1/*
   2 * Copyright (C) 2009-2011 Red Hat, Inc.
   3 *
   4 * Author: Mikulas Patocka <mpatocka@redhat.com>
   5 *
   6 * This file is released under the GPL.
   7 */
   8
   9#include "dm-bufio.h"
  10
  11#include <linux/device-mapper.h>
  12#include <linux/dm-io.h>
  13#include <linux/slab.h>
 
  14#include <linux/jiffies.h>
  15#include <linux/vmalloc.h>
  16#include <linux/shrinker.h>
  17#include <linux/module.h>
  18#include <linux/rbtree.h>
  19#include <linux/stacktrace.h>
  20
  21#define DM_MSG_PREFIX "bufio"
  22
  23/*
  24 * Memory management policy:
  25 *	Limit the number of buffers to DM_BUFIO_MEMORY_PERCENT of main memory
  26 *	or DM_BUFIO_VMALLOC_PERCENT of vmalloc memory (whichever is lower).
  27 *	Always allocate at least DM_BUFIO_MIN_BUFFERS buffers.
  28 *	Start background writeback when there are DM_BUFIO_WRITEBACK_PERCENT
  29 *	dirty buffers.
  30 */
  31#define DM_BUFIO_MIN_BUFFERS		8
  32
  33#define DM_BUFIO_MEMORY_PERCENT		2
  34#define DM_BUFIO_VMALLOC_PERCENT	25
  35#define DM_BUFIO_WRITEBACK_PERCENT	75
 
  36
  37/*
  38 * Check buffer ages in this interval (seconds)
  39 */
  40#define DM_BUFIO_WORK_TIMER_SECS	30
  41
  42/*
  43 * Free buffers when they are older than this (seconds)
  44 */
  45#define DM_BUFIO_DEFAULT_AGE_SECS	300
  46
  47/*
  48 * The nr of bytes of cached data to keep around.
  49 */
  50#define DM_BUFIO_DEFAULT_RETAIN_BYTES   (256 * 1024)
  51
  52/*
  53 * The number of bvec entries that are embedded directly in the buffer.
  54 * If the chunk size is larger, dm-io is used to do the io.
  55 */
  56#define DM_BUFIO_INLINE_VECS		16
  57
  58/*
  59 * Don't try to use kmem_cache_alloc for blocks larger than this.
  60 * For explanation, see alloc_buffer_data below.
  61 */
  62#define DM_BUFIO_BLOCK_SIZE_SLAB_LIMIT	(PAGE_SIZE >> 1)
  63#define DM_BUFIO_BLOCK_SIZE_GFP_LIMIT	(PAGE_SIZE << (MAX_ORDER - 1))
  64
  65/*
  66 * dm_buffer->list_mode
  67 */
  68#define LIST_CLEAN	0
  69#define LIST_DIRTY	1
  70#define LIST_SIZE	2
  71
  72/*
  73 * Linking of buffers:
  74 *	All buffers are linked to cache_hash with their hash_list field.
  75 *
  76 *	Clean buffers that are not being written (B_WRITING not set)
  77 *	are linked to lru[LIST_CLEAN] with their lru_list field.
  78 *
  79 *	Dirty and clean buffers that are being written are linked to
  80 *	lru[LIST_DIRTY] with their lru_list field. When the write
  81 *	finishes, the buffer cannot be relinked immediately (because we
  82 *	are in an interrupt context and relinking requires process
  83 *	context), so some clean-not-writing buffers can be held on
  84 *	dirty_lru too.  They are later added to lru in the process
  85 *	context.
  86 */
  87struct dm_bufio_client {
  88	struct mutex lock;
  89
  90	struct list_head lru[LIST_SIZE];
  91	unsigned long n_buffers[LIST_SIZE];
  92
  93	struct block_device *bdev;
  94	unsigned block_size;
  95	unsigned char sectors_per_block_bits;
  96	unsigned char pages_per_block_bits;
  97	unsigned char blocks_per_page_bits;
  98	unsigned aux_size;
  99	void (*alloc_callback)(struct dm_buffer *);
 100	void (*write_callback)(struct dm_buffer *);
 101
 
 
 102	struct dm_io_client *dm_io;
 103
 104	struct list_head reserved_buffers;
 105	unsigned need_reserved_buffers;
 106
 107	unsigned minimum_buffers;
 108
 109	struct rb_root buffer_tree;
 110	wait_queue_head_t free_buffer_wait;
 111
 
 
 112	int async_write_error;
 113
 114	struct list_head client_list;
 115	struct shrinker shrinker;
 116};
 117
 118/*
 119 * Buffer state bits.
 120 */
 121#define B_READING	0
 122#define B_WRITING	1
 123#define B_DIRTY		2
 124
 125/*
 126 * Describes how the block was allocated:
 127 * kmem_cache_alloc(), __get_free_pages() or vmalloc().
 128 * See the comment at alloc_buffer_data.
 129 */
 130enum data_mode {
 131	DATA_MODE_SLAB = 0,
 132	DATA_MODE_GET_FREE_PAGES = 1,
 133	DATA_MODE_VMALLOC = 2,
 134	DATA_MODE_LIMIT = 3
 135};
 136
 137struct dm_buffer {
 138	struct rb_node node;
 139	struct list_head lru_list;
 
 140	sector_t block;
 141	void *data;
 142	enum data_mode data_mode;
 143	unsigned char list_mode;		/* LIST_* */
 
 
 
 144	unsigned hold_count;
 145	int read_error;
 146	int write_error;
 147	unsigned long state;
 148	unsigned long last_accessed;
 
 
 
 
 149	struct dm_bufio_client *c;
 150	struct list_head write_list;
 151	struct bio bio;
 152	struct bio_vec bio_vec[DM_BUFIO_INLINE_VECS];
 153#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
 154#define MAX_STACK 10
 155	struct stack_trace stack_trace;
 156	unsigned long stack_entries[MAX_STACK];
 157#endif
 158};
 159
 160/*----------------------------------------------------------------*/
 161
 162static struct kmem_cache *dm_bufio_caches[PAGE_SHIFT - SECTOR_SHIFT];
 163static char *dm_bufio_cache_names[PAGE_SHIFT - SECTOR_SHIFT];
 164
 165static inline int dm_bufio_cache_index(struct dm_bufio_client *c)
 166{
 167	unsigned ret = c->blocks_per_page_bits - 1;
 168
 169	BUG_ON(ret >= ARRAY_SIZE(dm_bufio_caches));
 170
 171	return ret;
 172}
 173
 174#define DM_BUFIO_CACHE(c)	(dm_bufio_caches[dm_bufio_cache_index(c)])
 175#define DM_BUFIO_CACHE_NAME(c)	(dm_bufio_cache_names[dm_bufio_cache_index(c)])
 176
 177#define dm_bufio_in_request()	(!!current->bio_list)
 178
 179static void dm_bufio_lock(struct dm_bufio_client *c)
 180{
 181	mutex_lock_nested(&c->lock, dm_bufio_in_request());
 182}
 183
 184static int dm_bufio_trylock(struct dm_bufio_client *c)
 185{
 186	return mutex_trylock(&c->lock);
 187}
 188
 189static void dm_bufio_unlock(struct dm_bufio_client *c)
 190{
 191	mutex_unlock(&c->lock);
 192}
 193
 194/*----------------------------------------------------------------*/
 195
 196/*
 197 * Default cache size: available memory divided by the ratio.
 198 */
 199static unsigned long dm_bufio_default_cache_size;
 200
 201/*
 202 * Total cache size set by the user.
 203 */
 204static unsigned long dm_bufio_cache_size;
 205
 206/*
 207 * A copy of dm_bufio_cache_size because dm_bufio_cache_size can change
 208 * at any time.  If it disagrees, the user has changed cache size.
 209 */
 210static unsigned long dm_bufio_cache_size_latch;
 211
 212static DEFINE_SPINLOCK(param_spinlock);
 
 
 
