1/*
   2 * dm-snapshot.c
   3 *
   4 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
   5 *
   6 * This file is released under the GPL.
   7 */
   8
   9#include <linux/blkdev.h>
  10#include <linux/device-mapper.h>
  11#include <linux/delay.h>
  12#include <linux/fs.h>
  13#include <linux/init.h>
  14#include <linux/kdev_t.h>
  15#include <linux/list.h>
 
  16#include <linux/mempool.h>
  17#include <linux/module.h>
  18#include <linux/slab.h>
  19#include <linux/vmalloc.h>
  20#include <linux/log2.h>
  21#include <linux/dm-kcopyd.h>
  22
  23#include "dm.h"
  24
  25#include "dm-exception-store.h"
  26
  27#define DM_MSG_PREFIX "snapshots"
  28
  29static const char dm_snapshot_merge_target_name[] = "snapshot-merge";
  30
  31#define dm_target_is_snapshot_merge(ti) \
  32	((ti)->type->name == dm_snapshot_merge_target_name)
  33
  34/*
  35 * The size of the mempool used to track chunks in use.
  36 */
  37#define MIN_IOS 256
  38
  39#define DM_TRACKED_CHUNK_HASH_SIZE	16
  40#define DM_TRACKED_CHUNK_HASH(x)	((unsigned long)(x) & \
  41					 (DM_TRACKED_CHUNK_HASH_SIZE - 1))
  42
  43struct dm_exception_table {
  44	uint32_t hash_mask;
  45	unsigned hash_shift;
  46	struct list_head *table;
  47};
  48
  49struct dm_snapshot {
  50	struct rw_semaphore lock;
  51
  52	struct dm_dev *origin;
  53	struct dm_dev *cow;
  54
  55	struct dm_target *ti;
  56
  57	/* List of snapshots per Origin */
  58	struct list_head list;
  59
  60	/*
  61	 * You can't use a snapshot if this is 0 (e.g. if full).
  62	 * A snapshot-merge target never clears this.
  63	 */
  64	int valid;
  65
  66	/*
  67	 * The snapshot overflowed because of a write to the snapshot device.
  68	 * We don't have to invalidate the snapshot in this case, but we need
  69	 * to prevent further writes.
  70	 */
  71	int snapshot_overflowed;
  72
  73	/* Origin writes don't trigger exceptions until this is set */
  74	int active;
  75
  76	atomic_t pending_exceptions_count;
  77
  78	/* Protected by "lock" */
 
 
  79	sector_t exception_start_sequence;
  80
  81	/* Protected by kcopyd single-threaded callback */
  82	sector_t exception_complete_sequence;
  83
  84	/*
  85	 * A list of pending exceptions that completed out of order.
  86	 * Protected by kcopyd single-threaded callback.
  87	 */
  88	struct list_head out_of_order_list;
  89
  90	mempool_t *pending_pool;
  91
  92	struct dm_exception_table pending;
  93	struct dm_exception_table complete;
  94
  95	/*
  96	 * pe_lock protects all pending_exception operations and access
  97	 * as well as the snapshot_bios list.
  98	 */
  99	spinlock_t pe_lock;
 100
 101	/* Chunks with outstanding reads */
 102	spinlock_t tracked_chunk_lock;
 103	struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
 104
 105	/* The on disk metadata handler */
 106	struct dm_exception_store *store;
 107
 
 
 
 108	struct dm_kcopyd_client *kcopyd_client;
 109
 110	/* Wait for events based on state_bits */
 111	unsigned long state_bits;
 112
 113	/* Range of chunks currently being merged. */
 114	chunk_t first_merging_chunk;
 115	int num_merging_chunks;
 116
 117	/*
 118	 * The merge operation failed if this flag is set.
 119	 * Failure modes are handled as follows:
 120	 * - I/O error reading the header
 121	 *   	=> don't load the target; abort.
 122	 * - Header does not have "valid" flag set
 123	 *   	=> use the origin; forget about the snapshot.
 124	 * - I/O error when reading exceptions
 125	 *   	=> don't load the target; abort.
 126	 *         (We can't use the intermediate origin state.)
 127	 * - I/O error while merging
 128	 *	=> stop merging; set merge_failed; process I/O normally.
 129	 */
 130	int merge_failed;
 
 
 
 131
 132	/*
 133	 * Incoming bios that overlap with chunks being merged must wait
 134	 * for them to be committed.
 135	 */
 136	struct bio_list bios_queued_during_merge;
 137};
 138
 139/*
 140 * state_bits:
 141 *   RUNNING_MERGE  - Merge operation is in progress.
 142 *   SHUTDOWN_MERGE - Set to signal that merge needs to be stopped;
 143 *                    cleared afterwards.
 144 */
 145#define RUNNING_MERGE          0
 146#define SHUTDOWN_MERGE         1
 147
 
 
 
 
 
 
 
 
 
 
 
 
 
 148DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(snapshot_copy_throttle,
 149		"A percentage of time allocated for copy on write");
 150
 151struct dm_dev *dm_snap_origin(struct dm_snapshot *s)
 152{
 153	return s->origin;
 154}
 155EXPORT_SYMBOL(dm_snap_origin);
 156
 157struct dm_dev *dm_snap_cow(struct dm_snapshot *s)
 158{
 159	return s->cow;
 160}
 161EXPORT_SYMBOL(dm_snap_cow);
 162
 163static sector_t chunk_to_sector(struct dm_exception_store *store,
 164				chunk_t chunk)
 165{
 166	return chunk << store->chunk_shift;
 167}
 168
 169static int bdev_equal(struct block_device *lhs, struct block_device *rhs)
 170{
 171	/*
 172	 * There is only ever one instance of a particular block
 173	 * device so we can compare pointers safely.
 174	 */
 175	return lhs == rhs;
 176}
 177
 178struct dm_snap_pending_exception {
 179	struct dm_exception e;
 180
 181	/*
 182	 * Origin buffers waiting for this to complete are held
 183	 * in a bio list
 184	 */
 185	struct bio_list origin_bios;
 186	struct bio_list snapshot_bios;
 187
 188	/* Pointer back to snapshot context */
 189	struct dm_snapshot *snap;
 190
 191	/*
 192	 * 1 indicates the exception has already been sent to
 193	 * kcopyd.
 194	 */
 195	int started;
 196
 197	/* There was copying error. */
 198	int copy_error;
 199
 200	/* A sequence number, it is used for in-order completion. */
 201	sector_t exception_sequence;
 202
 203	struct list_head out_of_order_entry;
 204
 205	/*
 206	 * For writing a complete chunk, bypassing the copy.
 207	 */
 208	struct bio *full_bio;
 209	bio_end_io_t *full_bio_end_io;
 210};
 211
 212/*
 213 * Hash table mapping origin volumes to lists of snapshots and
 214 * a lock to protect it
 215 */
 216static struct kmem_cache *exception_cache;
 217static struct kmem_cache *pending_cache;
 218
 219struct dm_snap_tracked_chunk {
 220	struct hlist_node node;
 221	chunk_t chunk;
 222};
 223
 224static void init_tracked_chunk(struct bio *bio)
 225{
 226	struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
 
 227	INIT_HLIST_NODE(&c->node);
 228}
 229
 230static bool is_bio_tracked(struct bio *bio)
 231{
 232	struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
 
 233	return !hlist_unhashed(&c->node);
 234}
 235
 236static void track_chunk(struct dm_snapshot *s, struct bio *bio, chunk_t chunk)
 237{
 238	struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
 239
 240	c->chunk = chunk;
 241
 242	spin_lock_irq(&s->tracked_chunk_lock);
 243	hlist_add_head(&c->node,
 244		       &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]);
 245	spin_unlock_irq(&s->tracked_chunk_lock);
 246}
 247
 248static void stop_tracking_chunk(struct dm_snapshot *s, struct bio *bio)
 249{
 250	struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));
 251	unsigned long flags;
 252
 253	spin_lock_irqsave(&s->tracked_chunk_lock, flags);
 254	hlist_del(&c->node);
 255	spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
 256}
 257
 258static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk)
 259{
 260	struct dm_snap_tracked_chunk *c;
 261	int found = 0;
 262
 263	spin_lock_irq(&s->tracked_chunk_lock);
 264
 265	hlist_for_each_entry(c,
 266	    &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)], node) {
 267		if (c->chunk == chunk) {
 268			found = 1;
 269			break;
 270		}
 271	}
 272
 273	spin_unlock_irq(&s->tracked_chunk_lock);
 274
 275	return found;
 276}
 277
 278/*
 279 * This conflicting I/O is extremely improbable in the caller,
 280 * so msleep(1) is sufficient and there is no need for a wait queue.
 281 */
 282static void __check_for_conflicting_io(struct dm_snapshot *s, chunk_t chunk)
 283{
 284	while (__chunk_is_tracked(s, chunk))
 285		msleep(1);
 286}
 287
 288/*
 289 * One of these per registered origin, held in the snapshot_origins hash
 290 */
 291struct origin {
 292	/* The origin device */
 293	struct block_device *bdev;
 294
 295	struct list_head hash_list;
 296
 297	/* List of snapshots for this origin */
 298	struct list_head snapshots;
 299};
 300
 301/*
 302 * This structure is allocated for each origin target
 303 */
 304struct dm_origin {
 305	struct dm_dev *dev;
 306	struct dm_target *ti;
 307	unsigned split_boundary;
 308	struct list_head hash_list;
 309};
 310
 311/*
 312 * Size of the hash table for origin volumes. If we make this
 313 * the size of the minors list then it should be nearly perfect
 314 */
 315#define ORIGIN_HASH_SIZE 256
 316#define ORIGIN_MASK      0xFF
 317static struct list_head *_origins;
 318static struct list_head *_dm_origins;
 319static struct rw_semaphore _origins_lock;
 320
 321static DECLARE_WAIT_QUEUE_HEAD(_pending_exceptions_done);
 322static DEFINE_SPINLOCK(_pending_exceptions_done_spinlock);
 323static uint64_t _pending_exceptions_done_count;
 324
 325static int init_origin_hash(void)
 326{
 327	int i;
 328
 329	_origins = kmalloc(ORIGIN_HASH_SIZE * sizeof(struct list_head),
 330			   GFP_KERNEL);
 331	if (!_origins) {
 332		DMERR("unable to allocate memory for _origins");
 333		return -ENOMEM;
 334	}
 335	for (i = 0; i < ORIGIN_HASH_SIZE; i++)
 336		INIT_LIST_HEAD(_origins + i);
 337
 338	_dm_origins = kmalloc(ORIGIN_HASH_SIZE * sizeof(struct list_head),
 339			      GFP_KERNEL);
 
