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 */
  82struct 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
 112	struct shrinker shrinker;
 113	struct work_struct shrink_work;
 114	atomic_long_t need_shrink;
 115};
 116
 117/*
 118 * Buffer state bits.
 119 */
 120#define B_READING	0
 121#define B_WRITING	1
 122#define B_DIRTY		2
 123
 124/*
 125 * Describes how the block was allocated:
 126 * kmem_cache_alloc(), __get_free_pages() or vmalloc().
 127 * See the comment at alloc_buffer_data.
 128 */
 129enum data_mode {
 130	DATA_MODE_SLAB = 0,
 131	DATA_MODE_GET_FREE_PAGES = 1,
 132	DATA_MODE_VMALLOC = 2,
 133	DATA_MODE_LIMIT = 3
 134};
 135
 136struct dm_buffer {
 137	struct rb_node node;
 138	struct list_head lru_list;
 139	struct list_head global_list;
 140	sector_t block;
 141	void *data;
 142	unsigned char data_mode;		/* DATA_MODE_* */
 143	unsigned char list_mode;		/* LIST_* */
 144	blk_status_t read_error;
 145	blk_status_t write_error;
 146	unsigned accessed;
 147	unsigned hold_count;
 148	unsigned long state;
 149	unsigned long last_accessed;
 150	unsigned dirty_start;
 151	unsigned dirty_end;
 152	unsigned write_start;
 153	unsigned write_end;
 154	struct dm_bufio_client *c;
 155	struct list_head write_list;
 156	void (*end_io)(struct dm_buffer *, blk_status_t);
 157#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
 158#define MAX_STACK 10
 159	unsigned int stack_len;
 160	unsigned long stack_entries[MAX_STACK];
 161#endif
 162};
 163
 164/*----------------------------------------------------------------*/
 165
 166#define dm_bufio_in_request()	(!!current->bio_list)
 167
 168static void dm_bufio_lock(struct dm_bufio_client *c)
 169{
 170	mutex_lock_nested(&c->lock, dm_bufio_in_request());
 171}
 172
 173static int dm_bufio_trylock(struct dm_bufio_client *c)
 174{
 175	return mutex_trylock(&c->lock);
 176}
 177
 178static void dm_bufio_unlock(struct dm_bufio_client *c)
 179{
 180	mutex_unlock(&c->lock);
 181}
 182
 183/*----------------------------------------------------------------*/
 184
 185/*
 186 * Default cache size: available memory divided by the ratio.
 187 */
 188static unsigned long dm_bufio_default_cache_size;
 189
 190/*
 191 * Total cache size set by the user.
 192 */
 193static unsigned long dm_bufio_cache_size;
 194
 195/*
 196 * A copy of dm_bufio_cache_size because dm_bufio_cache_size can change
 197 * at any time.  If it disagrees, the user has changed cache size.
 198 */
 199static unsigned long dm_bufio_cache_size_latch;
 200
 201static DEFINE_SPINLOCK(global_spinlock);
 202
 203static LIST_HEAD(global_queue);
 204
 205static unsigned long global_num = 0;
 206
 207/*
 208 * Buffers are freed after this timeout
 209 */
 210static unsigned dm_bufio_max_age = DM_BUFIO_DEFAULT_AGE_SECS;
 211static unsigned long dm_bufio_retain_bytes = DM_BUFIO_DEFAULT_RETAIN_BYTES;
 212
 213static unsigned long dm_bufio_peak_allocated;
 214static unsigned long dm_bufio_allocated_kmem_cache;
 215static unsigned long dm_bufio_allocated_get_free_pages;
 216static unsigned long dm_bufio_allocated_vmalloc;
 217static unsigned long dm_bufio_current_allocated;
 218
 219/*----------------------------------------------------------------*/
 220
 221/*
 222 * The current number of clients.
 223 */
 224static int dm_bufio_client_count;
 225
 226/*
 227 * The list of all clients.
 228 */
 229static LIST_HEAD(dm_bufio_all_clients);
 230
 231/*
 232 * This mutex protects dm_bufio_cache_size_latch and dm_bufio_client_count
 233 */
 234static DEFINE_MUTEX(dm_bufio_clients_lock);
 235
 236static struct workqueue_struct *dm_bufio_wq;
 237static struct delayed_work dm_bufio_cleanup_old_work;
 238static struct work_struct dm_bufio_replacement_work;
 239
 240
 241#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
 242static void buffer_record_stack(struct dm_buffer *b)
 243{
 244	b->stack_len = stack_trace_save(b->stack_entries, MAX_STACK, 2);
 245}
 246#endif
 247
 248/*----------------------------------------------------------------
 249 * A red/black tree acts as an index for all the buffers.
 250 *--------------------------------------------------------------*/
 251static struct dm_buffer *__find(struct dm_bufio_client *c, sector_t block)
 252{
 253	struct rb_node *n = c->buffer_tree.rb_node;
 254	struct dm_buffer *b;
 255
 256	while (n) {
 257		b = container_of(n, struct dm_buffer, node);
 258
 259		if (b->block == block)
 260			return b;
 261
 262		n = block < b->block ? n->rb_left : n->rb_right;
 263	}
 264
 265	return NULL;
 266}
 267
 268static struct dm_buffer *__find_next(struct dm_bufio_client *c, sector_t block)
 269{
 270	struct rb_node *n = c->buffer_tree.rb_node;
 271	struct dm_buffer *b;
 272	struct dm_buffer *best = NULL;
 273
 274	while (n) {
 275		b = container_of(n, struct dm_buffer, node);
 276
 277		if (b->block == block)
 278			return b;
 279
 280		if (block <= b->block) {
 281			n = n->rb_left;
 282			best = b;
 283		} else {
 284			n = n->rb_right;
 285		}
 286	}
 287
 288	return best;
 289}
 290
 291static void __insert(struct dm_bufio_client *c, struct dm_buffer *b)
 292{
 293	struct rb_node **new = &c->buffer_tree.rb_node, *parent = NULL;
 294	struct dm_buffer *found;
 295
 296	while (*new) {
 297		found = container_of(*new, struct dm_buffer, node);
 298
 299		if (found->block == b->block) {
 300			BUG_ON(found != b);
 301			return;
 302		}
 303
 304		parent = *new;
 305		new = b->block < found->block ?
 306			&found->node.rb_left : &found->node.rb_right;
 307	}
 308
 309	rb_link_node(&b->node, parent, new);
 310	rb_insert_color(&b->node, &c->buffer_tree);
 311}
 312
 313static void __remove(struct dm_bufio_client *c, struct dm_buffer *b)
 314{
 315	rb_erase(&b->node, &c->buffer_tree);
 316}
 317
 318/*----------------------------------------------------------------*/
 319
 320static void adjust_total_allocated(struct dm_buffer *b, bool unlink)
 321{
 322	unsigned char data_mode;
 323	long diff;
 324
 325	static unsigned long * const class_ptr[DATA_MODE_LIMIT] = {
 326		&dm_bufio_allocated_kmem_cache,
 327		&dm_bufio_allocated_get_free_pages,
 328		&dm_bufio_allocated_vmalloc,
 329	};
 330
 331	data_mode = b->data_mode;
 332	diff = (long)b->c->block_size;
 333	if (unlink)
 334		diff = -diff;
 335
 336	spin_lock(&global_spinlock);
 337
 338	*class_ptr[data_mode] += diff;
 339
 340	dm_bufio_current_allocated += diff;
 341
 342	if (dm_bufio_current_allocated > dm_bufio_peak_allocated)
 343		dm_bufio_peak_allocated = dm_bufio_current_allocated;
 344
 345	b->accessed = 1;
 346
 347	if (!unlink) {
 348		list_add(&b->global_list, &global_queue);
 349		global_num++;
 350		if (dm_bufio_current_allocated > dm_bufio_cache_size)
 351			queue_work(dm_bufio_wq, &dm_bufio_replacement_work);
 352	} else {
 353		list_del(&b->global_list);
 354		global_num--;
 355	}
 356
 357	spin_unlock(&global_spinlock);
 358}
 359
 360/*
 361 * Change the number of clients and recalculate per-client limit.
 362 */
 363static void __cache_size_refresh(void)
 364{
 365	BUG_ON(!mutex_is_locked(&dm_bufio_clients_lock));
 366	BUG_ON(dm_bufio_client_count < 0);
 367
 368	dm_bufio_cache_size_latch = READ_ONCE(dm_bufio_cache_size);
 369
 370	/*
 371	 * Use default if set to 0 and report the actual cache size used.
 372	 */
 373	if (!dm_bufio_cache_size_latch) {
 374		(void)cmpxchg(&dm_bufio_cache_size, 0,
 375			      dm_bufio_default_cache_size);
 376		dm_bufio_cache_size_latch = dm_bufio_default_cache_size;
 377	}
 378}
 379
 380/*
 381 * Allocating buffer data.
 382 *
 383 * Small buffers are allocated with kmem_cache, to use space optimally.
 384 *
 385 * For large buffers, we choose between get_free_pages and vmalloc.