 
 213
 214/*
 215 * Buffers are freed after this timeout
 216 */
 217static unsigned dm_bufio_max_age = DM_BUFIO_DEFAULT_AGE_SECS;
 218static unsigned dm_bufio_retain_bytes = DM_BUFIO_DEFAULT_RETAIN_BYTES;
 219
 220static unsigned long dm_bufio_peak_allocated;
 221static unsigned long dm_bufio_allocated_kmem_cache;
 222static unsigned long dm_bufio_allocated_get_free_pages;
 223static unsigned long dm_bufio_allocated_vmalloc;
 224static unsigned long dm_bufio_current_allocated;
 225
 226/*----------------------------------------------------------------*/
 227
 228/*
 229 * Per-client cache: dm_bufio_cache_size / dm_bufio_client_count
 230 */
 231static unsigned long dm_bufio_cache_size_per_client;
 232
 233/*
 234 * The current number of clients.
 235 */
 236static int dm_bufio_client_count;
 237
 238/*
 239 * The list of all clients.
 240 */
 241static LIST_HEAD(dm_bufio_all_clients);
 242
 243/*
 244 * This mutex protects dm_bufio_cache_size_latch,
 245 * dm_bufio_cache_size_per_client and dm_bufio_client_count
 246 */
 247static DEFINE_MUTEX(dm_bufio_clients_lock);
 248
 
 
 
 
 
 249#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
 250static void buffer_record_stack(struct dm_buffer *b)
 251{
 252	b->stack_trace.nr_entries = 0;
 253	b->stack_trace.max_entries = MAX_STACK;
 254	b->stack_trace.entries = b->stack_entries;
 255	b->stack_trace.skip = 2;
 256	save_stack_trace(&b->stack_trace);
 257}
 258#endif
 259
 260/*----------------------------------------------------------------
 261 * A red/black tree acts as an index for all the buffers.
 262 *--------------------------------------------------------------*/
 263static struct dm_buffer *__find(struct dm_bufio_client *c, sector_t block)
 264{
 265	struct rb_node *n = c->buffer_tree.rb_node;
 266	struct dm_buffer *b;
 267
 268	while (n) {
 269		b = container_of(n, struct dm_buffer, node);
 270
 271		if (b->block == block)
 272			return b;
 273
 274		n = (b->block < block) ? n->rb_left : n->rb_right;
 275	}
 276
 277	return NULL;
 278}
 279
 280static void __insert(struct dm_bufio_client *c, struct dm_buffer *b)
 281{
 282	struct rb_node **new = &c->buffer_tree.rb_node, *parent = NULL;
 283	struct dm_buffer *found;
 284
 285	while (*new) {
 286		found = container_of(*new, struct dm_buffer, node);
 287
 288		if (found->block == b->block) {
 289			BUG_ON(found != b);
 290			return;
 291		}
 292
 293		parent = *new;
 294		new = (found->block < b->block) ?
 295			&((*new)->rb_left) : &((*new)->rb_right);
 296	}
 297
 298	rb_link_node(&b->node, parent, new);
 299	rb_insert_color(&b->node, &c->buffer_tree);
 300}
 301
 302static void __remove(struct dm_bufio_client *c, struct dm_buffer *b)
 303{
 304	rb_erase(&b->node, &c->buffer_tree);
 305}
 306
 307/*----------------------------------------------------------------*/
 308
 309static void adjust_total_allocated(enum data_mode data_mode, long diff)
 310{
 
 
 
 311	static unsigned long * const class_ptr[DATA_MODE_LIMIT] = {
 312		&dm_bufio_allocated_kmem_cache,
 313		&dm_bufio_allocated_get_free_pages,
 314		&dm_bufio_allocated_vmalloc,
 315	};
 316
 317	spin_lock(&param_spinlock);
 
 
 
 
 
 318
 319	*class_ptr[data_mode] += diff;
 320
 321	dm_bufio_current_allocated += diff;
 322
 323	if (dm_bufio_current_allocated > dm_bufio_peak_allocated)
 324		dm_bufio_peak_allocated = dm_bufio_current_allocated;
 325
 326	spin_unlock(&param_spinlock);
 
 
 
 
 
 
 
 
 
 
 
 
 327}
 328
 329/*
 330 * Change the number of clients and recalculate per-client limit.
 331 */
 332static void __cache_size_refresh(void)
 333{
 334	BUG_ON(!mutex_is_locked(&dm_bufio_clients_lock));
 335	BUG_ON(dm_bufio_client_count < 0);
 336
 337	dm_bufio_cache_size_latch = ACCESS_ONCE(dm_bufio_cache_size);
 338
 339	/*
 340	 * Use default if set to 0 and report the actual cache size used.
 341	 */
 342	if (!dm_bufio_cache_size_latch) {
 343		(void)cmpxchg(&dm_bufio_cache_size, 0,
 344			      dm_bufio_default_cache_size);
 345		dm_bufio_cache_size_latch = dm_bufio_default_cache_size;
 346	}
 347
 348	dm_bufio_cache_size_per_client = dm_bufio_cache_size_latch /
 349					 (dm_bufio_client_count ? : 1);
 350}
 351
 352/*
 353 * Allocating buffer data.
 354 *
 355 * Small buffers are allocated with kmem_cache, to use space optimally.
 356 *
 357 * For large buffers, we choose between get_free_pages and vmalloc.
 358 * Each has advantages and disadvantages.
 359 *
 360 * __get_free_pages can randomly fail if the memory is fragmented.
 361 * __vmalloc won't randomly fail, but vmalloc space is limited (it may be
 362 * as low as 128M) so using it for caching is not appropriate.
 363 *
 364 * If the allocation may fail we use __get_free_pages. Memory fragmentation
 365 * won't have a fatal effect here, but it just causes flushes of some other
 366 * buffers and more I/O will be performed. Don't use __get_free_pages if it
 367 * always fails (i.e. order >= MAX_ORDER).
 368 *
 369 * If the allocation shouldn't fail we use __vmalloc. This is only for the
 370 * initial reserve allocation, so there's no risk of wasting all vmalloc
 371 * space.
 372 */
 373static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask,
 374			       enum data_mode *data_mode)
 375{
 376	unsigned noio_flag;
 377	void *ptr;
 378
 379	if (c->block_size <= DM_BUFIO_BLOCK_SIZE_SLAB_LIMIT) {
 380		*data_mode = DATA_MODE_SLAB;
 381		return kmem_cache_alloc(DM_BUFIO_CACHE(c), gfp_mask);
 382	}
 383
 384	if (c->block_size <= DM_BUFIO_BLOCK_SIZE_GFP_LIMIT &&
 385	    gfp_mask & __GFP_NORETRY) {
 386		*data_mode = DATA_MODE_GET_FREE_PAGES;
 387		return (void *)__get_free_pages(gfp_mask,
 388						c->pages_per_block_bits);
 389	}
 390
 391	*data_mode = DATA_MODE_VMALLOC;
 392
 393	/*
 394	 * __vmalloc allocates the data pages and auxiliary structures with
 395	 * gfp_flags that were specified, but pagetables are always allocated
 396	 * with GFP_KERNEL, no matter what was specified as gfp_mask.
 397	 *
 398	 * Consequently, we must set per-process flag PF_MEMALLOC_NOIO so that
 399	 * all allocations done by this process (including pagetables) are done
 400	 * as if GFP_NOIO was specified.
 401	 */
 
 
 
 402
 403	if (gfp_mask & __GFP_NORETRY)
 404		noio_flag = memalloc_noio_save();
 405
 406	ptr = __vmalloc(c->block_size, gfp_mask | __GFP_HIGHMEM, PAGE_KERNEL);
 407
 408	if (gfp_mask & __GFP_NORETRY)
 409		memalloc_noio_restore(noio_flag);
 
 
 410
 411	return ptr;
 412}
 413
 414/*
 415 * Free buffer's data.
 416 */
 417static void free_buffer_data(struct dm_bufio_client *c,
 418			     void *data, enum data_mode data_mode)
 419{
 420	switch (data_mode) {
 421	case DATA_MODE_SLAB:
 422		kmem_cache_free(DM_BUFIO_CACHE(c), data);
 423		break;
 424
 425	case DATA_MODE_GET_FREE_PAGES:
 426		free_pages((unsigned long)data, c->pages_per_block_bits);
 
