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 <linux/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_RATIO        3
  37 #define DM_BUFIO_LOW_WATERMARK_RATIO    16
  38
  39 /*
  40  * Check buffer ages in this interval (seconds)
  41  */
  42 #define DM_BUFIO_WORK_TIMER_SECS        30
  43
  44 /*
  45  * Free buffers when they are older than this (seconds)
  46  */
  47 #define DM_BUFIO_DEFAULT_AGE_SECS       300
  48
  49 /*
  50  * The nr of bytes of cached data to keep around.
  51  */
  52 #define DM_BUFIO_DEFAULT_RETAIN_BYTES   (256 * 1024)
  53
  54 /*
  55  * Align buffer writes to this boundary.
  56  * Tests show that SSDs have the highest IOPS when using 4k writes.
  57  */
  58 #define DM_BUFIO_WRITE_ALIGN            4096
  59
  60 /*
  61  * dm_buffer->list_mode
  62  */
  63 #define LIST_CLEAN      0
  64 #define LIST_DIRTY      1
  65 #define LIST_SIZE       2
  66
  67 /*
  68  * Linking of buffers:
  69  *      All buffers are linked to buffer_tree with their node field.
  70  *
  71  *      Clean buffers that are not being written (B_WRITING not set)
  72  *      are linked to lru[LIST_CLEAN] with their lru_list field.
  73  *
  74  *      Dirty and clean buffers that are being written are linked to
  75  *      lru[LIST_DIRTY] with their lru_list field. When the write
  76  *      finishes, the buffer cannot be relinked immediately (because we
  77  *      are in an interrupt context and relinking requires process
  78  *      context), so some clean-not-writing buffers can be held on
  79  *      dirty_lru too.  They are later added to lru in the process
  80  *      context.
  81  */
  82 struct dm_bufio_client {
  83         struct mutex lock;
  84
  85         struct list_head lru[LIST_SIZE];
  86         unsigned long n_buffers[LIST_SIZE];
  87
  88         struct block_device *bdev;
  89         unsigned block_size;
  90         s8 sectors_per_block_bits;
  91         void (*alloc_callback)(struct dm_buffer *);
  92         void (*write_callback)(struct dm_buffer *);
  93
  94         struct kmem_cache *slab_buffer;
  95         struct kmem_cache *slab_cache;
  96         struct dm_io_client *dm_io;
  97
  98         struct list_head reserved_buffers;
  99         unsigned need_reserved_buffers;
 100
 101         unsigned minimum_buffers;
 102
 103         struct rb_root buffer_tree;
 104         wait_queue_head_t free_buffer_wait;
 105
 106         sector_t start;
 107
 108         int async_write_error;
 109
 110         struct list_head client_list;
 111         struct shrinker shrinker;
 112 };
 113
 114 /*
 115  * Buffer state bits.
 116  */
 117 #define B_READING       0
 118 #define B_WRITING       1
 119 #define B_DIRTY         2
 120
 121 /*
 122  * Describes how the block was allocated:
 123  * kmem_cache_alloc(), __get_free_pages() or vmalloc().
 124  * See the comment at alloc_buffer_data.
 125  */
 126 enum data_mode {
 127         DATA_MODE_SLAB = 0,
 128         DATA_MODE_GET_FREE_PAGES = 1,
 129         DATA_MODE_VMALLOC = 2,
 130         DATA_MODE_LIMIT = 3
 131 };
 132
 133 struct dm_buffer {
 134         struct rb_node node;
 135         struct list_head lru_list;
 136         struct list_head global_list;
 137         sector_t block;
 138         void *data;
 139         unsigned char data_mode;                /* DATA_MODE_* */
 140         unsigned char list_mode;                /* LIST_* */
 141         blk_status_t read_error;
 142         blk_status_t write_error;
 143         unsigned accessed;
 144         unsigned hold_count;
 145         unsigned long state;
 146         unsigned long last_accessed;
 147         unsigned dirty_start;
 148         unsigned dirty_end;
 149         unsigned write_start;
 150         unsigned write_end;
 151         struct dm_bufio_client *c;
 152         struct list_head write_list;
 153         void (*end_io)(struct dm_buffer *, blk_status_t);
 154 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
 155 #define MAX_STACK 10
 156         unsigned int stack_len;
 157         unsigned long stack_entries[MAX_STACK];
 158 #endif
 159 };
 160
 161 /*----------------------------------------------------------------*/
 162
 163 #define dm_bufio_in_request()   (!!current->bio_list)
 164
 165 static void dm_bufio_lock(struct dm_bufio_client *c)
 166 {
 167         mutex_lock_nested(&c->lock, dm_bufio_in_request());
 168 }
 169
 170 static int dm_bufio_trylock(struct dm_bufio_client *c)
 171 {
 172         return mutex_trylock(&c->lock);
 173 }
 174
 175 static void dm_bufio_unlock(struct dm_bufio_client *c)
 176 {
 177         mutex_unlock(&c->lock);
 178 }
 179
 180 /*----------------------------------------------------------------*/
 181
 182 /*
 183  * Default cache size: available memory divided by the ratio.
 184  */
 185 static unsigned long dm_bufio_default_cache_size;
 186
 187 /*
 188  * Total cache size set by the user.
 189  */
 190 static unsigned long dm_bufio_cache_size;
 191
 192 /*
 193  * A copy of dm_bufio_cache_size because dm_bufio_cache_size can change
 194  * at any time.  If it disagrees, the user has changed cache size.
 195  */
 196 static unsigned long dm_bufio_cache_size_latch;
 197
 198 static DEFINE_SPINLOCK(global_spinlock);
 199
 200 static LIST_HEAD(global_queue);
 201
 202 static unsigned long global_num = 0;
 203
 204 /*
 205  * Buffers are freed after this timeout
 206  */
 207 static unsigned dm_bufio_max_age = DM_BUFIO_DEFAULT_AGE_SECS;
 208 static unsigned long dm_bufio_retain_bytes = DM_BUFIO_DEFAULT_RETAIN_BYTES;
 209
 210 static unsigned long dm_bufio_peak_allocated;
 211 static unsigned long dm_bufio_allocated_kmem_cache;
 212 static unsigned long dm_bufio_allocated_get_free_pages;
 213 static unsigned long dm_bufio_allocated_vmalloc;
 214 static unsigned long dm_bufio_current_allocated;
 215
 216 /*----------------------------------------------------------------*/
 217
 218 /*
 219  * The current number of clients.
 220  */
 221 static int dm_bufio_client_count;
 222
 223 /*
 224  * The list of all clients.
 225  */
 226 static LIST_HEAD(dm_bufio_all_clients);
 227
 228 /*
 229  * This mutex protects dm_bufio_cache_size_latch and dm_bufio_client_count
 230  */
 231 static DEFINE_MUTEX(dm_bufio_clients_lock);
 232
 233 static struct workqueue_struct *dm_bufio_wq;
 234 static struct delayed_work dm_bufio_cleanup_old_work;
 235 static struct work_struct dm_bufio_replacement_work;
 236
 237
 238 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
 239 static void buffer_record_stack(struct dm_buffer *b)
 240 {
 241         b->stack_len = stack_trace_save(b->stack_entries, MAX_STACK, 2);
 242 }
 243 #endif
 244
 245 /*----------------------------------------------------------------
 246  * A red/black tree acts as an index for all the buffers.
 247  *--------------------------------------------------------------*/
 248 static struct dm_buffer *__find(struct dm_bufio_client *c, sector_t block)
 249 {
 250         struct rb_node *n = c->buffer_tree.rb_node;
 251         struct dm_buffer *b;
 252
 253         while (n) {
 254                 b = container_of(n, struct dm_buffer, node);
 255
 256                 if (b->block == block)
 257                         return b;
 258
 259                 n = (b->block < block) ? n->rb_left : n->rb_right;
 260         }
 261
 262         return NULL;
 263 }
 264
 265 static void __insert(struct dm_bufio_client *c, struct dm_buffer *b)
 266 {
 267         struct rb_node **new = &c->buffer_tree.rb_node, *parent = NULL;
 268         struct dm_buffer *found;
 269
 270         while (*new) {
 271                 found = container_of(*new, struct dm_buffer, node);
 272
 273                 if (found->block == b->block) {
 274                         BUG_ON(found != b);
 275                         return;
 276                 }
 277
 278                 parent = *new;
 279                 new = (found->block < b->block) ?