 386 * Each has advantages and disadvantages.
 387 *
 388 * __get_free_pages can randomly fail if the memory is fragmented.
 389 * __vmalloc won't randomly fail, but vmalloc space is limited (it may be
 390 * as low as 128M) so using it for caching is not appropriate.
 391 *
 392 * If the allocation may fail we use __get_free_pages. Memory fragmentation
 393 * won't have a fatal effect here, but it just causes flushes of some other
 394 * buffers and more I/O will be performed. Don't use __get_free_pages if it
 395 * always fails (i.e. order >= MAX_ORDER).
 396 *
 397 * If the allocation shouldn't fail we use __vmalloc. This is only for the
 398 * initial reserve allocation, so there's no risk of wasting all vmalloc
 399 * space.
 400 */
 401static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask,
 402			       unsigned char *data_mode)
 403{
 404	if (unlikely(c->slab_cache != NULL)) {
 405		*data_mode = DATA_MODE_SLAB;
 406		return kmem_cache_alloc(c->slab_cache, gfp_mask);
 407	}
 408
 409	if (c->block_size <= KMALLOC_MAX_SIZE &&
 410	    gfp_mask & __GFP_NORETRY) {
 411		*data_mode = DATA_MODE_GET_FREE_PAGES;
 412		return (void *)__get_free_pages(gfp_mask,
 413						c->sectors_per_block_bits - (PAGE_SHIFT - SECTOR_SHIFT));
 414	}
 415
 416	*data_mode = DATA_MODE_VMALLOC;
 417
 418	/*
 419	 * __vmalloc allocates the data pages and auxiliary structures with
 420	 * gfp_flags that were specified, but pagetables are always allocated
 421	 * with GFP_KERNEL, no matter what was specified as gfp_mask.
 422	 *
 423	 * Consequently, we must set per-process flag PF_MEMALLOC_NOIO so that
 424	 * all allocations done by this process (including pagetables) are done
 425	 * as if GFP_NOIO was specified.
 426	 */
 427	if (gfp_mask & __GFP_NORETRY) {
 428		unsigned noio_flag = memalloc_noio_save();
 429		void *ptr = __vmalloc(c->block_size, gfp_mask);
 430
 431		memalloc_noio_restore(noio_flag);
 432		return ptr;
 433	}
 434
 435	return __vmalloc(c->block_size, gfp_mask);
 436}
 437
 438/*
 439 * Free buffer's data.
 440 */
 441static void free_buffer_data(struct dm_bufio_client *c,
 442			     void *data, unsigned char data_mode)
 443{
 444	switch (data_mode) {
 445	case DATA_MODE_SLAB:
 446		kmem_cache_free(c->slab_cache, data);
 447		break;
 448
 449	case DATA_MODE_GET_FREE_PAGES:
 450		free_pages((unsigned long)data,
 451			   c->sectors_per_block_bits - (PAGE_SHIFT - SECTOR_SHIFT));
 452		break;
 453
 454	case DATA_MODE_VMALLOC:
 455		vfree(data);
 456		break;
 457
 458	default:
 459		DMCRIT("dm_bufio_free_buffer_data: bad data mode: %d",
 460		       data_mode);
 461		BUG();
 462	}
 463}
 464
 465/*
 466 * Allocate buffer and its data.
 467 */
 468static struct dm_buffer *alloc_buffer(struct dm_bufio_client *c, gfp_t gfp_mask)
 469{
 470	struct dm_buffer *b = kmem_cache_alloc(c->slab_buffer, gfp_mask);
 471
 472	if (!b)
 473		return NULL;
 474
 475	b->c = c;
 476
 477	b->data = alloc_buffer_data(c, gfp_mask, &b->data_mode);
 478	if (!b->data) {
 479		kmem_cache_free(c->slab_buffer, b);
 480		return NULL;
 481	}
 482
 483#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
 484	b->stack_len = 0;
 485#endif
 486	return b;
 487}
 488
 489/*
 490 * Free buffer and its data.
 491 */
 492static void free_buffer(struct dm_buffer *b)
 493{
 494	struct dm_bufio_client *c = b->c;
 495
 496	free_buffer_data(c, b->data, b->data_mode);
 497	kmem_cache_free(c->slab_buffer, b);
 498}
 499
 500/*
 501 * Link buffer to the buffer tree and clean or dirty queue.
 502 */
 503static void __link_buffer(struct dm_buffer *b, sector_t block, int dirty)
 504{
 505	struct dm_bufio_client *c = b->c;
 506
 507	c->n_buffers[dirty]++;
 508	b->block = block;
 509	b->list_mode = dirty;
 510	list_add(&b->lru_list, &c->lru[dirty]);
 511	__insert(b->c, b);
 512	b->last_accessed = jiffies;
 513
 514	adjust_total_allocated(b, false);
 515}
 516
 517/*
 518 * Unlink buffer from the buffer tree and dirty or clean queue.
 519 */
 520static void __unlink_buffer(struct dm_buffer *b)
 521{
 522	struct dm_bufio_client *c = b->c;
 523
 524	BUG_ON(!c->n_buffers[b->list_mode]);
 525
 526	c->n_buffers[b->list_mode]--;
 527	__remove(b->c, b);
 528	list_del(&b->lru_list);
 529
 530	adjust_total_allocated(b, true);
 531}
 532
 533/*
 534 * Place the buffer to the head of dirty or clean LRU queue.
 535 */
 536static void __relink_lru(struct dm_buffer *b, int dirty)
 537{
 538	struct dm_bufio_client *c = b->c;
 539
 540	b->accessed = 1;
 541
 542	BUG_ON(!c->n_buffers[b->list_mode]);
 543
 544	c->n_buffers[b->list_mode]--;
 545	c->n_buffers[dirty]++;
 546	b->list_mode = dirty;
 547	list_move(&b->lru_list, &c->lru[dirty]);
 548	b->last_accessed = jiffies;
 549}
 550
 551/*----------------------------------------------------------------
 552 * Submit I/O on the buffer.
 553 *
 554 * Bio interface is faster but it has some problems:
 555 *	the vector list is limited (increasing this limit increases
 556 *	memory-consumption per buffer, so it is not viable);
 557 *
 558 *	the memory must be direct-mapped, not vmalloced;
 559 *
 560 * If the buffer is small enough (up to DM_BUFIO_INLINE_VECS pages) and
 561 * it is not vmalloced, try using the bio interface.
 562 *
 563 * If the buffer is big, if it is vmalloced or if the underlying device
 564 * rejects the bio because it is too large, use dm-io layer to do the I/O.
 565 * The dm-io layer splits the I/O into multiple requests, avoiding the above
 566 * shortcomings.
 567 *--------------------------------------------------------------*/
 568
 569/*
 570 * dm-io completion routine. It just calls b->bio.bi_end_io, pretending
 571 * that the request was handled directly with bio interface.