 427		break;
 428
 429	case DATA_MODE_VMALLOC:
 430		vfree(data);
 431		break;
 432
 433	default:
 434		DMCRIT("dm_bufio_free_buffer_data: bad data mode: %d",
 435		       data_mode);
 436		BUG();
 437	}
 438}
 439
 440/*
 441 * Allocate buffer and its data.
 442 */
 443static struct dm_buffer *alloc_buffer(struct dm_bufio_client *c, gfp_t gfp_mask)
 444{
 445	struct dm_buffer *b = kmalloc(sizeof(struct dm_buffer) + c->aux_size,
 446				      gfp_mask);
 447
 448	if (!b)
 449		return NULL;
 450
 451	b->c = c;
 452
 453	b->data = alloc_buffer_data(c, gfp_mask, &b->data_mode);
 454	if (!b->data) {
 455		kfree(b);
 456		return NULL;
 457	}
 458
 459	adjust_total_allocated(b->data_mode, (long)c->block_size);
 460
 461#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
 462	memset(&b->stack_trace, 0, sizeof(b->stack_trace));
 463#endif
 464	return b;
 465}
 466
 467/*
 468 * Free buffer and its data.
 469 */
 470static void free_buffer(struct dm_buffer *b)
 471{
 472	struct dm_bufio_client *c = b->c;
 473
 474	adjust_total_allocated(b->data_mode, -(long)c->block_size);
 475
 476	free_buffer_data(c, b->data, b->data_mode);
 477	kfree(b);
 478}
 479
 480/*
 481 * Link buffer to the hash list and clean or dirty queue.
 482 */
 483static void __link_buffer(struct dm_buffer *b, sector_t block, int dirty)
 484{
 485	struct dm_bufio_client *c = b->c;
 486
 487	c->n_buffers[dirty]++;
 488	b->block = block;
 489	b->list_mode = dirty;
 490	list_add(&b->lru_list, &c->lru[dirty]);
 491	__insert(b->c, b);
 492	b->last_accessed = jiffies;
 
 
 493}
 494
 495/*
 496 * Unlink buffer from the hash list and dirty or clean queue.
 497 */
 498static void __unlink_buffer(struct dm_buffer *b)
 499{
 500	struct dm_bufio_client *c = b->c;
 501
 502	BUG_ON(!c->n_buffers[b->list_mode]);
 503
 504	c->n_buffers[b->list_mode]--;
 505	__remove(b->c, b);
 506	list_del(&b->lru_list);
 
 
 507}
 508
 509/*
 510 * Place the buffer to the head of dirty or clean LRU queue.
 511 */
 512static void __relink_lru(struct dm_buffer *b, int dirty)
 513{
 514	struct dm_bufio_client *c = b->c;
 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 *	the I/O driver can reject requests spuriously if it thinks that
 535 *	the requests are too big for the device or if they cross a
 536 *	controller-defined memory boundary.
 537 *
 538 * If the buffer is small enough (up to DM_BUFIO_INLINE_VECS pages) and
 539 * it is not vmalloced, try using the bio interface.
 540 *
 541 * If the buffer is big, if it is vmalloced or if the underlying device
 542 * rejects the bio because it is too large, use dm-io layer to do the I/O.
 543 * The dm-io layer splits the I/O into multiple requests, avoiding the above
 544 * shortcomings.
 545 *--------------------------------------------------------------*/
 546
 547/*
 548 * dm-io completion routine. It just calls b->bio.bi_end_io, pretending
 549 * that the request was handled directly with bio interface.
 550 */
 551static void dmio_complete(unsigned long error, void *context)
 552{
 553	struct dm_buffer *b = context;
 554
 555	b->bio.bi_error = error ? -EIO : 0;
 556	b->bio.bi_end_io(&b->bio);
 557}
 558
 559static void use_dmio(struct dm_buffer *b, int rw, sector_t block,
 560		     bio_end_io_t *end_io)
 561{
 562	int r;
 563	struct dm_io_request io_req = {
 564		.bi_op = rw,
 565		.bi_op_flags = 0,
 566		.notify.fn = dmio_complete,
 567		.notify.context = b,
 568		.client = b->c->dm_io,
 569	};
 570	struct dm_io_region region = {
 571		.bdev = b->c->bdev,
 572		.sector = block << b->c->sectors_per_block_bits,
 573		.count = b->c->block_size >> SECTOR_SHIFT,
 574	};
 575
 576	if (b->data_mode != DATA_MODE_VMALLOC) {
 577		io_req.mem.type = DM_IO_KMEM;
 578		io_req.mem.ptr.addr = b->data;
 579	} else {
 580		io_req.mem.type = DM_IO_VMA;
 581		io_req.mem.ptr.vma = b->data;
 582	}
 583
 584	b->bio.bi_end_io = end_io;
 585
 586	r = dm_io(&io_req, 1, &region, NULL);
 587	if (r) {
 588		b->bio.bi_error = r;
 589		end_io(&b->bio);
 590	}
 591}
 592
 593static void inline_endio(struct bio *bio)
 594{
 595	bio_end_io_t *end_fn = bio->bi_private;
 596	int error = bio->bi_error;
 597
 598	/*
 599	 * Reset the bio to free any attached resources
 600	 * (e.g. bio integrity profiles).
 601	 */
 602	bio_reset(bio);
 603
 604	bio->bi_error = error;
 605	end_fn(bio);
 606}
 607
 608static void use_inline_bio(struct dm_buffer *b, int rw, sector_t block,
 609			   bio_end_io_t *end_io)
 610{
 
 611	char *ptr;
 612	int len;
 613
 614	bio_init(&b->bio, b->bio_vec, DM_BUFIO_INLINE_VECS);
 615	b->bio.bi_iter.bi_sector = block << b->c->sectors_per_block_bits;
 616	b->bio.bi_bdev = b->c->bdev;
 617	b->bio.bi_end_io = inline_endio;
 618	/*
 619	 * Use of .bi_private isn't a problem here because
 620	 * the dm_buffer's inline bio is local to bufio.
 621	 */
 622	b->bio.bi_private = end_io;
 623	bio_set_op_attrs(&b->bio, rw, 0);
 624
 625	/*
 626	 * We assume that if len >= PAGE_SIZE ptr is page-aligned.
 627	 * If len < PAGE_SIZE the buffer doesn't cross page boundary.
 628	 */
 629	ptr = b->data;
 630	len = b->c->block_size;
 631
 632	if (len >= PAGE_SIZE)
 633		BUG_ON((unsigned long)ptr & (PAGE_SIZE - 1));
 634	else
 635		BUG_ON((unsigned long)ptr & (len - 1));
 636
 637	do {
 638		if (!bio_add_page(&b->bio, virt_to_page(ptr),
 639				  len < PAGE_SIZE ? len : PAGE_SIZE,
 640				  offset_in_page(ptr))) {
 641			BUG_ON(b->c->block_size <= PAGE_SIZE);
 642			use_dmio(b, rw, block, end_io);
 643			return;
 644		}
 645
 646		len -= PAGE_SIZE;
 647		ptr += PAGE_SIZE;
 648	} while (len > 0);
 649
 650	submit_bio(&b->bio);
 651}
 652
 653static void submit_io(struct dm_buffer *b, int rw, sector_t block,
 654		      bio_end_io_t *end_io)
 655{
 656	if (rw == WRITE && b->c->write_callback)
 657		b->c->write_callback(b);
 
 658
 659	if (b->c->block_size <= DM_BUFIO_INLINE_VECS * PAGE_SIZE &&
 660	    b->data_mode != DATA_MODE_VMALLOC)
 661		use_inline_bio(b, rw, block, end_io);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 662	else
 663		use_dmio(b, rw, block, end_io);
 664}
 665
 666/*----------------------------------------------------------------
 667 * Writing dirty buffers
 668 *--------------------------------------------------------------*/
 669
 670/*
 671 * The endio routine for write.
 672 *
 673 * Set the error, clear B_WRITING bit and wake anyone who was waiting on
 674 * it.
 675 */
 676static void write_endio(struct bio *bio)
 677{
 678	struct dm_buffer *b = container_of(bio, struct dm_buffer, bio);
 679
 680	b->write_error = bio->bi_error;
 681	if (unlikely(bio->bi_error)) {
 682		struct dm_bufio_client *c = b->c;
 683		int error = bio->bi_error;
 684		(void)cmpxchg(&c->async_write_error, 0, error);
 
