_SIZE; i++)
1553                 list_for_each_entry(b, &c->lru[i], lru_list) {
1554                         WARN_ON(!warned);
1555                         warned = true;
1556                         DMERR("leaked buffer %llx, hold count %u, list %d",
1557                               (unsigned long long)b->block, b->hold_count, i);
1558 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1559                         print_stack_trace(&b->stack_trace, 1);
1560                         b->hold_count = 0; /* mark unclaimed to avoid BUG_ON below */
1561 #endif
1562                 }
1563
1564 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1565         while ((b = __get_unclaimed_buffer(c)))
1566                 __free_buffer_wake(b);
1567 #endif
1568
1569         for (i = 0; i < LIST_SIZE; i++)
1570                 BUG_ON(!list_empty(&c->lru[i]));
1571
1572         dm_bufio_unlock(c);
1573 }
1574
1575 /*
1576  * We may not be able to evict this buffer if IO pending or the client
1577  * is still using it.  Caller is expected to know buffer is too old.
1578  *
1579  * And if GFP_NOFS is used, we must not do any I/O because we hold
1580  * dm_bufio_clients_lock and we would risk deadlock if the I/O gets
1581  * rerouted to different bufio client.
1582  */
1583 static bool __try_evict_buffer(struct dm_buffer *b, gfp_t gfp)
1584 {
1585         if (!(gfp & __GFP_FS)) {
1586                 if (test_bit(B_READING, &b->state) ||
1587                     test_bit(B_WRITING, &b->state) ||
1588                     test_bit(B_DIRTY, &b->state))
1589                         return false;
1590         }
1591
1592         if (b->hold_count)
1593                 return false;
1594
1595         __make_buffer_clean(b);
1596         __unlink_buffer(b);
1597         __free_buffer_wake(b);
1598
1599         return true;
1600 }
1601
1602 static unsigned long get_retain_buffers(struct dm_bufio_client *c)
1603 {
1604         unsigned long retain_bytes = READ_ONCE(dm_bufio_retain_bytes);
1605         return retain_bytes >> (c->sectors_per_block_bits + SECTOR_SHIFT);
1606 }
1607
1608 static unsigned long __scan(struct dm_bufio_client *c, unsigned long nr_to_scan,
1609                             gfp_t gfp_mask)
1610 {
1611         int l;
1612         struct dm_buffer *b, *tmp;
1613         unsigned long freed = 0;
1614         unsigned long count = c->n_buffers[LIST_CLEAN] +
1615                               c->n_buffers[LIST_DIRTY];
1616         unsigned long retain_target = get_retain_buffers(c);
1617
1618         for (l = 0; l < LIST_SIZE; l++) {
1619                 list_for_each_entry_safe_reverse(b, tmp, &c->lru[l], lru_list) {
1620                         if (__try_evict_buffer(b, gfp_mask))
1621                                 freed++;
1622                         if (!--nr_to_scan || ((count - freed) <= retain_target))
1623                                 return freed;
1624                         cond_resched();
1625                 }
1626         }
1627         return freed;
1628 }
1629
1630 static unsigned long
1631 dm_bufio_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
1632 {
1633         struct dm_bufio_client *c;
1634         unsigned long freed;
1635
1636         c = container_of(shrink, struct dm_bufio_client, shrinker);
1637         if (sc->gfp_mask & __GFP_FS)
1638                 dm_bufio_lock(c);
1639         else if (!dm_bufio_trylock(c))
1640                 return SHRINK_STOP;
1641
1642         freed  = __scan(c, sc->nr_to_scan, sc->gfp_mask);
1643         dm_bufio_unlock(c);
1644         return freed;
1645 }
1646
1647 static unsigned long
