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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.4 *5 * This file is released under the GPL.6 */7 8#include <linux/blkdev.h>9#include <linux/device-mapper.h>10#include <linux/delay.h>11#include <linux/fs.h>12#include <linux/init.h>13#include <linux/kdev_t.h>14#include <linux/list.h>15#include <linux/list_bl.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 25638 39#define DM_TRACKED_CHUNK_HASH_SIZE 1640#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 int hash_shift;46 struct hlist_bl_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 need69 * 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 spinlock_t pe_allocation_lock;79 80 /* Protected by "pe_allocation_lock" */81 sector_t exception_start_sequence;82 83 /* Protected by kcopyd single-threaded callback */84 sector_t exception_complete_sequence;85 86 /*87 * A list of pending exceptions that completed out of order.88 * Protected by kcopyd single-threaded callback.89 */90 struct rb_root out_of_order_tree;91 92 mempool_t pending_pool;93 94 struct dm_exception_table pending;95 struct dm_exception_table complete;96 97 /*98 * pe_lock protects all pending_exception operations and access99 * as well as the snapshot_bios list.100 */101 spinlock_t pe_lock;102 103 /* Chunks with outstanding reads */104 spinlock_t tracked_chunk_lock;105 struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];106 107 /* The on disk metadata handler */108 struct dm_exception_store *store;109 110 unsigned int in_progress;111 struct wait_queue_head in_progress_wait;112 113 struct dm_kcopyd_client *kcopyd_client;114 115 /* Wait for events based on state_bits */116 unsigned long state_bits;117 118 /* Range of chunks currently being merged. */119 chunk_t first_merging_chunk;120 int num_merging_chunks;121 122 /*123 * The merge operation failed if this flag is set.124 * Failure modes are handled as follows:125 * - I/O error reading the header126 * => don't load the target; abort.127 * - Header does not have "valid" flag set128 * => use the origin; forget about the snapshot.129 * - I/O error when reading exceptions130 * => don't load the target; abort.131 * (We can't use the intermediate origin state.)132 * - I/O error while merging133 * => stop merging; set merge_failed; process I/O normally.134 */135 bool merge_failed:1;136 137 bool discard_zeroes_cow:1;138 bool discard_passdown_origin:1;139 140 /*141 * Incoming bios that overlap with chunks being merged must wait142 * for them to be committed.143 */144 struct bio_list bios_queued_during_merge;145};146 147/*148 * state_bits:149 * RUNNING_MERGE - Merge operation is in progress.150 * SHUTDOWN_MERGE - Set to signal that merge needs to be stopped;151 * cleared afterwards.152 */153#define RUNNING_MERGE 0154#define SHUTDOWN_MERGE 1155 156/*157 * Maximum number of chunks being copied on write.158 *159 * The value was decided experimentally as a trade-off between memory160 * consumption, stalling the kernel's workqueues and maintaining a high enough161 * throughput.162 */163#define DEFAULT_COW_THRESHOLD 2048164 165static unsigned int cow_threshold = DEFAULT_COW_THRESHOLD;166module_param_named(snapshot_cow_threshold, cow_threshold, uint, 0644);167MODULE_PARM_DESC(snapshot_cow_threshold, "Maximum number of chunks being copied on write");168 169DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(snapshot_copy_throttle,170 "A percentage of time allocated for copy on write");171 172struct dm_dev *dm_snap_origin(struct dm_snapshot *s)173{174 return s->origin;175}176EXPORT_SYMBOL(dm_snap_origin);177 178struct dm_dev *dm_snap_cow(struct dm_snapshot *s)179{180 return s->cow;181}182EXPORT_SYMBOL(dm_snap_cow);183 184static sector_t chunk_to_sector(struct dm_exception_store *store,185 chunk_t chunk)186{187 return chunk << store->chunk_shift;188}189 190static int bdev_equal(struct block_device *lhs, struct block_device *rhs)191{192 /*193 * There is only ever one instance of a particular block194 * device so we can compare pointers safely.195 */196 return lhs == rhs;197}198 199struct dm_snap_pending_exception {200 struct dm_exception e;201 202 /*203 * Origin buffers waiting for this to complete are held204 * in a bio list205 */206 struct bio_list origin_bios;207 struct bio_list snapshot_bios;208 209 /* Pointer back to snapshot context */210 struct dm_snapshot *snap;211 212 /*213 * 1 indicates the exception has already been sent to214 * kcopyd.215 */216 int started;217 218 /* There was copying error. */219 int copy_error;220 221 /* A sequence number, it is used for in-order completion. */222 sector_t exception_sequence;223 224 struct rb_node out_of_order_node;225 226 /*227 * For writing a complete chunk, bypassing the copy.228 */229 struct bio *full_bio;230 bio_end_io_t *full_bio_end_io;231};232 233/*234 * Hash table mapping origin volumes to lists of snapshots and235 * a lock to protect it236 */237static struct kmem_cache *exception_cache;238static struct kmem_cache *pending_cache;239 240struct dm_snap_tracked_chunk {241 struct hlist_node node;242 chunk_t chunk;243};244 245static void init_tracked_chunk(struct bio *bio)246{247 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));248 249 INIT_HLIST_NODE(&c->node);250}251 252static bool is_bio_tracked(struct bio *bio)253{254 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));255 256 return !hlist_unhashed(&c->node);257}258 259static void track_chunk(struct dm_snapshot *s, struct bio *bio, chunk_t chunk)260{261 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));262 263 c->chunk = chunk;264 265 spin_lock_irq(&s->tracked_chunk_lock);266 hlist_add_head(&c->node,267 &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]);268 spin_unlock_irq(&s->tracked_chunk_lock);269}270 271static void stop_tracking_chunk(struct dm_snapshot *s, struct bio *bio)272{273 struct dm_snap_tracked_chunk *c = dm_per_bio_data(bio, sizeof(struct dm_snap_tracked_chunk));274 unsigned long flags;275 276 spin_lock_irqsave(&s->tracked_chunk_lock, flags);277 hlist_del(&c->node);278 spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);279}280 281static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk)282{283 struct dm_snap_tracked_chunk *c;284 int found = 0;285 286 spin_lock_irq(&s->tracked_chunk_lock);287 288 hlist_for_each_entry(c,289 &s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)], node) {290 if (c->chunk == chunk) {291 found = 1;292 break;293 }294 }295 296 spin_unlock_irq(&s->tracked_chunk_lock);297 298 return found;299}300 301/*302 * This conflicting I/O is extremely improbable in the caller,303 * so fsleep(1000) is sufficient and there is no need for a wait queue.304 */305static void __check_for_conflicting_io(struct dm_snapshot *s, chunk_t chunk)306{307 while (__chunk_is_tracked(s, chunk))308 fsleep(1000);309}310 311/*312 * One of these per registered origin, held in the snapshot_origins hash313 */314struct origin {315 /* The origin device */316 struct block_device *bdev;317 318 struct list_head hash_list;319 320 /* List of snapshots for this origin */321 struct list_head snapshots;322};323 324/*325 * This structure is allocated for each origin target326 */327struct dm_origin {328 struct dm_dev *dev;329 struct dm_target *ti;330 unsigned int split_boundary;331 struct list_head hash_list;332};333 334/*335 * Size of the hash table for origin volumes. If we make this336 * the size of the minors list then it should be nearly perfect337 */338#define ORIGIN_HASH_SIZE 256339#define ORIGIN_MASK 0xFF340static struct list_head *_origins;341static struct list_head *_dm_origins;342static struct rw_semaphore _origins_lock;343 344static DECLARE_WAIT_QUEUE_HEAD(_pending_exceptions_done);345static DEFINE_SPINLOCK(_pending_exceptions_done_spinlock);346static uint64_t _pending_exceptions_done_count;347 348static int init_origin_hash(void)349{350 int i;351 352 _origins = kmalloc_array(ORIGIN_HASH_SIZE, sizeof(struct list_head),353 GFP_KERNEL);354 if (!_origins) {355 DMERR("unable to allocate memory for _origins");356 return -ENOMEM;357 }358 for (i = 0; i < ORIGIN_HASH_SIZE; i++)359 INIT_LIST_HEAD(_origins + i);360 361 _dm_origins = kmalloc_array(ORIGIN_HASH_SIZE,362 sizeof(struct list_head),363 GFP_KERNEL);364 if (!