 685	}
 686
 687	BUG_ON(!test_bit(B_WRITING, &b->state));
 688
 689	smp_mb__before_atomic();
 690	clear_bit(B_WRITING, &b->state);
 691	smp_mb__after_atomic();
 692
 693	wake_up_bit(&b->state, B_WRITING);
 694}
 695
 696/*
 697 * Initiate a write on a dirty buffer, but don't wait for it.
 698 *
 699 * - If the buffer is not dirty, exit.
 700 * - If there some previous write going on, wait for it to finish (we can't
 701 *   have two writes on the same buffer simultaneously).
 702 * - Submit our write and don't wait on it. We set B_WRITING indicating
 703 *   that there is a write in progress.
 704 */
 705static void __write_dirty_buffer(struct dm_buffer *b,
 706				 struct list_head *write_list)
 707{
 708	if (!test_bit(B_DIRTY, &b->state))
 709		return;
 710
 711	clear_bit(B_DIRTY, &b->state);
 712	wait_on_bit_lock_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
 713
 
 
 
 714	if (!write_list)
 715		submit_io(b, WRITE, b->block, write_endio);
 716	else
 717		list_add_tail(&b->write_list, write_list);
 718}
 719
 720static void __flush_write_list(struct list_head *write_list)
 721{
 722	struct blk_plug plug;
 723	blk_start_plug(&plug);
 724	while (!list_empty(write_list)) {
 725		struct dm_buffer *b =
 726			list_entry(write_list->next, struct dm_buffer, write_list);
 727		list_del(&b->write_list);
 728		submit_io(b, WRITE, b->block, write_endio);
 729		cond_resched();
 730	}
 731	blk_finish_plug(&plug);
 732}
 733
 734/*
 735 * Wait until any activity on the buffer finishes.  Possibly write the
 736 * buffer if it is dirty.  When this function finishes, there is no I/O
 737 * running on the buffer and the buffer is not dirty.
 738 */
 739static void __make_buffer_clean(struct dm_buffer *b)
 740{
 741	BUG_ON(b->hold_count);
 742
 743	if (!b->state)	/* fast case */
 744		return;
 745
 746	wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
 747	__write_dirty_buffer(b, NULL);
 748	wait_on_bit_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
 749}
 750
 751/*
 752 * Find some buffer that is not held by anybody, clean it, unlink it and
 753 * return it.
 754 */
 755static struct dm_buffer *__get_unclaimed_buffer(struct dm_bufio_client *c)
 756{
 757	struct dm_buffer *b;
 758
 759	list_for_each_entry_reverse(b, &c->lru[LIST_CLEAN], lru_list) {
 760		BUG_ON(test_bit(B_WRITING, &b->state));
 761		BUG_ON(test_bit(B_DIRTY, &b->state));
 762
 763		if (!b->hold_count) {
 764			__make_buffer_clean(b);
 765			__unlink_buffer(b);
 766			return b;
 767		}
 768		cond_resched();
 769	}
 770
 771	list_for_each_entry_reverse(b, &c->lru[LIST_DIRTY], lru_list) {
 772		BUG_ON(test_bit(B_READING, &b->state));
 773
 774		if (!b->hold_count) {
 775			__make_buffer_clean(b);
 776			__unlink_buffer(b);
 777			return b;
 778		}
 779		cond_resched();
 780	}
 781
 782	return NULL;
 783}
 784
 785/*
 786 * Wait until some other threads free some buffer or release hold count on
 787 * some buffer.
 788 *
 789 * This function is entered with c->lock held, drops it and regains it
 790 * before exiting.
 791 */
 792static void __wait_for_free_buffer(struct dm_bufio_client *c)
 793{
 794	DECLARE_WAITQUEUE(wait, current);
 795
 796	add_wait_queue(&c->free_buffer_wait, &wait);
 797	set_task_state(current, TASK_UNINTERRUPTIBLE);
 798	dm_bufio_unlock(c);
 799
 800	io_schedule();
 801
 802	remove_wait_queue(&c->free_buffer_wait, &wait);
 803
 804	dm_bufio_lock(c);
 805}
 806
 807enum new_flag {
 808	NF_FRESH = 0,
 809	NF_READ = 1,
 810	NF_GET = 2,
 811	NF_PREFETCH = 3
 812};
 813
 814/*
 815 * Allocate a new buffer. If the allocation is not possible, wait until
 816 * some other thread frees a buffer.
 817 *
 818 * May drop the lock and regain it.
 819 */
 820static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client *c, enum new_flag nf)
 821{
 822	struct dm_buffer *b;
 823	bool tried_noio_alloc = false;
 824
 825	/*
 826	 * dm-bufio is resistant to allocation failures (it just keeps
 827	 * one buffer reserved in cases all the allocations fail).
 828	 * So set flags to not try too hard:
 829	 *	GFP_NOWAIT: don't wait; if we need to sleep we'll release our
 830	 *		    mutex and wait ourselves.
 831	 *	__GFP_NORETRY: don't retry and rather return failure
 832	 *	__GFP_NOMEMALLOC: don't use emergency reserves
 833	 *	__GFP_NOWARN: don't print a warning in case of failure
 834	 *
 835	 * For debugging, if we set the cache size to 1, no new buffers will
 836	 * be allocated.
 837	 */
 838	while (1) {
 839		if (dm_bufio_cache_size_latch != 1) {
 840			b = alloc_buffer(c, GFP_NOWAIT | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
 841			if (b)
 842				return b;
 843		}
 844
 845		if (nf == NF_PREFETCH)
 846			return NULL;
 847
 848		if (dm_bufio_cache_size_latch != 1 && !tried_noio_alloc) {
 849			dm_bufio_unlock(c);
 850			b = alloc_buffer(c, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
 851			dm_bufio_lock(c);
 852			if (b)
 853				return b;
 854			tried_noio_alloc = true;
 855		}
 856
 857		if (!list_empty(&c->reserved_buffers)) {
 858			b = list_entry(c->reserved_buffers.next,
 859				       struct dm_buffer, lru_list);
 860			list_del(&b->lru_list);
 861			c->need_reserved_buffers++;
 862
 863			return b;
 864		}
 865
 866		b = __get_unclaimed_buffer(c);
 867		if (b)
 868			return b;
 869
 870		__wait_for_free_buffer(c);
 871	}
 872}
 873
 874static struct dm_buffer *__alloc_buffer_wait(struct dm_bufio_client *c, enum new_flag nf)
 875{
 876	struct dm_buffer *b = __alloc_buffer_wait_no_callback(c, nf);
 877
 878	if (!b)
 879		return NULL;
 880
 881	if (c->alloc_callback)
 882		c->alloc_callback(b);
 883
 884	return b;
 885}
 886
 887/*
 888 * Free a buffer and wake other threads waiting for free buffers.
 889 */
 890static void __free_buffer_wake(struct dm_buffer *b)
 891{
 892	struct dm_bufio_client *c = b->c;
 893
 894	if (!c->need_reserved_buffers)
 895		free_buffer(b);
 896	else {
 897		list_add(&b->lru_list, &c->reserved_buffers);
 898		c->need_reserved_buffers--;
 899	}
 900
 901	wake_up(&c->free_buffer_wait);
 902}
 903
 904static void __write_dirty_buffers_async(struct dm_bufio_client *c, int no_wait,
 905					struct list_head *write_list)
 906{
 907	struct dm_buffer *b, *tmp;
 908
 909	list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) {
 910		BUG_ON(test_bit(B_READING, &b->state));
 911
 912		if (!test_bit(B_DIRTY, &b->state) &&
 913		    !test_bit(B_WRITING, &b->state)) {
 914			__relink_lru(b, LIST_CLEAN);
 915			continue;
 916		}
 917
 918		if (no_wait && test_bit(B_WRITING, &b->state))
 919			return;
 920
 921		__write_dirty_buffer(b, write_list);
 922		cond_resched();
 923	}
 924}
 925
 926/*
 927 * Get writeback threshold and buffer limit for a given client.
 928 */
 929static void __get_memory_limit(struct dm_bufio_client *c,
 930			       unsigned long *threshold_buffers,
 931			       unsigned long *limit_buffers)
 932{
 933	unsigned long buffers;
 934
 935	if (ACCESS_ONCE(dm_bufio_cache_size) != dm_bufio_cache_size_latch) {
 936		mutex_lock(&dm_bufio_clients_lock);
 937		__cache_size_refresh();
 938		mutex_unlock(&dm_bufio_clients_lock);
 939	}
 940
 941	buffers = dm_bufio_cache_size_per_client >>
 942		  (c->sectors_per_block_bits + SECTOR_SHIFT);
 943
 944	if (buffers < c->minimum_buffers)
 945		buffers = c->minimum_buffers;
 946
 947	*limit_buffers = buffers;
 948	*threshold_buffers = buffers * DM_BUFIO_WRITEBACK_PERCENT / 100;
 949}
 950
 951/*
 952 * Check if we're over watermark.
 953 * If we are over threshold_buffers, start freeing buffers.
 954 * If we're over "limit_buffers", block until we get under the limit.
 955 */
 956static void __check_watermark(struct dm_bufio_client *c,
 957			      struct list_head *write_list)
 958{
 959	unsigned long threshold_buffers, limit_buffers;
 960
 961	__get_memory_limit(c, &threshold_buffers, &limit_buffers);
 962
 963	while (c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY] >
 964	       limit_buffers) {
 965
 966		struct dm_buffer *b = __get_unclaimed_buffer(c);
 967
 968		if (!b)
 969			return;
 970
 971		__free_buffer_wake(b);
 972		cond_resched();
 973	}
 974
 975	if (c->n_buffers[LIST_DIRTY] > threshold_buffers)
 976		__write_dirty_buffers_async(c, 1, write_list);
 977}
 978
 979/*----------------------------------------------------------------
 980 * Getting a buffer
 981 *--------------------------------------------------------------*/
 982
 983static struct dm_buffer *__bufio_new(struct dm_bufio_client *c, sector_t block,
 984				     enum new_flag nf, int *need_submit,
 985				     struct list_head *write_list)
 986{
 987	struct dm_buffer *b, *new_b = NULL;
 988
 989	*need_submit = 0;
 990
 991	b = __find(c, block);
 992	if (b)
 993		goto found_buffer;
 994
 995	if (nf == NF_GET)
 996		return NULL;
 997
 998	new_b = __alloc_buffer_wait(c, nf);
 999	if (!new_b)
1000		return NULL;
1001
1002	/*
1003	 * We've had a period where the mutex was unlocked, so need to
1004	 * recheck the hash table.
1005	 */
1006	b = __find(c, block);
1007	if (b) {
1008		__free_buffer_wake(new_b);
1009		goto found_buffer;
1010	}
1011
1012	__check_watermark(c, write_list);
1013
1014	b = new_b;
1015	b->hold_count = 1;
1016	b->read_error = 0;
1017	b->write_error = 0;
1018	__link_buffer(b, block, LIST_CLEAN);
1019
1020	if (nf == NF_FRESH) {
1021		b->state = 0;
1022		return b;
1023	}
1024
1025	b->state = 1 << B_READING;
1026	*need_submit = 1;
1027
1028	return b;
1029
1030found_buffer:
1031	if (nf == NF_PREFETCH)
1032		return NULL;
1033	/*
1034	 * Note: it is essential that we don't wait for the buffer to be
1035	 * read if dm_bufio_get function is used. Both dm_bufio_get and
1036	 * dm_bufio_prefetch can be used in the driver request routine.
1037	 * If the user called both dm_bufio_prefetch and dm_bufio_get on
1038	 * the same buffer, it would deadlock if we waited.
1039	 */
1040	if (nf == NF_GET && unlikely(test_bit(B_READING, &b->state)))
1041		return NULL;
1042
1043	b->hold_count++;
1044	__relink_lru(b, test_bit(B_DIRTY, &b->state) ||
1045		     test_bit(B_WRITING, &b->state));
1046	return b;
1047}
1048
1049/*
1050 * The endio routine for reading: set the error, clear the bit and wake up
1051 * anyone waiting on the buffer.
1052 */
1053static void read_endio(struct bio *bio)
1054{
1055	struct dm_buffer *b = container_of(bio, struct dm_buffer, bio);
1056
1057	b->read_error = bio->bi_error;
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, READ, b->block, read_endio);
1097
1098	wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
1099
1100	if (b->read_error) {
1101		int error = 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, READ, b->block, 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_buffer_dirty(struct dm_buffer *b)
 