 280                         &((*new)->rb_left) : &((*new)->rb_right);
 281         }
 282
 283         rb_link_node(&b->node, parent, new);
 284         rb_insert_color(&b->node, &c->buffer_tree);
 285 }
 286
 287 static void __remove(struct dm_bufio_client *c, struct dm_buffer *b)
 288 {
 289         rb_erase(&b->node, &c->buffer_tree);
 290 }
 291
 292 /*----------------------------------------------------------------*/
 293
 294 static void adjust_total_allocated(struct dm_buffer *b, bool unlink)
 295 {
 296         unsigned char data_mode;
 297         long diff;
 298
 299         static unsigned long * const class_ptr[DATA_MODE_LIMIT] = {
 300                 &dm_bufio_allocated_kmem_cache,
 301                 &dm_bufio_allocated_get_free_pages,
 302                 &dm_bufio_allocated_vmalloc,
 303         };
 304
 305         data_mode = b->data_mode;
 306         diff = (long)b->c->block_size;
 307         if (unlink)
 308                 diff = -diff;
 309
 310         spin_lock(&global_spinlock);
 311
 312         *class_ptr[data_mode] += diff;
 313
 314         dm_bufio_current_allocated += diff;
 315
 316         if (dm_bufio_current_allocated > dm_bufio_peak_allocated)
 317                 dm_bufio_peak_allocated = dm_bufio_current_allocated;
 318
 319         b->accessed = 1;
 320
 321         if (!unlink) {
 322                 list_add(&b->global_list, &global_queue);
 323                 global_num++;
 324                 if (dm_bufio_current_allocated > dm_bufio_cache_size)
 325                         queue_work(dm_bufio_wq, &dm_bufio_replacement_work);
 326         } else {
 327                 list_del(&b->global_list);
 328                 global_num--;
 329         }
 330
 331         spin_unlock(&global_spinlock);
 332 }
 333
 334 /*
 335  * Change the number of clients and recalculate per-client limit.
 336  */
 337 static void __cache_size_refresh(void)
 338 {
 339         BUG_ON(!mutex_is_locked(&dm_bufio_clients_lock));
 340         BUG_ON(dm_bufio_client_count < 0);
 341
 342         dm_bufio_cache_size_latch = READ_ONCE(dm_bufio_cache_size);
 343
 344         /*
 345          * Use default if set to 0 and report the actual cache size used.
 346          */
 347         if (!dm_bufio_cache_size_latch) {
 348                 (void)cmpxchg(&dm_bufio_cache_size, 0,
 349                               dm_bufio_default_cache_size);
 350                 dm_bufio_cache_size_latch = dm_bufio_default_cache_size;
 351         }
 352 }
 353
 354 /*
 355  * Allocating buffer data.
 356  *
 357  * Small buffers are allocated with kmem_cache, to use space optimally.
 358  *
 359  * For large buffers, we choose between get_free_pages and vmalloc.
 360  * Each has advantages and disadvantages.
 361  *
 362  * __get_free_pages can randomly fail if the memory is fragmented.
 363  * __vmalloc won't randomly fail, but vmalloc space is limited (it may be
 364  * as low as 128M) so using it for caching is not appropriate.
 365  *
 366  * If the allocation may fail we use __get_free_pages. Memory fragmentation
 367  * won't have a fatal effect here, but it just causes flushes of some other
 368  * buffers and more I/O will be performed. Don't use __get_free_pages if it
 369  * always fails (i.e. order >= MAX_ORDER).
 370  *
 371  * If the allocation shouldn't fail we use __vmalloc. This is only for the
 372  * initial reserve allocation, so there's no risk of wasting all vmalloc
 373  * space.
 374  */
 375 static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask,
 376                                unsigned char *data_mode)
 377 {
 378         if (unlikely(c->slab_cache != NULL)) {
 379                 *data_mode = DATA_MODE_SLAB;
 380                 return kmem_cache_alloc(c->slab_cache, gfp_mask);
 381         }
 382
 383         if (c->block_size <= KMALLOC_MAX_SIZE &&
 384             gfp_mask & __GFP_NORETRY) {
 385                 *data_mode = DATA_MODE_GET_FREE_PAGES;
 386                 return (void *)__get_free_pages(gfp_mask,
 387                                                 c->sectors_per_block_bits - (PAGE_SHIFT - SECTOR_SHIFT));
 388         }
 389
 390         *data_mode = DATA_MODE_VMALLOC;
 391
 392         /*
 393          * __vmalloc allocates the data pages and auxiliary structures with
 394          * gfp_flags that were specified, but pagetables are always allocated
 395          * with GFP_KERNEL, no matter what was specified as gfp_mask.
 396          *
 397          * Consequently, we must set per-process flag PF_MEMALLOC_NOIO so that
 398          * all allocations done by this process (including pagetables) are done
 399          * as if GFP_NOIO was specified.
 400          */
 401         if (gfp_mask & __GFP_NORETRY) {
 402                 unsigned noio_flag = memalloc_noio_save();
 403                 void *ptr = __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL);
 404
 405                 memalloc_noio_restore(noio_flag);
 406                 return ptr;
 407         }
 408
 409         return __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL);
 410 }
 411
 412 /*
 413  * Free buffer's data.
 414  */
 415 static void free_buffer_data(struct dm_bufio_client *c,
 416                              void *data, unsigned char data_mode)
 417 {
 418         switch (data_mode) {
 419         case DATA_MODE_SLAB:
 420                 kmem_cache_free(c->slab_cache, data);
 421                 break;
 422
 423         case DATA_MODE_GET_FREE_PAGES:
 424                 free_pages((unsigned long)data,
 425                            c->sectors_per_block_bits - (PAGE_SHIFT - SECTOR_SHIFT));
 426                 break;
 427
 428         case DATA_MODE_VMALLOC:
 429                 vfree(data);
 430                 break;
 431
 432         default:
 433                 DMCRIT("dm_bufio_free_buffer_data: bad data mode: %d",
 434                        data_mode);
 435                 BUG();
 436         }
 437 }
 438
 439 /*
 440  * Allocate buffer and its data.
 441  */
 442 static struct dm_buffer *alloc_buffer(struct dm_bufio_client *c, gfp_t gfp_mask)
 443 {
 444         struct dm_buffer *b = kmem_cache_alloc(c->slab_buffer, gfp_mask);
 445
 446         if (!b)
 447                 return NULL;
 448
 449         b->c = c;
 450
 451         b->data = alloc_buffer_data(c, gfp_mask, &b->data_mode);
 452         if (!b->data) {
 453                 kmem_cache_free(c->slab_buffer, b);
 454                 return NULL;
 455         }
 456
 457 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
 458         b->stack_len = 0;
 459 #endif
 460         return b;
 461 }
 462
 463 /*
 464  * Free buffer and its data.
 465  */
 466 static void free_buffer(struct dm_buffer *b)
 467 {
 468         struct dm_bufio_client *c = b->c;
 469
 470         free_buffer_data(c, b->data, b->data_mode);
 471         kmem_cache_free(c->slab_buffer, b);
 472 }
 473
 474 /*
 475  * Link buffer to the buffer tree and clean or dirty queue.
 476  */
 477 static void __link_buffer(struct dm_buffer *b, sector_t block, int dirty)
 478 {
 479         struct dm_bufio_client *c = b->c;
 480
 481         c->n_buffers[dirty]++;
 482         b->block = block;
 483         b->list_mode = dirty;
 484         list_add(&b->lru_list, &c->lru[dirty]);
 485         __insert(b->c, b);
 486         b->last_accessed = jiffies;
 487
 488         adjust_total_allocated(b, false);
 489 }
 490
 491 /*
 492  * Unlink buffer from the buffer tree and dirty or clean queue.
 493  */
 494 static void __unlink_buffer(struct dm_buffer *b)
 495 {
 496         struct dm_bufio_client *c = b->c;
 497
 498         BUG_ON(!c->n_buffers[b->list_mode]);
 499
 500         c->n_buffers[b->list_mode]--;
 501         __remove(b->c, b);
 502         list_del(&b->lru_list);
 503
 504         adjust_total_allocated(b, true);
 505 }
 506
 507 /*
 508  * Place the buffer to the head of dirty or clean LRU queue.
 509  */
 510 static void __relink_lru(struct dm_buffer *b, int dirty)
 511 {
 512         struct dm_bufio_client *c = b->c;
 513
 514         b->accessed = 1;
 515
 516         BUG_ON(!c->n_buffers[b->list_mode]);
 517
 518         c->n_buffers[b->list_mode]--;
 519         c->n_buffers[dirty]++;
 520         b->list_mode = dirty;
 521         list_move(&b->lru_list, &c->lru[dirty]);
 522         b->last_accessed = jiffies;
 523 }
 524
 525 /*----------------------------------------------------------------
 526  * Submit I/O on the buffer.
 527  *
 528  * Bio interface is faster but it has some problems:
 529  *      the vector list is limited (increasing this limit increases
 530  *      memory-consumption per buffer, so it is not viable);
 531  *
 532  *      the memory must be direct-mapped, not vmalloced;
 533  *
 534  * If the buffer is small enough (up to DM_BUFIO_INLINE_VECS pages) and
 535  * it is not vmalloced, try using the bio interface.
 536  *
 537  * If the buffer is big, if it is vmalloced or if the underlying device
 538  * rejects the bio because it is too large, use dm-io layer to do the I/O.
 539  * The dm-io layer splits the I/O into multiple requests, avoiding the above
 540  * shortcomings.
 541  *--------------------------------------------------------------*/
 542
 543 /*
 544  * dm-io completion routine. It just calls b->bio.bi_end_io, pretending
 545  * that the request was handled directly with bio interface.