 340	if (!_dm_origins) {
 341		DMERR("unable to allocate memory for _dm_origins");
 342		kfree(_origins);
 343		return -ENOMEM;
 344	}
 345	for (i = 0; i < ORIGIN_HASH_SIZE; i++)
 346		INIT_LIST_HEAD(_dm_origins + i);
 347
 348	init_rwsem(&_origins_lock);
 349
 350	return 0;
 351}
 352
 353static void exit_origin_hash(void)
 354{
 355	kfree(_origins);
 356	kfree(_dm_origins);
 357}
 358
 359static unsigned origin_hash(struct block_device *bdev)
 360{
 361	return bdev->bd_dev & ORIGIN_MASK;
 362}
 363
 364static struct origin *__lookup_origin(struct block_device *origin)
 365{
 366	struct list_head *ol;
 367	struct origin *o;
 368
 369	ol = &_origins[origin_hash(origin)];
 370	list_for_each_entry (o, ol, hash_list)
 371		if (bdev_equal(o->bdev, origin))
 372			return o;
 373
 374	return NULL;
 375}
 376
 377static void __insert_origin(struct origin *o)
 378{
 379	struct list_head *sl = &_origins[origin_hash(o->bdev)];
 
 380	list_add_tail(&o->hash_list, sl);
 381}
 382
 383static struct dm_origin *__lookup_dm_origin(struct block_device *origin)
 384{
 385	struct list_head *ol;
 386	struct dm_origin *o;
 387
 388	ol = &_dm_origins[origin_hash(origin)];
 389	list_for_each_entry (o, ol, hash_list)
 390		if (bdev_equal(o->dev->bdev, origin))
 391			return o;
 392
 393	return NULL;
 394}
 395
 396static void __insert_dm_origin(struct dm_origin *o)
 397{
 398	struct list_head *sl = &_dm_origins[origin_hash(o->dev->bdev)];
 
 399	list_add_tail(&o->hash_list, sl);
 400}
 401
 402static void __remove_dm_origin(struct dm_origin *o)
 403{
 404	list_del(&o->hash_list);
 405}
 406
 407/*
 408 * _origins_lock must be held when calling this function.
 409 * Returns number of snapshots registered using the supplied cow device, plus:
 410 * snap_src - a snapshot suitable for use as a source of exception handover
 411 * snap_dest - a snapshot capable of receiving exception handover.
 412 * snap_merge - an existing snapshot-merge target linked to the same origin.
 413 *   There can be at most one snapshot-merge target. The parameter is optional.
 414 *
 415 * Possible return values and states of snap_src and snap_dest.
 416 *   0: NULL, NULL  - first new snapshot
 417 *   1: snap_src, NULL - normal snapshot
 418 *   2: snap_src, snap_dest  - waiting for handover
 419 *   2: snap_src, NULL - handed over, waiting for old to be deleted
 420 *   1: NULL, snap_dest - source got destroyed without handover
 421 */
 422static int __find_snapshots_sharing_cow(struct dm_snapshot *snap,
 423					struct dm_snapshot **snap_src,
 424					struct dm_snapshot **snap_dest,
 425					struct dm_snapshot **snap_merge)
 426{
 427	struct dm_snapshot *s;
 428	struct origin *o;
 429	int count = 0;
 430	int active;
 431
 432	o = __lookup_origin(snap->origin->bdev);
 433	if (!o)
 434		goto out;
 435
 436	list_for_each_entry(s, &o->snapshots, list) {
 437		if (dm_target_is_snapshot_merge(s->ti) && snap_merge)
 438			*snap_merge = s;
 439		if (!bdev_equal(s->cow->bdev, snap->cow->bdev))
 440			continue;
 441
 442		down_read(&s->lock);
 443		active = s->active;
 444		up_read(&s->lock);
 445
 446		if (active) {
 447			if (snap_src)
 448				*snap_src = s;
 449		} else if (snap_dest)
 450			*snap_dest = s;
 451
 452		count++;
 453	}
 454
 455out:
 456	return count;
 457}
 458
 459/*
 460 * On success, returns 1 if this snapshot is a handover destination,
 461 * otherwise returns 0.
 462 */
 463static int __validate_exception_handover(struct dm_snapshot *snap)
 464{
 465	struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
 466	struct dm_snapshot *snap_merge = NULL;
 467
 468	/* Does snapshot need exceptions handed over to it? */
 469	if ((__find_snapshots_sharing_cow(snap, &snap_src, &snap_dest,
 470					  &snap_merge) == 2) ||
 471	    snap_dest) {
 472		snap->ti->error = "Snapshot cow pairing for exception "
 473				  "table handover failed";
 474		return -EINVAL;
 475	}
 476
 477	/*
 478	 * If no snap_src was found, snap cannot become a handover
 479	 * destination.
 480	 */
 481	if (!snap_src)
 482		return 0;
 483
 484	/*
 485	 * Non-snapshot-merge handover?
 486	 */
 487	if (!dm_target_is_snapshot_merge(snap->ti))
 488		return 1;
 489
 490	/*
 491	 * Do not allow more than one merging snapshot.
 492	 */
 493	if (snap_merge) {
 494		snap->ti->error = "A snapshot is already merging.";
 495		return -EINVAL;
 496	}
 497
 498	if (!snap_src->store->type->prepare_merge ||
 499	    !snap_src->store->type->commit_merge) {
 500		snap->ti->error = "Snapshot exception store does not "
 501				  "support snapshot-merge.";
 502		return -EINVAL;
 503	}
 504
 505	return 1;
 506}
 507
 508static void __insert_snapshot(struct origin *o, struct dm_snapshot *s)
 509{
 510	struct dm_snapshot *l;
 511
 512	/* Sort the list according to chunk size, largest-first smallest-last */
 513	list_for_each_entry(l, &o->snapshots, list)
 514		if (l->store->chunk_size < s->store->chunk_size)
 515			break;
 516	list_add_tail(&s->list, &l->list);
 517}
 518
 519/*
 520 * Make a note of the snapshot and its origin so we can look it
 521 * up when the origin has a write on it.
 522 *
 523 * Also validate snapshot exception store handovers.
 524 * On success, returns 1 if this registration is a handover destination,
 525 * otherwise returns 0.
 526 */
 527static int register_snapshot(struct dm_snapshot *snap)
 528{
 529	struct origin *o, *new_o = NULL;
 530	struct block_device *bdev = snap->origin->bdev;
 531	int r = 0;
 532
 533	new_o = kmalloc(sizeof(*new_o), GFP_KERNEL);
 534	if (!new_o)
 535		return -ENOMEM;
 536
 537	down_write(&_origins_lock);
 538
 539	r = __validate_exception_handover(snap);
 540	if (r < 0) {
 541		kfree(new_o);
 542		goto out;
 543	}
 544
 545	o = __lookup_origin(bdev);
 546	if (o)
 547		kfree(new_o);
 548	else {
 549		/* New origin */
 550		o = new_o;
 551
 552		/* Initialise the struct */
 553		INIT_LIST_HEAD(&o->snapshots);
 554		o->bdev = bdev;
 555
 556		__insert_origin(o);
 557	}
 558
 559	__insert_snapshot(o, snap);
 560
 561out:
 562	up_write(&_origins_lock);
 563
 564	return r;
 565}
 566
 567/*
 568 * Move snapshot to correct place in list according to chunk size.
 569 */
 570static void reregister_snapshot(struct dm_snapshot *s)
 571{
 572	struct block_device *bdev = s->origin->bdev;
 573
 574	down_write(&_origins_lock);
 575
 576	list_del(&s->list);
 577	__insert_snapshot(__lookup_origin(bdev), s);
 578
 579	up_write(&_origins_lock);
 580}
 581
 582static void unregister_snapshot(struct dm_snapshot *s)
 583{
 584	struct origin *o;
 585
 586	down_write(&_origins_lock);
 587	o = __lookup_origin(s->origin->bdev);
 588
 589	list_del(&s->list);
 590	if (o && list_empty(&o->snapshots)) {
 591		list_del(&o->hash_list);
 592		kfree(o);
 593	}
 594
 595	up_write(&_origins_lock);
 596}
 597
 598/*
 599 * Implementation of the exception hash tables.
 600 * The lowest hash_shift bits of the chunk number are ignored, allowing
 601 * some consecutive chunks to be grouped together.
 602 */
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 603static int dm_exception_table_init(struct dm_exception_table *et,
 604				   uint32_t size, unsigned hash_shift)
 605{
 606	unsigned int i;
 607
 608	et->hash_shift = hash_shift;
 609	et->hash_mask = size - 1;
 610	et->table = dm_vcalloc(size, sizeof(struct list_head));
 
 611	if (!et->table)
 612		return -ENOMEM;
 613
 614	for (i = 0; i < size; i++)
 615		INIT_LIST_HEAD(et->table + i);
 616
 617	return 0;
 618}
 619
 620static void dm_exception_table_exit(struct dm_exception_table *et,
 621				    struct kmem_cache *mem)
 622{
 623	struct list_head *slot;
 624	struct dm_exception *ex, *next;
 
 625	int i, size;
 626
 627	size = et->hash_mask + 1;
 628	for (i = 0; i < size; i++) {
 629		slot = et->table + i;
 630
 631		list_for_each_entry_safe (ex, next, slot, hash_list)
 632			kmem_cache_free(mem, ex);
 
 
 633	}
 634
 635	vfree(et->table);
 636}
 637
 638static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk)
 639{
 640	return (chunk >> et->hash_shift) & et->hash_mask;
 641}
 642
 643static void dm_remove_exception(struct dm_exception *e)
 644{
 645	list_del(&e->hash_list);
 646}
 647
 648/*
 649 * Return the exception data for a sector, or NULL if not
 650 * remapped.
 651 */
 652static struct dm_exception *dm_lookup_exception(struct dm_exception_table *et,
 653						chunk_t chunk)
 654{
 655	struct list_head *slot;
 