 572 */
 573static void dmio_complete(unsigned long error, void *context)
 574{
 575	struct dm_buffer *b = context;
 576
 577	b->end_io(b, unlikely(error != 0) ? BLK_STS_IOERR : 0);
 578}
 579
 580static void use_dmio(struct dm_buffer *b, int rw, sector_t sector,
 581		     unsigned n_sectors, unsigned offset)
 582{
 583	int r;
 584	struct dm_io_request io_req = {
 585		.bi_op = rw,
 586		.bi_op_flags = 0,
 587		.notify.fn = dmio_complete,
 588		.notify.context = b,
 589		.client = b->c->dm_io,
 590	};
 591	struct dm_io_region region = {
 592		.bdev = b->c->bdev,
 593		.sector = sector,
 594		.count = n_sectors,
 595	};
 596
 597	if (b->data_mode != DATA_MODE_VMALLOC) {
 598		io_req.mem.type = DM_IO_KMEM;
 599		io_req.mem.ptr.addr = (char *)b->data + offset;
 600	} else {
 601		io_req.mem.type = DM_IO_VMA;
 602		io_req.mem.ptr.vma = (char *)b->data + offset;
 603	}
 604
 605	r = dm_io(&io_req, 1, &region, NULL);
 606	if (unlikely(r))
 607		b->end_io(b, errno_to_blk_status(r));
 608}
 609
 610static void bio_complete(struct bio *bio)
 611{
 612	struct dm_buffer *b = bio->bi_private;
 613	blk_status_t status = bio->bi_status;
 614	bio_put(bio);
 615	b->end_io(b, status);
 616}
 617
 618static void use_bio(struct dm_buffer *b, int rw, sector_t sector,
 619		    unsigned n_sectors, unsigned offset)
 620{
 621	struct bio *bio;
 622	char *ptr;
 623	unsigned vec_size, len;
 624
 625	vec_size = b->c->block_size >> PAGE_SHIFT;
 626	if (unlikely(b->c->sectors_per_block_bits < PAGE_SHIFT - SECTOR_SHIFT))
 627		vec_size += 2;
 628
 629	bio = bio_kmalloc(GFP_NOWAIT | __GFP_NORETRY | __GFP_NOWARN, vec_size);
 630	if (!bio) {
 631dmio:
 632		use_dmio(b, rw, sector, n_sectors, offset);
 633		return;
 634	}
 635
 636	bio->bi_iter.bi_sector = sector;
 637	bio_set_dev(bio, b->c->bdev);
 638	bio_set_op_attrs(bio, rw, 0);
 639	bio->bi_end_io = bio_complete;
 640	bio->bi_private = b;
 641
 642	ptr = (char *)b->data + offset;
 643	len = n_sectors << SECTOR_SHIFT;
 644
 645	do {
 646		unsigned this_step = min((unsigned)(PAGE_SIZE - offset_in_page(ptr)), len);
 647		if (!bio_add_page(bio, virt_to_page(ptr), this_step,
 648				  offset_in_page(ptr))) {
 649			bio_put(bio);
 650			goto dmio;
 651		}
 652
 653		len -= this_step;
 654		ptr += this_step;
 655	} while (len > 0);
 656
 657	submit_bio(bio);
 658}
 659
 660static inline sector_t block_to_sector(struct dm_bufio_client *c, sector_t block)
 661{
 662	sector_t sector;
 663
 664	if (likely(c->sectors_per_block_bits >= 0))
 665		sector = block << c->sectors_per_block_bits;
 666	else
 667		sector = block * (c->block_size >> SECTOR_SHIFT);
 668	sector += c->start;
 669
 670	return sector;
 671}
 672
 673static void submit_io(struct dm_buffer *b, int rw, void (*end_io)(struct dm_buffer *, blk_status_t))
 674{
 675	unsigned n_sectors;
 676	sector_t sector;
 677	unsigned offset, end;
 678
 679	b->end_io = end_io;
 680
 681	sector = block_to_sector(b->c, b->block);
 
 
 
 
 682
 683	if (rw != REQ_OP_WRITE) {
 684		n_sectors = b->c->block_size >> SECTOR_SHIFT;
 685		offset = 0;
 686	} else {
 687		if (b->c->write_callback)
 688			b->c->write_callback(b);
 689		offset = b->write_start;
 690		end = b->write_end;
 691		offset &= -DM_BUFIO_WRITE_ALIGN;
 692		end += DM_BUFIO_WRITE_ALIGN - 1;
 693		end &= -DM_BUFIO_WRITE_ALIGN;
 694		if (unlikely(end > b->c->block_size))
 695			end = b->c->block_size;
 696
 697		sector += offset >> SECTOR_SHIFT;
 698		n_sectors = (end - offset) >> SECTOR_SHIFT;
 699	}
 700
 701	if (b->data_mode != DATA_MODE_VMALLOC)
 702		use_bio(b, rw, sector, n_sectors, offset);
 703	else
 704		use_dmio(b, rw, sector, n_sectors, offset);
 705}
 706
 707/*----------------------------------------------------------------
 708 * Writing dirty buffers
 709 *--------------------------------------------------------------*/
 710
 711/*
 712 * The endio routine for write.
 713 *
 714 * Set the error, clear B_WRITING bit and wake anyone who was waiting on
 715 * it.
 716 */
 717static void write_endio(struct dm_buffer *b, blk_status_t status)
 718{
 719	b->write_error = status;
 720	if (unlikely(status)) {
 721		struct dm_bufio_client *c = b->c;
 722
 723		(void)cmpxchg(&c->async_write_error, 0,
 724				blk_status_to_errno(status));
 725	}
 726
 727	BUG_ON(!test_bit(B_WRITING, &b->state));
 728
 729	smp_mb__before_atomic();
 730	clear_bit(B_WRITING, &b->state);
 731	smp_mb__after_atomic();
 732
 733	wake_up_bit(&b->state, B_WRITING);
 734}
 735
 736/*
 737 * Initiate a write on a dirty buffer, but don't wait for it.
 738 *
 739 * - If the buffer is not dirty, exit.
 740 * - If there some previous write going on, wait for it to finish (we can't
 741 *   have two writes on the same buffer simultaneously).
 742 * - Submit our write and don't wait on it. We set B_WRITING indicating
 743 *   that there is a write in progress.
 744 */
 745static void __write_dirty_buffer(struct dm_buffer *b,
 746				 struct list_head *write_list)
 747{
 748	if (!test_bit(B_DIRTY, &b->state))
 749		return;
 750
 751	clear_bit(B_DIRTY, &b->state);
 752	wait_on_bit_lock_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
 753
 754	b->write_start = b->dirty_start;
 755	b->write_end = b->dirty_end;
 756
 757	if (!write_list)
 758		submit_io(b, REQ_OP_WRITE, write_endio);
 759	else
 760		list_add_tail(&b->write_list, write_list);
 761}
 762
 763static void __flush_write_list(struct list_head *write_list)
 764{
 765	struct blk_plug plug;
 766	blk_start_plug(&plug);
 767	while (!list_empty(write_list)) {
 768		struct dm_buffer *b =
 769			list_entry(write_list->next, struct dm_buffer, write_list);
 770		list_del(&b->write_list);
 771		submit_io(b, REQ_OP_WRITE, write_endio);
 772		cond_resched();
 773	}
 774	blk_finish_plug(&plug);
 775}
 776
 777/*
 778 * Wait until any activity on the buffer finishes.  Possibly write the
 779 * buffer if it is dirty.  When this function finishes, there is no I/O
 780 * running on the buffer and the buffer is not dirty.
 781 */
 782static void __make_buffer_clean(struct dm_buffer *b)
 783{
 784	BUG_ON(b->hold_count);
 785
 786	if (!b->state)	/* fast case */
 787		return;
 788
 789	wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
 790	__write_dirty_buffer(b, NULL);
 791	wait_on_bit_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
 792}
 793
 794/*
 795 * Find some buffer that is not held by anybody, clean it, unlink it and
 796 * return it.
 797 */
 798static struct dm_buffer *__get_unclaimed_buffer(struct dm_bufio_client *c)
 799{
 800	struct dm_buffer *b;
 801
 802	list_for_each_entry_reverse(b, &c->lru[LIST_CLEAN], lru_list) {
 803		BUG_ON(test_bit(B_WRITING, &b->state));
 804		BUG_ON(test_bit(B_DIRTY, &b->state));
 805
 806		if (!b->hold_count) {
 807			__make_buffer_clean(b);
 808			__unlink_buffer(b);
 809			return b;
 810		}
 811		cond_resched();
 812	}
 813
 814	list_for_each_entry_reverse(b, &c->lru[LIST_DIRTY], lru_list) {
 815		BUG_ON(test_bit(B_READING, &b->state));
 816
 817		if (!b->hold_count) {
 818			__make_buffer_clean(b);
 819			__unlink_buffer(b);
 820			return b;
 821		}
 822		cond_resched();
 823	}
 824
 825	return NULL;
 826}
 827
 828/*
 829 * Wait until some other threads free some buffer or release hold count on
 830 * some buffer.
 831 *
 832 * This function is entered with c->lock held, drops it and regains it
 833 * before exiting.
 834 */
 835static void __wait_for_free_buffer(struct dm_bufio_client *c)
 836{
 837	DECLARE_WAITQUEUE(wait, current);
 838
 839	add_wait_queue(&c->free_buffer_wait, &wait);
 840	set_current_state(TASK_UNINTERRUPTIBLE);
 841	dm_bufio_unlock(c);
 842
 843	io_schedule();
 844
 845	remove_wait_queue(&c->free_buffer_wait, &wait);
 846
 847	dm_bufio_lock(c);
 848}
 849
 850enum new_flag {
 851	NF_FRESH = 0,
 852	NF_READ = 1,
 853	NF_GET = 2,
 854	NF_PREFETCH = 3
 855};
 856
 857/*
 858 * Allocate a new buffer. If the allocation is not possible, wait until
 859 * some other thread frees a buffer.
 860 *
 861 * May drop the lock and regain it.
 862 */
 863static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client *c, enum new_flag nf)
 864{
 865	struct dm_buffer *b;
 866	bool tried_noio_alloc = false;
 867
 868	/*
 869	 * dm-bufio is resistant to allocation failures (it just keeps
 870	 * one buffer reserved in cases all the allocations fail).
 871	 * So set flags to not try too hard:
 872	 *	GFP_NOWAIT: don't wait; if we need to sleep we'll release our
 873	 *		    mutex and wait ourselves.
 874	 *	__GFP_NORETRY: don't retry and rather return failure
 875	 *	__GFP_NOMEMALLOC: don't use emergency reserves
 876	 *	__GFP_NOWARN: don't print a warning in case of failure
 877	 *
 878	 * For debugging, if we set the cache size to 1, no new buffers will
 879	 * be allocated.