 546  */
 547 static void dmio_complete(unsigned long error, void *context)
 548 {
 549         struct dm_buffer *b = context;
 550
 551         b->end_io(b, unlikely(error != 0) ? BLK_STS_IOERR : 0);
 552 }
 553
 554 static void use_dmio(struct dm_buffer *b, int rw, sector_t sector,
 555                      unsigned n_sectors, unsigned offset)
 556 {
 557         int r;
 558         struct dm_io_request io_req = {
 559                 .bi_op = rw,
 560                 .bi_op_flags = 0,
 561                 .notify.fn = dmio_complete,
 562                 .notify.context = b,
 563                 .client = b->c->dm_io,
 564         };
 565         struct dm_io_region region = {
 566                 .bdev = b->c->bdev,
 567                 .sector = sector,
 568                 .count = n_sectors,
 569         };
 570
 571         if (b->data_mode != DATA_MODE_VMALLOC) {
 572                 io_req.mem.type = DM_IO_KMEM;
 573                 io_req.mem.ptr.addr = (char *)b->data + offset;
 574         } else {
 575                 io_req.mem.type = DM_IO_VMA;
 576                 io_req.mem.ptr.vma = (char *)b->data + offset;
 577         }
 578
 579         r = dm_io(&io_req, 1, &region, NULL);
 580         if (unlikely(r))
 581                 b->end_io(b, errno_to_blk_status(r));
 582 }
 583
 584 static void bio_complete(struct bio *bio)
 585 {
 586         struct dm_buffer *b = bio->bi_private;
 587         blk_status_t status = bio->bi_status;
 588         bio_put(bio);
 589         b->end_io(b, status);
 590 }
 591
 592 static void use_bio(struct dm_buffer *b, int rw, sector_t sector,
 593                     unsigned n_sectors, unsigned offset)
 594 {
 595         struct bio *bio;
 596         char *ptr;
 597         unsigned vec_size, len;
 598
 599         vec_size = b->c->block_size >> PAGE_SHIFT;
 600         if (unlikely(b->c->sectors_per_block_bits < PAGE_SHIFT - SECTOR_SHIFT))
 601                 vec_size += 2;
 602
 603         bio = bio_kmalloc(GFP_NOWAIT | __GFP_NORETRY | __GFP_NOWARN, vec_size);
 604         if (!bio) {
 605 dmio:
 606                 use_dmio(b, rw, sector, n_sectors, offset);
 607                 return;
 608         }
 609
 610         bio->bi_iter.bi_sector = sector;
 611         bio_set_dev(bio, b->c->bdev);
 612         bio_set_op_attrs(bio, rw, 0);
 613         bio->bi_end_io = bio_complete;
 614         bio->bi_private = b;
 615
 616         ptr = (char *)b->data + offset;
 617         len = n_sectors << SECTOR_SHIFT;
 618
 619         do {
 620                 unsigned this_step = min((unsigned)(PAGE_SIZE - offset_in_page(ptr)), len);
 621                 if (!bio_add_page(bio, virt_to_page(ptr), this_step,
 622                                   offset_in_page(ptr))) {
 623                         bio_put(bio);
 624                         goto dmio;
 625                 }
 626
 627                 len -= this_step;
 628                 ptr += this_step;
 629         } while (len > 0);
 630
 631         submit_bio(bio);
 632 }
 633
 634 static void submit_io(struct dm_buffer *b, int rw, void (*end_io)(struct dm_buffer *, blk_status_t))
 635 {
 636         unsigned n_sectors;
 637         sector_t sector;
 638         unsigned offset, end;
 639
 640         b->end_io = end_io;
 641
 642         if (likely(b->c->sectors_per_block_bits >= 0))
 643                 sector = b->block << b->c->sectors_per_block_bits;
 644         else
 645                 sector = b->block * (b->c->block_size >> SECTOR_SHIFT);
 646         sector += b->c->start;
 647
 648         if (rw != REQ_OP_WRITE) {
 649                 n_sectors = b->c->block_size >> SECTOR_SHIFT;
 650                 offset = 0;
 651         } else {
 652                 if (b->c->write_callback)
 653                         b->c->write_callback(b);
 654                 offset = b->write_start;
 655                 end = b->write_end;
 656                 offset &= -DM_BUFIO_WRITE_ALIGN;
 657                 end += DM_BUFIO_WRITE_ALIGN - 1;
 658                 end &= -DM_BUFIO_WRITE_ALIGN;
 659                 if (unlikely(end > b->c->block_size))
 660                         end = b->c->block_size;
 661
 662                 sector += offset >> SECTOR_SHIFT;
 663                 n_sectors = (end - offset) >> SECTOR_SHIFT;
 664         }
 665
 666         if (b->data_mode != DATA_MODE_VMALLOC)
 667                 use_bio(b, rw, sector, n_sectors, offset);
 668         else
 669                 use_dmio(b, rw, sector, n_sectors, offset);
 670 }
 671
 672 /*----------------------------------------------------------------
 673  * Writing dirty buffers
 674  *--------------------------------------------------------------*/
 675
 676 /*
 677  * The endio routine for write.
 678  *
 679  * Set the error, clear B_WRITING bit and wake anyone who was waiting on
 680  * it.
 681  */
 682 static void write_endio(struct dm_buffer *b, blk_status_t status)
 683 {
 684         b->write_error = status;
 685         if (unlikely(status)) {
 686                 struct dm_bufio_client *c = b->c;
 687
 688                 (void)cmpxchg(&c->async_write_error, 0,
 689                                 blk_status_to_errno(status));
 690         }
 691
 692         BUG_ON(!test_bit(B_WRITING, &b->state));
 693
 694         smp_mb__before_atomic();
 695         clear_bit(B_WRITING, &b->state);
 696         smp_mb__after_atomic();
 697
 698         wake_up_bit(&b->state, B_WRITING);
 699 }
 700
 701 /*
 702  * Initiate a write on a dirty buffer, but don't wait for it.
 703  *
 704  * - If the buffer is not dirty, exit.
 705  * - If there some previous write going on, wait for it to finish (we can't
 706  *   have two writes on the same buffer simultaneously).
 707  * - Submit our write and don't wait on it. We set B_WRITING indicating
 708  *   that there is a write in progress.
 709  */
 710 static void __write_dirty_buffer(struct dm_buffer *b,
 711                                  struct list_head *write_list)
 712 {
 713         if (!test_bit(B_DIRTY, &b->state))
 714                 return;
 715
 716         clear_bit(B_DIRTY, &b->state);
 717         wait_on_bit_lock_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
 718
 719         b->write_start = b->dirty_start;
 720         b->write_end = b->dirty_end;
 721
 722         if (!write_list)
 723                 submit_io(b, REQ_OP_WRITE, write_endio);
 724         else
 725                 list_add_tail(&b->write_list, write_list);
 726 }
 727
 728 static void __flush_write_list(struct list_head *write_list)
 729 {
 730         struct blk_plug plug;
 731         blk_start_plug(&plug);
 732         while (!list_empty(write_list)) {
 733                 struct dm_buffer *b =
 734                         list_entry(write_list->next, struct dm_buffer, write_list);
 735                 list_del(&b->write_list);
 736                 submit_io(b, REQ_OP_WRITE, write_endio);
 737                 cond_resched();
 738         }
 739         blk_finish_plug(&plug);
 740 }
 741
 742 /*
 743  * Wait until any activity on the buffer finishes.  Possibly write the
 744  * buffer if it is dirty.  When this function finishes, there is no I/O
 745  * running on the buffer and the buffer is not dirty.
 746  */
 747 static void __make_buffer_clean(struct dm_buffer *b)
 748 {
 749         BUG_ON(b->hold_count);
 750
 751         if (!b->state)  /* fast case */
 752                 return;
 753
 754         wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
 755         __write_dirty_buffer(b, NULL);
 756         wait_on_bit_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
 757 }
 758
 759 /*
 760  * Find some buffer that is not held by anybody, clean it, unlink it and
 761  * return it.
 762  */
 763 static struct dm_buffer *__get_unclaimed_buffer(struct dm_bufio_client *c)
 764 {
 765         struct dm_buffer *b;
 766
 767         list_for_each_entry_reverse(b, &c->lru[LIST_CLEAN], lru_list) {
 768                 BUG_ON(test_bit(B_WRITING, &b->state));
 769                 BUG_ON(test_bit(B_DIRTY, &b->state));
 770
 771                 if (!b->hold_count) {
 772                         __make_buffer_clean(b);
 773                         __unlink_buffer(b);
 774                         return b;
 775                 }
 776                 cond_resched();
 777         }
 778
 779         list_for_each_entry_reverse(b, &c->lru[LIST_DIRTY], lru_list) {
 780                 BUG_ON(test_bit(B_READING, &b->state));
 781
 782                 if (!b->hold_count) {
 783                         __make_buffer_clean(b);
 784                         __unlink_buffer(b);
 785                         return b;
 786                 }
 787                 cond_resched();
 788         }
 789
 790         return NULL;
 791 }
 792
 793 /*
 794  * Wait until some other threads free some buffer or release hold count on
 795  * some buffer.
 796  *
 797  * This function is entered with c->lock held, drops it and regains it
 798  * before exiting.