1215{
1216	struct dm_bufio_client *c = b->c;
1217
 
 
 
1218	dm_bufio_lock(c);
1219
1220	BUG_ON(test_bit(B_READING, &b->state));
1221
1222	if (!test_and_set_bit(B_DIRTY, &b->state))
 
 
1223		__relink_lru(b, LIST_DIRTY);
 
 
 
 
 
 
1224
1225	dm_bufio_unlock(c);
1226}
 
 
 
 
 
 
1227EXPORT_SYMBOL_GPL(dm_bufio_mark_buffer_dirty);
1228
1229void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c)
1230{
1231	LIST_HEAD(write_list);
1232
1233	BUG_ON(dm_bufio_in_request());
1234
1235	dm_bufio_lock(c);
1236	__write_dirty_buffers_async(c, 0, &write_list);
1237	dm_bufio_unlock(c);
1238	__flush_write_list(&write_list);
1239}
1240EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers_async);
1241
1242/*
1243 * For performance, it is essential that the buffers are written asynchronously
1244 * and simultaneously (so that the block layer can merge the writes) and then
1245 * waited upon.
1246 *
1247 * Finally, we flush hardware disk cache.
1248 */
1249int dm_bufio_write_dirty_buffers(struct dm_bufio_client *c)
1250{
1251	int a, f;
1252	unsigned long buffers_processed = 0;
1253	struct dm_buffer *b, *tmp;
1254
1255	LIST_HEAD(write_list);
1256
1257	dm_bufio_lock(c);
1258	__write_dirty_buffers_async(c, 0, &write_list);
1259	dm_bufio_unlock(c);
1260	__flush_write_list(&write_list);
1261	dm_bufio_lock(c);
1262
1263again:
1264	list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) {
1265		int dropped_lock = 0;
1266
1267		if (buffers_processed < c->n_buffers[LIST_DIRTY])
1268			buffers_processed++;
1269
1270		BUG_ON(test_bit(B_READING, &b->state));
1271
1272		if (test_bit(B_WRITING, &b->state)) {
1273			if (buffers_processed < c->n_buffers[LIST_DIRTY]) {
1274				dropped_lock = 1;
1275				b->hold_count++;
1276				dm_bufio_unlock(c);
1277				wait_on_bit_io(&b->state, B_WRITING,
1278					       TASK_UNINTERRUPTIBLE);
1279				dm_bufio_lock(c);
1280				b->hold_count--;
1281			} else
1282				wait_on_bit_io(&b->state, B_WRITING,
1283					       TASK_UNINTERRUPTIBLE);
1284		}
1285
1286		if (!test_bit(B_DIRTY, &b->state) &&
1287		    !test_bit(B_WRITING, &b->state))
1288			__relink_lru(b, LIST_CLEAN);
1289
1290		cond_resched();
1291
1292		/*
1293		 * If we dropped the lock, the list is no longer consistent,
1294		 * so we must restart the search.
1295		 *
1296		 * In the most common case, the buffer just processed is
1297		 * relinked to the clean list, so we won't loop scanning the
1298		 * same buffer again and again.
1299		 *
1300		 * This may livelock if there is another thread simultaneously
1301		 * dirtying buffers, so we count the number of buffers walked
1302		 * and if it exceeds the total number of buffers, it means that
1303		 * someone is doing some writes simultaneously with us.  In
1304		 * this case, stop, dropping the lock.
1305		 */
1306		if (dropped_lock)
1307			goto again;
1308	}
1309	wake_up(&c->free_buffer_wait);
1310	dm_bufio_unlock(c);
1311
1312	a = xchg(&c->async_write_error, 0);
1313	f = dm_bufio_issue_flush(c);
1314	if (a)
1315		return a;
1316
1317	return f;
1318}
1319EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers);
1320
1321/*
1322 * Use dm-io to send and empty barrier flush the device.
1323 */
1324int dm_bufio_issue_flush(struct dm_bufio_client *c)
1325{
1326	struct dm_io_request io_req = {
1327		.bi_op = REQ_OP_WRITE,
1328		.bi_op_flags = REQ_PREFLUSH,
1329		.mem.type = DM_IO_KMEM,
1330		.mem.ptr.addr = NULL,
1331		.client = c->dm_io,
1332	};
1333	struct dm_io_region io_reg = {
1334		.bdev = c->bdev,
1335		.sector = 0,
1336		.count = 0,
1337	};
1338
1339	BUG_ON(dm_bufio_in_request());
1340
1341	return dm_io(&io_req, 1, &io_reg, NULL);
1342}
1343EXPORT_SYMBOL_GPL(dm_bufio_issue_flush);
1344
1345/*
1346 * We first delete any other buffer that may be at that new location.
1347 *
1348 * Then, we write the buffer to the original location if it was dirty.
1349 *
1350 * Then, if we are the only one who is holding the buffer, relink the buffer
1351 * in the hash queue for the new location.
1352 *
1353 * If there was someone else holding the buffer, we write it to the new
1354 * location but not relink it, because that other user needs to have the buffer
1355 * at the same place.
1356 */
1357void dm_bufio_release_move(struct dm_buffer *b, sector_t new_block)
1358{
1359	struct dm_bufio_client *c = b->c;
1360	struct dm_buffer *new;
1361
1362	BUG_ON(dm_bufio_in_request());
1363
1364	dm_bufio_lock(c);
1365
1366retry:
1367	new = __find(c, new_block);
1368	if (new) {
1369		if (new->hold_count) {
1370			__wait_for_free_buffer(c);
1371			goto retry;
1372		}
1373
1374		/*
1375		 * FIXME: Is there any point waiting for a write that's going
1376		 * to be overwritten in a bit?
1377		 */
1378		__make_buffer_clean(new);
1379		__unlink_buffer(new);
1380		__free_buffer_wake(new);
1381	}
1382
1383	BUG_ON(!b->hold_count);
1384	BUG_ON(test_bit(B_READING, &b->state));
1385
1386	__write_dirty_buffer(b, NULL);
1387	if (b->hold_count == 1) {
1388		wait_on_bit_io(&b->state, B_WRITING,
1389			       TASK_UNINTERRUPTIBLE);
1390		set_bit(B_DIRTY, &b->state);
 