 880	 */
 881	while (1) {
 882		if (dm_bufio_cache_size_latch != 1) {
 883			b = alloc_buffer(c, GFP_NOWAIT | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
 884			if (b)
 885				return b;
 886		}
 887
 888		if (nf == NF_PREFETCH)
 889			return NULL;
 890
 891		if (dm_bufio_cache_size_latch != 1 && !tried_noio_alloc) {
 892			dm_bufio_unlock(c);
 893			b = alloc_buffer(c, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
 894			dm_bufio_lock(c);
 895			if (b)
 896				return b;
 897			tried_noio_alloc = true;
 898		}
 899
 900		if (!list_empty(&c->reserved_buffers)) {
 901			b = list_entry(c->reserved_buffers.next,
 902				       struct dm_buffer, lru_list);
 903			list_del(&b->lru_list);
 904			c->need_reserved_buffers++;
 905
 906			return b;
 907		}
 908
 909		b = __get_unclaimed_buffer(c);
 910		if (b)
 911			return b;
 912
 913		__wait_for_free_buffer(c);
 914	}
 915}
 916
 917static struct dm_buffer *__alloc_buffer_wait(struct dm_bufio_client *c, enum new_flag nf)
 918{
 919	struct dm_buffer *b = __alloc_buffer_wait_no_callback(c, nf);
 920
 921	if (!b)
 922		return NULL;
 923
 924	if (c->alloc_callback)
 925		c->alloc_callback(b);
 926
 927	return b;
 928}
 929
 930/*
 931 * Free a buffer and wake other threads waiting for free buffers.
 932 */
 933static void __free_buffer_wake(struct dm_buffer *b)
 934{
 935	struct dm_bufio_client *c = b->c;
 936
 937	if (!c->need_reserved_buffers)
 938		free_buffer(b);
 939	else {
 940		list_add(&b->lru_list, &c->reserved_buffers);
 941		c->need_reserved_buffers--;
 942	}
 943
 944	wake_up(&c->free_buffer_wait);
 945}
 946
 947static void __write_dirty_buffers_async(struct dm_bufio_client *c, int no_wait,
 948					struct list_head *write_list)
 949{
 950	struct dm_buffer *b, *tmp;
 951
 952	list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) {
 953		BUG_ON(test_bit(B_READING, &b->state));
 954
 955		if (!test_bit(B_DIRTY, &b->state) &&
 956		    !test_bit(B_WRITING, &b->state)) {
 957			__relink_lru(b, LIST_CLEAN);
 958			continue;
 959		}
 960
 961		if (no_wait && test_bit(B_WRITING, &b->state))
 962			return;
 963
 964		__write_dirty_buffer(b, write_list);
 965		cond_resched();
 966	}
 967}
 968
 969/*
 970 * Check if we're over watermark.
 971 * If we are over threshold_buffers, start freeing buffers.
 972 * If we're over "limit_buffers", block until we get under the limit.
 973 */
 974static void __check_watermark(struct dm_bufio_client *c,
 975			      struct list_head *write_list)
 976{
 977	if (c->n_buffers[LIST_DIRTY] > c->n_buffers[LIST_CLEAN] * DM_BUFIO_WRITEBACK_RATIO)
 978		__write_dirty_buffers_async(c, 1, write_list);
 979}
 980
 981/*----------------------------------------------------------------
 982 * Getting a buffer
 983 *--------------------------------------------------------------*/
 984
 985static struct dm_buffer *__bufio_new(struct dm_bufio_client *c, sector_t block,
 986				     enum new_flag nf, int *need_submit,
 987				     struct list_head *write_list)
 988{
 989	struct dm_buffer *b, *new_b = NULL;
 990
 991	*need_submit = 0;
 992
 993	b = __find(c, block);
 994	if (b)
 995		goto found_buffer;
 996
 997	if (nf == NF_GET)
 998		return NULL;
 999
1000	new_b = __alloc_buffer_wait(c, nf);
1001	if (!new_b)
1002		return NULL;
1003
1004	/*
1005	 * We've had a period where the mutex was unlocked, so need to
1006	 * recheck the buffer tree.
1007	 */
1008	b = __find(c, block);
1009	if (b) {
1010		__free_buffer_wake(new_b);
1011		goto found_buffer;
1012	}
1013
1014	__check_watermark(c, write_list);
1015
1016	b = new_b;
1017	b->hold_count = 1;
1018	b->read_error = 0;
1019	b->write_error = 0;
1020	__link_buffer(b, block, LIST_CLEAN);
1021
1022	if (nf == NF_FRESH) {
1023		b->state = 0;
1024		return b;
1025	}
1026
1027	b->state = 1 << B_READING;
1028	*need_submit = 1;
1029
1030	return b;
1031
1032found_buffer:
1033	if (nf == NF_PREFETCH)
1034		return NULL;
1035	/*
1036	 * Note: it is essential that we don't wait for the buffer to be
1037	 * read if dm_bufio_get function is used. Both dm_bufio_get and
1038	 * dm_bufio_prefetch can be used in the driver request routine.
1039	 * If the user called both dm_bufio_prefetch and dm_bufio_get on
1040	 * the same buffer, it would deadlock if we waited.
1041	 */
1042	if (nf == NF_GET && unlikely(test_bit(B_READING, &b->state)))
1043		return NULL;
1044
1045	b->hold_count++;
1046	__relink_lru(b, test_bit(B_DIRTY, &b->state) ||
1047		     test_bit(B_WRITING, &b->state));
1048	return b;
1049}
1050
1051/*
1052 * The endio routine for reading: set the error, clear the bit and wake up
1053 * anyone waiting on the buffer.
1054 */
1055static void read_endio(struct dm_buffer *b, blk_status_t status)
1056{
1057	b->read_error = status;
1058
1059	BUG_ON(!test_bit(B_READING, &b->state));
1060
1061	smp_mb__before_atomic();
1062	clear_bit(B_READING, &b->state);
1063	smp_mb__after_atomic();
1064
1065	wake_up_bit(&b->state, B_READING);
1066}
1067
1068/*
1069 * A common routine for dm_bufio_new and dm_bufio_read.  Operation of these
1070 * functions is similar except that dm_bufio_new doesn't read the
1071 * buffer from the disk (assuming that the caller overwrites all the data
1072 * and uses dm_bufio_mark_buffer_dirty to write new data back).
1073 */
1074static void *new_read(struct dm_bufio_client *c, sector_t block,
1075		      enum new_flag nf, struct dm_buffer **bp)
1076{
1077	int need_submit;
1078	struct dm_buffer *b;
1079
1080	LIST_HEAD(write_list);
1081
1082	dm_bufio_lock(c);
1083	b = __bufio_new(c, block, nf, &need_submit, &write_list);
1084#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1085	if (b && b->hold_count == 1)
1086		buffer_record_stack(b);
1087#endif
1088	dm_bufio_unlock(c);
1089
1090	__flush_write_list(&write_list);
1091
1092	if (!b)
1093		return NULL;
1094
1095	if (need_submit)
1096		submit_io(b, REQ_OP_READ, read_endio);
1097
1098	wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
1099
1100	if (b->read_error) {
1101		int error = blk_status_to_errno(b->read_error);
1102
1103		dm_bufio_release(b);
1104
1105		return ERR_PTR(error);
1106	}
1107
1108	*bp = b;
1109
1110	return b->data;
1111}
1112
1113void *dm_bufio_get(struct dm_bufio_client *c, sector_t block,
1114		   struct dm_buffer **bp)
1115{
1116	return new_read(c, block, NF_GET, bp);
1117}
1118EXPORT_SYMBOL_GPL(dm_bufio_get);
1119
1120void *dm_bufio_read(struct dm_bufio_client *c, sector_t block,
1121		    struct dm_buffer **bp)
1122{
1123	BUG_ON(dm_bufio_in_request());
1124
1125	return new_read(c, block, NF_READ, bp);
1126}
1127EXPORT_SYMBOL_GPL(dm_bufio_read);
1128
1129void *dm_bufio_new(struct dm_bufio_client *c, sector_t block,
1130		   struct dm_buffer **bp)
1131{
1132	BUG_ON(dm_bufio_in_request());
1133
1134	return new_read(c, block, NF_FRESH, bp);
1135}
1136EXPORT_SYMBOL_GPL(dm_bufio_new);
1137
1138void dm_bufio_prefetch(struct dm_bufio_client *c,
1139		       sector_t block, unsigned n_blocks)
1140{
1141	struct blk_plug plug;
1142
1143	LIST_HEAD(write_list);
1144
1145	BUG_ON(dm_bufio_in_request());
1146
1147	blk_start_plug(&plug);
1148	dm_bufio_lock(c);
1149
1150	for (; n_blocks--; block++) {
1151		int need_submit;
1152		struct dm_buffer *b;
1153		b = __bufio_new(c, block, NF_PREFETCH, &need_submit,
1154				&write_list);
1155		if (unlikely(!list_empty(&write_list))) {
1156			dm_bufio_unlock(c);
1157			blk_finish_plug(&plug);
1158			__flush_write_list(&write_list);
1159			blk_start_plug(&plug);
1160			dm_bufio_lock(c);
1161		}
1162		if (unlikely(b != NULL)) {
1163			dm_bufio_unlock(c);
1164
1165			if (need_submit)
1166				submit_io(b, REQ_OP_READ, read_endio);
1167			dm_bufio_release(b);
1168
1169			cond_resched();
1170
1171			if (!n_blocks)
1172				goto flush_plug;
1173			dm_bufio_lock(c);
1174		}
1175	}
1176
1177	dm_bufio_unlock(c);
1178
1179flush_plug:
1180	blk_finish_plug(&plug);
1181}
1182EXPORT_SYMBOL_GPL(dm_bufio_prefetch);
1183
1184void dm_bufio_release(struct dm_buffer *b)
1185{
1186	struct dm_bufio_client *c = b->c;
1187
1188	dm_bufio_lock(c);
1189
1190	BUG_ON(!b->hold_count);
1191
1192	b->hold_count--;
1193	if (!b->hold_count) {
1194		wake_up(&c->free_buffer_wait);
1195
1196		/*
1197		 * If there were errors on the buffer, and the buffer is not
1198		 * to be written, free the buffer. There is no point in caching
1199		 * invalid buffer.