1648 dm_bufio_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
1649 {
1650         struct dm_bufio_client *c = container_of(shrink, struct dm_bufio_client, shrinker);
1651         unsigned long count = READ_ONCE(c->n_buffers[LIST_CLEAN]) +
1652                               READ_ONCE(c->n_buffers[LIST_DIRTY]);
1653         unsigned long retain_target = get_retain_buffers(c);
1654
1655         return (count < retain_target) ? 0 : (count - retain_target);
1656 }
1657
1658 /*
1659  * Create the buffering interface
1660  */
1661 struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsigned block_size,
1662                                                unsigned reserved_buffers, unsigned aux_size,
1663                                                void (*alloc_callback)(struct dm_buffer *),
1664                                                void (*write_callback)(struct dm_buffer *))
1665 {
1666         int r;
1667         struct dm_bufio_client *c;
1668         unsigned i;
1669
1670         BUG_ON(block_size < 1 << SECTOR_SHIFT ||
1671                (block_size & (block_size - 1)));
1672
1673         c = kzalloc(sizeof(*c), GFP_KERNEL);
1674         if (!c) {
1675                 r = -ENOMEM;
1676                 goto bad_client;
1677         }
1678         c->buffer_tree = RB_ROOT;
1679
1680         c->bdev = bdev;
1681         c->block_size = block_size;
1682         c->sectors_per_block_bits = __ffs(block_size) - SECTOR_SHIFT;
1683         c->pages_per_block_bits = (__ffs(block_size) >= PAGE_SHIFT) ?
1684                                   __ffs(block_size) - PAGE_SHIFT : 0;
1685         c->blocks_per_page_bits = (__ffs(block_size) < PAGE_SHIFT ?
1686                                   PAGE_SHIFT - __ffs(block_size) : 0);
1687
1688         c->aux_size = aux_size;
1689         c->alloc_callback = alloc_callback;
1690         c->write_callback = write_callback;
1691
1692         for (i = 0; i < LIST_SIZE; i++) {
1693                 INIT_LIST_HEAD(&c->lru[i]);
1694                 c->n_buffers[i] = 0;
1695         }
1696
1697         mutex_init(&c->lock);
1698         INIT_LIST_HEAD(&c->reserved_buffers);
1699         c->need_reserved_buffers = reserved_buffers;
1700
1701         c->minimum_buffers = DM_BUFIO_MIN_BUFFERS;
1702
1703         init_waitqueue_head(&c->free_buffer_wait);
1704         c->async_write_error = 0;
1705
1706         c->dm_io = dm_io_client_create();
1707         if (IS_ERR(c->dm_io)) {
1708                 r = PTR_ERR(c->dm_io);
1709                 goto bad_dm_io;
1710         }
1711
1712         mutex_lock(&dm_bufio_clients_lock);
1713         if (c->blocks_per_page_bits) {
1714                 if (!DM_BUFIO_CACHE_NAME(c)) {
1715                         DM_BUFIO_CACHE_NAME(c) = kasprintf(GFP_KERNEL, "dm_bufio_cache-%u", c->block_size);
1716                         if (!DM_BUFIO_CACHE_NAME(c)) {
1717                                 r = -ENOMEM;
1718                                 mutex_unlock(&dm_bufio_clients_lock);
1719                                 goto bad_cache;
1720                         }
1721                 }
1722
1723                 if (!DM_BUFIO_CACHE(c)) {
1724                         DM_BUFIO_CACHE(c) = kmem_cache_create(DM_BUFIO_CACHE_NAME(c),
1725                                                               c->block_size,
1726                                                               c->block_size, 0, NULL);
1727                         if (!DM_BUFIO_CACHE(c)) {
1728                                 r = -ENOMEM;
1729                                 mutex_unlock(&dm_bufio_clients_lock);