_dm_origins) {365 DMERR("unable to allocate memory for _dm_origins");366 kfree(_origins);367 return -ENOMEM;368 }369 for (i = 0; i < ORIGIN_HASH_SIZE; i++)370 INIT_LIST_HEAD(_dm_origins + i);371 372 init_rwsem(&_origins_lock);373 374 return 0;375}376 377static void exit_origin_hash(void)378{379 kfree(_origins);380 kfree(_dm_origins);381}382 383static unsigned int origin_hash(struct block_device *bdev)384{385 return bdev->bd_dev & ORIGIN_MASK;386}387 388static struct origin *__lookup_origin(struct block_device *origin)389{390 struct list_head *ol;391 struct origin *o;392 393 ol = &_origins[origin_hash(origin)];394 list_for_each_entry(o, ol, hash_list)395 if (bdev_equal(o->bdev, origin))396 return o;397 398 return NULL;399}400 401static void __insert_origin(struct origin *o)402{403 struct list_head *sl = &_origins[origin_hash(o->bdev)];404 405 list_add_tail(&o->hash_list, sl);406}407 408static struct dm_origin *__lookup_dm_origin(struct block_device *origin)409{410 struct list_head *ol;411 struct dm_origin *o;412 413 ol = &_dm_origins[origin_hash(origin)];414 list_for_each_entry(o, ol, hash_list)415 if (bdev_equal(o->dev->bdev, origin))416 return o;417 418 return NULL;419}420 421static void __insert_dm_origin(struct dm_origin *o)422{423 struct list_head *sl = &_dm_origins[origin_hash(o->dev->bdev)];424 425 list_add_tail(&o->hash_list, sl);426}427 428static void __remove_dm_origin(struct dm_origin *o)429{430 list_del(&o->hash_list);431}432 433/*434 * _origins_lock must be held when calling this function.435 * Returns number of snapshots registered using the supplied cow device, plus:436 * snap_src - a snapshot suitable for use as a source of exception handover437 * snap_dest - a snapshot capable of receiving exception handover.438 * snap_merge - an existing snapshot-merge target linked to the same origin.439 * There can be at most one snapshot-merge target. The parameter is optional.440 *441 * Possible return values and states of snap_src and snap_dest.442 * 0: NULL, NULL - first new snapshot443 * 1: snap_src, NULL - normal snapshot444 * 2: snap_src, snap_dest - waiting for handover445 * 2: snap_src, NULL - handed over, waiting for old to be deleted446 * 1: NULL, snap_dest - source got destroyed without handover447 */448static int __find_snapshots_sharing_cow(struct dm_snapshot *snap,449 struct dm_snapshot **snap_src,450 struct dm_snapshot **snap_dest,451 struct dm_snapshot **snap_merge)452{453 struct dm_snapshot *s;454 struct origin *o;455 int count = 0;456 int active;457 458 o = __lookup_origin(snap->origin->bdev);459 if (!o)460 goto out;461 462 list_for_each_entry(s, &o->snapshots, list) {463 if (dm_target_is_snapshot_merge(s->ti) && snap_merge)464 *snap_merge = s;465 if (!bdev_equal(s->cow->bdev, snap->cow->bdev))466 continue;467 468 down_read(&s->lock);469 active = s->active;470 up_read(&s->lock);471 472 if (active) {473 if (snap_src)474 *snap_src = s;475 } else if (snap_dest)476 *snap_dest = s;477 478 count++;479 }480 481out:482 return count;483}484 485/*486 * On success, returns 1 if this snapshot is a handover destination,487 * otherwise returns 0.488 */489static int __validate_exception_handover(struct dm_snapshot *snap)490{491 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;492 struct dm_snapshot *snap_merge = NULL;493 494 /* Does snapshot need exceptions handed over to it? */495 if ((__find_snapshots_sharing_cow(snap, &snap_src, &snap_dest,496 &snap_merge) == 2) ||497 snap_dest) {498 snap->ti->error = "Snapshot cow pairing for exception table handover failed";499 return -EINVAL;500 }501 502 /*503 * If no snap_src was found, snap cannot become a handover504 * destination.505 */506 if (!snap_src)507 return 0;508 509 /*510 * Non-snapshot-merge handover?511 */512 if (!dm_target_is_snapshot_merge(snap->ti))513 return 1;514 515 /*516 * Do not allow more than one merging snapshot.517 */518 if (snap_merge) {519 snap->ti->error = "A snapshot is already merging.";520 return -EINVAL;521 }522 523 if (!snap_src->store->type->prepare_merge ||524 !snap_src->store->type->commit_merge) {525 snap->ti->error = "Snapshot exception store does not support snapshot-merge.";526 return -EINVAL;527 }528 529 return 1;530}531 532static void __insert_snapshot(struct origin *o, struct dm_snapshot *s)533{534 struct dm_snapshot *l;535 536 /* Sort the list according to chunk size, largest-first smallest-last */537 list_for_each_entry(l, &o->snapshots, list)538 if (l->store->chunk_size < s->store->chunk_size)539 break;540 list_add_tail(&s->list, &l->list);541}542 543/*544 * Make a note of the snapshot and its origin so we can look it545 * up when the origin has a write on it.546 *547 * Also validate snapshot exception store handovers.548 * On success, returns 1 if this registration is a handover destination,549 * otherwise returns 0.550 */551static int register_snapshot(struct dm_snapshot *snap)552{553 struct origin *o, *new_o = NULL;554 struct block_device *bdev = snap->origin->bdev;555 int r = 0;556 557 new_o = kmalloc(sizeof(*new_o), GFP_KERNEL);558 if (!new_o)559 return -ENOMEM;560 561 down_write(&_origins_lock);562 563 r = __validate_exception_handover(snap);564 if (r < 0) {565 kfree(new_o);566 goto out;567 }568 569 o = __lookup_origin(bdev);570 if (o)571 kfree(new_o);572 else {573 /* New origin */574 o = new_o;575 576 /* Initialise the struct */577 INIT_LIST_HEAD(&o->snapshots);578 o->bdev = bdev;579 580 __insert_origin(o);581 }582 583 __insert_snapshot(o, snap);584 585out:586 up_write(&_origins_lock);587 588 return r;589}590 591/*592 * Move snapshot to correct place in list according to chunk size.593 */594static void reregister_snapshot(struct dm_snapshot *s)595{596 struct block_device *bdev = s->origin->bdev;597 598 down_write(&_origins_lock);599 600 list_del(&s->list);601 __insert_snapshot(__lookup_origin(bdev), s);602 603 up_write(&_origins_lock);604}605 606static void unregister_snapshot(struct dm_snapshot *s)607{608 struct origin *o;609 610 down_write(&_origins_lock);611 o = __lookup_origin(s->origin->bdev);612 613 list_del(&s->list);614 if (o && list_empty(&o->snapshots)) {615 list_del(&o->hash_list);616 kfree(o);617 }618 619 up_write(&_origins_lock);620}621 622/*623 * Implementation of the exception hash tables.624 * The lowest hash_shift bits of the chunk number are ignored, allowing625 * some consecutive chunks to be grouped together.626 */627static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk);628 629/* Lock to protect access to the completed and pending exception hash tables. */630struct dm_exception_table_lock {631 struct hlist_bl_head *complete_slot;632 struct hlist_bl_head *pending_slot;633};634 635static void dm_exception_table_lock_init(struct dm_snapshot *s, chunk_t chunk,636 struct dm_exception_table_lock *lock)637{638 struct dm_exception_table *complete = &s->complete;639 struct dm_exception_table *pending = &s->pending;640 641 lock->complete_slot = &complete->table[exception_hash(complete, chunk)];642 lock->pending_slot = &pending->table[exception_hash(pending, chunk)];643}644 645static void dm_exception_table_lock(struct dm_exception_table_lock *lock)646{647 hlist_bl_lock(lock->complete_slot);648 hlist_bl_lock(lock->pending_slot);649}650 651static void dm_exception_table_unlock(struct dm_exception_table_lock *lock)652{653 hlist_bl_unlock(lock->pending_slot);654 hlist_bl_unlock(lock->complete_slot);655}656 657static int dm_exception_table_init(struct dm_exception_table *et,658 uint32_t size, unsigned int hash_shift)659{660 unsigned int i;661 662 et->hash_shift = hash_shift;663 et->hash_mask = size - 1;664 et->table = kvmalloc_array(size, sizeof(struct hlist_bl_head),665 GFP_KERNEL);666 if (!et->table)667 return -ENOMEM;668 669 for (i = 0; i < size; i++)670 INIT_HLIST_BL_HEAD(et->table + i);671 672 return 0;673}674 675static void dm_exception_table_exit(struct dm_exception_table *et,676 struct kmem_cache *mem)677{678 struct hlist_bl_head *slot;679 struct dm_exception *ex;680 struct hlist_bl_node *pos, *n;681 int i, size;682 683 size = et->hash_mask + 1;684 for (i = 0; i < size; i++) {685 slot = et->table + i;686 687 hlist_bl_for_each_entry_safe(ex, pos, n, slot, hash_list) {688 kmem_cache_free(mem, ex);689 cond_resched();690 }691 }692 693 kvfree(et->table);694}695 696static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk)697{698 return (chunk >> et->hash_shift) & et->hash_mask;699}700 701static void dm_remove_exception(struct dm_exception *e)702{703 hlist_bl_del(&e->hash_list);704}705 706/*707 * Return the exception data for a sector, or NULL if not708 * remapped.709 */710static struct dm_exception *dm_lookup_exception(struct dm_exception_table *et,711 chunk_t chunk)712{713 struct hlist_bl_head *slot;714 struct hlist_bl_node *pos;715 struct dm_exception *e;716 717 slot = &et->table[exception_hash(et, chunk)];718 hlist_bl_for_each_entry(e, pos, slot, hash_list)719 if (chunk >= e->old_chunk &&720 chunk <= e->old_chunk + dm_consecutive_chunk_count(e))721 return e;722 723 return NULL;724}725 726static struct dm_exception *alloc_completed_exception(gfp_t gfp)727{728 struct dm_exception *e;729 730 e = kmem_cache_alloc(exception_cache, gfp);731 if (!e && gfp == GFP_NOIO)732 e = kmem_cache_alloc(exception_cache, GFP_ATOMIC);733 734 return e;735}736 737static void free_completed_exception(struct dm_exception *e)738{739 kmem_cache_free(exception_cache, e);740}741 742static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snapshot *s)743{744 struct dm_snap_pending_exception *pe = mempool_alloc(&s->pending_pool,745 GFP_NOIO);746 747 atomic_inc(&s->pending_exceptions_count);748 pe->snap = s;749 750 return pe;751}752 753static void free_pending_exception(struct dm_snap_pending_exception *pe)754{755 struct dm_snapshot *s = pe->snap;756 757 mempool_free(pe, &s->pending_pool);758 smp_mb__before_atomic();759 atomic_dec(&s->pending_exceptions_count);760}761 762static void dm_insert_exception(struct dm_exception_table *eh,763 struct dm_exception *new_e)764{765 struct hlist_bl_head *l;766 struct hlist_bl_node *pos;767 struct dm_exception *e = NULL;768 769 l = &eh->table[exception_hash(eh, new_e->old_chunk)];770 771 /* Add immediately if this table doesn't support consecutive chunks */772 if (!eh->hash_shift)773 goto out;774 775 /* List is ordered by old_chunk */776 hlist_bl_for_each_entry(e, pos, l, hash_list) {777 /* Insert after an existing chunk? */778 if (new_e->old_chunk == (e->old_chunk +779 dm_consecutive_chunk_count(e) + 1) &&780 new_e->new_chunk == (dm_chunk_number(e->new_chunk) +781 