1200		 */
1201		if ((b->read_error || b->write_error) &&
1202		    !test_bit(B_READING, &b->state) &&
1203		    !test_bit(B_WRITING, &b->state) &&
1204		    !test_bit(B_DIRTY, &b->state)) {
1205			__unlink_buffer(b);
1206			__free_buffer_wake(b);
1207		}
1208	}
1209
1210	dm_bufio_unlock(c);
1211}
1212EXPORT_SYMBOL_GPL(dm_bufio_release);
1213
1214void dm_bufio_mark_partial_buffer_dirty(struct dm_buffer *b,
1215					unsigned start, unsigned end)
1216{
1217	struct dm_bufio_client *c = b->c;
1218
1219	BUG_ON(start >= end);
1220	BUG_ON(end > b->c->block_size);
1221
1222	dm_bufio_lock(c);
1223
1224	BUG_ON(test_bit(B_READING, &b->state));
1225
1226	if (!test_and_set_bit(B_DIRTY, &b->state)) {
1227		b->dirty_start = start;
1228		b->dirty_end = end;
1229		__relink_lru(b, LIST_DIRTY);
1230	} else {
1231		if (start < b->dirty_start)
1232			b->dirty_start = start;
1233		if (end > b->dirty_end)
1234			b->dirty_end = end;
1235	}
1236
1237	dm_bufio_unlock(c);
1238}
1239EXPORT_SYMBOL_GPL(dm_bufio_mark_partial_buffer_dirty);
1240
1241void dm_bufio_mark_buffer_dirty(struct dm_buffer *b)
1242{
1243	dm_bufio_mark_partial_buffer_dirty(b, 0, b->c->block_size);
1244}
1245EXPORT_SYMBOL_GPL(dm_bufio_mark_buffer_dirty);
1246
1247void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c)
1248{
1249	LIST_HEAD(write_list);
1250
1251	BUG_ON(dm_bufio_in_request());
1252
1253	dm_bufio_lock(c);
1254	__write_dirty_buffers_async(c, 0, &write_list);
1255	dm_bufio_unlock(c);
1256	__flush_write_list(&write_list);
1257}
1258EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers_async);
1259
1260/*
1261 * For performance, it is essential that the buffers are written asynchronously
1262 * and simultaneously (so that the block layer can merge the writes) and then
1263 * waited upon.
1264 *
1265 * Finally, we flush hardware disk cache.
1266 */
1267int dm_bufio_write_dirty_buffers(struct dm_bufio_client *c)
1268{
1269	int a, f;
1270	unsigned long buffers_processed = 0;
1271	struct dm_buffer *b, *tmp;
1272
1273	LIST_HEAD(write_list);
1274
1275	dm_bufio_lock(c);
1276	__write_dirty_buffers_async(c, 0, &write_list);
1277	dm_bufio_unlock(c);
1278	__flush_write_list(&write_list);
1279	dm_bufio_lock(c);
1280
1281again:
1282	list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) {
1283		int dropped_lock = 0;
1284
1285		if (buffers_processed < c->n_buffers[LIST_DIRTY])
1286			buffers_processed++;
1287
1288		BUG_ON(test_bit(B_READING, &b->state));
1289
1290		if (test_bit(B_WRITING, &b->state)) {
1291			if (buffers_processed < c->n_buffers[LIST_DIRTY]) {
1292				dropped_lock = 1;
1293				b->hold_count++;
1294				dm_bufio_unlock(c);
1295				wait_on_bit_io(&b->state, B_WRITING,
1296					       TASK_UNINTERRUPTIBLE);
1297				dm_bufio_lock(c);
1298				b->hold_count--;
1299			} else
1300				wait_on_bit_io(&b->state, B_WRITING,
1301					       TASK_UNINTERRUPTIBLE);
1302		}
1303
1304		if (!test_bit(B_DIRTY, &b->state) &&
1305		    !test_bit(B_WRITING, &b->state))
1306			__relink_lru(b, LIST_CLEAN);
1307
1308		cond_resched();
1309
1310		/*
1311		 * If we dropped the lock, the list is no longer consistent,
1312		 * so we must restart the search.
1313		 *
1314		 * In the most common case, the buffer just processed is
1315		 * relinked to the clean list, so we won't loop scanning the
1316		 * same buffer again and again.
1317		 *
1318		 * This may livelock if there is another thread simultaneously
1319		 * dirtying buffers, so we count the number of buffers walked
1320		 * and if it exceeds the total number of buffers, it means that
1321		 * someone is doing some writes simultaneously with us.  In
1322		 * this case, stop, dropping the lock.
1323		 */
1324		if (dropped_lock)
1325			goto again;
1326	}
1327	wake_up(&c->free_buffer_wait);
1328	dm_bufio_unlock(c);
1329
1330	a = xchg(&c->async_write_error, 0);
1331	f = dm_bufio_issue_flush(c);
1332	if (a)
1333		return a;
1334
1335	return f;
1336}
1337EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers);
1338
1339/*
1340 * Use dm-io to send an empty barrier to flush the device.
1341 */
1342int dm_bufio_issue_flush(struct dm_bufio_client *c)
1343{
1344	struct dm_io_request io_req = {
1345		.bi_op = REQ_OP_WRITE,
1346		.bi_op_flags = REQ_PREFLUSH | REQ_SYNC,
1347		.mem.type = DM_IO_KMEM,
1348		.mem.ptr.addr = NULL,
1349		.client = c->dm_io,
1350	};
1351	struct dm_io_region io_reg = {
1352		.bdev = c->bdev,
1353		.sector = 0,
1354		.count = 0,
1355	};
1356
1357	BUG_ON(dm_bufio_in_request());
1358
1359	return dm_io(&io_req, 1, &io_reg, NULL);
1360}
1361EXPORT_SYMBOL_GPL(dm_bufio_issue_flush);
1362
1363/*
1364 * Use dm-io to send a discard request to flush the device.
1365 */
1366int dm_bufio_issue_discard(struct dm_bufio_client *c, sector_t block, sector_t count)
1367{
1368	struct dm_io_request io_req = {
1369		.bi_op = REQ_OP_DISCARD,
1370		.bi_op_flags = REQ_SYNC,
1371		.mem.type = DM_IO_KMEM,
1372		.mem.ptr.addr = NULL,
1373		.client = c->dm_io,
1374	};
1375	struct dm_io_region io_reg = {
1376		.bdev = c->bdev,
1377		.sector = block_to_sector(c, block),
1378		.count = block_to_sector(c, count),
1379	};
1380
1381	BUG_ON(dm_bufio_in_request());
1382
1383	return dm_io(&io_req, 1, &io_reg, NULL);
1384}
1385EXPORT_SYMBOL_GPL(dm_bufio_issue_discard);
1386
1387/*
1388 * We first delete any other buffer that may be at that new location.
1389 *
1390 * Then, we write the buffer to the original location if it was dirty.
1391 *
1392 * Then, if we are the only one who is holding the buffer, relink the buffer
1393 * in the buffer tree for the new location.
1394 *
1395 * If there was someone else holding the buffer, we write it to the new
1396 * location but not relink it, because that other user needs to have the buffer
1397 * at the same place.
1398 */
1399void dm_bufio_release_move(struct dm_buffer *b, sector_t new_block)
1400{
1401	struct dm_bufio_client *c = b->c;
1402	struct dm_buffer *new;
1403
1404	BUG_ON(dm_bufio_in_request());
1405
1406	dm_bufio_lock(c);
1407
1408retry:
1409	new = __find(c, new_block);
1410	if (new) {
1411		if (new->hold_count) {
1412			__wait_for_free_buffer(c);
1413			goto retry;
1414		}
1415
1416		/*
1417		 * FIXME: Is there any point waiting for a write that's going
1418		 * to be overwritten in a bit?