 656	struct dm_exception *e;
 657
 658	slot = &et->table[exception_hash(et, chunk)];
 659	list_for_each_entry (e, slot, hash_list)
 660		if (chunk >= e->old_chunk &&
 661		    chunk <= e->old_chunk + dm_consecutive_chunk_count(e))
 662			return e;
 663
 664	return NULL;
 665}
 666
 667static struct dm_exception *alloc_completed_exception(gfp_t gfp)
 668{
 669	struct dm_exception *e;
 670
 671	e = kmem_cache_alloc(exception_cache, gfp);
 672	if (!e && gfp == GFP_NOIO)
 673		e = kmem_cache_alloc(exception_cache, GFP_ATOMIC);
 674
 675	return e;
 676}
 677
 678static void free_completed_exception(struct dm_exception *e)
 679{
 680	kmem_cache_free(exception_cache, e);
 681}
 682
 683static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snapshot *s)
 684{
 685	struct dm_snap_pending_exception *pe = mempool_alloc(s->pending_pool,
 686							     GFP_NOIO);
 687
 688	atomic_inc(&s->pending_exceptions_count);
 689	pe->snap = s;
 690
 691	return pe;
 692}
 693
 694static void free_pending_exception(struct dm_snap_pending_exception *pe)
 695{
 696	struct dm_snapshot *s = pe->snap;
 697
 698	mempool_free(pe, s->pending_pool);
 699	smp_mb__before_atomic();
 700	atomic_dec(&s->pending_exceptions_count);
 701}
 702
 703static void dm_insert_exception(struct dm_exception_table *eh,
 704				struct dm_exception *new_e)
 705{
 706	struct list_head *l;
 
 707	struct dm_exception *e = NULL;
 708
 709	l = &eh->table[exception_hash(eh, new_e->old_chunk)];
 710
 711	/* Add immediately if this table doesn't support consecutive chunks */
 712	if (!eh->hash_shift)
 713		goto out;
 714
 715	/* List is ordered by old_chunk */
 716	list_for_each_entry_reverse(e, l, hash_list) {
 717		/* Insert after an existing chunk? */
 718		if (new_e->old_chunk == (e->old_chunk +
 719					 dm_consecutive_chunk_count(e) + 1) &&
 720		    new_e->new_chunk == (dm_chunk_number(e->new_chunk) +
 721					 dm_consecutive_chunk_count(e) + 1)) {
 722			dm_consecutive_chunk_count_inc(e);
 723			free_completed_exception(new_e);
 724			return;
 725		}
 726
 727		/* Insert before an existing chunk? */
 728		if (new_e->old_chunk == (e->old_chunk - 1) &&
 729		    new_e->new_chunk == (dm_chunk_number(e->new_chunk) - 1)) {
 730			dm_consecutive_chunk_count_inc(e);
 731			e->old_chunk--;
 732			e->new_chunk--;
 733			free_completed_exception(new_e);
 734			return;
 735		}
 736
 737		if (new_e->old_chunk > e->old_chunk)
 738			break;
 739	}
 740
 741out:
 742	list_add(&new_e->hash_list, e ? &e->hash_list : l);
 
 
 
 
 
 
 
 
 
 
 
 
 743}
 744
 745/*
 746 * Callback used by the exception stores to load exceptions when
 747 * initialising.
 748 */
 749static int dm_add_exception(void *context, chunk_t old, chunk_t new)
 750{
 
 751	struct dm_snapshot *s = context;
 752	struct dm_exception *e;
 753
 754	e = alloc_completed_exception(GFP_KERNEL);
 755	if (!e)
 756		return -ENOMEM;
 757
 758	e->old_chunk = old;
 759
 760	/* Consecutive_count is implicitly initialised to zero */
 761	e->new_chunk = new;
 762
 
 
 
 
 
 
 
 
 
 763	dm_insert_exception(&s->complete, e);
 
 764
 765	return 0;
 766}
 767
 768/*
 769 * Return a minimum chunk size of all snapshots that have the specified origin.
 770 * Return zero if the origin has no snapshots.
 771 */
 772static uint32_t __minimum_chunk_size(struct origin *o)
 773{
 774	struct dm_snapshot *snap;
 775	unsigned chunk_size = 0;
 776
 777	if (o)
 778		list_for_each_entry(snap, &o->snapshots, list)
 779			chunk_size = min_not_zero(chunk_size,
 780						  snap->store->chunk_size);
 781
 782	return (uint32_t) chunk_size;
 783}
 784
 785/*
 786 * Hard coded magic.
 787 */
 788static int calc_max_buckets(void)
 789{
 790	/* use a fixed size of 2MB */
 791	unsigned long mem = 2 * 1024 * 1024;
 792	mem /= sizeof(struct list_head);
 
 793
 794	return mem;
 795}
 796
 797/*
 798 * Allocate room for a suitable hash table.
 799 */
 800static int init_hash_tables(struct dm_snapshot *s)
 801{
 802	sector_t hash_size, cow_dev_size, max_buckets;
 803
 804	/*
 805	 * Calculate based on the size of the original volume or
 806	 * the COW volume...
 807	 */
 808	cow_dev_size = get_dev_size(s->cow->bdev);
 809	max_buckets = calc_max_buckets();
 810
 811	hash_size = cow_dev_size >> s->store->chunk_shift;
 812	hash_size = min(hash_size, max_buckets);
 813
 814	if (hash_size < 64)
 815		hash_size = 64;
 816	hash_size = rounddown_pow_of_two(hash_size);
 817	if (dm_exception_table_init(&s->complete, hash_size,
 818				    DM_CHUNK_CONSECUTIVE_BITS))
 819		return -ENOMEM;
 820
 821	/*
 822	 * Allocate hash table for in-flight exceptions
 823	 * Make this smaller than the real hash table
 824	 */
 825	hash_size >>= 3;
 826	if (hash_size < 64)
 827		hash_size = 64;
 828
 829	if (dm_exception_table_init(&s->pending, hash_size, 0)) {
 830		dm_exception_table_exit(&s->complete, exception_cache);
 831		return -ENOMEM;
 832	}
 833
 834	return 0;
 835}
 836
 837static void merge_shutdown(struct dm_snapshot *s)
 838{
 839	clear_bit_unlock(RUNNING_MERGE, &s->state_bits);
 840	smp_mb__after_atomic();
 841	wake_up_bit(&s->state_bits, RUNNING_MERGE);
 842}
 843
 844static struct bio *__release_queued_bios_after_merge(struct dm_snapshot *s)
 845{
 846	s->first_merging_chunk = 0;
 847	s->num_merging_chunks = 0;
 848
 849	return bio_list_get(&s->bios_queued_during_merge);
 850}
 851
 852/*
 853 * Remove one chunk from the index of completed exceptions.
 854 */
 855static int __remove_single_exception_chunk(struct dm_snapshot *s,
 856					   chunk_t old_chunk)
 857{
 858	struct dm_exception *e;
 859
 860	e = dm_lookup_exception(&s->complete, old_chunk);
 861	if (!e) {
 862		DMERR("Corruption detected: exception for block %llu is "
 863		      "on disk but not in memory",
 864		      (unsigned long long)old_chunk);
 865		return -EINVAL;
 866	}
 867
 868	/*
 869	 * If this is the only chunk using this exception, remove exception.
 870	 */
 871	if (!dm_consecutive_chunk_count(e)) {
 872		dm_remove_exception(e);
 873		free_completed_exception(e);
 874		return 0;
 875	}
 876
 877	/*
 878	 * The chunk may be either at the beginning or the end of a
 879	 * group of consecutive chunks - never in the middle.  We are
 880	 * removing chunks in the opposite order to that in which they
 881	 * were added, so this should always be true.
 882	 * Decrement the consecutive chunk counter and adjust the
 883	 * starting point if necessary.
 884	 */
 885	if (old_chunk == e->old_chunk) {
 886		e->old_chunk++;
 887		e->new_chunk++;
 888	} else if (old_chunk != e->old_chunk +
 889		   dm_consecutive_chunk_count(e)) {
 890		DMERR("Attempt to merge block %llu from the "
 891		      "middle of a chunk range [%llu - %llu]",
 892		      (unsigned long long)old_chunk,
 893		      (unsigned long long)e->old_chunk,
 894		      (unsigned long long)
 895		      e->old_chunk + dm_consecutive_chunk_count(e));
 896		return -EINVAL;
 897	}
 898
 899	dm_consecutive_chunk_count_dec(e);
 900
 901	return 0;
 902}
 903
 904static void flush_bios(struct bio *bio);
 905
 906static int remove_single_exception_chunk(struct dm_snapshot *s)
 907{
 908	struct bio *b = NULL;
 909	int r;
 910	chunk_t old_chunk = s->first_merging_chunk + s->num_merging_chunks - 1;
 911
 912	down_write(&s->lock);
 913
 914	/*
 915	 * Process chunks (and associated exceptions) in reverse order
 916	 * so that dm_consecutive_chunk_count_dec() accounting works.
 917	 */
 918	do {
 919		r = __remove_single_exception_chunk(s, old_chunk);
 920		if (r)
 921			goto out;
 922	} while (old_chunk-- > s->first_merging_chunk);
 923
 924	b = __release_queued_bios_after_merge(s);
 925
 926out:
 927	up_write(&s->lock);
 928	if (b)
 929		flush_bios(b);
 930
 931	return r;
 932}
 933
 934static int origin_write_extent(struct dm_snapshot *merging_snap,
 935			       sector_t sector, unsigned chunk_size);
 936
 937static void merge_callback(int read_err, unsigned long write_err,
 938			   void *context);
 939
 940static uint64_t read_pending_exceptions_done_count(void)
 941{
 942	uint64_t pending_exceptions_done;
 943
 944	spin_lock(&_pending_exceptions_done_spinlock);
 945	pending_exceptions_done = _pending_exceptions_done_count;
 946	spin_unlock(&_pending_exceptions_done_spinlock);
 947
 948	return pending_exceptions_done;
 949}
 950
 951static void increment_pending_exceptions_done_count(void)
 952{
 953	spin_lock(&_pending_exceptions_done_spinlock);
 954	_pending_exceptions_done_count++;
 955	spin_unlock(&_pending_exceptions_done_spinlock);
 956
 957	wake_up_all(&_pending_exceptions_done);
 958}
 959
 960static void snapshot_merge_next_chunks(struct dm_snapshot *s)
 961{
 962	int i, linear_chunks;
 963	chunk_t old_chunk, new_chunk;
 964	struct dm_io_region src, dest;
 965	sector_t io_size;
 966	uint64_t previous_count;
 967
 968	BUG_ON(!test_bit(RUNNING_MERGE, &s->state_bits));
 969	if (unlikely(test_bit(SHUTDOWN_MERGE, &s->state_bits)))
 970		goto shut;
 971
 972	/*
 973	 * valid flag never changes during merge, so no lock required.
 974	 */
 975	if (!s->valid) {
 976		DMERR("Snapshot is invalid: can't merge");
 977		goto shut;
 978	}
 979
 980	linear_chunks = s->store->type->prepare_merge(s->store, &old_chunk,
 981						      &new_chunk);
 982	if (linear_chunks <= 0) {
 983		if (linear_chunks < 0) {
 984			DMERR("Read error in exception store: "
 985			      "shutting down merge");
 986			down_write(&s->lock);
 987			s->merge_failed = 1;
 988			up_write(&s->lock);
 989		}
 990		goto shut;
 991	}
 992
 993	/* Adjust old_chunk and new_chunk to reflect start of linear region */
 994	old_chunk = old_chunk + 1 - linear_chunks;
 995	new_chunk = new_chunk + 1 - linear_chunks;
 996
 997	/*
 998	 * Use one (potentially large) I/O to copy all 'linear_chunks'
 999	 * from the exception store to the origin
1000	 */
1001	io_size = linear_chunks * s->store->chunk_size;
1002
1003	dest.bdev = s->origin->bdev;
1004	dest.sector = chunk_to_sector(s->store, old_chunk);
1005	dest.count = min(io_size, get_dev_size(dest.bdev) - dest.sector);
1006
1007	src.bdev = s->cow->bdev;
1008	src.sector = chunk_to_sector(s->store, new_chunk);
1009	src.count = dest.count;
1010
1011	/*
1012	 * Reallocate any exceptions needed in other snapshots then
1013	 * wait for the pending exceptions to complete.
1014	 * Each time any pending exception (globally on the system)
1015	 * completes we are woken and repeat the process to find out
1016	 * if we can proceed.  While this may not seem a particularly
1017	 * efficient algorithm, it is not expected to have any
1018	 * significant impact on performance.
1019	 */
1020	previous_count = read_pending_exceptions_done_count();
1021	while (origin_write_extent(s, dest.sector, io_size)) {
1022		wait_event(_pending_exceptions_done,
1023			   (read_pending_exceptions_done_count() !=
1024			    previous_count));
1025		/* Retry after the wait, until all exceptions are done. */
1026		previous_count = read_pending_exceptions_done_count();
1027	}
1028
1029	down_write(&s->lock);
1030	s->first_merging_chunk = old_chunk;
1031	s->num_merging_chunks = linear_chunks;
1032	up_write(&s->lock);
1033
1034	/* Wait until writes to all 'linear_chunks' drain */
1035	for (i = 0; i < linear_chunks; i++)
1036		__check_for_conflicting_io(s, old_chunk + i);
1037
1038	dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, merge_callback, s);
1039	return;
1040
1041shut:
1042	merge_shutdown(s);
1043}
1044
1045static void error_bios(struct bio *bio);
1046
1047static void merge_callback(int read_err, unsigned long write_err, void *context)
1048{
1049	struct dm_snapshot *s = context;
1050	struct bio *b = NULL;
1051
1052	if (read_err || write_err) {
1053		if (read_err)
1054			DMERR("Read error: shutting down merge.");
1055		else
1056			DMERR("Write error: shutting down merge.");
1057		goto shut;
1058	}
1059
 