 799  */
 800 static void __wait_for_free_buffer(struct dm_bufio_client *c)
 801 {
 802         DECLARE_WAITQUEUE(wait, current);
 803
 804         add_wait_queue(&c->free_buffer_wait, &wait);
 805         set_current_state(TASK_UNINTERRUPTIBLE);
 806         dm_bufio_unlock(c);
 807
 808         io_schedule();
 809
 810         remove_wait_queue(&c->free_buffer_wait, &wait);
 811
 812         dm_bufio_lock(c);
 813 }
 814
 815 enum new_flag {
 816         NF_FRESH = 0,
 817         NF_READ = 1,
 818         NF_GET = 2,
 819         NF_PREFETCH = 3
 820 };
 821
 822 /*
 823  * Allocate a new buffer. If the allocation is not possible, wait until
 824  * some other thread frees a buffer.
 825  *
 826  * May drop the lock and regain it.
 827  */
 828 static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client *c, enum new_flag nf)
 829 {
 830         struct dm_buffer *b;
 831         bool tried_noio_alloc = false;
 832
 833         /*
 834          * dm-bufio is resistant to allocation failures (it just keeps
 835          * one buffer reserved in cases all the allocations fail).
 836          * So set flags to not try too hard:
 837          *      GFP_NOWAIT: don't wait; if we need to sleep we'll release our
 838          *                  mutex and wait ourselves.
 839          *      __GFP_NORETRY: don't retry and rather return failure
 840          *      __GFP_NOMEMALLOC: don't use emergency reserves
 841          *      __GFP_NOWARN: don't print a warning in case of failure
 842          *
 843          * For debugging, if we set the cache size to 1, no new buffers will
 844          * be allocated.
 845          */
 846         while (1) {
 847                 if (dm_bufio_cache_size_latch != 1) {
 848                         b = alloc_buffer(c, GFP_NOWAIT | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
 849                         if (b)
 850                                 return b;
 851                 }
 852
 853                 if (nf == NF_PREFETCH)
 854                         return NULL;
 855
 856                 if (dm_bufio_cache_size_latch != 1 && !tried_noio_alloc) {
 857                         dm_bufio_unlock(c);
 858                         b = alloc_buffer(c, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
 859                         dm_bufio_lock(c);
 860                         if (b)
 861                                 return b;
 862                         tried_noio_alloc = true;
 863                 }
 864
 865                 if (!list_empty(&c->reserved_buffers)) {
 866                         b = list_entry(c->reserved_buffers.next,
 867                                        struct dm_buffer, lru_list);
 868                         list_del(&b->lru_list);
 869                         c->need_reserved_buffers++;
 870
 871                         return b;
 872                 }
 873
 874                 b = __get_unclaimed_buffer(c);
 875                 if (b)
 876                         return b;
 877
 878                 __wait_for_free_buffer(c);
 879         }
 880 }
 881
 882 static struct dm_buffer *__alloc_buffer_wait(struct dm_bufio_client *c, enum new_flag nf)
 883 {
 884         struct dm_buffer *b = __alloc_buffer_wait_no_callback(c, nf);
 885
 886         if (!b)
 887                 return NULL;
 888
 889         if (c->alloc_callback)
 890                 c->alloc_callback(b);
 891
 892         return b;
 893 }
 894
 895 /*
 896  * Free a buffer and wake other threads waiting for free buffers.
 897  */
 898 static void __free_buffer_wake(struct dm_buffer *b)
 899 {
 900         struct dm_bufio_client *c = b->c;
 901
 902         if (!c->need_reserved_buffers)
 903                 free_buffer(b);
 904         else {
 905                 list_add(&b->lru_list, &c->reserved_buffers);
 906                 c->need_reserved_buffers--;
 907         }
 908
 909         wake_up(&c->free_buffer_wait);
 910 }
 911
 912 static void __write_dirty_buffers_async(struct dm_bufio_client *c, int no_wait,
 913                                         struct list_head *write_list)
 914 {
 915         struct dm_buffer *b, *tmp;
 916
 917         list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) {
 918                 BUG_ON(test_bit(B_READING, &b->state));
 919
 920                 if (!test_bit(B_DIRTY, &b->state) &&
 921                     !test_bit(B_WRITING, &b->state)) {
 922                         __relink_lru(b, LIST_CLEAN);
 923                         continue;
 924                 }
 925
 926                 if (no_wait && test_bit(B_WRITING, &b->state))
 927                         return;
 928
 929                 __write_dirty_buffer(b, write_list);
 930                 cond_resched();
 931         }
 932 }
 933
 934 /*
 935  * Check if we're over watermark.
 936  * If we are over threshold_buffers, start freeing buffers.
 937  * If we're over "limit_buffers", block until we get under the limit.
 938  */
 939 static void __check_watermark(struct dm_bufio_client *c,
 940                               struct list_head *write_list)
 941 {
 942         if (c->n_buffers[LIST_DIRTY] > c->n_buffers[LIST_CLEAN] * DM_BUFIO_WRITEBACK_RATIO)
 943                 __write_dirty_buffers_async(c, 1, write_list);
 944 }
 945
 946 /*----------------------------------------------------------------
 947  * Getting a buffer
 948  *--------------------------------------------------------------*/
 949
 950 static struct dm_buffer *__bufio_new(struct dm_bufio_client *c, sector_t block,
 951                                      enum new_flag nf, int *need_submit,
 952                                      struct list_head *write_list)
 953 {
 954         struct dm_buffer *b, *new_b = NULL;
 955
 956         *need_submit = 0;
 957
 958         b = __find(c, block);
 959         if (b)
 960                 goto found_buffer;
 961
 962         if (nf == NF_GET)
 963                 return NULL;
 964
 965         new_b = __alloc_buffer_wait(c, nf);
 966         if (!new_b)
 967                 return NULL;
 968
 969         /*
 970          * We've had a period where the mutex was unlocked, so need to
 971          * recheck the buffer tree.
 972          */
 973         b = __find(c, block);
 974         if (b) {
 975                 __free_buffer_wake(new_b);
 976                 goto found_buffer;
 977         }
 978
 979         __check_watermark(c, write_list);
 980
 981         b = new_b;
 982         b->hold_count = 1;
 983         b->read_error = 0;
 984         b->write_error = 0;
 985         __link_buffer(b, block, LIST_CLEAN);
 986
 987         if (nf == NF_FRESH) {
 988                 b->state = 0;
 989                 return b;
 990         }
 991
 992         b->state = 1 << B_READING;
 993         *need_submit = 1;
 994
 995         return b;
 996
 997 found_buffer:
 998         if (nf == NF_PREFETCH)
 999                 return NULL;
1000         /*
1001          * Note: it is essential that we don't wait for the buffer to be
1002          * read if dm_bufio_get function is used. Both dm_bufio_get and
1003          * dm_bufio_prefetch can be used in the driver request routine.
1004          * If the user called both dm_bufio_prefetch and dm_bufio_get on
1005          * the same buffer, it would deadlock if we waited.
1006          */
1007         if (nf == NF_GET && unlikely(test_bit(B_READING, &b->state)))
1008                 return NULL;
1009
1010         b->hold_count++;
1011         __relink_lru(b, test_bit(B_DIRTY, &b->state) ||
1012                      test_bit(B_WRITING, &b->state));
1013         return b;
1014 }
1015
1016 /*
1017  * The endio routine for reading: set the error, clear the bit and wake up
1018  * anyone waiting on the buffer.
1019  */
1020 static void read_endio(struct dm_buffer *b, blk_status_t status)
1021 {
1022         b->read_error = status;
1023
1024         BUG_ON(!test_bit(B_READING, &b->state));
1025
1026         smp_mb__before_atomic();
1027         clear_bit(B_READING, &b->state);
1028         smp_mb__after_atomic();
1029
1030         wake_up_bit(&b->state, B_READING);
1031 }
1032
1033 /*
1034  * A common routine for dm_bufio_new and dm_bufio_read.  Operation of these
1035  * functions is similar except that dm_bufio_new doesn't read the
1036  * buffer from the disk (assuming that the caller overwrites all the data
1037  * and uses dm_bufio_mark_buffer_dirty to write new data back).