1419		 */
1420		__make_buffer_clean(new);
1421		__unlink_buffer(new);
1422		__free_buffer_wake(new);
1423	}
1424
1425	BUG_ON(!b->hold_count);
1426	BUG_ON(test_bit(B_READING, &b->state));
1427
1428	__write_dirty_buffer(b, NULL);
1429	if (b->hold_count == 1) {
1430		wait_on_bit_io(&b->state, B_WRITING,
1431			       TASK_UNINTERRUPTIBLE);
1432		set_bit(B_DIRTY, &b->state);
1433		b->dirty_start = 0;
1434		b->dirty_end = c->block_size;
1435		__unlink_buffer(b);
1436		__link_buffer(b, new_block, LIST_DIRTY);
1437	} else {
1438		sector_t old_block;
1439		wait_on_bit_lock_io(&b->state, B_WRITING,
1440				    TASK_UNINTERRUPTIBLE);
1441		/*
1442		 * Relink buffer to "new_block" so that write_callback
1443		 * sees "new_block" as a block number.
1444		 * After the write, link the buffer back to old_block.
1445		 * All this must be done in bufio lock, so that block number
1446		 * change isn't visible to other threads.
1447		 */
1448		old_block = b->block;
1449		__unlink_buffer(b);
1450		__link_buffer(b, new_block, b->list_mode);
1451		submit_io(b, REQ_OP_WRITE, write_endio);
1452		wait_on_bit_io(&b->state, B_WRITING,
1453			       TASK_UNINTERRUPTIBLE);
1454		__unlink_buffer(b);
1455		__link_buffer(b, old_block, b->list_mode);
1456	}
1457
1458	dm_bufio_unlock(c);
1459	dm_bufio_release(b);
1460}
1461EXPORT_SYMBOL_GPL(dm_bufio_release_move);
1462
1463static void forget_buffer_locked(struct dm_buffer *b)
1464{
1465	if (likely(!b->hold_count) && likely(!b->state)) {
1466		__unlink_buffer(b);
1467		__free_buffer_wake(b);
1468	}
1469}
1470
1471/*
1472 * Free the given buffer.
1473 *
1474 * This is just a hint, if the buffer is in use or dirty, this function
1475 * does nothing.
1476 */
1477void dm_bufio_forget(struct dm_bufio_client *c, sector_t block)
1478{
1479	struct dm_buffer *b;
1480
1481	dm_bufio_lock(c);
1482
1483	b = __find(c, block);
1484	if (b)
1485		forget_buffer_locked(b);
 
 
1486
1487	dm_bufio_unlock(c);
1488}
1489EXPORT_SYMBOL_GPL(dm_bufio_forget);
1490
1491void dm_bufio_forget_buffers(struct dm_bufio_client *c, sector_t block, sector_t n_blocks)
1492{
1493	struct dm_buffer *b;
1494	sector_t end_block = block + n_blocks;
1495
1496	while (block < end_block) {
1497		dm_bufio_lock(c);
1498
1499		b = __find_next(c, block);
1500		if (b) {
1501			block = b->block + 1;
1502			forget_buffer_locked(b);
1503		}
1504
1505		dm_bufio_unlock(c);
1506
1507		if (!b)
1508			break;
1509	}
1510
1511}
1512EXPORT_SYMBOL_GPL(dm_bufio_forget_buffers);
1513
1514void dm_bufio_set_minimum_buffers(struct dm_bufio_client *c, unsigned n)
1515{
1516	c->minimum_buffers = n;
1517}
1518EXPORT_SYMBOL_GPL(dm_bufio_set_minimum_buffers);
1519
1520unsigned dm_bufio_get_block_size(struct dm_bufio_client *c)
1521{
1522	return c->block_size;
1523}
1524EXPORT_SYMBOL_GPL(dm_bufio_get_block_size);
1525
1526sector_t dm_bufio_get_device_size(struct dm_bufio_client *c)
1527{
1528	sector_t s = i_size_read(c->bdev->bd_inode) >> SECTOR_SHIFT;
1529	if (likely(c->sectors_per_block_bits >= 0))
1530		s >>= c->sectors_per_block_bits;
1531	else
1532		sector_div(s, c->block_size >> SECTOR_SHIFT);
1533	return s;
1534}
1535EXPORT_SYMBOL_GPL(dm_bufio_get_device_size);
1536
1537sector_t dm_bufio_get_block_number(struct dm_buffer *b)
1538{
1539	return b->block;
1540}
1541EXPORT_SYMBOL_GPL(dm_bufio_get_block_number);
1542
1543void *dm_bufio_get_block_data(struct dm_buffer *b)
1544{
1545	return b->data;
1546}
1547EXPORT_SYMBOL_GPL(dm_bufio_get_block_data);
1548
1549void *dm_bufio_get_aux_data(struct dm_buffer *b)
1550{
1551	return b + 1;
1552}
1553EXPORT_SYMBOL_GPL(dm_bufio_get_aux_data);
1554
1555struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b)
1556{
1557	return b->c;
1558}
1559EXPORT_SYMBOL_GPL(dm_bufio_get_client);
1560
1561static void drop_buffers(struct dm_bufio_client *c)
1562{
1563	struct dm_buffer *b;
1564	int i;
1565	bool warned = false;
1566
1567	BUG_ON(dm_bufio_in_request());
1568
1569	/*
1570	 * An optimization so that the buffers are not written one-by-one.
1571	 */
1572	dm_bufio_write_dirty_buffers_async(c);
1573
1574	dm_bufio_lock(c);
1575
1576	while ((b = __get_unclaimed_buffer(c)))
1577		__free_buffer_wake(b);
1578
1579	for (i = 0; i < LIST_SIZE; i++)
1580		list_for_each_entry(b, &c->lru[i], lru_list) {
1581			WARN_ON(!warned);
1582			warned = true;
1583			DMERR("leaked buffer %llx, hold count %u, list %d",
1584			      (unsigned long long)b->block, b->hold_count, i);
1585#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1586			stack_trace_print(b->stack_entries, b->stack_len, 1);
1587			/* mark unclaimed to avoid BUG_ON below */
1588			b->hold_count = 0;
1589#endif
1590		}
1591
1592#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1593	while ((b = __get_unclaimed_buffer(c)))
1594		__free_buffer_wake(b);
1595#endif
1596
1597	for (i = 0; i < LIST_SIZE; i++)
1598		BUG_ON(!list_empty(&c->lru[i]));
1599
1600	dm_bufio_unlock(c);
1601}
1602
1603/*
1604 * We may not be able to evict this buffer if IO pending or the client
1605 * is still using it.  Caller is expected to know buffer is too old.
1606 *
1607 * And if GFP_NOFS is used, we must not do any I/O because we hold
1608 * dm_bufio_clients_lock and we would risk deadlock if the I/O gets
1609 * rerouted to different bufio client.