dm_consecutive_chunk_count(e) + 1)) {782 dm_consecutive_chunk_count_inc(e);783 free_completed_exception(new_e);784 return;785 }786 787 /* Insert before an existing chunk? */788 if (new_e->old_chunk == (e->old_chunk - 1) &&789 new_e->new_chunk == (dm_chunk_number(e->new_chunk) - 1)) {790 dm_consecutive_chunk_count_inc(e);791 e->old_chunk--;792 e->new_chunk--;793 free_completed_exception(new_e);794 return;795 }796 797 if (new_e->old_chunk < e->old_chunk)798 break;799 }800 801out:802 if (!e) {803 /*804 * Either the table doesn't support consecutive chunks or slot805 * l is empty.806 */807 hlist_bl_add_head(&new_e->hash_list, l);808 } else if (new_e->old_chunk < e->old_chunk) {809 /* Add before an existing exception */810 hlist_bl_add_before(&new_e->hash_list, &e->hash_list);811 } else {812 /* Add to l's tail: e is the last exception in this slot */813 hlist_bl_add_behind(&new_e->hash_list, &e->hash_list);814 }815}816 817/*818 * Callback used by the exception stores to load exceptions when819 * initialising.820 */821static int dm_add_exception(void *context, chunk_t old, chunk_t new)822{823 struct dm_exception_table_lock lock;824 struct dm_snapshot *s = context;825 struct dm_exception *e;826 827 e = alloc_completed_exception(GFP_KERNEL);828 if (!e)829 return -ENOMEM;830 831 e->old_chunk = old;832 833 /* Consecutive_count is implicitly initialised to zero */834 e->new_chunk = new;835 836 /*837 * Although there is no need to lock access to the exception tables838 * here, if we don't then hlist_bl_add_head(), called by839 * dm_insert_exception(), will complain about accessing the840 * corresponding list without locking it first.841 */842 dm_exception_table_lock_init(s, old, &lock);843 844 dm_exception_table_lock(&lock);845 dm_insert_exception(&s->complete, e);846 dm_exception_table_unlock(&lock);847 848 return 0;849}850 851/*852 * Return a minimum chunk size of all snapshots that have the specified origin.853 * Return zero if the origin has no snapshots.854 */855static uint32_t __minimum_chunk_size(struct origin *o)856{857 struct dm_snapshot *snap;858 unsigned int chunk_size = rounddown_pow_of_two(UINT_MAX);859 860 if (o)861 list_for_each_entry(snap, &o->snapshots, list)862 chunk_size = min_not_zero(chunk_size,863 snap->store->chunk_size);864 865 return (uint32_t) chunk_size;866}867 868/*869 * Hard coded magic.870 */871static int calc_max_buckets(void)872{873 /* use a fixed size of 2MB */874 unsigned long mem = 2 * 1024 * 1024;875 876 mem /= sizeof(struct hlist_bl_head);877 878 return mem;879}880 881/*882 * Allocate room for a suitable hash table.883 */884static int init_hash_tables(struct dm_snapshot *s)885{886 sector_t hash_size, cow_dev_size, max_buckets;887 888 /*889 * Calculate based on the size of the original volume or890 * the COW volume...891 */892 cow_dev_size = get_dev_size(s->cow->bdev);893 max_buckets = calc_max_buckets();894 895 hash_size = cow_dev_size >> s->store->chunk_shift;896 hash_size = min(hash_size, max_buckets);897 898 if (hash_size < 64)899 hash_size = 64;900 hash_size = rounddown_pow_of_two(hash_size);901 if (dm_exception_table_init(&s->complete, hash_size,902 DM_CHUNK_CONSECUTIVE_BITS))903 return -ENOMEM;904 905 /*906 * Allocate hash table for in-flight exceptions907 * Make this smaller than the real hash table908 */909 hash_size >>= 3;910 if (hash_size < 64)911 hash_size = 64;912 913 if (dm_exception_table_init(&s->pending, hash_size, 0)) {914 dm_exception_table_exit(&s->complete, exception_cache);915 return -ENOMEM;916 }917 918 return 0;919}920 921static void merge_shutdown(struct dm_snapshot *s)922{923 clear_bit_unlock(RUNNING_MERGE, &s->state_bits);924 smp_mb__after_atomic();925 wake_up_bit(&s->state_bits, RUNNING_MERGE);926}927 928static struct bio *__release_queued_bios_after_merge(struct dm_snapshot *s)929{930 s->first_merging_chunk = 0;931 s->num_merging_chunks = 0;932 933 return bio_list_get(&s->bios_queued_during_merge);934}935 936/*937 * Remove one chunk from the index of completed exceptions.938 */939static int __remove_single_exception_chunk(struct dm_snapshot *s,940 chunk_t old_chunk)941{942 struct dm_exception *e;943 944 e = dm_lookup_exception(&s->complete, old_chunk);945 if (!e) {946 DMERR("Corruption detected: exception for block %llu is on disk but not in memory",947 (unsigned long long)old_chunk);948 return -EINVAL;949 }950 951 /*952 * If this is the only chunk using this exception, remove exception.953 */954 if (!dm_consecutive_chunk_count(e)) {955 dm_remove_exception(e);956 free_completed_exception(e);957 return 0;958 }959 960 /*961 * The chunk may be either at the beginning or the end of a962 * group of consecutive chunks - never in the middle. We are963 * removing chunks in the opposite order to that in which they964 * were added, so this should always be true.965 * Decrement the consecutive chunk counter and adjust the966 * starting point if necessary.967 */968 if (old_chunk == e->old_chunk) {969 e->old_chunk++;970 e->new_chunk++;971 } else if (old_chunk != e->old_chunk +972 dm_consecutive_chunk_count(e)) {973 DMERR("Attempt to merge block %llu from the middle of a chunk range [%llu - %llu]",974 (unsigned long long)old_chunk,975 (unsigned long long)e->old_chunk,976 (unsigned long long)977 e->old_chunk + dm_consecutive_chunk_count(e));978 return -EINVAL;979 }980 981 dm_consecutive_chunk_count_dec(e);982 983 return 0;984}985 986static void flush_bios(struct bio *bio);987 988static int remove_single_exception_chunk(struct dm_snapshot *s)989{990 struct bio *b = NULL;991 int r;992 chunk_t old_chunk = s->first_merging_chunk + s->num_merging_chunks - 1;993 994 down_write(&s->lock);995 996 /*997 * Process chunks (and associated exceptions) in reverse order998 * so that dm_consecutive_chunk_count_dec() accounting works.999 */1000 do {1001 r = __remove_single_exception_chunk(s, old_chunk);1002 if (r)1003 goto out;1004 } while (old_chunk-- > s->first_merging_chunk);1005 1006 b = __release_queued_bios_after_merge(s);1007 1008out:1009 up_write(&s->lock);1010 if (b)1011 flush_bios(b);1012 1013 return r;1014}1015 1016static int origin_write_extent(struct dm_snapshot *merging_snap,1017 sector_t sector, unsigned int chunk_size);1018 1019static void merge_callback(int read_err, unsigned long write_err,1020 void *context);1021 1022static uint64_t read_pending_exceptions_done_count(void)1023{1024 uint64_t pending_exceptions_done;1025 1026 spin_lock(&_pending_exceptions_done_spinlock);1027 pending_exceptions_done = _pending_exceptions_done_count;1028 spin_unlock(&_pending_exceptions_done_spinlock);1029 1030 return pending_exceptions_done;1031}1032 1033static void increment_pending_exceptions_done_count(void)1034{1035 spin_lock(&_pending_exceptions_done_spinlock);1036 _pending_exceptions_done_count++;1037 spin_unlock(&_pending_exceptions_done_spinlock);1038 1039 wake_up_all(&_pending_exceptions_done);1040}1041 1042static void snapshot_merge_next_chunks(struct dm_snapshot *s)1043{1044 int i, linear_chunks;1045 chunk_t old_chunk, new_chunk;1046 struct dm_io_region src, dest;1047 sector_t io_size;1048 uint64_t previous_count;1049 1050 BUG_ON(!test_bit(RUNNING_MERGE, &s->state_bits));1051 if (unlikely(test_bit(SHUTDOWN_MERGE, &s->state_bits)))1052 goto shut;1053 1054 /*1055 * valid flag never changes during merge, so no lock required.1056 */1057 if (!s->valid) {1058 DMERR("Snapshot is invalid: can't merge");1059 goto shut;1060 }1061 1062 linear_chunks = s->store->type->prepare_merge(s->store, &old_chunk,1063 &new_chunk);1064 if (linear_chunks <= 0) {1065 if (linear_chunks < 0) {1066 DMERR("Read error in exception store: shutting down merge");1067 down_write(&s->lock);1068 s->merge_failed = true;1069 up_write(&s->lock);1070 }1071 goto shut;1072 }1073 1074 /* Adjust old_chunk and new_chunk to reflect start of linear region */1075 old_chunk = old_chunk + 1 - linear_chunks;1076 new_chunk = new_chunk + 1 - linear_chunks;1077 1078 /*1079 * Use one (potentially large) I/O to copy all 'linear_chunks'1080 * from the exception store to the origin1081 */1082 io_size = linear_chunks * s->store->chunk_size;1083 1084 dest.bdev = s->origin->bdev;1085 dest.sector = chunk_to_sector(s->store, old_chunk);1086 dest.count = min(io_size, get_dev_size(dest.bdev) - dest.sector);1087 1088 src.bdev = s->cow->bdev;1089 src.sector = chunk_to_sector(s->store, new_chunk);1090 src.count = dest.count;1091 1092 /*1093 * Reallocate any exceptions needed in other snapshots then1094 * wait for the pending exceptions to complete.1095 * Each time any pending exception (globally on the system)1096 * completes we are woken and repeat the process to find out1097 * if we can proceed. While this may not seem a particularly1098 * efficient algorithm, it is not expected to have any1099 * significant impact on performance.1100 */1101 previous_count = read_pending_exceptions_done_count();1102 while (origin_write_extent(s, dest.sector, io_size)) {1103 wait_event(_pending_exceptions_done,1104 (read_pending_exceptions_done_count() !