 
1391		__unlink_buffer(b);
1392		__link_buffer(b, new_block, LIST_DIRTY);
1393	} else {
1394		sector_t old_block;
1395		wait_on_bit_lock_io(&b->state, B_WRITING,
1396				    TASK_UNINTERRUPTIBLE);
1397		/*
1398		 * Relink buffer to "new_block" so that write_callback
1399		 * sees "new_block" as a block number.
1400		 * After the write, link the buffer back to old_block.
1401		 * All this must be done in bufio lock, so that block number
1402		 * change isn't visible to other threads.
1403		 */
1404		old_block = b->block;
1405		__unlink_buffer(b);
1406		__link_buffer(b, new_block, b->list_mode);
1407		submit_io(b, WRITE, new_block, write_endio);
1408		wait_on_bit_io(&b->state, B_WRITING,
1409			       TASK_UNINTERRUPTIBLE);
1410		__unlink_buffer(b);
1411		__link_buffer(b, old_block, b->list_mode);
1412	}
1413
1414	dm_bufio_unlock(c);
1415	dm_bufio_release(b);
1416}
1417EXPORT_SYMBOL_GPL(dm_bufio_release_move);
1418
1419/*
1420 * Free the given buffer.
1421 *
1422 * This is just a hint, if the buffer is in use or dirty, this function
1423 * does nothing.
1424 */
1425void dm_bufio_forget(struct dm_bufio_client *c, sector_t block)
1426{
1427	struct dm_buffer *b;
1428
1429	dm_bufio_lock(c);
1430
1431	b = __find(c, block);
1432	if (b && likely(!b->hold_count) && likely(!b->state)) {
1433		__unlink_buffer(b);
1434		__free_buffer_wake(b);
1435	}
1436
1437	dm_bufio_unlock(c);
1438}
1439EXPORT_SYMBOL(dm_bufio_forget);
1440
1441void dm_bufio_set_minimum_buffers(struct dm_bufio_client *c, unsigned n)
1442{
1443	c->minimum_buffers = n;
1444}
1445EXPORT_SYMBOL(dm_bufio_set_minimum_buffers);
1446
1447unsigned dm_bufio_get_block_size(struct dm_bufio_client *c)
1448{
1449	return c->block_size;
1450}
1451EXPORT_SYMBOL_GPL(dm_bufio_get_block_size);
1452
1453sector_t dm_bufio_get_device_size(struct dm_bufio_client *c)
1454{
1455	return i_size_read(c->bdev->bd_inode) >>
1456			   (SECTOR_SHIFT + c->sectors_per_block_bits);
 
 
 
 
1457}
1458EXPORT_SYMBOL_GPL(dm_bufio_get_device_size);
1459
1460sector_t dm_bufio_get_block_number(struct dm_buffer *b)
1461{
1462	return b->block;
1463}
1464EXPORT_SYMBOL_GPL(dm_bufio_get_block_number);
1465
1466void *dm_bufio_get_block_data(struct dm_buffer *b)
1467{
1468	return b->data;
1469}
1470EXPORT_SYMBOL_GPL(dm_bufio_get_block_data);
1471
1472void *dm_bufio_get_aux_data(struct dm_buffer *b)
1473{
1474	return b + 1;
1475}
1476EXPORT_SYMBOL_GPL(dm_bufio_get_aux_data);
1477
1478struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b)
1479{
1480	return b->c;
1481}
1482EXPORT_SYMBOL_GPL(dm_bufio_get_client);
1483
1484static void drop_buffers(struct dm_bufio_client *c)
1485{
1486	struct dm_buffer *b;
1487	int i;
1488	bool warned = false;
1489
1490	BUG_ON(dm_bufio_in_request());
1491
1492	/*
1493	 * An optimization so that the buffers are not written one-by-one.
1494	 */
1495	dm_bufio_write_dirty_buffers_async(c);
1496
1497	dm_bufio_lock(c);
1498
1499	while ((b = __get_unclaimed_buffer(c)))
1500		__free_buffer_wake(b);
1501
1502	for (i = 0; i < LIST_SIZE; i++)
1503		list_for_each_entry(b, &c->lru[i], lru_list) {
1504			WARN_ON(!warned);
1505			warned = true;
1506			DMERR("leaked buffer %llx, hold count %u, list %d",
1507			      (unsigned long long)b->block, b->hold_count, i);
1508#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1509			print_stack_trace(&b->stack_trace, 1);
1510			b->hold_count = 0; /* mark unclaimed to avoid BUG_ON below */
 
1511#endif
1512		}
1513
1514#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1515	while ((b = __get_unclaimed_buffer(c)))
1516		__free_buffer_wake(b);
1517#endif
1518
1519	for (i = 0; i < LIST_SIZE; i++)
1520		BUG_ON(!list_empty(&c->lru[i]));
1521
1522	dm_bufio_unlock(c);
1523}
1524
1525/*
1526 * We may not be able to evict this buffer if IO pending or the client
1527 * is still using it.  Caller is expected to know buffer is too old.
1528 *
1529 * And if GFP_NOFS is used, we must not do any I/O because we hold
1530 * dm_bufio_clients_lock and we would risk deadlock if the I/O gets
1531 * rerouted to different bufio client.
1532 */
1533static bool __try_evict_buffer(struct dm_buffer *b, gfp_t gfp)
1534{
1535	if (!(gfp & __GFP_FS)) {
1536		if (test_bit(B_READING, &b->state) ||
1537		    test_bit(B_WRITING, &b->state) ||
1538		    test_bit(B_DIRTY, &b->state))
1539			return false;
1540	}
1541
1542	if (b->hold_count)
1543		return false;
1544
1545	__make_buffer_clean(b);
1546	__unlink_buffer(b);
1547	__free_buffer_wake(b);
1548
1549	return true;
1550}
1551
1552static unsigned get_retain_buffers(struct dm_bufio_client *c)
1553{
1554        unsigned retain_bytes = ACCESS_ONCE(dm_bufio_retain_bytes);
1555        return retain_bytes / c->block_size;
 