1038  */
1039 static void *new_read(struct dm_bufio_client *c, sector_t block,
1040                       enum new_flag nf, struct dm_buffer **bp)
1041 {
1042         int need_submit;
1043         struct dm_buffer *b;
1044
1045         LIST_HEAD(write_list);
1046
1047         dm_bufio_lock(c);
1048         b = __bufio_new(c, block, nf, &need_submit, &write_list);
1049 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1050         if (b && b->hold_count == 1)
1051                 buffer_record_stack(b);
1052 #endif
1053         dm_bufio_unlock(c);
1054
1055         __flush_write_list(&write_list);
1056
1057         if (!b)
1058                 return NULL;
1059
1060         if (need_submit)
1061                 submit_io(b, REQ_OP_READ, read_endio);
1062
1063         wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
1064
1065         if (b->read_error) {
1066                 int error = blk_status_to_errno(b->read_error);
1067
1068                 dm_bufio_release(b);
1069
1070                 return ERR_PTR(error);
1071         }
1072
1073         *bp = b;
1074
1075         return b->data;
1076 }
1077
1078 void *dm_bufio_get(struct dm_bufio_client *c, sector_t block,
1079                    struct dm_buffer **bp)
1080 {
1081         return new_read(c, block, NF_GET, bp);
1082 }
1083 EXPORT_SYMBOL_GPL(dm_bufio_get);
1084
1085 void *dm_bufio_read(struct dm_bufio_client *c, sector_t block,
1086                     struct dm_buffer **bp)
1087 {
1088         BUG_ON(dm_bufio_in_request());
1089
1090         return new_read(c, block, NF_READ, bp);
1091 }
1092 EXPORT_SYMBOL_GPL(dm_bufio_read);
1093
1094 void *dm_bufio_new(struct dm_bufio_client *c, sector_t block,
1095                    struct dm_buffer **bp)
1096 {
1097         BUG_ON(dm_bufio_in_request());
1098
1099         return new_read(c, block, NF_FRESH, bp);
1100 }
1101 EXPORT_SYMBOL_GPL(dm_bufio_new);
1102
1103 void dm_bufio_prefetch(struct dm_bufio_client *c,
1104                        sector_t block, unsigned n_blocks)
1105 {
1106         struct blk_plug plug;
1107
1108         LIST_HEAD(write_list);
1109
1110         BUG_ON(dm_bufio_in_request());
1111
1112         blk_start_plug(&plug);
1113         dm_bufio_lock(c);
1114
1115         for (; n_blocks--; block++) {
1116                 int need_submit;
1117                 struct dm_buffer *b;
1118                 b = __bufio_new(c, block, NF_PREFETCH, &need_submit,
1119                                 &write_list);
1120                 if (unlikely(!list_empty(&write_list))) {
1121                         dm_bufio_unlock(c);
1122                         blk_finish_plug(&plug);
1123                         __flush_write_list(&write_list);
1124                         blk_start_plug(&plug);
1125                         dm_bufio_lock(c);
1126                 }
1127                 if (unlikely(b != NULL)) {
1128                         dm_bufio_unlock(c);
1129
1130                         if (need_submit)
1131                                 submit_io(b, REQ_OP_READ, read_endio);
1132                         dm_bufio_release(b);
1133
1134                         cond_resched();
1135
1136                         if (!n_blocks)
1137                                 goto flush_plug;
1138                         dm_bufio_lock(c);
1139                 }
1140         }
1141
1142         dm_bufio_unlock(c);
1143
1144 flush_plug:
1145         blk_finish_plug(&plug);
1146 }
1147 EXPORT_SYMBOL_GPL(dm_bufio_prefetch);
1148
1149 void dm_bufio_release(struct dm_buffer *b)
1150 {
1151         struct dm_bufio_client *c = b->c;
1152
1153         dm_bufio_lock(c);
1154
1155         BUG_ON(!b->hold_count);
1156
1157         b->hold_count--;
1158         if (!b->hold_count) {
1159                 wake_up(&c->free_buffer_wait);
1160
1161                 /*
1162                  * If there were errors on the buffer, and the buffer is not
1163                  * to be written, free the buffer. There is no point in caching
1164                  * invalid buffer.
1165                  */
1166                 if ((b->read_error || b->write_error) &&
1167                     !test_bit(B_READING, &b->state) &&
1168                     !test_bit(B_WRITING, &b->state) &&
1169                     !test_bit(B_DIRTY, &b->state)) {
1170                         __unlink_buffer(b);
1171                         __free_buffer_wake(b);
1172                 }
1173         }
1174
1175         dm_bufio_unlock(c);
1176 }
1177 EXPORT_SYMBOL_GPL(dm_bufio_release);
1178
1179 void dm_bufio_mark_partial_buffer_dirty(struct dm_buffer *b,
1180                                         unsigned start, unsigned end)
1181 {
1182         struct dm_bufio_client *c = b->c;
1183
1184         BUG_ON(start >= end);
1185         BUG_ON(end > b->c->block_size);
1186
1187         dm_bufio_lock(c);
1188
1189         BUG_ON(test_bit(B_READING, &b->state));
1190
1191         if (!test_and_set_bit(B_DIRTY, &b->state)) {
1192                 b->dirty_start = start;
1193                 b->dirty_end = end;
1194                 __relink_lru(b, LIST_DIRTY);
1195         } else {
1196                 if (start < b->dirty_start)
1197                         b->dirty_start = start;
1198                 if (end > b->dirty_end)
1199                         b->dirty_end = end;
1200         }
1201
1202         dm_bufio_unlock(c);
1203 }
1204 EXPORT_SYMBOL_GPL(dm_bufio_mark_partial_buffer_dirty);
1205
1206 void dm_bufio_mark_buffer_dirty(struct dm_buffer *b)
1207 {
1208         dm_bufio_mark_partial_buffer_dirty(b, 0, b->c->block_size);
1209 }
1210 EXPORT_SYMBOL_GPL(dm_bufio_mark_buffer_dirty);
1211
1212 void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c)
1213 {
1214         LIST_HEAD(write_list);
1215
1216         BUG_ON(dm_bufio_in_request());
1217
1218         dm_bufio_lock(c);
1219         __write_dirty_buffers_async(c, 0, &write_list);
1220         dm_bufio_unlock(c);
1221         __flush_write_list(&write_list);
1222 }
1223 EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers_async);
1224
1225 /*
1226  * For performance, it is essential that the buffers are written asynchronously
1227  * and simultaneously (so that the block layer can merge the writes) and then
1228  * waited upon.
1229  *
1230  * Finally, we flush hardware disk cache.
1231  */
1232 int dm_bufio_write_dirty_buffers(struct dm_bufio_client *c)
1233 {
1234         int a, f;
1235         unsigned long buffers_processed = 0;
1236         struct dm_buffer *b, *tmp;
1237
1238         LIST_HEAD(write_list);
1239
1240         dm_bufio_lock(c);
1241         __write_dirty_buffers_async(c, 0, &write_list);
1242         dm_bufio_unlock(c);
1243         __flush_write_list(&write_list);
1244         dm_bufio_lock(c);
1245
1246 again:
1247         list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) {
1248                 int dropped_lock = 0;
1249
1250                 if (buffers_processed < c->n_buffers[LIST_DIRTY])
1251                         buffers_processed++;
1252
1253                 BUG_ON(test_bit(B_READING, &b->state));
1254
1255                 if (test_bit(B_WRITING, &b->state)) {
1256                         if (buffers_processed < c->n_buffers[LIST_DIRTY]) {
1257                                 dropped_lock = 1;
1258                                 b->hold_count++;
1259                                 dm_bufio_unlock(c);
1260                                 wait_on_bit_io(&b->state, B_WRITING,
1261                                                TASK_UNINTERRUPTIBLE);
1262                                 dm_bufio_lock(c);
1263                                 b->hold_count--;
1264                         } else
1265                                 wait_on_bit_io(&b->state, B_WRITING,
1266                                                TASK_UNINTERRUPTIBLE);
1267                 }
1268
1269                 if (!test_bit(B_DIRTY, &b->state) &&
1270                     !test_bit(B_WRITING, &b->state))
1271                         __relink_lru(b, LIST_CLEAN);
1272
1273                 cond_resched();
1274
1275                 /*
1276                  * If we dropped the lock, the list is no longer consistent,
1277                  * so we must restart the search.
1278                  *
1279                  * In the most common case, the buffer just processed is
1280                  * relinked to the clean list, so we won't loop scanning the
1281                  * same buffer again and again.
1282                  *
1283                  * This may livelock if there is another thread simultaneously
1284                  * dirtying buffers, so we count the number of buffers walked
1285                  * and if it exceeds the total number of buffers, it means that
1286                  * someone is doing some writes simultaneously with us.  In
1287                  * this case, stop, dropping the lock.
1288                  */
1289                 if (dropped_lock)
1290                         goto again;
1291         }
1292         wake_up(&c->free_buffer_wait);
1293         dm_bufio_unlock(c);
1294
1295         a = xchg(&c->async_write_error, 0);
1296         f = dm_bufio_issue_flush(c);
1297         if (a)
1298                 return a;
1299
1300         return f;
1301 }
1302 EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers);
1303
1304 /*
1305  * Use dm-io to send an empty barrier to flush the device.
1306  */
1307 int dm_bufio_issue_flush(struct dm_bufio_client *c)
1308 {
1309         struct dm_io_request io_req = {
1310                 .bi_op = REQ_OP_WRITE,
1311                 .bi_op_flags = REQ_PREFLUSH | REQ_SYNC,
1312                 .mem.type = DM_IO_KMEM,
1313                 .mem.ptr.addr = NULL,
1314                 .client = c->dm_io,
1315         };
1316         struct dm_io_region io_reg = {
1317                 .bdev = c->bdev,
1318                 .sector = 0,
1319                 .count = 0,
1320         };
1321
1322         BUG_ON(dm_bufio_in_request());
1323
1324         return dm_io(&io_req, 1, &io_reg, NULL);
1325 }
1326 EXPORT_SYMBOL_GPL(dm_bufio_issue_flush);
1327
1328 /*
1329  * We first delete any other buffer that may be at that new location.
1330  *
1331  * Then, we write the buffer to the original location if it was dirty.
1332  *
1333  * Then, if we are the only one who is holding the buffer, relink the buffer
1334  * in the buffer tree for the new location.