=1105 previous_count));1106 /* Retry after the wait, until all exceptions are done. */1107 previous_count = read_pending_exceptions_done_count();1108 }1109 1110 down_write(&s->lock);1111 s->first_merging_chunk = old_chunk;1112 s->num_merging_chunks = linear_chunks;1113 up_write(&s->lock);1114 1115 /* Wait until writes to all 'linear_chunks' drain */1116 for (i = 0; i < linear_chunks; i++)1117 __check_for_conflicting_io(s, old_chunk + i);1118 1119 dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, merge_callback, s);1120 return;1121 1122shut:1123 merge_shutdown(s);1124}1125 1126static void error_bios(struct bio *bio);1127 1128static void merge_callback(int read_err, unsigned long write_err, void *context)1129{1130 struct dm_snapshot *s = context;1131 struct bio *b = NULL;1132 1133 if (read_err || write_err) {1134 if (read_err)1135 DMERR("Read error: shutting down merge.");1136 else1137 DMERR("Write error: shutting down merge.");1138 goto shut;1139 }1140 1141 if (blkdev_issue_flush(s->origin->bdev) < 0) {1142 DMERR("Flush after merge failed: shutting down merge");1143 goto shut;1144 }1145 1146 if (s->store->type->commit_merge(s->store,1147 s->num_merging_chunks) < 0) {1148 DMERR("Write error in exception store: shutting down merge");1149 goto shut;1150 }1151 1152 if (remove_single_exception_chunk(s) < 0)1153 goto shut;1154 1155 snapshot_merge_next_chunks(s);1156 1157 return;1158 1159shut:1160 down_write(&s->lock);1161 s->merge_failed = true;1162 b = __release_queued_bios_after_merge(s);1163 up_write(&s->lock);1164 error_bios(b);1165 1166 merge_shutdown(s);1167}1168 1169static void start_merge(struct dm_snapshot *s)1170{1171 if (!test_and_set_bit(RUNNING_MERGE, &s->state_bits))1172 snapshot_merge_next_chunks(s);1173}1174 1175/*1176 * Stop the merging process and wait until it finishes.1177 */1178static void stop_merge(struct dm_snapshot *s)1179{1180 set_bit(SHUTDOWN_MERGE, &s->state_bits);1181 wait_on_bit(&s->state_bits, RUNNING_MERGE, TASK_UNINTERRUPTIBLE);1182 clear_bit(SHUTDOWN_MERGE, &s->state_bits);1183}1184 1185static int parse_snapshot_features(struct dm_arg_set *as, struct dm_snapshot *s,1186 struct dm_target *ti)1187{1188 int r;1189 unsigned int argc;1190 const char *arg_name;1191 1192 static const struct dm_arg _args[] = {1193 {0, 2, "Invalid number of feature arguments"},1194 };1195 1196 /*1197 * No feature arguments supplied.1198 */1199 if (!as->argc)1200 return 0;1201 1202 r = dm_read_arg_group(_args, as, &argc, &ti->error);1203 if (r)1204 return -EINVAL;1205 1206 while (argc && !r) {1207 arg_name = dm_shift_arg(as);1208 argc--;1209 1210 if (!strcasecmp(arg_name, "discard_zeroes_cow"))1211 s->discard_zeroes_cow = true;1212 1213 else if (!strcasecmp(arg_name, "discard_passdown_origin"))1214 s->discard_passdown_origin = true;1215 1216 else {1217 ti->error = "Unrecognised feature requested";1218 r = -EINVAL;1219 break;1220 }1221 }1222 1223 if (!s->discard_zeroes_cow && s->discard_passdown_origin) {1224 /*1225 * TODO: really these are disjoint.. but ti->num_discard_bios1226 * and dm_bio_get_target_bio_nr() require rigid constraints.1227 */1228 ti->error = "discard_passdown_origin feature depends on discard_zeroes_cow";1229 r = -EINVAL;1230 }1231 1232 return r;1233}1234 1235/*1236 * Construct a snapshot mapping:1237 * <origin_dev> <COW-dev> <p|po|n> <chunk-size> [<# feature args> [<arg>]*]1238 */1239static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)1240{1241 struct dm_snapshot *s;1242 struct dm_arg_set as;1243 int i;1244 int r = -EINVAL;1245 char *origin_path, *cow_path;1246 unsigned int args_used, num_flush_bios = 1;1247 blk_mode_t origin_mode = BLK_OPEN_READ;1248 1249 if (argc < 4) {1250 ti->error = "requires 4 or more arguments";1251 r = -EINVAL;1252 goto bad;1253 }1254 1255 if (dm_target_is_snapshot_merge(ti)) {1256 num_flush_bios = 2;1257 origin_mode = BLK_OPEN_WRITE;1258 }1259 1260 s = kzalloc(sizeof(*s), GFP_KERNEL);1261 if (!s) {1262 ti->error = "Cannot allocate private snapshot structure";1263 r = -ENOMEM;1264 goto bad;1265 }1266 1267 as.argc = argc;1268 as.argv = argv;1269 dm_consume_args(&as, 4);1270 r = parse_snapshot_features(&as, s, ti);1271 if (r)1272 goto bad_features;1273 1274 origin_path = argv[0];1275 argv++;1276 argc--;1277 1278 r = dm_get_device(ti, origin_path, origin_mode, &s->origin);1279 if (r) {1280 ti->error = "Cannot get origin device";1281 goto bad_origin;1282 }1283 1284 cow_path = argv[0];1285 argv++;1286 argc--;1287 1288 r = dm_get_device(ti, cow_path, dm_table_get_mode(ti->table), &s->cow);1289 if (r) {1290 ti->error = "Cannot get COW device";1291 goto bad_cow;1292 }1293 if (s->cow->bdev && s->cow->bdev == s->origin->bdev) {1294 ti->error = "COW device cannot be the same as origin device";1295 r = -EINVAL;1296 goto bad_store;1297 }1298 1299 r = dm_exception_store_create(ti, argc, argv, s, &args_used, &s->store);1300 if (r) {1301 ti->error = "Couldn't create exception store";1302 r = -EINVAL;1303 goto bad_store;1304 }1305 1306 argv += args_used;1307 argc -= args_used;1308 1309 s->ti = ti;1310 s->valid = 1;1311 s->snapshot_overflowed = 0;1312 s->active = 0;1313 atomic_set(&s->pending_exceptions_count, 0);1314 spin_lock_init(&s->pe_allocation_lock);1315 s->exception_start_sequence = 0;1316 s->exception_complete_sequence = 0;1317 s->out_of_order_tree = RB_ROOT;1318 init_rwsem(&s->lock);1319 INIT_LIST_HEAD(&s->list);1320 spin_lock_init(&s->pe_lock);1321 s->state_bits = 0;1322 s->merge_failed = false;1323 s->first_merging_chunk = 0;1324 s->num_merging_chunks = 0;1325 bio_list_init(&s->bios_queued_during_merge);1326 1327 /* Allocate hash table for COW data */1328 if (init_hash_tables(s)) {1329 ti->error = "Unable to allocate hash table space";1330 r = -ENOMEM;1331 goto bad_hash_tables;1332 }1333 1334 init_waitqueue_head(&s->in_progress_wait);1335 1336 s->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle);1337 if (IS_ERR(s->kcopyd_client)) {1338 r = PTR_ERR(s->kcopyd_client);1339 ti->error = "Could not create kcopyd client";1340 goto bad_kcopyd;1341 }1342 1343 r = mempool_init_slab_pool(&s->pending_pool, MIN_IOS, pending_cache);1344 if (r) {1345 ti->error = "Could not allocate mempool for pending exceptions";1346 goto bad_pending_pool;1347 }1348 1349 for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)1350 INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);1351 1352 spin_lock_init(&s->tracked_chunk_lock);1353 1354 ti->private = s;1355 ti->num_flush_bios = num_flush_bios;1356 if (s->discard_zeroes_cow)1357 ti->num_discard_bios = (s->discard_passdown_origin ? 2 : 1);1358 ti->per_io_data_size = sizeof(struct dm_snap_tracked_chunk);1359 1360 /* Add snapshot to the list of snapshots for this origin */1361 /* Exceptions aren't triggered till snapshot_resume() is called */1362 r = register_snapshot(s);1363 if (r == -ENOMEM) {1364 ti->error = "Snapshot origin struct allocation failed";1365 goto bad_load_and_register;1366 } else if (r < 0) {1367 /* invalid handover, register_snapshot has set ti->error */1368 goto bad_load_and_register;1369 }1370 1371 /*1372 * Metadata must only be loaded into one table at once, so skip this1373 * if metadata will be handed over during resume.1374 * Chunk size will be set during the handover - set it to zero to1375 * ensure it's ignored.1376 */1377 if (r > 0) {1378 s->store->chunk_size = 0;1379 return 0;1380 }1381 1382 r = s->store->type->read_metadata(s->store, dm_add_exception,1383 (void *)s);1384 if (r < 0) {1385 ti->error = "Failed to read snapshot metadata";1386 goto bad_read_metadata;1387 } else if (r > 0) {1388 s->valid = 0;1389 DMWARN("Snapshot is marked invalid.");1390 }1391 1392 if (!s->store->chunk_size) {1393 ti->error = "Chunk size not set";1394 r = -EINVAL;1395 goto bad_read_metadata;1396 }1397 1398 r = dm_set_target_max_io_len(ti, s->store->chunk_size);1399 if (r)1400 goto bad_read_metadata;1401 1402 return 0;1403 1404bad_read_metadata:1405 unregister_snapshot(s);1406bad_load_and_register:1407 mempool_exit(&s->pending_pool);1408bad_pending_pool:1409 dm_kcopyd_client_destroy(s->kcopyd_client);1410bad_kcopyd:1411 dm_exception_table_exit(&s->pending, pending_cache);1412 dm_exception_table_exit(&s->complete, exception_cache);1413bad_hash_tables:1414 dm_exception_store_destroy(s->store);1415bad_store:1416 dm_put_device(ti, s->cow);1417bad_cow:1418 dm_put_device(ti, s->origin);1419bad_origin:1420bad_features:1421 kfree(s);1422bad:1423 return r;1424}1425 1426static void __free_exceptions(struct dm_snapshot *s)1427{1428 dm_kcopyd_client_destroy(s->kcopyd_client);1429 s->kcopyd_client = NULL;1430 1431 dm_exception_table_exit(&s->pending, pending_cache);1432 dm_exception_table_exit(&s->complete, exception_cache);1433}1434 1435static void __handover_exceptions(struct dm_snapshot *snap_src,1436 struct dm_snapshot *snap_dest)1437{1438 union {1439 struct dm_exception_table table_swap;1440 struct dm_exception_store *store_swap;1441 } u;1442 1443 /*1444 * Swap all snapshot context information between the two instances.1445 */1446 u.table_swap = snap_dest->complete;1447 snap_dest->complete = snap_src->complete;1448 snap_src->complete = u.table_swap;1449 1450 u.store_swap = snap_dest->store;1451 snap_dest->store = snap_src->store;1452 snap_dest->store->userspace_supports_overflow = u.store_swap->userspace_supports_overflow;1453 snap_src->store = u.store_swap;1454 1455 snap_dest->store->snap = snap_dest;1456 snap_src->store->snap = snap_src;1457 1458 snap_dest->ti->max_io_len = snap_dest->store->chunk_size;1459 snap_dest->valid = snap_src->valid;1460 snap_dest->snapshot_overflowed = snap_src->snapshot_overflowed;1461 1462 /*1463 * Set source invalid to ensure it receives no further I/O.1464 */1465 snap_src->valid = 0;1466}1467 1468static void snapshot_dtr(struct dm_target *ti)1469{1470#ifdef CONFIG_DM_DEBUG1471 int i;1472#endif1473 struct dm_snapshot *s = ti->private;1474 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;1475 1476 down_read(&_origins_lock);1477 /* Check whether exception handover must be cancelled */1478 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);1479 if (snap_src && snap_dest && (s == snap_src)) {1480 down_write(&snap_dest->lock);1481 snap_dest->valid = 0;1482 up_write(&snap_dest->lock);1483 DMERR("Cancelling snapshot handover.");1484 }1485 up_read(&_origins_lock);1486 1487 if (dm_target_is_snapshot_merge(ti))1488 stop_merge(s);1489 1490 /* Prevent further origin writes from using this snapshot. */1491 /* After this returns there can be no new kcopyd jobs. */1492 unregister_snapshot(s);1493 1494 while (atomic_read(&s->pending_exceptions_count))1495 fsleep(1000);1496 /*1497 * Ensure instructions in mempool_exit aren't reordered1498 * before atomic_read.1499 */1500 smp_mb();1501 1502#ifdef CONFIG_DM_DEBUG1503 for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)1504 BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i]));1505#endif1506 1507 __free_exceptions(s);1508 1509 mempool_exit(&s->pending_pool);1510 1511 dm_exception_store_destroy(s->store);1512 1513 dm_put_device(ti, s->cow);1514 1515 dm_put_device(ti, s->origin);1516 1517 WARN_ON(s->in_progress);1518 1519 kfree(s);1520}1521 1522static void account_start_copy(struct dm_snapshot *s)1523{1524 spin_lock(&s->in_progress_wait.lock);1525 s->in_progress++;1526 spin_unlock(&s->in_progress_wait.lock);1527}1528 1529static void account_end_copy(struct dm_snapshot *s)1530{1531 spin_lock(&s->in_progress_wait.lock);1532 BUG_ON(!s->in_progress);1533 s->in_progress--;1534 if (likely(s->in_progress <= cow_threshold) &&1535 unlikely(waitqueue_active(&s->in_progress_wait)))1536 wake_up_locked(&s->in_progress_wait);1537 spin_unlock(&s->in_progress_wait.lock);1538}1539 1540static bool wait_for_in_progress(struct dm_snapshot *s, bool unlock_origins)1541{1542 if (unlikely(s->in_progress > cow_threshold)) {1543 spin_lock(&s->in_progress_wait.lock);1544 if (likely(s->in_progress > cow_threshold)) {1545 /*1546 * NOTE: this throttle doesn't account for whether1547 * the caller is servicing an IO that will trigger a COW1548 * so excess throttling may result for chunks not required1549 * to be COW'd. But if cow_threshold was reached, extra1550 * throttling is unlikely to negatively impact performance.1551 */1552 DECLARE_WAITQUEUE(wait, current);1553 1554 __add_wait_queue(&s->in_progress_wait, &wait);1555 __set_current_state(TASK_UNINTERRUPTIBLE);1556 spin_unlock(&s->in_progress_wait.lock);1557 if (unlock_origins)1558 up_read(&_origins_lock);1559 io_schedule();1560 remove_wait_queue(&s->in_progress_wait, &wait);1561 return false;1562 }1563 spin_unlock(&s->in_progress_wait.lock);1564 }1565 return true;1566}1567 1568/*1569 * Flush a list of buffers.1570 */1571static void flush_bios(struct bio *bio)1572{1573 struct bio *n;1574 1575 while (bio) {1576 n = bio->bi_next;1577 bio->bi_next = NULL;1578 submit_bio_noacct(bio);1579 bio = n;1580 }1581}1582 1583static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit);1584 1585/*1586 * Flush a list of buffers.1587 */1588static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio)1589{1590 struct bio *n;1591 int r;1592 1593 while (bio) {1594 n = bio->bi_next;1595 bio->bi_next = NULL;1596 r = do_origin(s->origin, bio, false);1597 if (r == DM_MAPIO_REMAPPED)1598 submit_bio_noacct(bio);1599 bio = n;1600 }1601}1602 1603/*1604 * Error a list of buffers.1605 */1606static void error_bios(struct bio *bio)1607{1608 struct bio *n;1609 1610 while (bio) {1611 n = bio->bi_next;1612 bio->bi_next = NULL;1613 bio_io_error(bio);1614 bio = n;1615 }1616}1617 1618static void __invalidate_snapshot(struct dm_snapshot *s, int err)1619{1620 if (!s->valid)1621 return;1622 1623 if (err == -EIO)1624 DMERR("Invalidating snapshot: Error reading/writing.");1625 else if (err == -ENOMEM)1626 DMERR("Invalidating snapshot: Unable to allocate exception.");1627 1628 if (s->store->type->drop_snapshot)1629 s->store->type->drop_snapshot(s->store);1630 1631 s->valid = 0;1632 1633 dm_table_event(s->ti->table);1634}1635 1636static void invalidate_snapshot(struct dm_snapshot *s, int err)1637{1638 down_write(&s->lock);1639 __invalidate_snapshot(s, err);1640 up_write(&s->lock);1641}1642 1643static void pending_complete(void *context, int success)1644{1645 struct dm_snap_pending_exception *pe = context;1646 struct dm_exception *e;1647 struct dm_snapshot *s = pe->snap;1648 struct bio *origin_bios = NULL;1649 struct bio *snapshot_bios = NULL;1650 struct bio *full_bio = NULL;1651 struct dm_exception_table_lock lock;1652 int error = 0;1653 1654 dm_exception_table_lock_init(s, pe->e.old_chunk, &lock);1655 1656 if (!success) {1657 /* Read/write error - snapshot is unusable */1658 invalidate_snapshot(s, -EIO);1659 error = 1;1660 1661 dm_exception_table_lock(&lock);1662 goto out;1663 }1664 1665 e = alloc_completed_exception(GFP_NOIO);1666 if (!e) {1667 invalidate_snapshot(s, -ENOMEM);1668 error = 1;1669 1670 dm_exception_table_lock(&lock);1671 goto out;1672 }1673 *e = pe->e;1674 1675 down_read(&s->lock);1676 dm_exception_table_lock(&lock);1677 if (!s->valid) {1678 up_read(&s->lock);1679 free_completed_exception(e);1680 error = 1;1681 1682 goto out;1683 }1684 1685 /*1686 * Add a proper exception. After inserting the completed exception all1687 * subsequent snapshot reads to this chunk will be redirected to the1688 * COW device. This ensures that we do not starve. Moreover, as long1689 * as the pending exception exists, neither origin writes nor snapshot1690 * merging can overwrite the chunk in origin.1691 */1692 dm_insert_exception(&s->complete, e);1693 up_read(&s->lock);1694 1695 /* Wait for conflicting reads to drain */1696 if (__chunk_is_tracked(s, pe->e.old_chunk)) {1697 dm_exception_table_unlock(&lock);1698 __check_for_conflicting_io(s, pe->e.old_chunk);1699 dm_exception_table_lock(&lock);1700 }1701 1702out:1703 /* Remove the in-flight exception from the list */1704 dm_remove_exception(&pe->e);1705 1706 dm_exception_table_unlock(&lock);1707 1708 snapshot_bios = bio_list_get(&pe->snapshot_bios);1709 origin_bios = bio_list_get(&pe->origin_bios);1710 full_bio = pe->full_bio;1711 if (full_bio)1712 full_bio->bi_end_io = pe->full_bio_end_io;1713 increment_pending_exceptions_done_count();1714 1715 /* Submit any pending write bios */1716 if (error) {1717 if (full_bio)1718 bio_io_error(full_bio);1719 error_bios(snapshot_bios);1720 } else {1721 if (full_bio)1722 bio_endio(full_bio);1723 flush_bios(snapshot_bios);1724 }1725 1726 retry_origin_bios(s, origin_bios);1727 1728 free_pending_exception(pe);1729}1730 1731static void complete_exception(struct dm_snap_pending_exception *pe)1732{1733 struct dm_snapshot *s = pe->snap;1734 1735 /* Update the metadata if we are persistent */1736 s->store->type->commit_exception(s->store, &pe->e, !pe->copy_error,1737 pending_complete, pe);1738}1739 1740/*1741 * Called when the copy I/O has finished. kcopyd actually runs1742 * this code so don't block.1743 */1744static void copy_callback(int read_err, unsigned long write_err, void *context)1745{1746 struct dm_snap_pending_exception *pe = context;1747 struct dm_snapshot *s = pe->snap;1748 1749 pe->copy_error = read_err || write_err;1750 1751 if (pe->exception_sequence == s->exception_complete_sequence) {1752 struct rb_node *next;1753 1754 s->exception_complete_sequence++;1755 complete_exception(pe);1756 1757 next = rb_first(&s->out_of_order_tree);1758 while (next) {1759 pe = rb_entry(next, struct dm_snap_pending_exception,1760 out_of_order_node);1761 if (pe->exception_sequence != s->exception_complete_sequence)1762 break;1763 next = rb_next(next);1764 s->exception_complete_sequence++;1765 rb_erase(&pe->out_of_order_node, &s->out_of_order_tree);1766 complete_exception(pe);1767 cond_resched();1768 }1769 } else {1770 struct rb_node *parent = NULL;1771 struct rb_node **p = &s->out_of_order_tree.rb_node;1772 struct dm_snap_pending_exception *pe2;1773 1774 while (*p) {1775 pe2 = rb_entry(*p, struct dm_snap_pending_exception, out_of_order_node);1776 parent = *p;1777 1778 BUG_ON(pe->exception_sequence == pe2->exception_sequence);1779 if (pe->exception_sequence < pe2->exception_sequence)1780 p = &((*p)->rb_left);1781 else1782 p = &((*p)->rb_right);1783 }1784 1785 rb_link_node(&pe->out_of_order_node, parent, p);1786 rb_insert_color(&pe->out_of_order_node, &s->out_of_order_tree);1787 }1788 account_end_copy(s);1789}1790 1791/*1792 * Dispatches the copy operation to kcopyd.1793 */1794static void start_copy(struct dm_snap_pending_exception *pe)1795{1796 struct dm_snapshot *s = pe->snap;1797 struct dm_io_region src, dest;1798 struct block_device *bdev = s->origin->bdev;1799 sector_t dev_size;1800 1801 dev_size = get_dev_size(bdev);1802 1803 src.bdev = bdev;1804 src.sector = chunk_to_sector(s->store, pe->e.old_chunk);1805 src.count = min((sector_t)s->store->chunk_size, dev_size - src.sector);1806 1807 dest.bdev = s->cow->bdev;1808 dest.sector = chunk_to_sector(s->store, pe->e.new_chunk);1809 dest.count = src.count;1810 1811 /* Hand over to kcopyd */1812 account_start_copy(s);1813 dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, copy_callback, pe);1814}1815 1816static void full_bio_end_io(struct bio *bio)1817{1818 void *callback_data = bio->bi_private;1819 1820 dm_kcopyd_do_callback(callback_data, 0, bio->bi_status ? 