1610 */
1611static bool __try_evict_buffer(struct dm_buffer *b, gfp_t gfp)
1612{
1613	if (!(gfp & __GFP_FS)) {
1614		if (test_bit(B_READING, &b->state) ||
1615		    test_bit(B_WRITING, &b->state) ||
1616		    test_bit(B_DIRTY, &b->state))
1617			return false;
1618	}
1619
1620	if (b->hold_count)
1621		return false;
1622
1623	__make_buffer_clean(b);
1624	__unlink_buffer(b);
1625	__free_buffer_wake(b);
1626
1627	return true;
1628}
1629
1630static unsigned long get_retain_buffers(struct dm_bufio_client *c)
1631{
1632	unsigned long retain_bytes = READ_ONCE(dm_bufio_retain_bytes);
1633	if (likely(c->sectors_per_block_bits >= 0))
1634		retain_bytes >>= c->sectors_per_block_bits + SECTOR_SHIFT;
1635	else
1636		retain_bytes /= c->block_size;
1637	return retain_bytes;
1638}
1639
1640static void __scan(struct dm_bufio_client *c)
 
1641{
1642	int l;
1643	struct dm_buffer *b, *tmp;
1644	unsigned long freed = 0;
1645	unsigned long count = c->n_buffers[LIST_CLEAN] +
1646			      c->n_buffers[LIST_DIRTY];
1647	unsigned long retain_target = get_retain_buffers(c);
1648
1649	for (l = 0; l < LIST_SIZE; l++) {
1650		list_for_each_entry_safe_reverse(b, tmp, &c->lru[l], lru_list) {
1651			if (count - freed <= retain_target)
1652				atomic_long_set(&c->need_shrink, 0);
1653			if (!atomic_long_read(&c->need_shrink))
1654				return;
1655			if (__try_evict_buffer(b, GFP_KERNEL)) {
1656				atomic_long_dec(&c->need_shrink);
1657				freed++;
1658			}
 
1659			cond_resched();
1660		}
1661	}
 
1662}
1663
1664static void shrink_work(struct work_struct *w)
1665{
1666	struct dm_bufio_client *c = container_of(w, struct dm_bufio_client, shrink_work);
1667
1668	dm_bufio_lock(c);
1669	__scan(c);
1670	dm_bufio_unlock(c);
1671}
1672
1673static unsigned long dm_bufio_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
1674{
1675	struct dm_bufio_client *c;
 
1676
1677	c = container_of(shrink, struct dm_bufio_client, shrinker);
1678	atomic_long_add(sc->nr_to_scan, &c->need_shrink);
1679	queue_work(dm_bufio_wq, &c->shrink_work);
 
 
1680
1681	return sc->nr_to_scan;
 
 
1682}
1683
1684static unsigned long dm_bufio_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
 
1685{
1686	struct dm_bufio_client *c = container_of(shrink, struct dm_bufio_client, shrinker);
1687	unsigned long count = READ_ONCE(c->n_buffers[LIST_CLEAN]) +
1688			      READ_ONCE(c->n_buffers[LIST_DIRTY]);
1689	unsigned long retain_target = get_retain_buffers(c);
1690	unsigned long queued_for_cleanup = atomic_long_read(&c->need_shrink);
1691
1692	if (unlikely(count < retain_target))
1693		count = 0;
1694	else
1695		count -= retain_target;
1696
1697	if (unlikely(count < queued_for_cleanup))
1698		count = 0;
1699	else
1700		count -= queued_for_cleanup;
1701
1702	return count;
1703}
1704
1705/*
1706 * Create the buffering interface
1707 */
1708struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsigned block_size,
1709					       unsigned reserved_buffers, unsigned aux_size,
1710					       void (*alloc_callback)(struct dm_buffer *),
1711					       void (*write_callback)(struct dm_buffer *))
1712{
1713	int r;
1714	struct dm_bufio_client *c;
1715	unsigned i;
1716	char slab_name[27];
1717
1718	if (!block_size || block_size & ((1 << SECTOR_SHIFT) - 1)) {
1719		DMERR("%s: block size not specified or is not multiple of 512b", __func__);
1720		r = -EINVAL;
1721		goto bad_client;
1722	}
1723
1724	c = kzalloc(sizeof(*c), GFP_KERNEL);
1725	if (!c) {
1726		r = -ENOMEM;
1727		goto bad_client;
1728	}
1729	c->buffer_tree = RB_ROOT;
1730
1731	c->bdev = bdev;
1732	c->block_size = block_size;
1733	if (is_power_of_2(block_size))
1734		c->sectors_per_block_bits = __ffs(block_size) - SECTOR_SHIFT;
1735	else
1736		c->sectors_per_block_bits = -1;
1737
1738	c->alloc_callback = alloc_callback;
1739	c->write_callback = write_callback;
1740
1741	for (i = 0; i < LIST_SIZE; i++) {
1742		INIT_LIST_HEAD(&c->lru[i]);
1743		c->n_buffers[i] = 0;
1744	}
1745
1746	mutex_init(&c->lock);
1747	INIT_LIST_HEAD(&c->reserved_buffers);
1748	c->need_reserved_buffers = reserved_buffers;
1749
1750	dm_bufio_set_minimum_buffers(c, DM_BUFIO_MIN_BUFFERS);
1751
1752	init_waitqueue_head(&c->free_buffer_wait);
1753	c->async_write_error = 0;
1754
1755	c->dm_io = dm_io_client_create();
1756	if (IS_ERR(c->dm_io)) {
1757		r = PTR_ERR(c->dm_io);
1758		goto bad_dm_io;
1759	}
1760
1761	if (block_size <= KMALLOC_MAX_SIZE &&
1762	    (block_size < PAGE_SIZE || !is_power_of_2(block_size))) {
1763		unsigned align = min(1U << __ffs(block_size), (unsigned)PAGE_SIZE);
1764		snprintf(slab_name, sizeof slab_name, "dm_bufio_cache-%u", block_size);
1765		c->slab_cache = kmem_cache_create(slab_name, block_size, align,
1766						  SLAB_RECLAIM_ACCOUNT, NULL);
1767		if (!c->slab_cache) {
1768			r = -ENOMEM;
1769			goto bad;
1770		}
1771	}
1772	if (aux_size)
1773		snprintf(slab_name, sizeof slab_name, "dm_bufio_buffer-%u", aux_size);
1774	else
1775		snprintf(slab_name, sizeof slab_name, "dm_bufio_buffer");
1776	c->slab_buffer = kmem_cache_create(slab_name, sizeof(struct dm_buffer) + aux_size,
1777					   0, SLAB_RECLAIM_ACCOUNT, NULL);
1778	if (!c->slab_buffer) {
1779		r = -ENOMEM;
1780		goto bad;
1781	}
1782
1783	while (c->need_reserved_buffers) {
1784		struct dm_buffer *b = alloc_buffer(c, GFP_KERNEL);
1785
1786		if (!b) {
1787			r = -ENOMEM;
1788			goto bad;
1789		}
1790		__free_buffer_wake(b);
1791	}
1792
1793	INIT_WORK(&c->shrink_work, shrink_work);
1794	atomic_long_set(&c->need_shrink, 0);
1795
1796	c->shrinker.count_objects = dm_bufio_shrink_count;
1797	c->shrinker.scan_objects = dm_bufio_shrink_scan;
1798	c->shrinker.seeks = 1;
1799	c->shrinker.batch = 0;
1800	r = register_shrinker(&c->shrinker);
1801	if (r)
1802		goto bad;
1803
1804	mutex_lock(&dm_bufio_clients_lock);
1805	dm_bufio_client_count++;
1806	list_add(&c->client_list, &dm_bufio_all_clients);
1807	__cache_size_refresh();
1808	mutex_unlock(&dm_bufio_clients_lock);
1809
1810	return c;
1811
1812bad:
1813	while (!list_empty(&c->reserved_buffers)) {
1814		struct dm_buffer *b = list_entry(c->reserved_buffers.next,
1815						 struct dm_buffer, lru_list);
1816		list_del(&b->lru_list);
1817		free_buffer(b);
1818	}
1819	kmem_cache_destroy(c->slab_cache);
1820	kmem_cache_destroy(c->slab_buffer);
1821	dm_io_client_destroy(c->dm_io);
1822bad_dm_io:
1823	mutex_destroy(&c->lock);
1824	kfree(c);
1825bad_client:
1826	return ERR_PTR(r);
1827}
1828EXPORT_SYMBOL_GPL(dm_bufio_client_create);
1829
1830/*
1831 * Free the buffering interface.
1832 * It is required that there are no references on any buffers.
1833 */
1834void dm_bufio_client_destroy(struct dm_bufio_client *c)
1835{
1836	unsigned i;
1837
1838	drop_buffers(c);
1839
1840	unregister_shrinker(&c->shrinker);
1841	flush_work(&c->shrink_work);
1842
1843	mutex_lock(&dm_bufio_clients_lock);
1844
1845	list_del(&c->client_list);
1846	dm_bufio_client_count--;
1847	__cache_size_refresh();
1848
1849	mutex_unlock(&dm_bufio_clients_lock);
1850
1851	BUG_ON(!RB_EMPTY_ROOT(&c->buffer_tree));
1852	BUG_ON(c->need_reserved_buffers);
1853
1854	while (!list_empty(&c->reserved_buffers)) {
1855		struct dm_buffer *b = list_entry(c->reserved_buffers.next,
1856						 struct dm_buffer, lru_list);
1857		list_del(&b->lru_list);
1858		free_buffer(b);
1859	}
1860
1861	for (i = 0; i < LIST_SIZE; i++)
1862		if (c->n_buffers[i])
1863			DMERR("leaked buffer count %d: %ld", i, c->n_buffers[i]);
1864
1865	for (i = 0; i < LIST_SIZE; i++)
1866		BUG_ON(c->n_buffers[i]);
1867
1868	kmem_cache_destroy(c->slab_cache);
1869	kmem_cache_destroy(c->slab_buffer);
1870	dm_io_client_destroy(c->dm_io);
1871	mutex_destroy(&c->lock);
1872	kfree(c);
1873}
1874EXPORT_SYMBOL_GPL(dm_bufio_client_destroy);
1875
1876void dm_bufio_set_sector_offset(struct dm_bufio_client *c, sector_t start)
1877{
1878	c->start = start;
1879}