1335  *
1336  * If there was someone else holding the buffer, we write it to the new
1337  * location but not relink it, because that other user needs to have the buffer
1338  * at the same place.
1339  */
1340 void dm_bufio_release_move(struct dm_buffer *b, sector_t new_block)
1341 {
1342         struct dm_bufio_client *c = b->c;
1343         struct dm_buffer *new;
1344
1345         BUG_ON(dm_bufio_in_request());
1346
1347         dm_bufio_lock(c);
1348
1349 retry:
1350         new = __find(c, new_block);
1351         if (new) {
1352                 if (new->hold_count) {
1353                         __wait_for_free_buffer(c);
1354                         goto retry;
1355                 }
1356
1357                 /*
1358                  * FIXME: Is there any point waiting for a write that's going
1359                  * to be overwritten in a bit?
1360                  */
1361                 __make_buffer_clean(new);
1362                 __unlink_buffer(new);
1363                 __free_buffer_wake(new);
1364         }
1365
1366         BUG_ON(!b->hold_count);
1367         BUG_ON(test_bit(B_READING, &b->state));
1368
1369         __write_dirty_buffer(b, NULL);
1370         if (b->hold_count == 1) {
1371                 wait_on_bit_io(&b->state, B_WRITING,
1372                                TASK_UNINTERRUPTIBLE);
1373                 set_bit(B_DIRTY, &b->state);
1374                 b->dirty_start = 0;
1375                 b->dirty_end = c->block_size;
1376                 __unlink_buffer(b);
1377                 __link_buffer(b, new_block, LIST_DIRTY);
1378         } else {
1379                 sector_t old_block;
1380                 wait_on_bit_lock_io(&b->state, B_WRITING,
1381                                     TASK_UNINTERRUPTIBLE);
1382                 /*
1383                  * Relink buffer to "new_block" so that write_callback
1384                  * sees "new_block" as a block number.
1385                  * After the write, link the buffer back to old_block.
1386                  * All this must be done in bufio lock, so that block number
1387                  * change isn't visible to other threads.
1388                  */
1389                 old_block = b->block;
1390                 __unlink_buffer(b);
1391                 __link_buffer(b, new_block, b->list_mode);
1392                 submit_io(b, REQ_OP_WRITE, write_endio);
1393                 wait_on_bit_io(&b->state, B_WRITING,
1394                                TASK_UNINTERRUPTIBLE);
1395                 __unlink_buffer(b);
1396                 __link_buffer(b, old_block, b->list_mode);
1397         }
1398
1399         dm_bufio_unlock(c);
1400         dm_bufio_release(b);
1401 }
1402 EXPORT_SYMBOL_GPL(dm_bufio_release_move);
1403
1404 /*
1405  * Free the given buffer.
1406  *
1407  * This is just a hint, if the buffer is in use or dirty, this function
1408  * does nothing.
1409  */
1410 void dm_bufio_forget(struct dm_bufio_client *c, sector_t block)
1411 {
1412         struct dm_buffer *b;
1413
1414         dm_bufio_lock(c);
1415
1416         b = __find(c, block);
1417         if (b && likely(!b->hold_count) && likely(!b->state)) {
1418                 __unlink_buffer(b);
1419                 __free_buffer_wake(b);
1420         }
1421
1422         dm_bufio_unlock(c);
1423 }
1424 EXPORT_SYMBOL_GPL(dm_bufio_forget);
1425
1426 void dm_bufio_set_minimum_buffers(struct dm_bufio_client *c, unsigned n)
1427 {
1428         c->minimum_buffers = n;
1429 }
1430 EXPORT_SYMBOL_GPL(dm_bufio_set_minimum_buffers);
1431
1432 unsigned dm_bufio_get_block_size(struct dm_bufio_client *c)
1433 {
1434         return c->block_size;
1435 }
1436 EXPORT_SYMBOL_GPL(dm_bufio_get_block_size);
1437
1438 sector_t dm_bufio_get_device_size(struct dm_bufio_client *c)
1439 {
1440         sector_t s = i_size_read(c->bdev->bd_inode) >> SECTOR_SHIFT;
1441         if (likely(c->sectors_per_block_bits >= 0))
1442                 s >>= c->sectors_per_block_bits;
1443         else
1444                 sector_div(s, c->block_size >> SECTOR_SHIFT);
1445         return s;
1446 }
1447 EXPORT_SYMBOL_GPL(dm_bufio_get_device_size);
1448
1449 sector_t dm_bufio_get_block_number(struct dm_buffer *b)
1450 {
1451         return b->block;
1452 }
1453 EXPORT_SYMBOL_GPL(dm_bufio_get_block_number);
1454
1455 void *dm_bufio_get_block_data(struct dm_buffer *b)
1456 {
1457         return b->data;
1458 }
1459 EXPORT_SYMBOL_GPL(dm_bufio_get_block_data);
1460
1461 void *dm_bufio_get_aux_data(struct dm_buffer *b)
1462 {
1463         return b + 1;
1464 }
1465 EXPORT_SYMBOL_GPL(dm_bufio_get_aux_data);
1466
1467 struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b)
1468 {
1469         return b->c;
1470 }
1471 EXPORT_SYMBOL_GPL(dm_bufio_get_client);
1472
1473 static void drop_buffers(struct dm_bufio_client *c)
1474 {
1475         struct dm_buffer *b;
1476         int i;
1477         bool warned = false;
1478
1479         BUG_ON(dm_bufio_in_request());
1480
1481         /*
1482          * An optimization so that the buffers are not written one-by-one.
1483          */
1484         dm_bufio_write_dirty_buffers_async(c);
1485
1486         dm_bufio_lock(c);
1487
1488         while ((b = __get_unclaimed_buffer(c)))
1489                 __free_buffer_wake(b);
1490
1491         for (i = 0; i < LIST_SIZE; i++)
1492                 list_for_each_entry(b, &c->lru[i], lru_list) {
1493                         WARN_ON(!warned);
1494                         warned = true;
1495                         DMERR("leaked buffer %llx, hold count %u, list %d",
1496                               (unsigned long long)b->block, b->hold_count, i);
1497 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1498                         stack_trace_print(b->stack_entries, b->stack_len, 1);
1499                         /* mark unclaimed to avoid BUG_ON below */
1500                         b->hold_count = 0;
1501 #endif
1502                 }
1503
1504 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1505         while ((b = __get_unclaimed_buffer(c)))
1506                 __free_buffer_wake(b);
1507 #endif
1508
1509         for (i = 0; i < LIST_SIZE; i++)
1510                 BUG_ON(!list_empty(&c->lru[i]));
1511
1512         dm_bufio_unlock(c);
1513 }
1514
1515 /*
1516  * We may not be able to evict this buffer if IO pending or the client
1517  * is still using it.  Caller is expected to know buffer is too old.
1518  *
1519  * And if GFP_NOFS is used, we must not do any I/O because we hold
1520  * dm_bufio_clients_lock and we would risk deadlock if the I/O gets
1521  * rerouted to different bufio client.