1 : 0);1821}1822 1823static void start_full_bio(struct dm_snap_pending_exception *pe,1824 struct bio *bio)1825{1826 struct dm_snapshot *s = pe->snap;1827 void *callback_data;1828 1829 pe->full_bio = bio;1830 pe->full_bio_end_io = bio->bi_end_io;1831 1832 account_start_copy(s);1833 callback_data = dm_kcopyd_prepare_callback(s->kcopyd_client,1834 copy_callback, pe);1835 1836 bio->bi_end_io = full_bio_end_io;1837 bio->bi_private = callback_data;1838 1839 submit_bio_noacct(bio);1840}1841 1842static struct dm_snap_pending_exception *1843__lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk)1844{1845 struct dm_exception *e = dm_lookup_exception(&s->pending, chunk);1846 1847 if (!e)1848 return NULL;1849 1850 return container_of(e, struct dm_snap_pending_exception, e);1851}1852 1853/*1854 * Inserts a pending exception into the pending table.1855 *1856 * NOTE: a write lock must be held on the chunk's pending exception table slot1857 * before calling this.1858 */1859static struct dm_snap_pending_exception *1860__insert_pending_exception(struct dm_snapshot *s,1861 struct dm_snap_pending_exception *pe, chunk_t chunk)1862{1863 pe->e.old_chunk = chunk;1864 bio_list_init(&pe->origin_bios);1865 bio_list_init(&pe->snapshot_bios);1866 pe->started = 0;1867 pe->full_bio = NULL;1868 1869 spin_lock(&s->pe_allocation_lock);1870 if (s->store->type->prepare_exception(s->store, &pe->e)) {1871 spin_unlock(&s->pe_allocation_lock);1872 free_pending_exception(pe);1873 return NULL;1874 }1875 1876 pe->exception_sequence = s->exception_start_sequence++;1877 spin_unlock(&s->pe_allocation_lock);1878 1879 dm_insert_exception(&s->pending, &pe->e);1880 1881 return pe;1882}1883 1884/*1885 * Looks to see if this snapshot already has a pending exception1886 * for this chunk, otherwise it allocates a new one and inserts1887 * it into the pending table.1888 *1889 * NOTE: a write lock must be held on the chunk's pending exception table slot1890 * before calling this.1891 */1892static struct dm_snap_pending_exception *1893__find_pending_exception(struct dm_snapshot *s,1894 struct dm_snap_pending_exception *pe, chunk_t chunk)1895{1896 struct dm_snap_pending_exception *pe2;1897 1898 pe2 = __lookup_pending_exception(s, chunk);1899 if (pe2) {1900 free_pending_exception(pe);1901 return pe2;1902 }1903 1904 return __insert_pending_exception(s, pe, chunk);1905}1906 1907static void remap_exception(struct dm_snapshot *s, struct dm_exception *e,1908 struct bio *bio, chunk_t chunk)1909{1910 bio_set_dev(bio, s->cow->bdev);1911 bio->bi_iter.bi_sector =1912 chunk_to_sector(s->store, dm_chunk_number(e->new_chunk) +1913 (chunk - e->old_chunk)) +1914 (bio->bi_iter.bi_sector & s->store->chunk_mask);1915}1916 1917static void zero_callback(int read_err, unsigned long write_err, void *context)1918{1919 struct bio *bio = context;1920 struct dm_snapshot *s = bio->bi_private;1921 1922 account_end_copy(s);1923 bio->bi_status = write_err ? BLK_STS_IOERR : 0;1924 bio_endio(bio);1925}1926 1927static void zero_exception(struct dm_snapshot *s, struct dm_exception *e,1928 struct bio *bio, chunk_t chunk)1929{1930 struct dm_io_region dest;1931 1932 dest.bdev = s->cow->bdev;1933 dest.sector = bio->bi_iter.bi_sector;1934 dest.count = s->store->chunk_size;1935 1936 account_start_copy(s);1937 WARN_ON_ONCE(bio->bi_private);1938 bio->bi_private = s;1939 dm_kcopyd_zero(s->kcopyd_client, 1, &dest, 0, zero_callback, bio);1940}1941 1942static bool io_overlaps_chunk(struct dm_snapshot *s, struct bio *bio)1943{1944 return bio->bi_iter.bi_size ==1945 (s->store->chunk_size << SECTOR_SHIFT);1946}1947 1948static int snapshot_map(struct dm_target *ti, struct bio *bio)1949{1950 struct dm_exception *e;1951 struct dm_snapshot *s = ti->private;1952 int r = DM_MAPIO_REMAPPED;1953 chunk_t chunk;1954 struct dm_snap_pending_exception *pe = NULL;1955 struct dm_exception_table_lock lock;1956 1957 init_tracked_chunk(bio);1958 1959 if (bio->bi_opf & REQ_PREFLUSH) {1960 bio_set_dev(bio, s->cow->bdev);1961 return DM_MAPIO_REMAPPED;1962 }1963 1964 chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector);1965 dm_exception_table_lock_init(s, chunk, &lock);1966 1967 /* Full snapshots are not usable */1968 /* To get here the table must be live so s->active is always set. */1969 if (!s->valid)1970 return DM_MAPIO_KILL;1971 1972 if (bio_data_dir(bio) == WRITE) {1973 while (unlikely(!wait_for_in_progress(s, false)))1974 ; /* wait_for_in_progress() has slept */1975 }1976 1977 down_read(&s->lock);1978 dm_exception_table_lock(&lock);1979 1980 if (!s->valid || (unlikely(s->snapshot_overflowed) &&1981 bio_data_dir(bio) == WRITE)) {1982 r = DM_MAPIO_KILL;1983 goto out_unlock;1984 }1985 1986 if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {1987 if (s->discard_passdown_origin && dm_bio_get_target_bio_nr(bio)) {1988 /*1989 * passdown discard to origin (without triggering1990 * snapshot exceptions via do_origin; doing so would1991 * defeat the goal of freeing space in origin that is1992 * implied by the "discard_passdown_origin" feature)1993 */1994 bio_set_dev(bio, s->origin->bdev);1995 track_chunk(s, bio, chunk);1996 goto out_unlock;1997 }1998 /* discard to snapshot (target_bio_nr == 0) zeroes exceptions */1999 }2000 2001 /* If the block is already remapped - use that, else remap it */2002 e = dm_lookup_exception(&s->complete, chunk);2003 if (e) {2004 remap_exception(s, e, bio, chunk);2005 if (unlikely(bio_op(bio) == REQ_OP_DISCARD) &&2006 io_overlaps_chunk(s, bio)) {2007 dm_exception_table_unlock(&lock);2008 up_read(&s->lock);2009 zero_exception(s, e, bio, chunk);2010 r = DM_MAPIO_SUBMITTED; /* discard is not issued */2011 goto out;2012 }2013 goto out_unlock;2014 }2015 2016 if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {2017 /*2018 * If no exception exists, complete discard immediately2019 * otherwise it'll trigger copy-out.2020 */2021 bio_endio(bio);2022 r = DM_MAPIO_SUBMITTED;2023 goto out_unlock;2024 }2025 2026 /*2027 * Write to snapshot - higher level takes care of RW/RO2028 * flags so we should only get this if we are2029 * writable.2030 */2031 if (bio_data_dir(bio) == WRITE) {2032 pe = __lookup_pending_exception(s, chunk);2033 if (!pe) {2034 dm_exception_table_unlock(&lock);2035 pe = alloc_pending_exception(s);2036 dm_exception_table_lock(&lock);2037 2038 e = dm_lookup_exception(&s->complete, chunk);2039 if (e) {2040 free_pending_exception(pe);2041 remap_exception(s, e, bio, chunk);2042 goto out_unlock;2043 }2044 2045 pe = __find_pending_exception(s, pe, chunk);2046 if (!pe) {2047 dm_exception_table_unlock(&lock);2048 up_read(&s->lock);2049 2050 down_write(&s->lock);2051 2052 if (s->store->userspace_supports_overflow) {2053 if (s->valid && !s->snapshot_overflowed) {2054 s->snapshot_overflowed = 1;2055 DMERR("Snapshot overflowed: Unable to allocate exception.");2056 }2057 } else2058 __invalidate_snapshot(s, -ENOMEM);2059 up_write(&s->lock);2060 2061 r = DM_MAPIO_KILL;2062 goto out;2063 }2064 }2065 2066 remap_exception(s, &pe->e, bio, chunk);2067 2068 r = DM_MAPIO_SUBMITTED;2069 2070 if (!pe->started && io_overlaps_chunk(s, bio)) {2071 pe->started = 1;2072 2073 dm_exception_table_unlock(&lock);2074 up_read(&s->lock);2075 2076 start_full_bio(pe, bio);2077 goto out;2078 }2079 2080 bio_list_add(&pe->snapshot_bios, bio);2081 2082 if (!pe->started) {2083 /* this is protected by the exception table lock */2084 pe->started = 1;2085 2086 dm_exception_table_unlock(&lock);2087 up_read(&s->lock);2088 2089 start_copy(pe);2090 goto out;2091 }2092 } else {2093 bio_set_dev(bio, s->origin->bdev);2094 track_chunk(s, bio, chunk);2095 }2096 2097out_unlock:2098 dm_exception_table_unlock(&lock);2099 up_read(&s->lock);2100out:2101 return r;2102}2103 2104/*2105 * A snapshot-merge target behaves like a combination of a snapshot2106 * target and a snapshot-origin target. It only generates new2107 * exceptions in other snapshots and not in the one that is being2108 * merged.2109 *2110 * For each chunk, if there is an existing exception, it is used to2111 * redirect I/O to the cow device. Otherwise I/O is sent to the origin,2112 * which in turn might generate exceptions in other snapshots.2113 * If merging is currently taking place on the chunk in question, the2114 * I/O is deferred by adding it to s->bios_queued_during_merge.2115 */2116static int snapshot_merge_map(struct dm_target *ti, struct bio *bio)2117{2118 struct dm_exception *e;2119 struct dm_snapshot *s = ti->private;2120 int r = DM_MAPIO_REMAPPED;2121 chunk_t chunk;2122 2123 init_tracked_chunk(bio);2124 2125 if (bio->bi_opf & REQ_PREFLUSH) {2126 if (!dm_bio_get_target_bio_nr(bio))2127 bio_set_dev(bio, s->origin->bdev);2128 else2129 bio_set_dev(bio, s->cow->bdev);2130 return DM_MAPIO_REMAPPED;2131 }2132 2133 if (unlikely(bio_op(bio) == REQ_OP_DISCARD)) {2134 /* Once merging, discards no longer effect change */2135 bio_endio(bio);2136 return DM_MAPIO_SUBMITTED;2137 }2138 2139 chunk = sector_to_chunk(s->store, bio->bi_iter.bi_sector);2140 2141 down_write(&s->lock);2142 2143 /* Full merging snapshots are redirected to the origin */2144 if (!s->valid)2145 goto redirect_to_origin;2146 2147 /* If the block is already remapped - use that */2148 e = dm_lookup_exception(&s->complete, chunk);2149 if (e) {2150 /* Queue writes overlapping with chunks being merged */2151 