1880EXPORT_SYMBOL_GPL(dm_bufio_set_sector_offset);
1881
1882static unsigned get_max_age_hz(void)
1883{
1884	unsigned max_age = READ_ONCE(dm_bufio_max_age);
1885
1886	if (max_age > UINT_MAX / HZ)
1887		max_age = UINT_MAX / HZ;
1888
1889	return max_age * HZ;
1890}
1891
1892static bool older_than(struct dm_buffer *b, unsigned long age_hz)
1893{
1894	return time_after_eq(jiffies, b->last_accessed + age_hz);
1895}
1896
1897static void __evict_old_buffers(struct dm_bufio_client *c, unsigned long age_hz)
1898{
1899	struct dm_buffer *b, *tmp;
1900	unsigned long retain_target = get_retain_buffers(c);
1901	unsigned long count;
1902	LIST_HEAD(write_list);
1903
1904	dm_bufio_lock(c);
1905
1906	__check_watermark(c, &write_list);
1907	if (unlikely(!list_empty(&write_list))) {
1908		dm_bufio_unlock(c);
1909		__flush_write_list(&write_list);
1910		dm_bufio_lock(c);
1911	}
1912
1913	count = c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY];
1914	list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_CLEAN], lru_list) {
1915		if (count <= retain_target)
1916			break;
1917
1918		if (!older_than(b, age_hz))
1919			break;
1920
1921		if (__try_evict_buffer(b, 0))
1922			count--;
1923
1924		cond_resched();
1925	}
1926
1927	dm_bufio_unlock(c);
1928}
1929
1930static void do_global_cleanup(struct work_struct *w)
1931{
1932	struct dm_bufio_client *locked_client = NULL;
1933	struct dm_bufio_client *current_client;
1934	struct dm_buffer *b;
1935	unsigned spinlock_hold_count;
1936	unsigned long threshold = dm_bufio_cache_size -
1937		dm_bufio_cache_size / DM_BUFIO_LOW_WATERMARK_RATIO;
1938	unsigned long loops = global_num * 2;
1939
1940	mutex_lock(&dm_bufio_clients_lock);
1941
1942	while (1) {
1943		cond_resched();
1944
1945		spin_lock(&global_spinlock);
1946		if (unlikely(dm_bufio_current_allocated <= threshold))
1947			break;
1948
1949		spinlock_hold_count = 0;
1950get_next:
1951		if (!loops--)
1952			break;
1953		if (unlikely(list_empty(&global_queue)))
1954			break;
1955		b = list_entry(global_queue.prev, struct dm_buffer, global_list);
1956
1957		if (b->accessed) {
1958			b->accessed = 0;
1959			list_move(&b->global_list, &global_queue);
1960			if (likely(++spinlock_hold_count < 16))
1961				goto get_next;
1962			spin_unlock(&global_spinlock);
1963			continue;
1964		}
1965
1966		current_client = b->c;
1967		if (unlikely(current_client != locked_client)) {
1968			if (locked_client)
1969				dm_bufio_unlock(locked_client);
1970
1971			if (!dm_bufio_trylock(current_client)) {
1972				spin_unlock(&global_spinlock);
1973				dm_bufio_lock(current_client);
1974				locked_client = current_client;
1975				continue;
1976			}
1977
1978			locked_client = current_client;
1979		}
1980
1981		spin_unlock(&global_spinlock);
1982
1983		if (unlikely(!__try_evict_buffer(b, GFP_KERNEL))) {
1984			spin_lock(&global_spinlock);
1985			list_move(&b->global_list, &global_queue);
1986			spin_unlock(&global_spinlock);
1987		}
1988	}
1989
1990	spin_unlock(&global_spinlock);
1991
1992	if (locked_client)
1993		dm_bufio_unlock(locked_client);
1994
1995	mutex_unlock(&dm_bufio_clients_lock);
1996}
1997
1998static void cleanup_old_buffers(void)
1999{
2000	unsigned long max_age_hz = get_max_age_hz();
2001	struct dm_bufio_client *c;
2002
2003	mutex_lock(&dm_bufio_clients_lock);
2004
2005	__cache_size_refresh();
2006
2007	list_for_each_entry(c, &dm_bufio_all_clients, client_list)
2008		__evict_old_buffers(c, max_age_hz);
2009
2010	mutex_unlock(&dm_bufio_clients_lock);
2011}
2012
2013static void work_fn(struct work_struct *w)
2014{
2015	cleanup_old_buffers();
2016
2017	queue_delayed_work(dm_bufio_wq, &dm_bufio_cleanup_old_work,
2018			   DM_BUFIO_WORK_TIMER_SECS * HZ);
2019}
2020
2021/*----------------------------------------------------------------
2022 * Module setup
2023 *--------------------------------------------------------------*/
2024
2025/*
2026 * This is called only once for the whole dm_bufio module.
2027 * It initializes memory limit.
2028 */
2029static int __init dm_bufio_init(void)
2030{
2031	__u64 mem;
2032
2033	dm_bufio_allocated_kmem_cache = 0;
2034	dm_bufio_allocated_get_free_pages = 0;
2035	dm_bufio_allocated_vmalloc = 0;
2036	dm_bufio_current_allocated = 0;
2037
2038	mem = (__u64)mult_frac(totalram_pages() - totalhigh_pages(),
2039			       DM_BUFIO_MEMORY_PERCENT, 100) << PAGE_SHIFT;
2040
2041	if (mem > ULONG_MAX)
2042		mem = ULONG_MAX;
2043
2044#ifdef CONFIG_MMU
2045	if (mem > mult_frac(VMALLOC_TOTAL, DM_BUFIO_VMALLOC_PERCENT, 100))
2046		mem = mult_frac(VMALLOC_TOTAL, DM_BUFIO_VMALLOC_PERCENT, 100);
2047#endif
2048
2049	dm_bufio_default_cache_size = mem;
2050
2051	mutex_lock(&dm_bufio_clients_lock);
2052	__cache_size_refresh();
2053	mutex_unlock(&dm_bufio_clients_lock);
2054
2055	dm_bufio_wq = alloc_workqueue("dm_bufio_cache", WQ_MEM_RECLAIM, 0);
2056	if (!dm_bufio_wq)
2057		return -ENOMEM;
2058
2059	INIT_DELAYED_WORK(&dm_bufio_cleanup_old_work, work_fn);
2060	INIT_WORK(&dm_bufio_replacement_work, do_global_cleanup);
2061	queue_delayed_work(dm_bufio_wq, &dm_bufio_cleanup_old_work,
2062			   DM_BUFIO_WORK_TIMER_SECS * HZ);
2063
2064	return 0;
2065}
2066
2067/*
2068 * This is called once when unloading the dm_bufio module.
2069 */
2070static void __exit dm_bufio_exit(void)
2071{
2072	int bug = 0;
2073
2074	cancel_delayed_work_sync(&dm_bufio_cleanup_old_work);
2075	flush_workqueue(dm_bufio_wq);
2076	destroy_workqueue(dm_bufio_wq);
2077
2078	if (dm_bufio_client_count) {
2079		DMCRIT("%s: dm_bufio_client_count leaked: %d",
2080			__func__, dm_bufio_client_count);
2081		bug = 1;
2082	}
2083
2084	if (dm_bufio_current_allocated) {
2085		DMCRIT("%s: dm_bufio_current_allocated leaked: %lu",
2086			__func__, dm_bufio_current_allocated);
2087		bug = 1;
2088	}
2089
2090	if (dm_bufio_allocated_get_free_pages) {
2091		DMCRIT("%s: dm_bufio_allocated_get_free_pages leaked: %lu",
2092		       __func__, dm_bufio_allocated_get_free_pages);
2093		bug = 1;
2094	}
2095
2096	if (dm_bufio_allocated_vmalloc) {
2097		DMCRIT("%s: dm_bufio_vmalloc leaked: %lu",
2098		       __func__, dm_bufio_allocated_vmalloc);
2099		bug = 1;
2100	}
2101
2102	BUG_ON(bug);
2103}
2104
2105module_init(dm_bufio_init)
2106module_exit(dm_bufio_exit)
2107
2108module_param_named(max_cache_size_bytes, dm_bufio_cache_size, ulong, S_IRUGO | S_IWUSR);
2109MODULE_PARM_DESC(max_cache_size_bytes, "Size of metadata cache");
2110
2111module_param_named(max_age_seconds, dm_bufio_max_age, uint, S_IRUGO | S_IWUSR);
2112MODULE_PARM_DESC(max_age_seconds, "Max age of a buffer in seconds");
2113
2114module_param_named(retain_bytes, dm_bufio_retain_bytes, ulong, S_IRUGO | S_IWUSR);
2115MODULE_PARM_DESC(retain_bytes, "Try to keep at least this many bytes cached in memory");
2116
2117module_param_named(peak_allocated_bytes, dm_bufio_peak_allocated, ulong, S_IRUGO | S_IWUSR);
2118MODULE_PARM_DESC(peak_allocated_bytes, "Tracks the maximum allocated memory");
2119
2120module_param_named(allocated_kmem_cache_bytes, dm_bufio_allocated_kmem_cache, ulong, S_IRUGO);
2121MODULE_PARM_DESC(allocated_kmem_cache_bytes, "Memory allocated with kmem_cache_alloc");
2122
2123module_param_named(allocated_get_free_pages_bytes, dm_bufio_allocated_get_free_pages, ulong, S_IRUGO);
2124MODULE_PARM_DESC(allocated_get_free_pages_bytes, "Memory allocated with get_free_pages");
2125
2126module_param_named(allocated_vmalloc_bytes, dm_bufio_allocated_vmalloc, ulong, S_IRUGO);
2127MODULE_PARM_DESC(allocated_vmalloc_bytes, "Memory allocated with vmalloc");
2128
2129module_param_named(current_allocated_bytes, dm_bufio_current_allocated, ulong, S_IRUGO);
2130MODULE_PARM_DESC(current_allocated_bytes, "Memory currently used by the cache");
2131
2132MODULE_AUTHOR("Mikulas Patocka <dm-devel@redhat.com>");
2133MODULE_DESCRIPTION(DM_NAME " buffered I/O library");
2134MODULE_LICENSE("GPL");