 
 
 
 
1060	if (s->store->type->commit_merge(s->store,
1061					 s->num_merging_chunks) < 0) {
1062		DMERR("Write error in exception store: shutting down merge");
1063		goto shut;
1064	}
1065
1066	if (remove_single_exception_chunk(s) < 0)
1067		goto shut;
1068
1069	snapshot_merge_next_chunks(s);
1070
1071	return;
1072
1073shut:
1074	down_write(&s->lock);
1075	s->merge_failed = 1;
1076	b = __release_queued_bios_after_merge(s);
1077	up_write(&s->lock);
1078	error_bios(b);
1079
1080	merge_shutdown(s);
1081}
1082
1083static void start_merge(struct dm_snapshot *s)
1084{
1085	if (!test_and_set_bit(RUNNING_MERGE, &s->state_bits))
1086		snapshot_merge_next_chunks(s);
1087}
1088
1089/*
1090 * Stop the merging process and wait until it finishes.
1091 */
1092static void stop_merge(struct dm_snapshot *s)
1093{
1094	set_bit(SHUTDOWN_MERGE, &s->state_bits);
1095	wait_on_bit(&s->state_bits, RUNNING_MERGE, TASK_UNINTERRUPTIBLE);
1096	clear_bit(SHUTDOWN_MERGE, &s->state_bits);
1097}
1098
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1099/*
1100 * Construct a snapshot mapping: <origin_dev> <COW-dev> <p|po|n> <chunk-size>
 
1101 */
1102static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
1103{
1104	struct dm_snapshot *s;
 
1105	int i;
1106	int r = -EINVAL;
1107	char *origin_path, *cow_path;
1108	dev_t origin_dev, cow_dev;
1109	unsigned args_used, num_flush_bios = 1;
1110	fmode_t origin_mode = FMODE_READ;
1111
1112	if (argc != 4) {
1113		ti->error = "requires exactly 4 arguments";
1114		r = -EINVAL;
1115		goto bad;
1116	}
1117
1118	if (dm_target_is_snapshot_merge(ti)) {
1119		num_flush_bios = 2;
1120		origin_mode = FMODE_WRITE;
1121	}
1122
1123	s = kmalloc(sizeof(*s), GFP_KERNEL);
1124	if (!s) {
1125		ti->error = "Cannot allocate private snapshot structure";
1126		r = -ENOMEM;
1127		goto bad;
1128	}
1129
 
 
 
 
 
 
 
1130	origin_path = argv[0];
1131	argv++;
1132	argc--;
1133
1134	r = dm_get_device(ti, origin_path, origin_mode, &s->origin);
1135	if (r) {
1136		ti->error = "Cannot get origin device";
1137		goto bad_origin;
1138	}
1139	origin_dev = s->origin->bdev->bd_dev;
1140
1141	cow_path = argv[0];
1142	argv++;
1143	argc--;
1144
1145	cow_dev = dm_get_dev_t(cow_path);
1146	if (cow_dev && cow_dev == origin_dev) {
1147		ti->error = "COW device cannot be the same as origin device";
1148		r = -EINVAL;
1149		goto bad_cow;
1150	}
1151
1152	r = dm_get_device(ti, cow_path, dm_table_get_mode(ti->table), &s->cow);
1153	if (r) {
1154		ti->error = "Cannot get COW device";
1155		goto bad_cow;
1156	}
 
 
 
 
 
1157
1158	r = dm_exception_store_create(ti, argc, argv, s, &args_used, &s->store);
1159	if (r) {
1160		ti->error = "Couldn't create exception store";
1161		r = -EINVAL;
1162		goto bad_store;
1163	}
1164
1165	argv += args_used;
1166	argc -= args_used;
1167
1168	s->ti = ti;
1169	s->valid = 1;
1170	s->snapshot_overflowed = 0;
1171	s->active = 0;
1172	atomic_set(&s->pending_exceptions_count, 0);
 
1173	s->exception_start_sequence = 0;
1174	s->exception_complete_sequence = 0;
1175	INIT_LIST_HEAD(&s->out_of_order_list);
1176	init_rwsem(&s->lock);
1177	INIT_LIST_HEAD(&s->list);
1178	spin_lock_init(&s->pe_lock);
1179	s->state_bits = 0;
1180	s->merge_failed = 0;
1181	s->first_merging_chunk = 0;
1182	s->num_merging_chunks = 0;
1183	bio_list_init(&s->bios_queued_during_merge);
1184
1185	/* Allocate hash table for COW data */
1186	if (init_hash_tables(s)) {
1187		ti->error = "Unable to allocate hash table space";
1188		r = -ENOMEM;
1189		goto bad_hash_tables;
1190	}
1191
 
 
1192	s->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle);
1193	if (IS_ERR(s->kcopyd_client)) {
1194		r = PTR_ERR(s->kcopyd_client);
1195		ti->error = "Could not create kcopyd client";
1196		goto bad_kcopyd;
1197	}
1198
1199	s->pending_pool = mempool_create_slab_pool(MIN_IOS, pending_cache);
1200	if (!s->pending_pool) {
1201		ti->error = "Could not allocate mempool for pending exceptions";
1202		r = -ENOMEM;
1203		goto bad_pending_pool;
1204	}
1205
1206	for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
1207		INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);
1208
1209	spin_lock_init(&s->tracked_chunk_lock);
1210
1211	ti->private = s;
1212	ti->num_flush_bios = num_flush_bios;
 
 
1213	ti->per_io_data_size = sizeof(struct dm_snap_tracked_chunk);
1214
1215	/* Add snapshot to the list of snapshots for this origin */
1216	/* Exceptions aren't triggered till snapshot_resume() is called */
1217	r = register_snapshot(s);
1218	if (r == -ENOMEM) {
1219		ti->error = "Snapshot origin struct allocation failed";
1220		goto bad_load_and_register;
1221	} else if (r < 0) {
1222		/* invalid handover, register_snapshot has set ti->error */
1223		goto bad_load_and_register;
1224	}
1225
1226	/*
1227	 * Metadata must only be loaded into one table at once, so skip this
1228	 * if metadata will be handed over during resume.
1229	 * Chunk size will be set during the handover - set it to zero to
1230	 * ensure it's ignored.
1231	 */
1232	if (r > 0) {
1233		s->store->chunk_size = 0;
1234		return 0;
1235	}
1236
1237	r = s->store->type->read_metadata(s->store, dm_add_exception,
1238					  (void *)s);
1239	if (r < 0) {
1240		ti->error = "Failed to read snapshot metadata";
1241		goto bad_read_metadata;
1242	} else if (r > 0) {
1243		s->valid = 0;
1244		DMWARN("Snapshot is marked invalid.");
1245	}
1246
1247	if (!s->store->chunk_size) {
1248		ti->error = "Chunk size not set";
 