1522  */
1523 static bool __try_evict_buffer(struct dm_buffer *b, gfp_t gfp)
1524 {
1525         if (!(gfp & __GFP_FS)) {
1526                 if (test_bit(B_READING, &b->state) ||
1527                     test_bit(B_WRITING, &b->state) ||
1528                     test_bit(B_DIRTY, &b->state))
1529                         return false;
1530         }
1531
1532         if (b->hold_count)
1533                 return false;
1534
1535         __make_buffer_clean(b);
1536         __unlink_buffer(b);
1537         __free_buffer_wake(b);
1538
1539         return true;
1540 }
1541
1542 static unsigned long get_retain_buffers(struct dm_bufio_client *c)
1543 {
1544         unsigned long retain_bytes = READ_ONCE(dm_bufio_retain_bytes);
1545         if (likely(c->sectors_per_block_bits >= 0))
1546                 retain_bytes >>= c->sectors_per_block_bits + SECTOR_SHIFT;
1547         else
1548                 retain_bytes /= c->block_size;
1549         return retain_bytes;
1550 }
1551
1552 static unsigned long __scan(struct dm_bufio_client *c, unsigned long nr_to_scan,
1553                             gfp_t gfp_mask)
1554 {
1555         int l;
1556         struct dm_buffer *b, *tmp;
1557         unsigned long freed = 0;
1558         unsigned long count = c->n_buffers[LIST_CLEAN] +
1559                               c->n_buffers[LIST_DIRTY];
1560         unsigned long retain_target = get_retain_buffers(c);
1561
1562         for (l = 0; l < LIST_SIZE; l++) {
1563                 list_for_each_entry_safe_reverse(b, tmp, &c->lru[l], lru_list) {
1564                         if (__try_evict_buffer(b, gfp_mask))
1565                                 freed++;
1566                         if (!--nr_to_scan || ((count - freed) <= retain_target))
1567                                 return freed;
1568                         cond_resched();
1569                 }
1570         }
1571         return freed;
1572 }
1573
1574 static unsigned long
1575 dm_bufio_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
1576 {
1577         struct dm_bufio_client *c;
1578         unsigned long freed;
1579
1580         c = container_of(shrink, struct dm_bufio_client, shrinker);
1581         if (sc->gfp_mask & __GFP_FS)
1582                 dm_bufio_lock(c);
1583         else if (!dm_bufio_trylock(c))
1584                 return SHRINK_STOP;
1585
1586         freed  = __scan(c, sc->nr_to_scan, sc->gfp_mask);
1587         dm_bufio_unlock(c);
1588         return freed;
1589 }
1590
1591 static unsigned long
1592 dm_bufio_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
1593 {
1594         struct dm_bufio_client *c = container_of(shrink, struct dm_bufio_client, shrinker);
1595         unsigned long count = READ_ONCE(c->n_buffers[LIST_CLEAN]) +
1596                               READ_ONCE(c->n_buffers[LIST_DIRTY]);
1597         unsigned long retain_target = get_retain_buffers(c);
1598
1599         return (count < retain_target) ? 0 : (count - retain_target);
1600 }
1601
1602 /*
1603  * Create the buffering interface
1604  */
1605 struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsigned block_size,
1606                                                unsigned reserved_buffers, unsigned aux_size,
1607                                                void (*alloc_callback)(struct dm_buffer *),
1608                                                void (*write_callback)(struct dm_buffer *))
1609 {
1610         int r;
1611         struct dm_bufio_client *c;
1612         unsigned i;
1613         char slab_name[27];
1614
1615         if (!block_size || block_size & ((1 << SECTOR_SHIFT) - 1)) {
1616                 DMERR("%s: block size not specified or is not multiple of 512b", __func__);
1617                 r = -EINVAL;
1618                 goto bad_client;
1619         }
1620
1621         c = kzalloc(sizeof(*c), GFP_KERNEL);
1622         if (!c) {
1623                 r = -ENOMEM;
1624                 goto bad_client;
1625         }
1626         c->buffer_tree = RB_ROOT;
1627
1628         c->bdev = bdev;
1629         c->block_size = block_size;
1630         if (is_power_of_2(block_size))
1631                 c->sectors_per_block_bits = __ffs(block_size) - SECTOR_SHIFT;
1632         else
1633                 c->sectors_per_block_bits = -1;
1634
1635         c->alloc_callback = alloc_callback;
1636         c->write_callback = write_callback;
1637
1638         for (i = 0; i < LIST_SIZE; i++) {
1639                 INIT_LIST_HEAD(&c->lru[i]);
1640                 c->n_buffers[i] = 0;
1641         }
1642
1643         mutex_init(&c->lock);
1644         INIT_LIST_HEAD(&c->reserved_buffers);
1645         c->need_reserved_buffers = reserved_buffers;
1646
1647         dm_bufio_set_minimum_buffers(c, DM_BUFIO_MIN_BUFFERS);
1648
1649         init_waitqueue_head(&c->free_buffer_wait);
1650         c->async_write_error = 0;
1651
1652         c->dm_io = dm_io_client_create();
1653         if (IS_ERR(c->dm_io)) {
1654                 r = PTR_ERR(c->dm_io);
1655                 goto bad_dm_io;
1656         }
1657
1658         if (block_size <= KMALLOC_MAX_SIZE &&
1659             (block_size < PAGE_SIZE || !is_power_of_2(block_size))) {
1660                 unsigned align = min(1U << __ffs(block_size), (unsigned)PAGE_SIZE);
1661                 snprintf(slab_name, sizeof slab_name, "dm_bufio_cache-%u", block_size);
1662                 c->slab_cache = kmem_cache_create(slab_name, block_size, align,
1663                                                   SLAB_RECLAIM_ACCOUNT, NULL);
1664                 if (!c->slab_cache) {
1665                         r = -ENOMEM;
1666                         goto bad;
1667                 }
1668         }
1669         if (aux_size)
1670                 snprintf(slab_name, sizeof slab_name, "dm_bufio_buffer-%u", aux_size);
1671         else
1672                 snprintf(slab_name, sizeof slab_name, "dm_bufio_buffer");
1673         c->slab_buffer = kmem_cache_create(slab_name, sizeof(struct dm_buffer) + aux_size,
1674                                            0, SLAB_RECLAIM_ACCOUNT, NULL);
1675         if (!c->slab_buffer) {
1676                 r = -ENOMEM;
1677                 goto bad;
1678         }
1679
1680         while (c->need_reserved_buffers) {
1681                 struct dm_buffer *b = alloc_buffer(c, GFP_KERNEL);
1682
1683                 if (!b) {
1684                         r = -ENOMEM;
1685                         goto bad;
1686                 }
1687                 __free_buffer_wake(b);
1688         }
1689
1690         c->shrinker.count_objects = dm_bufio_shrink_count;
1691         c->shrinker.scan_objects = dm_bufio_shrink_scan;
1692         c->shrinker.seeks = 1;
1693         c->shrinker.batch = 0;
1694         r = register_shrinker(&c->shrinker);
1695         if (r)
1696                 goto bad;
1697
1698         mutex_lock(&dm_bufio_clients_lock);
1699         dm_bufio_client_count++;
1700         list_add(&c->client_list, &dm_bufio_all_clients);
1701         __cache_size_refresh();
1702         mutex_unlock(&dm_bufio_clients_lock);
1703
1704         return c;
1705
1706 bad:
1707         while (!list_empty(&c->reserved_buffers)) {
1708                 struct dm_buffer *b = list_entry(c->reserved_buffers.next,
1709                                                  struct dm_buffer, lru_list);
1710                 list_del(&b->lru_list);
1711                 free_buffer(b);
1712         }
1713         kmem_cache_destroy(c->slab_cache);
1714         kmem_cache_destroy(c->slab_buffer);
1715         dm_io_client_destroy(c->dm_io);
1716 bad_dm_io:
1717         mutex_destroy(&c->lock);
1718         kfree(c);
1719 bad_client:
1720         return ERR_PTR(r);
1721 }
1722 EXPORT_SYMBOL_GPL(dm_bufio_client_create);
1723
1724 /*
1725  * Free the buffering interface.
1726  * It is required that there are no references on any buffers.
1727  */
1728 void dm_bufio_client_destroy(struct dm_bufio_client *c)
1729 {
1730         unsigned i;
1731
1732         drop_buffers(c);
1733
1734         unregister_shrinker(&c->shrinker);
1735
1736         mutex_lock(&dm_bufio_clients_lock);
1737
1738         list_del(&c->client_list);
1739         dm_bufio_client_count--;
1740         __cache_size_refresh();
1741
1742         mutex_unlock(&dm_bufio_clients_lock);
1743
1744         BUG_ON(!RB_EMPTY_ROOT(&c->buffer_tree));
1745         BUG_ON(c->need_reserved_buffers);
1746
1747         while (!list_empty(&c->reserved_buffers)) {
1748                 struct dm_buffer *b = list_entry(c->reserved_buffers.next,
1749                                                  struct dm_buffer, lru_list);
1750                 list_del(&b->lru_list);
1751                 free_buffer(b);
1752         }
1753
1754         for (i = 0; i < LIST_SIZE; i++)
1755                 if (c->n_buffers[i])
1756                         DMERR("leaked buffer count %d: %ld", i, c->n_buffers[i]);
1757
1758         for (i = 0; i < LIST_SIZE; i++)
1759                 BUG_ON(c->n_buffers[i]);
1760
1761         kmem_cache_destroy(c->slab_cache);
1762         kmem_cache_destroy(c->slab_buffer);
1763         dm_io_client_destroy(c->dm_io);
1764         mutex_destroy(&c->lock);
1765         kfree(c);
1766 }
1767 EXPORT_SYMBOL_GPL(dm_bufio_client_destroy);
1768
1769 void dm_bufio_set_sector_offset(struct dm_bufio_client *c, sector_t start)
1770 {
1771         c->start = start;
1772 }
1773 EXPORT_SYMBOL_GPL(dm_bufio_set_sector_offset);
1774
1775 static unsigned get_max_age_hz(void)
1776 {