 
 
 
1556}
1557
1558static unsigned long __scan(struct dm_bufio_client *c, unsigned long nr_to_scan,
1559			    gfp_t gfp_mask)
1560{
1561	int l;
1562	struct dm_buffer *b, *tmp;
1563	unsigned long freed = 0;
1564	unsigned long count = nr_to_scan;
1565	unsigned retain_target = get_retain_buffers(c);
 
1566
1567	for (l = 0; l < LIST_SIZE; l++) {
1568		list_for_each_entry_safe_reverse(b, tmp, &c->lru[l], lru_list) {
1569			if (__try_evict_buffer(b, gfp_mask))
1570				freed++;
1571			if (!--nr_to_scan || ((count - freed) <= retain_target))
1572				return freed;
1573			cond_resched();
1574		}
1575	}
1576	return freed;
1577}
1578
1579static unsigned long
1580dm_bufio_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
1581{
1582	struct dm_bufio_client *c;
1583	unsigned long freed;
1584
1585	c = container_of(shrink, struct dm_bufio_client, shrinker);
1586	if (sc->gfp_mask & __GFP_FS)
1587		dm_bufio_lock(c);
1588	else if (!dm_bufio_trylock(c))
1589		return SHRINK_STOP;
1590
1591	freed  = __scan(c, sc->nr_to_scan, sc->gfp_mask);
1592	dm_bufio_unlock(c);
1593	return freed;
1594}
1595
1596static unsigned long
1597dm_bufio_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
1598{
1599	struct dm_bufio_client *c = container_of(shrink, struct dm_bufio_client, shrinker);
 
 
 
1600
1601	return ACCESS_ONCE(c->n_buffers[LIST_CLEAN]) + ACCESS_ONCE(c->n_buffers[LIST_DIRTY]);
1602}
1603
1604/*
1605 * Create the buffering interface
1606 */
1607struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsigned block_size,
1608					       unsigned reserved_buffers, unsigned aux_size,
1609					       void (*alloc_callback)(struct dm_buffer *),
1610					       void (*write_callback)(struct dm_buffer *))
1611{
1612	int r;
1613	struct dm_bufio_client *c;
1614	unsigned i;
 
1615
1616	BUG_ON(block_size < 1 << SECTOR_SHIFT ||
1617	       (block_size & (block_size - 1)));
 
 
 
1618
1619	c = kzalloc(sizeof(*c), GFP_KERNEL);
1620	if (!c) {
1621		r = -ENOMEM;
1622		goto bad_client;
1623	}
1624	c->buffer_tree = RB_ROOT;
1625
1626	c->bdev = bdev;
1627	c->block_size = block_size;
1628	c->sectors_per_block_bits = __ffs(block_size) - SECTOR_SHIFT;
1629	c->pages_per_block_bits = (__ffs(block_size) >= PAGE_SHIFT) ?
1630				  __ffs(block_size) - PAGE_SHIFT : 0;
1631	c->blocks_per_page_bits = (__ffs(block_size) < PAGE_SHIFT ?
1632				  PAGE_SHIFT - __ffs(block_size) : 0);
1633
1634	c->aux_size = aux_size;
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	c->minimum_buffers = 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	mutex_lock(&dm_bufio_clients_lock);
1659	if (c->blocks_per_page_bits) {
1660		if (!DM_BUFIO_CACHE_NAME(c)) {
1661			DM_BUFIO_CACHE_NAME(c) = kasprintf(GFP_KERNEL, "dm_bufio_cache-%u", c->block_size);
1662			if (!DM_BUFIO_CACHE_NAME(c)) {
1663				r = -ENOMEM;
1664				mutex_unlock(&dm_bufio_clients_lock);
1665				goto bad_cache;
1666			}
1667		}
1668
1669		if (!DM_BUFIO_CACHE(c)) {
1670			DM_BUFIO_CACHE(c) = kmem_cache_create(DM_BUFIO_CACHE_NAME(c),
1671							      c->block_size,
1672							      c->block_size, 0, NULL);
1673			if (!DM_BUFIO_CACHE(c)) {
1674				r = -ENOMEM;
1675				mutex_unlock(&dm_bufio_clients_lock);
1676				goto bad_cache;
1677			}
1678		}
1679	}
1680	mutex_unlock(&dm_bufio_clients_lock);
 
 
 
 
 
 
 
 
 
1681
1682	while (c->need_reserved_buffers) {
1683		struct dm_buffer *b = alloc_buffer(c, GFP_KERNEL);
1684
1685		if (!b) {
1686			r = -ENOMEM;
1687			goto bad_buffer;
1688		}
1689		__free_buffer_wake(b);
1690	}
1691
 
 
 
 
 
 
 
 
1692	mutex_lock(&dm_bufio_clients_lock);
1693	dm_bufio_client_count++;
1694	list_add(&c->client_list, &dm_bufio_all_clients);
1695	__cache_size_refresh();
1696	mutex_unlock(&dm_bufio_clients_lock);
1697
1698	c->shrinker.count_objects = dm_bufio_shrink_count;
1699	c->shrinker.scan_objects = dm_bufio_shrink_scan;
1700	c->shrinker.seeks = 1;
1701	c->shrinker.batch = 0;
1702	register_shrinker(&c->shrinker);
1703
1704	return c;
1705
1706bad_buffer:
1707bad_cache:
1708	while (!list_empty(&c->reserved_buffers)) {
1709		struct dm_buffer *b = list_entry(c->reserved_buffers.next,
1710						 struct dm_buffer, lru_list);
1711		list_del(&b->lru_list);
1712		free_buffer(b);
1713	}
 
 
1714	dm_io_client_destroy(c->dm_io);
1715bad_dm_io:
 
1716	kfree(c);
1717bad_client:
1718	return ERR_PTR(r);
1719}
1720EXPORT_SYMBOL_GPL(dm_bufio_client_create);
1721
1722/*
1723 * Free the buffering interface.
1724 * It is required that there are no references on any buffers.
1725 */
1726void dm_bufio_client_destroy(struct dm_bufio_client *c)
1727{
1728	unsigned i;
1729
1730	drop_buffers(c);
1731
1732	unregister_shrinker(&c->shrinker);
1733
1734	mutex_lock(&dm_bufio_clients_lock);
1735
1736	list_del(&c->client_list);
1737	dm_bufio_client_count--;
1738	__cache_size_refresh();
1739
1740	mutex_unlock(&dm_bufio_clients_lock);
1741
1742	BUG_ON(!RB_EMPTY_ROOT(&c->buffer_tree));
1743	BUG_ON(c->need_reserved_buffers);
1744
1745	while (!list_empty(&c->reserved_buffers)) {
1746		struct dm_buffer *b = list_entry(c->reserved_buffers.next,
1747						 struct dm_buffer, lru_list);
1748		list_del(&b->lru_list);
1749		free_buffer(b);
1750	}
1751
1752	for (i = 0; i < LIST_SIZE; i++)
1753		if (c->n_buffers[i])
1754			DMERR("leaked buffer count %d: %ld", i, c->n_buffers[i]);
1755
1756	for (i = 0; i < LIST_SIZE; i++)
1757		BUG_ON(c->n_buffers[i]);
1758
 
 
1759	dm_io_client_destroy(c->dm_io);
 
1760	kfree(c);
1761}
1762EXPORT_SYMBOL_GPL(dm_bufio_client_destroy);
1763
 
 
 
 
 