1730                                 goto bad_cache;
1731                         }
1732                 }
1733         }
1734         mutex_unlock(&dm_bufio_clients_lock);
1735
1736         while (c->need_reserved_buffers) {
1737                 struct dm_buffer *b = alloc_buffer(c, GFP_KERNEL);
1738
1739                 if (!b) {
1740                         r = -ENOMEM;
1741                         goto bad_buffer;
1742                 }
1743                 __free_buffer_wake(b);
1744         }
1745
1746         mutex_lock(&dm_bufio_clients_lock);
1747         dm_bufio_client_count++;
1748         list_add(&c->client_list, &dm_bufio_all_clients);
1749         __cache_size_refresh();
1750         mutex_unlock(&dm_bufio_clients_lock);
1751
1752         c->shrinker.count_objects = dm_bufio_shrink_count;
1753         c->shrinker.scan_objects = dm_bufio_shrink_scan;
1754         c->shrinker.seeks = 1;
1755         c->shrinker.batch = 0;
1756         register_shrinker(&c->shrinker);
1757
1758         return c;
1759
1760 bad_buffer:
1761 bad_cache:
1762         while (!list_empty(&c->reserved_buffers)) {
1763                 struct dm_buffer *b = list_entry(c->reserved_buffers.next,
1764                                                  struct dm_buffer, lru_list);
1765                 list_del(&b->lru_list);
1766                 free_buffer(b);
1767         }
1768         dm_io_client_destroy(c->dm_io);
1769 bad_dm_io:
1770         kfree(c);
1771 bad_client:
1772         return ERR_PTR(r);
1773 }
1774 EXPORT_SYMBOL_GPL(dm_bufio_client_create);
1775
1776 /*
1777  * Free the buffering interface.
1778  * It is required that there are no references on any buffers.
1779  */
1780 void dm_bufio_client_destroy(struct dm_bufio_client *c)
1781 {
1782         unsigned i;
1783
1784         drop_buffers(c);
1785
1786         unregister_shrinker(&c->shrinker);
1787
1788         mutex_lock(&dm_bufio_clients_lock);
1789
1790         list_del(&c->client_list);
1791         dm_bufio_client_count--;
1792         __cache_size_refresh();
1793
1794         mutex_unlock(&dm_bufio_clients_lock);
1795
1796         BUG_ON(!RB_EMPTY_ROOT(&c->buffer_tree));
1797         BUG_ON(c->need_reserved_buffers);
1798
1799         while (!list_empty(&c->reserved_buffers)) {
1800                 struct dm_buffer *b = list_entry(c->reserved_buffers.next,
1801                                                  struct dm_buffer, lru_list);
1802                 list_del(&b->lru_list);
1803                 free_buffer(b);
1804         }
1805
1806         for (i = 0; i < LIST_SIZE; i++)
1807                 if (c->n_buffers[i])
1808                         DMERR("leaked buffer count %d: %ld", i, c->n_buffers[i]);
1809
1810         for (i = 0; i < LIST_SIZE; i++)
1811                 BUG_ON(c->n_buffers[i]);
1812
1813         dm_io_client_destroy(c->dm_io);
1814         kfree(c);
1815 }
1816 EXPORT_SYMBOL_GPL(dm_bufio_client_destroy);
1817
1818 void dm_bufio_set_sector_offset(struct dm_bufio_client *c, sector_t start)
1819 {
1820         c->start = start;
1821 }
1822 EXPORT_SYMBOL_GPL(dm_bufio_set_sector_offset);
1823
1824 static unsigned get_max_age_hz(void)
1825 {
1826         unsigned max_age = READ_ONCE(dm_bufio_max_age);
1827
1828         if (max_age > UINT_MAX / HZ)
1829                 max_age = UINT_MAX / HZ;
1830
1831         return max_age * HZ;
1832 }
1833
1834 static bool older_than(struct dm_buffer *b, unsigned long age_hz)
1835 {
1836         return time_after_eq(jiffies, b->last_accessed + age_hz);
1837 }
1838
1839 static void __evict_old_buffers(struct dm_bufio_client *c, unsigned long age_hz)