1777         unsigned max_age = READ_ONCE(dm_bufio_max_age);
1778
1779         if (max_age > UINT_MAX / HZ)
1780                 max_age = UINT_MAX / HZ;
1781
1782         return max_age * HZ;
1783 }
1784
1785 static bool older_than(struct dm_buffer *b, unsigned long age_hz)
1786 {
1787         return time_after_eq(jiffies, b->last_accessed + age_hz);
1788 }
1789
1790 static void __evict_old_buffers(struct dm_bufio_client *c, unsigned long age_hz)
1791 {
1792         struct dm_buffer *b, *tmp;
1793         unsigned long retain_target = get_retain_buffers(c);
1794         unsigned long count;
1795         LIST_HEAD(write_list);
1796
1797         dm_bufio_lock(c);
1798
1799         __check_watermark(c, &write_list);
1800         if (unlikely(!list_empty(&write_list))) {
1801                 dm_bufio_unlock(c);
1802                 __flush_write_list(&write_list);
1803                 dm_bufio_lock(c);
1804         }
1805
1806         count = c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY];
1807         list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_CLEAN], lru_list) {
1808                 if (count <= retain_target)
1809                         break;
1810
1811                 if (!older_than(b, age_hz))
1812                         break;
1813
1814                 if (__try_evict_buffer(b, 0))
1815                         count--;
1816
1817                 cond_resched();
1818         }
1819
1820         dm_bufio_unlock(c);
1821 }
1822
1823 static void do_global_cleanup(struct work_struct *w)
1824 {
1825         struct dm_bufio_client *locked_client = NULL;
1826         struct dm_bufio_client *current_client;
1827         struct dm_buffer *b;
1828         unsigned spinlock_hold_count;
1829         unsigned long threshold = dm_bufio_cache_size -
1830                 dm_bufio_cache_size / DM_BUFIO_LOW_WATERMARK_RATIO;
1831         unsigned long loops = global_num * 2;
1832
1833         mutex_lock(&dm_bufio_clients_lock);
1834
1835         while (1) {
1836                 cond_resched();
1837
1838                 spin_lock(&global_spinlock);
1839                 if (unlikely(dm_bufio_current_allocated <= threshold))
1840                         break;
1841
1842                 spinlock_hold_count = 0;
1843 get_next:
1844                 if (!loops--)
1845                         break;
1846                 if (unlikely(list_empty(&global_queue)))
1847                         break;
1848                 b = list_entry(global_queue.prev, struct dm_buffer, global_list);
1849
1850                 if (b->accessed) {
1851                         b->accessed = 0;
1852                         list_move(&b->global_list, &global_queue);
1853                         if (likely(++spinlock_hold_count < 16))
1854                                 goto get_next;
1855                         spin_unlock(&global_spinlock);
1856                         continue;
1857                 }
1858
1859                 current_client = b->c;
1860                 if (unlikely(current_client != locked_client)) {
1861                         if (locked_client)
1862                                 dm_bufio_unlock(locked_client);
1863
1864                         if (!dm_bufio_trylock(current_client)) {
1865                                 spin_unlock(&global_spinlock);
1866                                 dm_bufio_lock(current_client);
1867                                 locked_client = current_client;
1868                                 continue;
1869                         }
1870
1871                         locked_client = current_client;
1872                 }
1873
1874                 spin_unlock(&global_spinlock);
1875
1876                 if (unlikely(!__try_evict_buffer(b, GFP_KERNEL))) {
1877                         spin_lock(&global_spinlock);
1878                         list_move(&b->global_list, &global_queue);
1879                         spin_unlock(&global_spinlock);
1880                 }
1881         }
1882
1883         spin_unlock(&global_spinlock);
1884
1885         if (locked_client)
1886                 dm_bufio_unlock(locked_client);
1887
1888         mutex_unlock(&dm_bufio_clients_lock);
1889 }
1890
1891 static void cleanup_old_buffers(void)
1892 {
1893         unsigned long max_age_hz = get_max_age_hz();
1894         struct dm_bufio_client *c;
1895
1896         mutex_lock(&dm_bufio_clients_lock);
1897
1898         __cache_size_refresh();
1899
1900         list_for_each_entry(c, &dm_bufio_all_clients, client_list)
1901                 __evict_old_buffers(c, max_age_hz);
1902
1903         mutex_unlock(&dm_bufio_clients_lock);
1904 }
1905
1906 static void work_fn(struct work_struct *w)
1907 {
1908         cleanup_old_buffers();
1909
1910         queue_delayed_work(dm_bufio_wq, &dm_bufio_cleanup_old_work,
1911                            DM_BUFIO_WORK_TIMER_SECS * HZ);
1912 }
1913
1914 /*----------------------------------------------------------------
1915  * Module setup
1916  *--------------------------------------------------------------*/
1917
1918 /*
1919  * This is called only once for the whole dm_bufio module.
1920  * It initializes memory limit.
1921  */
1922 static int __init dm_bufio_init(void)
1923 {
1924         __u64 mem;
1925
1926         dm_bufio_allocated_kmem_cache = 0;
1927         dm_bufio_allocated_get_free_pages = 0;
1928         dm_bufio_allocated_vmalloc = 0;
1929         dm_bufio_current_allocated = 0;
1930
1931         mem = (__u64)mult_frac(totalram_pages() - totalhigh_pages(),
1932                                DM_BUFIO_MEMORY_PERCENT, 100) << PAGE_SHIFT;
1933
1934         if (mem > ULONG_MAX)
1935                 mem = ULONG_MAX;
1936
1937 #ifdef CONFIG_MMU
1938         if (mem > mult_frac(VMALLOC_TOTAL, DM_BUFIO_VMALLOC_PERCENT, 100))
1939                 mem = mult_frac(VMALLOC_TOTAL, DM_BUFIO_VMALLOC_PERCENT, 100);
1940 #endif
1941
1942         dm_bufio_default_cache_size = mem;
1943
1944         mutex_lock(&dm_bufio_clients_lock);
1945         __cache_size_refresh();
1946         mutex_unlock(&dm_bufio_clients_lock);
1947
1948         dm_bufio_wq = alloc_workqueue("dm_bufio_cache", WQ_MEM_RECLAIM, 0);
1949         if (!dm_bufio_wq)
1950                 return -ENOMEM;
1951
1952         INIT_DELAYED_WORK(&dm_bufio_cleanup_old_work, work_fn);
1953         INIT_WORK(&dm_bufio_replacement_work, do_global_cleanup);
1954         queue_delayed_work(dm_bufio_wq, &dm_bufio_cleanup_old_work,
1955                            DM_BUFIO_WORK_TIMER_SECS * HZ);
1956
1957         return 0;
1958 }
1959
1960 /*
1961  * This is called once when unloading the dm_bufio module.
1962  */
1963 static void __exit dm_bufio_exit(void)
1964 {
1965         int bug = 0;
1966
1967         cancel_delayed_work_sync(&dm_bufio_cleanup_old_work);
1968         flush_workqueue(dm_bufio_wq);
1969         destroy_workqueue(dm_bufio_wq);
1970
1971         if (dm_bufio_client_count) {
1972                 DMCRIT("%s: dm_bufio_client_count leaked: %d",
1973                         __func__, dm_bufio_client_count);
1974                 bug = 1;
1975         }
1976
1977         if (dm_bufio_current_allocated) {
1978                 DMCRIT("%s: dm_bufio_current_allocated leaked: %lu",
1979                         __func__, dm_bufio_current_allocated);
1980                 bug = 1;
1981         }
1982
1983         if (dm_bufio_allocated_get_free_pages) {
1984                 DMCRIT("%s: dm_bufio_allocated_get_free_pages leaked: %lu",
1985                        __func__, dm_bufio_allocated_get_free_pages);
1986                 bug = 1;
1987         }
1988
1989         if (dm_bufio_allocated_vmalloc) {
1990                 DMCRIT("%s: dm_bufio_vmalloc leaked: %lu",
1991                        __func__, dm_bufio_allocated_vmalloc);
1992                 bug = 1;
1993         }
1994
1995         BUG_ON(bug);
1996 }
1997
1998 module_init(dm_bufio_init)
1999 module_exit(dm_bufio_exit)
2000
2001 module_param_named(max_cache_size_bytes, dm_bufio_cache_size, ulong, S_IRUGO | S_IWUSR);
2002 MODULE_PARM_DESC(max_cache_size_bytes, "Size of metadata cache");
2003
2004 module_param_named(max_age_seconds, dm_bufio_max_age, uint, S_IRUGO | S_IWUSR);
2005 MODULE_PARM_DESC(max_age_seconds, "Max age of a buffer in seconds");
2006
2007 module_param_named(retain_bytes, dm_bufio_retain_bytes, ulong, S_IRUGO | S_IWUSR);
2008 MODULE_PARM_DESC(retain_bytes, "Try to keep at least this many bytes cached in memory");
2009
2010 module_param_named(peak_allocated_bytes, dm_bufio_peak_allocated, ulong, S_IRUGO | S_IWUSR);
2011 MODULE_PARM_DESC(peak_allocated_bytes, "Tracks the maximum allocated memory");
2012
2013 module_param_named(allocated_kmem_cache_bytes, dm_bufio_allocated_kmem_cache, ulong, S_IRUGO);
2014 MODULE_PARM_DESC(allocated_kmem_cache_bytes, "Memory allocated with kmem_cache_alloc");
2015
2016 module_param_named(allocated_get_free_pages_bytes, dm_bufio_allocated_get_free_pages, ulong, S_IRUGO);
2017 MODULE_PARM_DESC(allocated_get_free_pages_bytes, "Memory allocated with get_free_pages");
2018
2019 module_param_named(allocated_vmalloc_bytes, dm_bufio_allocated_vmalloc, ulong, S_IRUGO);
2020 MODULE_PARM_DESC(allocated_vmalloc_bytes, "Memory allocated with vmalloc");
2021
2022 module_param_named(current_allocated_bytes, dm_bufio_current_allocated, ulong, S_IRUGO);
2023 MODULE_PARM_DESC(current_allocated_bytes, "Memory currently used by the cache");
2024
2025 MODULE_AUTHOR("Mikulas Patocka <dm-devel@redhat.com>");
2026 MODULE_DESCRIPTION(DM_NAME " buffered I/O library");
2027 MODULE_LICENSE("GPL");