if (bio_data_dir(bio) == WRITE &&2152 chunk >= s->first_merging_chunk &&2153 chunk < (s->first_merging_chunk +2154 s->num_merging_chunks)) {2155 bio_set_dev(bio, s->origin->bdev);2156 bio_list_add(&s->bios_queued_during_merge, bio);2157 r = DM_MAPIO_SUBMITTED;2158 goto out_unlock;2159 }2160 2161 remap_exception(s, e, bio, chunk);2162 2163 if (bio_data_dir(bio) == WRITE)2164 track_chunk(s, bio, chunk);2165 goto out_unlock;2166 }2167 2168redirect_to_origin:2169 bio_set_dev(bio, s->origin->bdev);2170 2171 if (bio_data_dir(bio) == WRITE) {2172 up_write(&s->lock);2173 return do_origin(s->origin, bio, false);2174 }2175 2176out_unlock:2177 up_write(&s->lock);2178 2179 return r;2180}2181 2182static int snapshot_end_io(struct dm_target *ti, struct bio *bio,2183 blk_status_t *error)2184{2185 struct dm_snapshot *s = ti->private;2186 2187 if (is_bio_tracked(bio))2188 stop_tracking_chunk(s, bio);2189 2190 return DM_ENDIO_DONE;2191}2192 2193static void snapshot_merge_presuspend(struct dm_target *ti)2194{2195 struct dm_snapshot *s = ti->private;2196 2197 stop_merge(s);2198}2199 2200static int snapshot_preresume(struct dm_target *ti)2201{2202 int r = 0;2203 struct dm_snapshot *s = ti->private;2204 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;2205 2206 down_read(&_origins_lock);2207 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);2208 if (snap_src && snap_dest) {2209 down_read(&snap_src->lock);2210 if (s == snap_src) {2211 DMERR("Unable to resume snapshot source until handover completes.");2212 r = -EINVAL;2213 } else if (!dm_suspended(snap_src->ti)) {2214 DMERR("Unable to perform snapshot handover until source is suspended.");2215 r = -EINVAL;2216 }2217 up_read(&snap_src->lock);2218 }2219 up_read(&_origins_lock);2220 2221 return r;2222}2223 2224static void snapshot_resume(struct dm_target *ti)2225{2226 struct dm_snapshot *s = ti->private;2227 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL, *snap_merging = NULL;2228 struct dm_origin *o;2229 struct mapped_device *origin_md = NULL;2230 bool must_restart_merging = false;2231 2232 down_read(&_origins_lock);2233 2234 o = __lookup_dm_origin(s->origin->bdev);2235 if (o)2236 origin_md = dm_table_get_md(o->ti->table);2237 if (!origin_md) {2238 (void) __find_snapshots_sharing_cow(s, NULL, NULL, &snap_merging);2239 if (snap_merging)2240 origin_md = dm_table_get_md(snap_merging->ti->table);2241 }2242 if (origin_md == dm_table_get_md(ti->table))2243 origin_md = NULL;2244 if (origin_md) {2245 if (dm_hold(origin_md))2246 origin_md = NULL;2247 }2248 2249 up_read(&_origins_lock);2250 2251 if (origin_md) {2252 dm_internal_suspend_fast(origin_md);2253 if (snap_merging && test_bit(RUNNING_MERGE, &snap_merging->state_bits)) {2254 must_restart_merging = true;2255 stop_merge(snap_merging);2256 }2257 }2258 2259 down_read(&_origins_lock);2260 2261 (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);2262 if (snap_src && snap_dest) {2263 down_write(&snap_src->lock);2264 down_write_nested(&snap_dest->lock, SINGLE_DEPTH_NESTING);2265 __handover_exceptions(snap_src, snap_dest);2266 up_write(&snap_dest->lock);2267 up_write(&snap_src->lock);2268 }2269 2270 up_read(&_origins_lock);2271 2272 if (origin_md) {2273 if (must_restart_merging)2274 start_merge(snap_merging);2275 dm_internal_resume_fast(origin_md);2276 dm_put(origin_md);2277 }2278 2279 /* Now we have correct chunk size, reregister */2280 reregister_snapshot(s);2281 2282 down_write(&s->lock);2283 s->active = 1;2284 up_write(&s->lock);2285}2286 2287static uint32_t get_origin_minimum_chunksize(struct block_device *bdev)2288{2289 uint32_t min_chunksize;2290 2291 down_read(&_origins_lock);2292 min_chunksize = __minimum_chunk_size(__lookup_origin(bdev));2293 up_read(&_origins_lock);2294 2295 return min_chunksize;2296}2297 2298static void snapshot_merge_resume(struct dm_target *ti)2299{2300 struct dm_snapshot *s = ti->private;2301 2302 /*2303 * Handover exceptions from existing snapshot.2304 */2305 snapshot_resume(ti);2306 2307 /*2308 * snapshot-merge acts as an origin, so set ti->max_io_len2309 */2310 ti->max_io_len = get_origin_minimum_chunksize(s->origin->bdev);2311 2312 start_merge(s);2313}2314 2315static void snapshot_status(struct dm_target *ti, status_type_t type,2316 unsigned int status_flags, char *result, unsigned int maxlen)2317{2318 unsigned int sz = 0;2319 struct dm_snapshot *snap = ti->private;2320 unsigned int num_features;2321 2322 switch (type) {2323 case STATUSTYPE_INFO:2324 2325 down_write(&snap->lock);2326 2327 if (!snap->valid)2328 DMEMIT("Invalid");2329 else if (snap->merge_failed)2330 DMEMIT("Merge failed");2331 else if (snap->snapshot_overflowed)2332 DMEMIT("Overflow");2333 else {2334 if (snap->store->type->usage) {2335 sector_t total_sectors, sectors_allocated,2336 metadata_sectors;2337 snap->store->type->usage(snap->store,2338 &total_sectors,2339 §ors_allocated,2340 &metadata_sectors);2341 DMEMIT("%llu/%llu %llu",2342 (unsigned long long)sectors_allocated,2343 (unsigned long long)total_sectors,2344 (unsigned long long)metadata_sectors);2345 } else2346 DMEMIT("Unknown");2347 }2348 2349 up_write(&snap->lock);2350 2351 break;2352 2353 case STATUSTYPE_TABLE:2354 /*2355 * kdevname returns a static pointer so we need2356 * to make private copies if the output is to2357 * make sense.2358 */2359 DMEMIT("%s %s", snap->origin->name, snap->cow->name);2360 sz += snap->store->type->status(snap->store, type, result + sz,2361 maxlen - sz);2362 num_features = snap->discard_zeroes_cow + snap->discard_passdown_origin;2363 if (num_features) {2364 DMEMIT(" %u", num_features);2365 if (snap->discard_zeroes_cow)2366 DMEMIT(" discard_zeroes_cow");2367 if (snap->discard_passdown_origin)2368 DMEMIT(" discard_passdown_origin");2369 }2370 break;2371 2372 case STATUSTYPE_IMA:2373 DMEMIT_TARGET_NAME_VERSION(ti->type);2374 DMEMIT(",snap_origin_name=%s", snap->origin->name);2375 DMEMIT(",snap_cow_name=%s", snap->cow->name);2376 DMEMIT(",snap_valid=%c", snap->valid ? 'y' : 'n');2377 DMEMIT(",snap_merge_failed=%c", snap->merge_failed ? 'y' : 'n');2378 DMEMIT(",snapshot_overflowed=%c", snap->snapshot_overflowed ? 'y' : 'n');2379 DMEMIT(";");2380 break;2381 }2382}2383 2384static int snapshot_iterate_devices(struct dm_target *ti,2385 iterate_devices_callout_fn fn, void *data)2386{2387 struct dm_snapshot *snap = ti->private;2388 int r;2389 2390 r = fn(ti, snap->origin, 0, ti->len, data);2391 2392 if (!r)2393 r = fn(ti, snap->cow, 0, get_dev_size(snap->cow->bdev), data);2394 2395 return r;2396}2397 2398static void snapshot_io_hints(struct dm_target *ti, struct queue_limits *limits)2399{2400 struct dm_snapshot *snap = ti->private;2401 2402 if (snap->discard_zeroes_cow) {2403 struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;2404 2405 down_read(&_origins_lock);2406 2407 (void) __find_snapshots_sharing_cow(snap, &snap_src, &snap_dest, NULL);2408 if (snap_src && snap_dest)2409 snap = snap_src;2410 2411 /* All discards are split on chunk_size boundary */2412 limits->discard_granularity = snap->store->chunk_size;2413 limits->max_hw_discard_sectors = snap->store->chunk_size;2414 2415 up_read(&_origins_lock);2416 }2417}2418 2419/*2420 *---------------------------------------------------------------2421 * Origin methods2422 *---------------------------------------------------------------2423 */2424/*2425 * If no exceptions need creating, DM_MAPIO_REMAPPED is returned and any2426 * supplied bio was ignored. The caller may submit it immediately.2427 * (No remapping actually occurs as the origin is always a direct linear2428 * map.)2429 *2430 * If further exceptions are required, DM_MAPIO_SUBMITTED is returned2431 * and any supplied bio is added to a list to be submitted once all2432 * the necessary exceptions exist.2433 */2434static int __origin_write(struct list_head *snapshots, sector_t sector,2435 struct bio *bio)2436{2437 int r = DM_MAPIO_REMAPPED;2438 struct dm_snapshot *snap;2439 struct dm_exception *e;2440 struct dm_snap_pending_exception *pe, *pe2;2441 struct dm_snap_pending_exception *pe_to_start_now = NULL;2442 struct dm_snap_pending_exception *pe_to_start_last = NULL;2443 struct dm_exception_table_lock lock;2444 chunk_t chunk;2445 2446 /* Do all the snapshots on this origin */2447 list_for_each_entry(snap, snapshots, list) {2448 /*2449 * Don't make new exceptions in a merging snapshot2450 * because it has effectively been deleted2451 */2452 if (dm_target_is_snapshot_merge(snap->ti))2453 continue;2454 2455 /* Nothing to do if writing beyond end of snapshot */2456 if (sector >= dm_table_get_size(snap->ti->table))2457 continue;2458 2459 /*2460 * Remember, different snapshots can have2461 * different chunk sizes.2462 */2463 chunk = sector_to_chunk(snap->store, sector);2464 dm_exception_table_lock_init(snap, chunk, &lock);2465 2466 down_read(&snap->lock);2467 dm_exception_table_lock(&lock);2468 2469 /* Only deal with valid and active snapshots */2470 if (!snap->valid || !snap->active)2471 goto next_snapshot;2472 2473 pe = __lookup_pending_exception(snap, chunk);2474 if (!pe) {2475 /*2476 * Check exception table to see if block is already2477 * remapped in this snapshot and trigger an exception2478 * if not.2479 */2480 e = dm_lookup_exception(&snap->complete, chunk);2481 if (e)2482 goto next_snapshot;2483 2484 dm_exception_table_unlock(&lock);2485 pe = alloc_pending_exception(snap);2486 dm_exception_table_lock(&lock);2487 