1249		goto bad_read_metadata;
1250	}
1251
1252	r = dm_set_target_max_io_len(ti, s->store->chunk_size);
1253	if (r)
1254		goto bad_read_metadata;
1255
1256	return 0;
1257
1258bad_read_metadata:
1259	unregister_snapshot(s);
1260
1261bad_load_and_register:
1262	mempool_destroy(s->pending_pool);
1263
1264bad_pending_pool:
1265	dm_kcopyd_client_destroy(s->kcopyd_client);
1266
1267bad_kcopyd:
1268	dm_exception_table_exit(&s->pending, pending_cache);
1269	dm_exception_table_exit(&s->complete, exception_cache);
1270
1271bad_hash_tables:
1272	dm_exception_store_destroy(s->store);
1273
1274bad_store:
1275	dm_put_device(ti, s->cow);
1276
1277bad_cow:
1278	dm_put_device(ti, s->origin);
1279
1280bad_origin:
 
1281	kfree(s);
1282
1283bad:
1284	return r;
1285}
1286
1287static void __free_exceptions(struct dm_snapshot *s)
1288{
1289	dm_kcopyd_client_destroy(s->kcopyd_client);
1290	s->kcopyd_client = NULL;
1291
1292	dm_exception_table_exit(&s->pending, pending_cache);
1293	dm_exception_table_exit(&s->complete, exception_cache);
1294}
1295
1296static void __handover_exceptions(struct dm_snapshot *snap_src,
1297				  struct dm_snapshot *snap_dest)
1298{
1299	union {
1300		struct dm_exception_table table_swap;
1301		struct dm_exception_store *store_swap;
1302	} u;
1303
1304	/*
1305	 * Swap all snapshot context information between the two instances.
1306	 */
1307	u.table_swap = snap_dest->complete;
1308	snap_dest->complete = snap_src->complete;
1309	snap_src->complete = u.table_swap;
1310
1311	u.store_swap = snap_dest->store;
1312	snap_dest->store = snap_src->store;
1313	snap_dest->store->userspace_supports_overflow = u.store_swap->userspace_supports_overflow;
1314	snap_src->store = u.store_swap;
1315
1316	snap_dest->store->snap = snap_dest;
1317	snap_src->store->snap = snap_src;
1318
1319	snap_dest->ti->max_io_len = snap_dest->store->chunk_size;
1320	snap_dest->valid = snap_src->valid;
1321	snap_dest->snapshot_overflowed = snap_src->snapshot_overflowed;
1322
1323	/*
1324	 * Set source invalid to ensure it receives no further I/O.
1325	 */
1326	snap_src->valid = 0;
1327}
1328
1329static void snapshot_dtr(struct dm_target *ti)
1330{
1331#ifdef CONFIG_DM_DEBUG
1332	int i;
1333#endif
1334	struct dm_snapshot *s = ti->private;
1335	struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1336
1337	down_read(&_origins_lock);
1338	/* Check whether exception handover must be cancelled */
1339	(void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1340	if (snap_src && snap_dest && (s == snap_src)) {
1341		down_write(&snap_dest->lock);
1342		snap_dest->valid = 0;
1343		up_write(&snap_dest->lock);
1344		DMERR("Cancelling snapshot handover.");
1345	}
1346	up_read(&_origins_lock);
1347
1348	if (dm_target_is_snapshot_merge(ti))
1349		stop_merge(s);
1350
1351	/* Prevent further origin writes from using this snapshot. */
1352	/* After this returns there can be no new kcopyd jobs. */
1353	unregister_snapshot(s);
1354
1355	while (atomic_read(&s->pending_exceptions_count))
1356		msleep(1);
1357	/*
1358	 * Ensure instructions in mempool_destroy aren't reordered
1359	 * before atomic_read.
1360	 */
1361	smp_mb();
1362
1363#ifdef CONFIG_DM_DEBUG
1364	for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
1365		BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i]));
1366#endif
1367
1368	__free_exceptions(s);
1369
1370	mempool_destroy(s->pending_pool);
1371
1372	dm_exception_store_destroy(s->store);
1373
1374	dm_put_device(ti, s->cow);
1375
1376	dm_put_device(ti, s->origin);
1377
 
 
1378	kfree(s);
1379}
1380
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1381/*
1382 * Flush a list of buffers.
1383 */
1384static void flush_bios(struct bio *bio)
1385{
1386	struct bio *n;
1387
1388	while (bio) {
1389		n = bio->bi_next;
1390		bio->bi_next = NULL;
1391		generic_make_request(bio);
1392		bio = n;
1393	}
1394}
1395
1396static int do_origin(struct dm_dev *origin, struct bio *bio);
1397
1398/*
1399 * Flush a list of buffers.
1400 */
1401static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio)
1402{
1403	struct bio *n;
1404	int r;
1405
1406	while (bio) {
1407		n = bio->bi_next;
1408		bio->bi_next = NULL;
1409		r = do_origin(s->origin, bio);
1410		if (r == DM_MAPIO_REMAPPED)
1411			generic_make_request(bio);
1412		bio = n;
1413	}
1414}
1415
1416/*
1417 * Error a list of buffers.
1418 */
1419static void error_bios(struct bio *bio)
1420{
1421	struct bio *n;
1422
1423	while (bio) {
1424		n = bio->bi_next;
1425		bio->bi_next = NULL;
1426		bio_io_error(bio);
1427		bio = n;
1428	}
1429}
1430
1431static void __invalidate_snapshot(struct dm_snapshot *s, int err)
1432{
1433	if (!s->valid)
1434		return;
1435
1436	if (err == -EIO)
1437		DMERR("Invalidating snapshot: Error reading/writing.");
1438	else if (err == -ENOMEM)
1439		DMERR("Invalidating snapshot: Unable to allocate exception.");
1440
1441	if (s->store->type->drop_snapshot)
1442		s->store->type->drop_snapshot(s->store);
1443
1444	s->valid = 0;
1445
1446	dm_table_event(s->ti->table);
1447}
1448
 
 
 
 
 
 
 
1449static void pending_complete(void *context, int success)
1450{
1451	struct dm_snap_pending_exception *pe = context;
1452	struct dm_exception *e;
1453	struct dm_snapshot *s = pe->snap;
1454	struct bio *origin_bios = NULL;
1455	struct bio *snapshot_bios = NULL;
1456	struct bio *full_bio = NULL;
 
1457	int error = 0;
1458
 
 
1459	if (!success) {
1460		/* Read/write error - snapshot is unusable */
1461		down_write(&s->lock);
1462		__invalidate_snapshot(s, -EIO);
1463		error = 1;
 
 
1464		goto out;
1465	}
1466
1467	e = alloc_completed_exception(GFP_NOIO);
1468	if (!e) {
1469		down_write(&s->lock);
1470		__invalidate_snapshot(s, -ENOMEM);
1471		error = 1;
 
 
1472		goto out;
1473	}
1474	*e = pe->e;
1475
1476	down_write(&s->lock);
 
1477	if (!s->valid) {
 
1478		free_completed_exception(e);
1479		error = 1;
 
1480		goto out;
1481	}
1482
1483	/* Check for conflicting reads */
1484	__check_for_conflicting_io(s, pe->e.old_chunk);
1485
1486	/*
1487	 * Add a proper exception, and remove the
1488	 * in-flight exception from the list.
 
 
 
1489	 */
1490	dm_insert_exception(&s->complete, e);
 
 
 
 
 
 
 
 
1491
1492out:
 
1493	dm_remove_exception(&pe->e);
 
 
 
1494	snapshot_bios = bio_list_get(&pe->snapshot_bios);
1495	origin_bios = bio_list_get(&pe->origin_bios);
1496	full_bio = pe->full_bio;
1497	if (full_bio)
1498		full_bio->bi_end_io = pe->full_bio_end_io;
1499	increment_pending_exceptions_done_count();
1500
1501	up_write(&s->lock);
1502
1503	/* Submit any pending write bios */
1504	if (error) {
1505		if (full_bio)
1506			bio_io_error(full_bio);
1507		error_bios(snapshot_bios);
1508	} else {
1509		if (full_bio)
1510			bio_endio(full_bio);
1511		flush_bios(snapshot_bios);
1512	}
1513
1514	retry_origin_bios(s, origin_bios);
1515
1516	free_pending_exception(pe);
1517}
1518
1519static void complete_exception(struct dm_snap_pending_exception *pe)
1520{
1521	struct dm_snapshot *s = pe->snap;
1522
1523	/* Update the metadata if we are persistent */
1524	s->store->type->commit_exception(s->store, &pe->e, !pe->copy_error,
1525					 pending_complete, pe);
1526}
1527
1528/*
1529 * Called when the copy I/O has finished.  kcopyd actually runs
1530 * this code so don't block.
1531 */
1532static void copy_callback(int read_err, unsigned long write_err, void *context)
1533{
1534	struct dm_snap_pending_exception *pe = context;
1535	struct dm_snapshot *s = pe->snap;
1536
1537	pe->copy_error = read_err || write_err;
1538
1539	if (pe->exception_sequence == s->exception_complete_sequence) {
 
 
1540		s->exception_complete_sequence++;
1541		complete_exception(pe);
1542
1543		while (!list_empty(&s->out_of_order_list)) {
1544			pe = list_entry(s->out_of_order_list.next,
1545					struct dm_snap_pending_exception, out_of_order_entry);
 
1546			if (pe->exception_sequence != s->exception_complete_sequence)
1547				break;
 
1548			s->exception_complete_sequence++;
1549			list_del(&pe->out_of_order_entry);
1550			complete_exception(pe);
 
1551		}
1552	} else {
1553		struct list_head *lh;
 
1554		struct dm_snap_pending_exception *pe2;
1555
1556		list_for_each_prev(lh, &s->out_of_order_list) {
1557			pe2 = list_entry(lh, struct dm_snap_pending_exception, out_of_order_entry);
1558			if (pe2->exception_sequence < pe->exception_sequence)
1559				break;
 
 
 
 
 
1560		}
1561		list_add(&pe->out_of_order_entry, lh);
 