1840 {
1841         struct dm_buffer *b, *tmp;
1842         unsigned long retain_target = get_retain_buffers(c);
1843         unsigned long count;
1844         LIST_HEAD(write_list);
1845
1846         dm_bufio_lock(c);
1847
1848         __check_watermark(c, &write_list);
1849         if (unlikely(!list_empty(&write_list))) {
1850                 dm_bufio_unlock(c);
1851                 __flush_write_list(&write_list);
1852                 dm_bufio_lock(c);
1853         }
1854
1855         count = c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY];
1856         list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_CLEAN], lru_list) {
1857                 if (count <= retain_target)
1858                         break;
1859
1860                 if (!older_than(b, age_hz))
1861                         break;
1862
1863                 if (__try_evict_buffer(b, 0))
1864                         count--;
1865
1866                 cond_resched();
1867         }
1868
1869         dm_bufio_unlock(c);
1870 }
1871
1872 static void cleanup_old_buffers(void)
1873 {
1874         unsigned long max_age_hz = get_max_age_hz();
1875         struct dm_bufio_client *c;
1876
1877         mutex_lock(&dm_bufio_clients_lock);
1878
1879         __cache_size_refresh();
1880
1881         list_for_each_entry(c, &dm_bufio_all_clients, client_list)
1882                 __evict_old_buffers(c, max_age_hz);
1883
1884         mutex_unlock(&dm_bufio_clients_lock);
1885 }
1886
1887 static struct workqueue_struct *dm_bufio_wq;
1888 static struct delayed_work dm_bufio_work;
1889
1890 static void work_fn(struct work_struct *w)
1891 {
1892         cleanup_old_buffers();
1893
1894         queue_delayed_work(dm_bufio_wq, &dm_bufio_work,
1895                            DM_BUFIO_WORK_TIMER_SECS * HZ);
1896 }
1897
1898 /*----------------------------------------------------------------
1899  * Module setup
1900  *--------------------------------------------------------------*/
1901
1902 /*
1903  * This is called only once for the whole dm_bufio module.
1904  * It initializes memory limit.
1905  */
1906 static int __init dm_bufio_init(void)
1907 {
1908         __u64 mem;
1909
1910         dm_bufio_allocated_kmem_cache = 0;
1911         dm_bufio_allocated_get_free_pages = 0;
1912         dm_bufio_allocated_vmalloc = 0;
1913         dm_bufio_current_allocated = 0;
1914
1915         memset(&dm_bufio_caches, 0, sizeof dm_bufio_caches);
1916         memset(&dm_bufio_cache_names, 0, sizeof dm_bufio_cache_names);
1917
1918         mem = (__u64)mult_frac(totalram_pages - totalhigh_pages,
1919                                DM_BUFIO_MEMORY_PERCENT, 100) << PAGE_SHIFT;
1920
1921         if (mem > ULONG_MAX)
1922                 mem = ULONG_MAX;
1923
1924 #ifdef CONFIG_MMU
1925         if (mem > mult_frac(VMALLOC_TOTAL, DM_BUFIO_VMALLOC_PERCENT, 100))
1926                 mem = mult_frac(VMALLOC_TOTAL, DM_BUFIO_VMALLOC_PERCENT, 100);
1927 #endif
1928
1929         dm_bufio_default_cache_size = mem;
1930
1931         mutex_lock(&dm_bufio_clients_lock);
1932         __cache_size_refresh();
1933         mutex_unlock(&dm_bufio_clients_lock);
1934
1935         dm_bufio_wq = alloc_workqueue("dm_bufio_cache", WQ_MEM_RECLAIM, 0);
1936         if (!dm_bufio_wq)
1937                 return -ENOMEM;
1938
1939         INIT_DELAYED_WORK(&dm_bufio_work, work_fn);
1940         queue_delayed_work(dm_bufio_wq, &dm_bufio_work,
1941                            DM_BUFIO_WORK_TIMER_SECS * HZ);
1942
1943         return 0;
1944 }
1945
1946 /*
1947  * This is called once when unloading the dm_bufio module.