2488 pe2 = __lookup_pending_exception(snap, chunk);2489 2490 if (!pe2) {2491 e = dm_lookup_exception(&snap->complete, chunk);2492 if (e) {2493 free_pending_exception(pe);2494 goto next_snapshot;2495 }2496 2497 pe = __insert_pending_exception(snap, pe, chunk);2498 if (!pe) {2499 dm_exception_table_unlock(&lock);2500 up_read(&snap->lock);2501 2502 invalidate_snapshot(snap, -ENOMEM);2503 continue;2504 }2505 } else {2506 free_pending_exception(pe);2507 pe = pe2;2508 }2509 }2510 2511 r = DM_MAPIO_SUBMITTED;2512 2513 /*2514 * If an origin bio was supplied, queue it to wait for the2515 * completion of this exception, and start this one last,2516 * at the end of the function.2517 */2518 if (bio) {2519 bio_list_add(&pe->origin_bios, bio);2520 bio = NULL;2521 2522 if (!pe->started) {2523 pe->started = 1;2524 pe_to_start_last = pe;2525 }2526 }2527 2528 if (!pe->started) {2529 pe->started = 1;2530 pe_to_start_now = pe;2531 }2532 2533next_snapshot:2534 dm_exception_table_unlock(&lock);2535 up_read(&snap->lock);2536 2537 if (pe_to_start_now) {2538 start_copy(pe_to_start_now);2539 pe_to_start_now = NULL;2540 }2541 }2542 2543 /*2544 * Submit the exception against which the bio is queued last,2545 * to give the other exceptions a head start.2546 */2547 if (pe_to_start_last)2548 start_copy(pe_to_start_last);2549 2550 return r;2551}2552 2553/*2554 * Called on a write from the origin driver.2555 */2556static int do_origin(struct dm_dev *origin, struct bio *bio, bool limit)2557{2558 struct origin *o;2559 int r = DM_MAPIO_REMAPPED;2560 2561again:2562 down_read(&_origins_lock);2563 o = __lookup_origin(origin->bdev);2564 if (o) {2565 if (limit) {2566 struct dm_snapshot *s;2567 2568 list_for_each_entry(s, &o->snapshots, list)2569 if (unlikely(!wait_for_in_progress(s, true)))2570 goto again;2571 }2572 2573 r = __origin_write(&o->snapshots, bio->bi_iter.bi_sector, bio);2574 }2575 up_read(&_origins_lock);2576 2577 return r;2578}2579 2580/*2581 * Trigger exceptions in all non-merging snapshots.2582 *2583 * The chunk size of the merging snapshot may be larger than the chunk2584 * size of some other snapshot so we may need to reallocate multiple2585 * chunks in other snapshots.2586 *2587 * We scan all the overlapping exceptions in the other snapshots.2588 * Returns 1 if anything was reallocated and must be waited for,2589 * otherwise returns 0.2590 *2591 * size must be a multiple of merging_snap's chunk_size.2592 */2593static int origin_write_extent(struct dm_snapshot *merging_snap,2594 sector_t sector, unsigned int size)2595{2596 int must_wait = 0;2597 sector_t n;2598 struct origin *o;2599 2600 /*2601 * The origin's __minimum_chunk_size() got stored in max_io_len2602 * by snapshot_merge_resume().2603 */2604 down_read(&_origins_lock);2605 o = __lookup_origin(merging_snap->origin->bdev);2606 for (n = 0; n < size; n += merging_snap->ti->max_io_len)2607 if (__origin_write(&o->snapshots, sector + n, NULL) ==2608 DM_MAPIO_SUBMITTED)2609 must_wait = 1;2610 up_read(&_origins_lock);2611 2612 return must_wait;2613}2614 2615/*2616 * Origin: maps a linear range of a device, with hooks for snapshotting.2617 */2618 2619/*2620 * Construct an origin mapping: <dev_path>2621 * The context for an origin is merely a 'struct dm_dev *'2622 * pointing to the real device.2623 */2624static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv)2625{2626 int r;2627 struct dm_origin *o;2628 2629 if (argc != 1) {2630 ti->error = "origin: incorrect number of arguments";2631 return -EINVAL;2632 }2633 2634 o = kmalloc(sizeof(struct dm_origin), GFP_KERNEL);2635 if (!o) {2636 ti->error = "Cannot allocate private origin structure";2637 r = -ENOMEM;2638 goto bad_alloc;2639 }2640 2641 r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &o->dev);2642 if (r) {2643 ti->error = "Cannot get target device";2644 goto bad_open;2645 }2646 2647 o->ti = ti;2648 ti->private = o;2649 ti->num_flush_bios = 1;2650 2651 return 0;2652 2653bad_open:2654 kfree(o);2655bad_alloc:2656 return r;2657}2658 2659static void origin_dtr(struct dm_target *ti)2660{2661 struct dm_origin *o = ti->private;2662 2663 dm_put_device(ti, o->dev);2664 kfree(o);2665}2666 2667static int origin_map(struct dm_target *ti, struct bio *bio)2668{2669 struct dm_origin *o = ti->private;2670 unsigned int available_sectors;2671 2672 bio_set_dev(bio, o->dev->bdev);2673 2674 if (unlikely(bio->bi_opf & REQ_PREFLUSH))2675 return DM_MAPIO_REMAPPED;2676 2677 if (bio_data_dir(bio) != WRITE)2678 return DM_MAPIO_REMAPPED;2679 2680 available_sectors = o->split_boundary -2681 ((unsigned int)bio->bi_iter.bi_sector & (o->split_boundary - 1));2682 2683 if (bio_sectors(bio) > available_sectors)2684 dm_accept_partial_bio(bio, available_sectors);2685 2686 /* Only tell snapshots if this is a write */2687 return do_origin(o->dev, bio, true);2688}2689 2690/*2691 * Set the target "max_io_len" field to the minimum of all the snapshots'2692 * chunk sizes.2693 */2694static void origin_resume(struct dm_target *ti)2695{2696 struct dm_origin *o = ti->private;2697 2698 o->split_boundary = get_origin_minimum_chunksize(o->dev->bdev);2699 2700 down_write(&_origins_lock);2701 __insert_dm_origin(o);2702 up_write(&_origins_lock);2703}2704 2705static void origin_postsuspend(struct dm_target *ti)2706{2707 struct dm_origin *o = ti->private;2708 2709 down_write(&_origins_lock);2710 __remove_dm_origin(o);2711 up_write(&_origins_lock);2712}2713 2714static void origin_status(struct dm_target *ti, status_type_t type,2715 unsigned int status_flags, char *result, unsigned int maxlen)2716{2717 struct dm_origin *o = ti->private;2718 2719 switch (type) {2720 case STATUSTYPE_INFO:2721 result[0] = '\0';2722 break;2723 2724 case STATUSTYPE_TABLE:2725 snprintf(result, maxlen, "%s", o->dev->name);2726 break;2727 case STATUSTYPE_IMA:2728 result[0] = '\0';2729 break;2730 }2731}2732 2733static int origin_iterate_devices(struct dm_target *ti,2734 iterate_devices_callout_fn fn, void *data)2735{2736 struct dm_origin *o = ti->private;2737 2738 return fn(ti, o->dev, 0, ti->len, data);2739}2740 2741static struct target_type origin_target = {2742 .name = "snapshot-origin",2743 .version = {1, 9, 0},2744 .module = THIS_MODULE,2745 .ctr = origin_ctr,2746 .dtr = origin_dtr,2747 .map = origin_map,2748 .resume = origin_resume,2749 .postsuspend = origin_postsuspend,2750 .status = origin_status,2751 .iterate_devices = origin_iterate_devices,2752};2753 2754static struct target_type snapshot_target = {2755 .name = "snapshot",2756 .version = {1, 16, 0},2757 .module = THIS_MODULE,2758 .ctr = snapshot_ctr,2759 .dtr = snapshot_dtr,2760 .map = snapshot_map,2761 .end_io = snapshot_end_io,2762 .preresume = snapshot_preresume,2763 .resume = snapshot_resume,2764 .status = snapshot_status,2765 .iterate_devices = snapshot_iterate_devices,2766 .io_hints = snapshot_io_hints,2767};2768 2769static struct target_type merge_target = {2770 .name = dm_snapshot_merge_target_name,2771 .version = {1, 5, 0},2772 .module = THIS_MODULE,2773 .ctr = snapshot_ctr,2774 .dtr = snapshot_dtr,2775 .map = snapshot_merge_map,2776 .end_io = snapshot_end_io,2777 .presuspend = snapshot_merge_presuspend,2778 .preresume = snapshot_preresume,2779 .resume = snapshot_merge_resume,2780 .status = snapshot_status,2781 .iterate_devices = snapshot_iterate_devices,2782 .io_hints = snapshot_io_hints,2783};2784 2785static int __init dm_snapshot_init(void)2786{2787 int r;2788 2789 r = dm_exception_store_init();2790 if (r) {2791 DMERR("Failed to initialize exception stores");2792 return r;2793 }2794 2795 r = init_origin_hash();2796 if (r) {2797 DMERR("init_origin_hash failed.");2798 goto bad_origin_hash;2799 }2800 2801 exception_cache = KMEM_CACHE(dm_exception, 0);2802 if (!exception_cache) {2803 DMERR("Couldn't create exception cache.");2804 r = -ENOMEM;2805 goto bad_exception_cache;2806 }2807 2808 pending_cache = KMEM_CACHE(dm_snap_pending_exception, 0);2809 if (!pending_cache) {2810 DMERR("Couldn't create pending cache.");2811 r = -ENOMEM;2812 goto bad_pending_cache;2813 }2814 2815 r = dm_register_target(&snapshot_target);2816 if (r < 0)2817 goto bad_register_snapshot_target;2818 2819 r = dm_register_target(&origin_target);2820 if (r < 0)2821 goto bad_register_origin_target;2822 2823 r = dm_register_target(&merge_target);2824 if (r < 0)2825 goto bad_register_merge_target;2826 2827 return 0;2828 2829bad_register_merge_target:2830 dm_unregister_target(&origin_target);2831bad_register_origin_target:2832 dm_unregister_target(&snapshot_target);2833bad_register_snapshot_target:2834 kmem_cache_destroy(pending_cache);2835bad_pending_cache:2836 kmem_cache_destroy(exception_cache);2837bad_exception_cache:2838 exit_origin_hash();2839bad_origin_hash:2840 dm_exception_store_exit();2841 2842 return r;2843}2844 2845static void __exit dm_snapshot_exit(void)2846{2847 dm_unregister_target(&snapshot_target);2848 dm_unregister_target(&origin_target);2849 dm_unregister_target(&merge_target);2850 2851 exit_origin_hash();2852 kmem_cache_destroy(pending_cache);2853 kmem_cache_destroy(exception_cache);2854 2855 dm_exception_store_exit();2856}2857 2858/* Module hooks */2859module_init(dm_snapshot_init);2860module_exit(dm_snapshot_exit);2861 2862MODULE_DESCRIPTION(DM_NAME " snapshot target");2863MODULE_AUTHOR("Joe Thornber");2864MODULE_LICENSE("GPL");2865MODULE_ALIAS("dm-snapshot-origin");2866MODULE_ALIAS("dm-snapshot-merge");2867