 
1562	}
 
1563}
1564
1565/*
1566 * Dispatches the copy operation to kcopyd.
1567 */
1568static void start_copy(struct dm_snap_pending_exception *pe)
1569{
1570	struct dm_snapshot *s = pe->snap;
1571	struct dm_io_region src, dest;
1572	struct block_device *bdev = s->origin->bdev;
1573	sector_t dev_size;
1574
1575	dev_size = get_dev_size(bdev);
1576
1577	src.bdev = bdev;
1578	src.sector = chunk_to_sector(s->store, pe->e.old_chunk);
1579	src.count = min((sector_t)s->store->chunk_size, dev_size - src.sector);
1580
1581	dest.bdev = s->cow->bdev;
1582	dest.sector = chunk_to_sector(s->store, pe->e.new_chunk);
1583	dest.count = src.count;
1584
1585	/* Hand over to kcopyd */
 
1586	dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, copy_callback, pe);
1587}
1588
1589static void full_bio_end_io(struct bio *bio)
1590{
1591	void *callback_data = bio->bi_private;
1592
1593	dm_kcopyd_do_callback(callback_data, 0, bio->bi_error ? 1 : 0);
1594}
1595
1596static void start_full_bio(struct dm_snap_pending_exception *pe,
1597			   struct bio *bio)
1598{
1599	struct dm_snapshot *s = pe->snap;
1600	void *callback_data;
1601
1602	pe->full_bio = bio;
1603	pe->full_bio_end_io = bio->bi_end_io;
1604
 
1605	callback_data = dm_kcopyd_prepare_callback(s->kcopyd_client,
1606						   copy_callback, pe);
1607
1608	bio->bi_end_io = full_bio_end_io;
1609	bio->bi_private = callback_data;
1610
1611	generic_make_request(bio);
1612}
1613
1614static struct dm_snap_pending_exception *
1615__lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk)
1616{
1617	struct dm_exception *e = dm_lookup_exception(&s->pending, chunk);
1618
1619	if (!e)
1620		return NULL;
1621
1622	return container_of(e, struct dm_snap_pending_exception, e);
1623}
1624
1625/*
1626 * Looks to see if this snapshot already has a pending exception
1627 * for this chunk, otherwise it allocates a new one and inserts
1628 * it into the pending table.
1629 *
1630 * NOTE: a write lock must be held on snap->lock before calling
1631 * this.
1632 */
1633static struct dm_snap_pending_exception *
1634__find_pending_exception(struct dm_snapshot *s,
1635			 struct dm_snap_pending_exception *pe, chunk_t chunk)
1636{
1637	struct dm_snap_pending_exception *pe2;
1638
1639	pe2 = __lookup_pending_exception(s, chunk);
1640	if (pe2) {
1641		free_pending_exception(pe);
1642		return pe2;
1643	}
1644
1645	pe->e.old_chunk = chunk;
1646	bio_list_init(&pe->origin_bios);
1647	bio_list_init(&pe->snapshot_bios);
1648	pe->started = 0;
1649	pe->full_bio = NULL;
1650
 
1651	if (s->store->type->prepare_exception(s->store, &pe->e)) {
 
1652		free_pending_exception(pe);
1653		return NULL;
1654	}
1655
1656	pe->exception_sequence = s->exception_start_sequence++;
 
1657
1658	dm_insert_exception(&s->pending, &pe->e);
1659
1660	return pe;
1661}
1662
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1663static void remap_exception(struct dm_snapshot *s, struct dm_exception *e,
1664			    struct bio *bio, chunk_t chunk)
1665{
1666	bio->bi_bdev = s->cow->bdev;
1667	bio->bi_iter.bi_sector =
1668		chunk_to_sector(s->store, dm_chunk_number(e->new_chunk) +
1669				(chunk - e->old_chunk)) +
1670		(bio->bi_iter.bi_sector & s->store->chunk_mask);
1671}
1672
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1673static int snapshot_map(struct dm_target *ti, struct bio *bio)
1674{
1675	struct dm_exception *e;
1676	struct dm_snapshot *s = ti->private;
1677	int r = DM_MAPIO_REMAPPED;
1678	chunk_t chunk;
1679	struct dm_snap_pending_exception *pe = NULL;
 
1680
1681	init_tracked_chunk(bio);
1682
1683	if (bio->bi_opf & REQ_PREFLUSH) {
1684		bio->bi_bdev = s->cow->bdev;
1685		return DM_MAPIO_REMAPPED;
1686	}
1687
1688	chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector);
 
1689
1690	/* Full snapshots are not usable */
1691	/* To get here the table must be live so s->active is always set. */
1692	if (!s->valid)
1693		return -EIO;
1694
1695	/* FIXME: should only take write lock if we need
1696	 * to copy an exception */
1697	down_write(&s->lock);
 
 
 
 
1698
1699	if (!s->valid || (unlikely(s->snapshot_overflowed) &&
1700	    bio_data_dir(bio) == WRITE)) {
1701		r = -EIO;
1702		goto out_unlock;
1703	}
1704
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1705	/* If the block is already remapped - use that, else remap it */
1706	e = dm_lookup_exception(&s->complete, chunk);
1707	if (e) {
1708		remap_exception(s, e, bio, chunk);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1709		goto out_unlock;
1710	}
1711
1712	/*
1713	 * Write to snapshot - higher level takes care of RW/RO
1714	 * flags so we should only get this if we are
1715	 * writeable.
1716	 */
1717	if (bio_data_dir(bio) == WRITE) {
1718		pe = __lookup_pending_exception(s, chunk);
1719		if (!pe) {
1720			up_write(&s->lock);
1721			pe = alloc_pending_exception(s);
1722			down_write(&s->lock);
1723
1724			if (!s->valid || s->snapshot_overflowed) {
1725				free_pending_exception(pe);
1726				r = -EIO;
1727				goto out_unlock;
1728			}
1729
1730			e = dm_lookup_exception(&s->complete, chunk);
1731			if (e) {
1732				free_pending_exception(pe);
1733				remap_exception(s, e, bio, chunk);
1734				goto out_unlock;
1735			}
1736
1737			pe = __find_pending_exception(s, pe, chunk);
1738			if (!pe) {
 
 
 
 
 
1739				if (s->store->userspace_supports_overflow) {
1740					s->snapshot_overflowed = 1;
1741					DMERR("Snapshot overflowed: Unable to allocate exception.");
 
 
1742				} else
1743					__invalidate_snapshot(s, -ENOMEM);
1744				r = -EIO;
1745				goto out_unlock;
 
 
1746			}
1747		}
1748
1749		remap_exception(s, &pe->e, bio, chunk);
1750
1751		r = DM_MAPIO_SUBMITTED;
1752
1753		if (!pe->started &&
1754		    bio->bi_iter.bi_size ==
1755		    (s->store->chunk_size << SECTOR_SHIFT)) {
1756			pe->started = 1;
1757			up_write(&s->lock);
 
 
 
1758			start_full_bio(pe, bio);
1759			goto out;
1760		}
1761
1762		bio_list_add(&pe->snapshot_bios, bio);
1763
1764		if (!pe->started) {
1765			/* this is protected by snap->lock */
1766			pe->started = 1;
1767			up_write(&s->lock);
 
 
 
1768			start_copy(pe);
1769			goto out;
1770		}
1771	} else {
1772		bio->bi_bdev = s->origin->bdev;
1773		track_chunk(s, bio, chunk);
1774	}
1775
1776out_unlock:
1777	up_write(&s->lock);
 
1778out:
1779	return r;
1780}
1781
1782/*
1783 * A snapshot-merge target behaves like a combination of a snapshot
1784 * target and a snapshot-origin target.  It only generates new
1785 * exceptions in other snapshots and not in the one that is being
1786 * merged.
1787 *
1788 * For each chunk, if there is an existing exception, it is used to
1789 * redirect I/O to the cow device.  Otherwise I/O is sent to the origin,
1790 * which in turn might generate exceptions in other snapshots.
1791 * If merging is currently taking place on the chunk in question, the
1792 * I/O is deferred by adding it to s->bios_queued_during_merge.
1793 */
1794static int snapshot_merge_map(struct dm_target *ti, struct bio *bio)
1795{
1796	struct dm_exception *e;
1797	struct dm_snapshot *s = ti->private;
1798	int r = DM_MAPIO_REMAPPED;
1799	chunk_t chunk;
1800
1801	init_tracked_chunk(bio);
1802
1803	if (bio->bi_opf & REQ_PREFLUSH) {
1804		if (!dm_bio_get_target_bio_nr(bio))
1805			bio->bi_bdev = s->origin->bdev;
1806		else
1807			bio->bi_bdev = s->cow->bdev;
1808		return DM_MAPIO_REMAPPED;
1809	}
1810
 
 
 
 
 
 
1811	chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector);
1812
1813	down_write(&s->lock);
1814
1815	/* Full merging snapshots are redirected to the origin */
1816	if (!s->valid)
1817		goto redirect_to_origin;
1818
1819	/* If the block is already remapped - use that */
1820	e = dm_lookup_exception(&s->complete, chunk);
1821	if (e) {
1822		/* Queue writes overlapping with chunks being merged */
1823		if (bio_data_dir(bio) == WRITE &&
1824		    chunk >= s->first_merging_chunk &&
1825		    chunk < (s->first_merging_chunk +
1826			     s->num_merging_chunks)) {
1827			bio->bi_bdev = s->origin->bdev;
1828			bio_list_add(&s->bios_queued_during_merge, bio);
1829			r = DM_MAPIO_SUBMITTED;
1830			goto out_unlock;
1831		}
1832
1833		remap_exception(s, e, bio, chunk);
1834
1835		if (bio_data_dir(bio) == WRITE)
1836			track_chunk(s, bio, chunk);
1837		goto out_unlock;
1838	}
1839
1840redirect_to_origin:
1841	bio->bi_bdev = s->origin->bdev;
1842
1843	if (bio_data_dir(bio) == WRITE) {
1844		up_write(&s->lock);
1845		return do_origin(s->origin, bio);
1846	}
1847
1848out_unlock:
1849	up_write(&s->lock);
1850
1851	return r;
1852}
1853
1854static int snapshot_end_io(struct dm_target *ti, struct bio *bio, int error)
 