 
1764static unsigned get_max_age_hz(void)
1765{
1766	unsigned max_age = ACCESS_ONCE(dm_bufio_max_age);
1767
1768	if (max_age > UINT_MAX / HZ)
1769		max_age = UINT_MAX / HZ;
1770
1771	return max_age * HZ;
1772}
1773
1774static bool older_than(struct dm_buffer *b, unsigned long age_hz)
1775{
1776	return time_after_eq(jiffies, b->last_accessed + age_hz);
1777}
1778
1779static void __evict_old_buffers(struct dm_bufio_client *c, unsigned long age_hz)
1780{
1781	struct dm_buffer *b, *tmp;
1782	unsigned retain_target = get_retain_buffers(c);
1783	unsigned count;
 
1784
1785	dm_bufio_lock(c);
1786
 
 
 
 
 
 
 
1787	count = c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY];
1788	list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_CLEAN], lru_list) {
1789		if (count <= retain_target)
1790			break;
1791
1792		if (!older_than(b, age_hz))
1793			break;
1794
1795		if (__try_evict_buffer(b, 0))
1796			count--;
1797
1798		cond_resched();
1799	}
1800
1801	dm_bufio_unlock(c);
1802}
1803
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1804static void cleanup_old_buffers(void)
1805{
1806	unsigned long max_age_hz = get_max_age_hz();
1807	struct dm_bufio_client *c;
1808
1809	mutex_lock(&dm_bufio_clients_lock);
1810
 
 
1811	list_for_each_entry(c, &dm_bufio_all_clients, client_list)
1812		__evict_old_buffers(c, max_age_hz);
1813
1814	mutex_unlock(&dm_bufio_clients_lock);
1815}
1816
1817static struct workqueue_struct *dm_bufio_wq;
1818static struct delayed_work dm_bufio_work;
1819
1820static void work_fn(struct work_struct *w)
1821{
1822	cleanup_old_buffers();
1823
1824	queue_delayed_work(dm_bufio_wq, &dm_bufio_work,
1825			   DM_BUFIO_WORK_TIMER_SECS * HZ);
1826}
1827
1828/*----------------------------------------------------------------
1829 * Module setup
1830 *--------------------------------------------------------------*/
1831
1832/*
1833 * This is called only once for the whole dm_bufio module.
1834 * It initializes memory limit.
1835 */
1836static int __init dm_bufio_init(void)
1837{
1838	__u64 mem;
1839
1840	dm_bufio_allocated_kmem_cache = 0;
1841	dm_bufio_allocated_get_free_pages = 0;
1842	dm_bufio_allocated_vmalloc = 0;
1843	dm_bufio_current_allocated = 0;
1844
1845	memset(&dm_bufio_caches, 0, sizeof dm_bufio_caches);
1846	memset(&dm_bufio_cache_names, 0, sizeof dm_bufio_cache_names);
1847
1848	mem = (__u64)((totalram_pages - totalhigh_pages) *
1849		      DM_BUFIO_MEMORY_PERCENT / 100) << PAGE_SHIFT;
1850
1851	if (mem > ULONG_MAX)
1852		mem = ULONG_MAX;
1853
1854#ifdef CONFIG_MMU
1855	/*
1856	 * Get the size of vmalloc space the same way as VMALLOC_TOTAL
1857	 * in fs/proc/internal.h
1858	 */
1859	if (mem > (VMALLOC_END - VMALLOC_START) * DM_BUFIO_VMALLOC_PERCENT / 100)
1860		mem = (VMALLOC_END - VMALLOC_START) * DM_BUFIO_VMALLOC_PERCENT / 100;
1861#endif
1862
1863	dm_bufio_default_cache_size = mem;
1864
1865	mutex_lock(&dm_bufio_clients_lock);
1866	__cache_size_refresh();
1867	mutex_unlock(&dm_bufio_clients_lock);
1868
1869	dm_bufio_wq = alloc_workqueue("dm_bufio_cache", WQ_MEM_RECLAIM, 0);
1870	if (!dm_bufio_wq)
1871		return -ENOMEM;
1872
1873	INIT_DELAYED_WORK(&dm_bufio_work, work_fn);
1874	queue_delayed_work(dm_bufio_wq, &dm_bufio_work,
 
1875			   DM_BUFIO_WORK_TIMER_SECS * HZ);
1876
1877	return 0;
1878}
1879
1880/*
1881 * This is called once when unloading the dm_bufio module.
1882 */
1883static void __exit dm_bufio_exit(void)
1884{
1885	int bug = 0;
1886	int i;
1887
1888	cancel_delayed_work_sync(&dm_bufio_work);
 
1889	destroy_workqueue(dm_bufio_wq);
1890
1891	for (i = 0; i < ARRAY_SIZE(dm_bufio_caches); i++)
1892		kmem_cache_destroy(dm_bufio_caches[i]);
1893
1894	for (i = 0; i < ARRAY_SIZE(dm_bufio_cache_names); i++)
1895		kfree(dm_bufio_cache_names[i]);
1896
1897	if (dm_bufio_client_count) {
1898		DMCRIT("%s: dm_bufio_client_count leaked: %d",
1899			__func__, dm_bufio_client_count);
1900		bug = 1;
1901	}
1902
1903	if (dm_bufio_current_allocated) {
1904		DMCRIT("%s: dm_bufio_current_allocated leaked: %lu",
1905			__func__, dm_bufio_current_allocated);
1906		bug = 1;
1907	}
1908
1909	if (dm_bufio_allocated_get_free_pages) {
1910		DMCRIT("%s: dm_bufio_allocated_get_free_pages leaked: %lu",
1911		       __func__, dm_bufio_allocated_get_free_pages);
1912		bug = 1;
1913	}
1914
1915	if (dm_bufio_allocated_vmalloc) {
1916		DMCRIT("%s: dm_bufio_vmalloc leaked: %lu",
1917		       __func__, dm_bufio_allocated_vmalloc);
1918		bug = 1;
1919	}
1920
1921	BUG_ON(bug);
1922}
1923
1924module_init(dm_bufio_init)
1925module_exit(dm_bufio_exit)
1926
1927module_param_named(max_cache_size_bytes, dm_bufio_cache_size, ulong, S_IRUGO | S_IWUSR);
1928MODULE_PARM_DESC(max_cache_size_bytes, "Size of metadata cache");
1929
1930module_param_named(max_age_seconds, dm_bufio_max_age, uint, S_IRUGO | S_IWUSR);
1931MODULE_PARM_DESC(max_age_seconds, "Max age of a buffer in seconds");
1932
1933module_param_named(retain_bytes, dm_bufio_retain_bytes, uint, S_IRUGO | S_IWUSR);
1934MODULE_PARM_DESC(retain_bytes, "Try to keep at least this many bytes cached in memory");
1935
1936module_param_named(peak_allocated_bytes, dm_bufio_peak_allocated, ulong, S_IRUGO | S_IWUSR);
1937MODULE_PARM_DESC(peak_allocated_bytes, "Tracks the maximum allocated memory");
1938
1939module_param_named(allocated_kmem_cache_bytes, dm_bufio_allocated_kmem_cache, ulong, S_IRUGO);
1940MODULE_PARM_DESC(allocated_kmem_cache_bytes, "Memory allocated with kmem_cache_alloc");
1941
1942module_param_named(allocated_get_free_pages_bytes, dm_bufio_allocated_get_free_pages, ulong, S_IRUGO);
1943MODULE_PARM_DESC(allocated_get_free_pages_bytes, "Memory allocated with get_free_pages");
1944
1945module_param_named(allocated_vmalloc_bytes, dm_bufio_allocated_vmalloc, ulong, S_IRUGO);
1946MODULE_PARM_DESC(allocated_vmalloc_bytes, "Memory allocated with vmalloc");
1947
1948module_param_named(current_allocated_bytes, dm_bufio_current_allocated, ulong, S_IRUGO);
1949MODULE_PARM_DESC(current_allocated_bytes, "Memory currently used by the cache");
1950
1951MODULE_AUTHOR("Mikulas Patocka <dm-devel@redhat.com>");
1952MODULE_DESCRIPTION(DM_NAME " buffered I/O library");
1953MODULE_LICENSE("GPL");