1948  */
1949 static void __exit dm_bufio_exit(void)
1950 {
1951         int bug = 0;
1952         int i;
1953
1954         cancel_delayed_work_sync(&dm_bufio_work);
1955         destroy_workqueue(dm_bufio_wq);
1956
1957         for (i = 0; i < ARRAY_SIZE(dm_bufio_caches); i++)
1958                 kmem_cache_destroy(dm_bufio_caches[i]);
1959
1960         for (i = 0; i < ARRAY_SIZE(dm_bufio_cache_names); i++)
1961                 kfree(dm_bufio_cache_names[i]);
1962
1963         if (dm_bufio_client_count) {
1964                 DMCRIT("%s: dm_bufio_client_count leaked: %d",
1965                         __func__, dm_bufio_client_count);
1966                 bug = 1;
1967         }
1968
1969         if (dm_bufio_current_allocated) {
1970                 DMCRIT("%s: dm_bufio_current_allocated leaked: %lu",
1971                         __func__, dm_bufio_current_allocated);
1972                 bug = 1;
1973         }
1974
1975         if (dm_bufio_allocated_get_free_pages) {
1976                 DMCRIT("%s: dm_bufio_allocated_get_free_pages leaked: %lu",
1977                        __func__, dm_bufio_allocated_get_free_pages);
1978                 bug = 1;
1979         }
1980
1981         if (dm_bufio_allocated_vmalloc) {
1982                 DMCRIT("%s: dm_bufio_vmalloc leaked: %lu",
1983                        __func__, dm_bufio_allocated_vmalloc);
1984                 bug = 1;
1985         }
1986
1987         BUG_ON(bug);
1988 }
1989
1990 module_init(dm_bufio_init)
1991 module_exit(dm_bufio_exit)
1992
1993 module_param_named(max_cache_size_bytes, dm_bufio_cache_size, ulong, S_IRUGO | S_IWUSR);
1994 MODULE_PARM_DESC(max_cache_size_bytes, "Size of metadata cache");
1995
1996 module_param_named(max_age_seconds, dm_bufio_max_age, uint, S_IRUGO | S_IWUSR);
1997 MODULE_PARM_DESC(max_age_seconds, "Max age of a buffer in seconds");
1998
1999 module_param_named(retain_bytes, dm_bufio_retain_bytes, ulong, S_IRUGO | S_IWUSR);
2000 MODULE_PARM_DESC(retain_bytes, "Try to keep at least this many bytes cached in memory");
2001
2002 module_param_named(peak_allocated_bytes, dm_bufio_peak_allocated, ulong, S_IRUGO | S_IWUSR);
2003 MODULE_PARM_DESC(peak_allocated_bytes, "Tracks the maximum allocated memory");
2004
2005 module_param_named(allocated_kmem_cache_bytes, dm_bufio_allocated_kmem_cache, ulong, S_IRUGO);
2006 MODULE_PARM_DESC(allocated_kmem_cache_bytes, "Memory allocated with kmem_cache_alloc");
2007
2008 module_param_named(allocated_get_free_pages_bytes, dm_bufio_allocated_get_free_pages, ulong, S_IRUGO);
2009 MODULE_PARM_DESC(allocated_get_free_pages_bytes, "Memory allocated with get_free_pages");
2010
2011 module_param_named(allocated_vmalloc_bytes, dm_bufio_allocated_vmalloc, ulong, S_IRUGO);
2012 MODULE_PARM_DESC(allocated_vmalloc_bytes, "Memory allocated with vmalloc");
2013
2014 module_param_named(current_allocated_bytes, dm_bufio_current_allocated, ulong, S_IRUGO);
2015 MODULE_PARM_DESC(current_allocated_bytes, "Memory currently used by the cache");
2016
2017 MODULE_AUTHOR("Mikulas Patocka <dm-devel@redhat.com>");
2018 MODULE_DESCRIPTION(DM_NAME " buffered I/O library");
2019 MODULE_LICENSE("GPL");