1855{
1856	struct dm_snapshot *s = ti->private;
1857
1858	if (is_bio_tracked(bio))
1859		stop_tracking_chunk(s, bio);
1860
1861	return 0;
1862}
1863
1864static void snapshot_merge_presuspend(struct dm_target *ti)
1865{
1866	struct dm_snapshot *s = ti->private;
1867
1868	stop_merge(s);
1869}
1870
1871static int snapshot_preresume(struct dm_target *ti)
1872{
1873	int r = 0;
1874	struct dm_snapshot *s = ti->private;
1875	struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
1876
1877	down_read(&_origins_lock);
1878	(void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1879	if (snap_src && snap_dest) {
1880		down_read(&snap_src->lock);
1881		if (s == snap_src) {
1882			DMERR("Unable to resume snapshot source until "
1883			      "handover completes.");
1884			r = -EINVAL;
1885		} else if (!dm_suspended(snap_src->ti)) {
1886			DMERR("Unable to perform snapshot handover until "
1887			      "source is suspended.");
1888			r = -EINVAL;
1889		}
1890		up_read(&snap_src->lock);
1891	}
1892	up_read(&_origins_lock);
1893
1894	return r;
1895}
1896
1897static void snapshot_resume(struct dm_target *ti)
1898{
1899	struct dm_snapshot *s = ti->private;
1900	struct dm_snapshot *snap_src = NULL, *snap_dest = NULL, *snap_merging = NULL;
1901	struct dm_origin *o;
1902	struct mapped_device *origin_md = NULL;
1903	bool must_restart_merging = false;
1904
1905	down_read(&_origins_lock);
1906
1907	o = __lookup_dm_origin(s->origin->bdev);
1908	if (o)
1909		origin_md = dm_table_get_md(o->ti->table);
1910	if (!origin_md) {
1911		(void) __find_snapshots_sharing_cow(s, NULL, NULL, &snap_merging);
1912		if (snap_merging)
1913			origin_md = dm_table_get_md(snap_merging->ti->table);
1914	}
1915	if (origin_md == dm_table_get_md(ti->table))
1916		origin_md = NULL;
1917	if (origin_md) {
1918		if (dm_hold(origin_md))
1919			origin_md = NULL;
1920	}
1921
1922	up_read(&_origins_lock);
1923
1924	if (origin_md) {
1925		dm_internal_suspend_fast(origin_md);
1926		if (snap_merging && test_bit(RUNNING_MERGE, &snap_merging->state_bits)) {
1927			must_restart_merging = true;
1928			stop_merge(snap_merging);
1929		}
1930	}
1931
1932	down_read(&_origins_lock);
1933
1934	(void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
1935	if (snap_src && snap_dest) {
1936		down_write(&snap_src->lock);
1937		down_write_nested(&snap_dest->lock, SINGLE_DEPTH_NESTING);
1938		__handover_exceptions(snap_src, snap_dest);
1939		up_write(&snap_dest->lock);
1940		up_write(&snap_src->lock);
1941	}
1942
1943	up_read(&_origins_lock);
1944
1945	if (origin_md) {
1946		if (must_restart_merging)
1947			start_merge(snap_merging);
1948		dm_internal_resume_fast(origin_md);
1949		dm_put(origin_md);
1950	}
1951
1952	/* Now we have correct chunk size, reregister */
1953	reregister_snapshot(s);
1954
1955	down_write(&s->lock);
1956	s->active = 1;
1957	up_write(&s->lock);
1958}
1959
1960static uint32_t get_origin_minimum_chunksize(struct block_device *bdev)
1961{
1962	uint32_t min_chunksize;
1963
1964	down_read(&_origins_lock);
1965	min_chunksize = __minimum_chunk_size(__lookup_origin(bdev));
1966	up_read(&_origins_lock);
1967
1968	return min_chunksize;
1969}
1970
1971static void snapshot_merge_resume(struct dm_target *ti)
1972{
1973	struct dm_snapshot *s = ti->private;
1974
1975	/*
1976	 * Handover exceptions from existing snapshot.
1977	 */
1978	snapshot_resume(ti);
1979
1980	/*
1981	 * snapshot-merge acts as an origin, so set ti->max_io_len
1982	 */
1983	ti->max_io_len = get_origin_minimum_chunksize(s->origin->bdev);
1984
1985	start_merge(s);
1986}
1987
1988static void snapshot_status(struct dm_target *ti, status_type_t type,
1989			    unsigned status_flags, char *result, unsigned maxlen)
1990{
1991	unsigned sz = 0;
1992	struct dm_snapshot *snap = ti->private;
 
1993
1994	switch (type) {
1995	case STATUSTYPE_INFO:
1996
1997		down_write(&snap->lock);
1998
1999		if (!snap->valid)
2000			DMEMIT("Invalid");
2001		else if (snap->merge_failed)
2002			DMEMIT("Merge failed");
2003		else if (snap->snapshot_overflowed)
2004			DMEMIT("Overflow");
2005		else {
2006			if (snap->store->type->usage) {
2007				sector_t total_sectors, sectors_allocated,
2008					 metadata_sectors;
2009				snap->store->type->usage(snap->store,
2010							 &total_sectors,
2011							 &sectors_allocated,
2012							 &metadata_sectors);
2013				DMEMIT("%llu/%llu %llu",
2014				       (unsigned long long)sectors_allocated,
2015				       (unsigned long long)total_sectors,
2016				       (unsigned long long)metadata_sectors);
2017			}
2018			else
2019				DMEMIT("Unknown");
2020		}
2021
2022		up_write(&snap->lock);
2023
2024		break;
2025
2026	case STATUSTYPE_TABLE:
2027		/*
2028		 * kdevname returns a static pointer so we need
2029		 * to make private copies if the output is to
2030		 * make sense.
2031		 */
2032		DMEMIT("%s %s", snap->origin->name, snap->cow->name);
2033		snap->store->type->status(snap->store, type, result + sz,
2034					  maxlen - sz);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2035		break;
2036	}
2037}
2038
2039static int snapshot_iterate_devices(struct dm_target *ti,
2040				    iterate_devices_callout_fn fn, void *data)
2041{
2042	struct dm_snapshot *snap = ti->private;
2043	int r;
2044
2045	r = fn(ti, snap->origin, 0, ti->len, data);
2046
2047	if (!r)
2048		r = fn(ti, snap->cow, 0, get_dev_size(snap->cow->bdev), data);
2049
2050	return r;
2051}
2052
 
 
 
 
 
 
2053
2054/*-----------------------------------------------------------------
2055 * Origin methods
2056 *---------------------------------------------------------------*/
 
 
 
 
 
 
 
 
 
 
2057
2058/*
 
 
 
 
 
2059 * If no exceptions need creating, DM_MAPIO_REMAPPED is returned and any
2060 * supplied bio was ignored.  The caller may submit it immediately.
2061 * (No remapping actually occurs as the origin is always a direct linear
2062 * map.)
2063 *
2064 * If further exceptions are required, DM_MAPIO_SUBMITTED is returned
2065 * and any supplied bio is added to a list to be submitted once all
2066 * the necessary exceptions exist.
2067 */
2068static int __origin_write(struct list_head *snapshots, sector_t sector,
2069			  struct bio *bio)
2070{
2071	int r = DM_MAPIO_REMAPPED;
2072	struct dm_snapshot *snap;
2073	struct dm_exception *e;
2074	struct dm_snap_pending_exception *pe;
2075	struct dm_snap_pending_exception *pe_to_start_now = NULL;
2076	struct dm_snap_pending_exception *pe_to_start_last = NULL;
 
2077	chunk_t chunk;
2078
2079	/* Do all the snapshots on this origin */
2080	list_for_each_entry (snap, snapshots, list) {
2081		/*
2082		 * Don't make new exceptions in a merging snapshot
2083		 * because it has effectively been deleted
2084		 */
2085		if (dm_target_is_snapshot_merge(snap->ti))
2086			continue;
2087
2088		down_write(&snap->lock);
2089
2090		/* Only deal with valid and active snapshots */
2091		if (!snap->valid || !snap->active)
2092			goto next_snapshot;
2093
2094		/* Nothing to do if writing beyond end of snapshot */
2095		if (sector >= dm_table_get_size(snap->ti->table))
2096			goto next_snapshot;
2097
2098		/*
2099		 * Remember, different snapshots can have
2100		 * different chunk sizes.
2101		 */
2102		chunk = sector_to_chunk(snap->store, sector);
 
2103
2104		/*
2105		 * Check exception table to see if block
2106		 * is already remapped in this snapshot
2107		 * and trigger an exception if not.
2108		 */
2109		e = dm_lookup_exception(&snap->complete, chunk);
2110		if (e)
2111			goto next_snapshot;
2112
2113		pe = __lookup_pending_exception(snap, chunk);
2114		if (!pe) {
2115			up_write(&snap->lock);
 
 
 
 
 
 
 
 
 
2116			pe = alloc_pending_exception(snap);
2117			down_write(&snap->lock);
2118
2119			if (!snap->valid) {
2120				free_pending_exception(pe);
2121				goto next_snapshot;
2122			}
2123
2124			e = dm_lookup_exception(&snap->complete, chunk);
2125			if (e) {
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2126				free_pending_exception(pe);
2127				goto next_snapshot;
2128			}
2129
2130			pe = __find_pending_exception(snap, pe, chunk);
2131			if (!pe) {
2132				__invalidate_snapshot(snap, -ENOMEM);
2133				goto next_snapshot;
2134			}
2135		}
2136
2137		r = DM_MAPIO_SUBMITTED;
2138
2139		/*
2140		 * If an origin bio was supplied, queue it to wait for the
2141		 * completion of this exception, and start this one last,
2142		 * at the end of the function.
2143		 */
2144		if (bio) {
2145			bio_list_add(&pe->origin_bios, bio);
2146			bio = NULL;
2147
2148			if (!pe->started) {
2149				pe->started = 1;
2150				pe_to_start_last = pe;
2151			}
2152		}
2153
2154		if (!pe->started) {
2155			pe->started = 1;
2156			pe_to_start_now = pe;
2157		}
2158
2159next_snapshot:
2160		up_write(&snap->lock);
 
2161
2162		if (pe_to_start_now) {
2163			start_copy(pe_to_start_now);
2164			pe_to_start_now = NULL;
2165		}
2166	}
2167
2168	/*
2169	 * Submit the exception against which the bio is queued last,
2170	 * to give the other exceptions a head start.
2171	 */
2172	if (pe_to_start_last)
2173		start_copy(pe_to_start_last);
2174
2175	return r;
2176}
2177
2178/*
2179 * Called on a write from the origin driver.
2180 */
2181static int do_origin(struct dm_dev *origin, struct bio *bio)
2182{
2183	struct origin *o;
2184	int r = DM_MAPIO_REMAPPED;
2185
 
2186	down_read(&_origins_lock);
2187	o = __lookup_origin(origin->bdev);
2188	if (o)
 
 
 
 
 
 
 
 
2189		r = __origin_write(&o->snapshots, bio->bi_iter.bi_sector, bio);
 
2190	up_read(&_origins_lock);
2191
2192	return r;
2193}
2194
2195/*
2196 * Trigger exceptions in all non-merging snapshots.
2197 *
2198 * The chunk size of the merging snapshot may be larger than the chunk
2199 * size of some other snapshot so we may need to reallocate multiple
2200 * chunks in other snapshots.
2201 *
2202 * We scan all the overlapping exceptions in the other snapshots.
2203 * Returns 1 if anything was reallocated and must be waited for,
2204 * otherwise returns 0.
2205 *
2206 * size must be a multiple of merging_snap's chunk_size.
2207 */
2208static int origin_write_extent(struct dm_snapshot *merging_snap,
2209			       sector_t sector, unsigned size)
2210{
2211	int must_wait = 0;
2212	sector_t n;
2213	struct origin *o;
2214
2215	/*
2216	 * The origin's __minimum_chunk_size() got stored in max_io_len
2217	 * by snapshot_merge_resume().
2218	 */
2219	down_read(&_origins_lock);
2220	o = __lookup_origin(merging_snap->origin->bdev);
2221	for (n = 0; n < size; n += merging_snap->ti->max_io_len)
2222		if (__origin_write(&o->snapshots, sector + n, NULL) ==
2223		    DM_MAPIO_SUBMITTED)
2224			must_wait = 1;
2225	up_read(&_origins_lock);
2226
2227	return must_wait;
2228}
2229
2230/*
2231 * Origin: maps a linear range of a device, with hooks for snapshotting.
2232 */
2233
2234/*
2235 * Construct an origin mapping: <dev_path>
2236 * The context for an origin is merely a 'struct dm_dev *'
2237 * pointing to the real device.
2238 */
2239static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv)
2240{
2241	int r;
2242	struct dm_origin *o;
2243
2244	if (argc != 1) {
2245		ti->error = "origin: incorrect number of arguments";
2246		return -EINVAL;
2247	}
2248
2249	o = kmalloc(sizeof(struct dm_origin), GFP_KERNEL);
2250	if (!o) {
2251		ti->error = "Cannot allocate private origin structure";
2252		r = -ENOMEM;
2253		goto bad_alloc;
2254	}
2255
2256	r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &o->dev);
2257	if (r) {
2258		ti->error = "Cannot get target device";
2259		goto bad_open;
2260	}
2261
2262	o->ti = ti;
2263	ti->private = o;
2264	ti->num_flush_bios = 1;
2265
2266	return 0;
2267
2268bad_open:
2269	kfree(o);
2270bad_alloc:
2271	return r;
2272}
2273
2274static void origin_dtr(struct dm_target *ti)
2275{
2276	struct dm_origin *o = ti->private;
2277
2278	dm_put_device(ti, o->dev);
2279	kfree(o);
2280}
2281
2282static int origin_map(struct dm_target *ti, struct bio *bio)
2283{
2284	struct dm_origin *o = ti->private;
2285	unsigned available_sectors;
2286
2287	bio->bi_bdev = o->dev->bdev;
2288
2289	if (unlikely(bio->bi_opf & REQ_PREFLUSH))
2290		return DM_MAPIO_REMAPPED;
2291
2292	if (bio_data_dir(bio) != WRITE)
2293		return DM_MAPIO_REMAPPED;
2294
2295	available_sectors = o->split_boundary -
2296		((unsigned)bio->bi_iter.bi_sector & (o->split_boundary - 1));
2297
2298	if (bio_sectors(bio) > available_sectors)
2299		dm_accept_partial_bio(bio, available_sectors);
2300
2301	/* Only tell snapshots if this is a write */
2302	return do_origin(o->dev, bio);
2303}
2304
2305static long origin_direct_access(struct dm_target *ti, sector_t sector,
2306		void **kaddr, pfn_t *pfn, long size)
2307{
2308	DMWARN("device does not support dax.");
2309	return -EIO;
2310}
2311
2312/*
2313 * Set the target "max_io_len" field to the minimum of all the snapshots'
2314 * chunk sizes.
2315 */
2316static void origin_resume(struct dm_target *ti)
2317{
2318	struct dm_origin *o = ti->private;
2319
2320	o->split_boundary = get_origin_minimum_chunksize(o->dev->bdev);
2321
2322	down_write(&_origins_lock);
2323	__insert_dm_origin(o);
2324	up_write(&_origins_lock);
2325}
2326
2327static void origin_postsuspend(struct dm_target *ti)
2328{
2329	struct dm_origin *o = ti->private;
2330
2331	down_write(&_origins_lock);
2332	__remove_dm_origin(o);
2333	up_write(&_origins_lock);
2334}
2335
2336static void origin_status(struct dm_target *ti, status_type_t type,
2337			  unsigned status_flags, char *result, unsigned maxlen)
2338{
2339	struct dm_origin *o = ti->private;
2340
2341	switch (type) {
2342	case STATUSTYPE_INFO:
2343		result[0] = '\0';
2344		break;
2345
2346	case STATUSTYPE_TABLE:
2347		snprintf(result, maxlen, "%s", o->dev->name);
2348		break;
 
 
 
2349	}
2350}
2351
2352static int origin_iterate_devices(struct dm_target *ti,
2353				  iterate_devices_callout_fn fn, void *data)
2354{
2355	struct dm_origin *o = ti->private;
2356
2357	return fn(ti, o->dev, 0, ti->len, data);
2358}
2359
2360static struct target_type origin_target = {
2361	.name    = "snapshot-origin",
2362	.version = {1, 9, 0},
2363	.module  = THIS_MODULE,
2364	.ctr     = origin_ctr,
2365	.dtr     = origin_dtr,
2366	.map     = origin_map,
2367	.resume  = origin_resume,
2368	.postsuspend = origin_postsuspend,
2369	.status  = origin_status,
2370	.iterate_devices = origin_iterate_devices,
2371	.direct_access = origin_direct_access,
2372};
2373
2374static struct target_type snapshot_target = {
2375	.name    = "snapshot",
2376	.version = {1, 15, 0},
2377	.module  = THIS_MODULE,
2378	.ctr     = snapshot_ctr,
2379	.dtr     = snapshot_dtr,
2380	.map     = snapshot_map,
2381	.end_io  = snapshot_end_io,
2382	.preresume  = snapshot_preresume,
2383	.resume  = snapshot_resume,
2384	.status  = snapshot_status,
2385	.iterate_devices = snapshot_iterate_devices,
 
2386};
2387
2388static struct target_type merge_target = {
2389	.name    = dm_snapshot_merge_target_name,
2390	.version = {1, 4, 0},
2391	.module  = THIS_MODULE,
2392	.ctr     = snapshot_ctr,
2393	.dtr     = snapshot_dtr,
2394	.map     = snapshot_merge_map,
2395	.end_io  = snapshot_end_io,
2396	.presuspend = snapshot_merge_presuspend,
2397	.preresume  = snapshot_preresume,
2398	.resume  = snapshot_merge_resume,
2399	.status  = snapshot_status,
2400	.iterate_devices = snapshot_iterate_devices,
 
2401};
2402
2403static int __init dm_snapshot_init(void)
2404{
2405	int r;
2406
2407	r = dm_exception_store_init();
2408	if (r) {
2409		DMERR("Failed to initialize exception stores");
2410		return r;
2411	}
2412
2413	r = dm_register_target(&snapshot_target);
2414	if (r < 0) {
2415		DMERR("snapshot target register failed %d", r);
2416		goto bad_register_snapshot_target;
2417	}
2418
2419	r = dm_register_target(&origin_target);
2420	if (r < 0) {
2421		DMERR("Origin target register failed %d", r);
2422		goto bad_register_origin_target;
2423	}
2424
2425	r = dm_register_target(&merge_target);
2426	if (r < 0) {
2427		DMERR("Merge target register failed %d", r);
2428		goto bad_register_merge_target;
2429	}
2430
2431	r = init_origin_hash();
2432	if (r) {
2433		DMERR("init_origin_hash failed.");
2434		goto bad_origin_hash;
2435	}
2436
2437	exception_cache = KMEM_CACHE(dm_exception, 0);
2438	if (!exception_cache) {
2439		DMERR("Couldn't create exception cache.");
2440		r = -ENOMEM;
2441		goto bad_exception_cache;
2442	}
2443
2444	pending_cache = KMEM_CACHE(dm_snap_pending_exception, 0);
2445	if (!pending_cache) {
2446		DMERR("Couldn't create pending cache.");
2447		r = -ENOMEM;
2448		goto bad_pending_cache;
2449	}
2450
 
 
 
 
 
 
 
 
 
 
 
 
2451	return 0;
2452
2453bad_pending_cache:
2454	kmem_cache_destroy(exception_cache);
2455bad_exception_cache:
2456	exit_origin_hash();
2457bad_origin_hash:
2458	dm_unregister_target(&merge_target);
2459bad_register_merge_target:
2460	dm_unregister_target(&origin_target);
2461bad_register_origin_target:
2462	dm_unregister_target(&snapshot_target);
2463bad_register_snapshot_target:
 
 
 
 
 
 
2464	dm_exception_store_exit();
2465
2466	return r;
2467}
2468
2469static void __exit dm_snapshot_exit(void)
2470{
2471	dm_unregister_target(&snapshot_target);
2472	dm_unregister_target(&origin_target);
2473	dm_unregister_target(&merge_target);
2474
2475	exit_origin_hash();
2476	kmem_cache_destroy(pending_cache);
2477	kmem_cache_destroy(exception_cache);
2478
2479	dm_exception_store_exit();
2480}
2481
2482/* Module hooks */
2483module_init(dm_snapshot_init);
2484module_exit(dm_snapshot_exit);
2485
2486MODULE_DESCRIPTION(DM_NAME " snapshot target");
2487MODULE_AUTHOR("Joe Thornber");
2488MODULE_LICENSE("GPL");
2489MODULE_ALIAS("dm-snapshot-origin");
2490MODULE_ALIAS("dm-snapshot-merge");