linux/drivers/md/dm-snap.c

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/*
* dm-snapshot.c
*
* Copyright (C) 2001-2002 Sistina Software (UK) Limited.
*
* This file is released under the GPL.
*/
#include <linux/blkdev.h>
#include <linux/device-mapper.h>
#include <linux/delay.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/kdev_t.h>
#include <linux/list.h>
#include <linux/mempool.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/log2.h>
#include <linux/dm-kcopyd.h>
#include <linux/workqueue.h>
#include "dm-exception-store.h"
#define DM_MSG_PREFIX "snapshots"
static const char dm_snapshot_merge_target_name[] = "snapshot-merge";
#define dm_target_is_snapshot_merge(ti) \
((ti)->type->name == dm_snapshot_merge_target_name)
/*
* The percentage increment we will wake up users at
*/
#define WAKE_UP_PERCENT 5
/*
* kcopyd priority of snapshot operations
*/
#define SNAPSHOT_COPY_PRIORITY 2
/*
* Reserve 1MB for each snapshot initially (with minimum of 1 page).
*/
#define SNAPSHOT_PAGES (((1UL << 20) >> PAGE_SHIFT) ? : 1)
/*
* The size of the mempool used to track chunks in use.
*/
#define MIN_IOS 256
#define DM_TRACKED_CHUNK_HASH_SIZE 16
#define DM_TRACKED_CHUNK_HASH(x) ((unsigned long)(x) & \
(DM_TRACKED_CHUNK_HASH_SIZE - 1))
struct dm_exception_table {
uint32_t hash_mask;
unsigned hash_shift;
struct list_head *table;
};
struct dm_snapshot {
struct rw_semaphore lock;
struct dm_dev *origin;
struct dm_dev *cow;
struct dm_target *ti;
/* List of snapshots per Origin */
struct list_head list;
/* You can't use a snapshot if this is 0 (e.g. if full) */
int valid;
/* Origin writes don't trigger exceptions until this is set */
int active;
/* Whether or not owning mapped_device is suspended */
int suspended;
mempool_t *pending_pool;
atomic_t pending_exceptions_count;
struct dm_exception_table pending;
struct dm_exception_table complete;
/*
* pe_lock protects all pending_exception operations and access
* as well as the snapshot_bios list.
*/
spinlock_t pe_lock;
/* The on disk metadata handler */
struct dm_exception_store *store;
struct dm_kcopyd_client *kcopyd_client;
/* Queue of snapshot writes for ksnapd to flush */
struct bio_list queued_bios;
struct work_struct queued_bios_work;
/* Chunks with outstanding reads */
mempool_t *tracked_chunk_pool;
spinlock_t tracked_chunk_lock;
struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
};
struct dm_dev *dm_snap_cow(struct dm_snapshot *s)
{
return s->cow;
}
EXPORT_SYMBOL(dm_snap_cow);
static struct workqueue_struct *ksnapd;
static void flush_queued_bios(struct work_struct *work);
static sector_t chunk_to_sector(struct dm_exception_store *store,
chunk_t chunk)
{
return chunk << store->chunk_shift;
}
static int bdev_equal(struct block_device *lhs, struct block_device *rhs)
{
/*
* There is only ever one instance of a particular block
* device so we can compare pointers safely.
*/
return lhs == rhs;
}
struct dm_snap_pending_exception {
struct dm_exception e;
/*
* Origin buffers waiting for this to complete are held
* in a bio list
*/
struct bio_list origin_bios;
struct bio_list snapshot_bios;
/* Pointer back to snapshot context */
struct dm_snapshot *snap;
/*
* 1 indicates the exception has already been sent to
* kcopyd.
*/
int started;
};
/*
* Hash table mapping origin volumes to lists of snapshots and
* a lock to protect it
*/
static struct kmem_cache *exception_cache;
static struct kmem_cache *pending_cache;
struct dm_snap_tracked_chunk {
struct hlist_node node;
chunk_t chunk;
};
static struct kmem_cache *tracked_chunk_cache;
static struct dm_snap_tracked_chunk *track_chunk(struct dm_snapshot *s,
chunk_t chunk)
{
struct dm_snap_tracked_chunk *c = mempool_alloc(s->tracked_chunk_pool,
GFP_NOIO);
unsigned long flags;
c->chunk = chunk;
spin_lock_irqsave(&s->tracked_chunk_lock, flags);
hlist_add_head(&c->node,
&s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]);
spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
return c;
}
static void stop_tracking_chunk(struct dm_snapshot *s,
struct dm_snap_tracked_chunk *c)
{
unsigned long flags;
spin_lock_irqsave(&s->tracked_chunk_lock, flags);
hlist_del(&c->node);
spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
mempool_free(c, s->tracked_chunk_pool);
}
static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk)
{
struct dm_snap_tracked_chunk *c;
struct hlist_node *hn;
int found = 0;
spin_lock_irq(&s->tracked_chunk_lock);
hlist_for_each_entry(c, hn,
&s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)], node) {
if (c->chunk == chunk) {
found = 1;
break;
}
}
spin_unlock_irq(&s->tracked_chunk_lock);
return found;
}
/*
* This conflicting I/O is extremely improbable in the caller,
* so msleep(1) is sufficient and there is no need for a wait queue.
*/
static void __check_for_conflicting_io(struct dm_snapshot *s, chunk_t chunk)
{
while (__chunk_is_tracked(s, chunk))
msleep(1);
}
/*
* One of these per registered origin, held in the snapshot_origins hash
*/
struct origin {
/* The origin device */
struct block_device *bdev;
struct list_head hash_list;
/* List of snapshots for this origin */
struct list_head snapshots;
};
/*
* Size of the hash table for origin volumes. If we make this
* the size of the minors list then it should be nearly perfect
*/
#define ORIGIN_HASH_SIZE 256
#define ORIGIN_MASK 0xFF
static struct list_head *_origins;
static struct rw_semaphore _origins_lock;
static int init_origin_hash(void)
{
int i;
_origins = kmalloc(ORIGIN_HASH_SIZE * sizeof(struct list_head),
GFP_KERNEL);
if (!_origins) {
DMERR("unable to allocate memory");
return -ENOMEM;
}
for (i = 0; i < ORIGIN_HASH_SIZE; i++)
INIT_LIST_HEAD(_origins + i);
init_rwsem(&_origins_lock);
return 0;
}
static void exit_origin_hash(void)
{
kfree(_origins);
}
static unsigned origin_hash(struct block_device *bdev)
{
return bdev->bd_dev & ORIGIN_MASK;
}
static struct origin *__lookup_origin(struct block_device *origin)
{
struct list_head *ol;
struct origin *o;
ol = &_origins[origin_hash(origin)];
list_for_each_entry (o, ol, hash_list)
if (bdev_equal(o->bdev, origin))
return o;
return NULL;
}
static void __insert_origin(struct origin *o)
{
struct list_head *sl = &_origins[origin_hash(o->bdev)];
list_add_tail(&o->hash_list, sl);
}
/*
* _origins_lock must be held when calling this function.
* Returns number of snapshots registered using the supplied cow device, plus:
* snap_src - a snapshot suitable for use as a source of exception handover
* snap_dest - a snapshot capable of receiving exception handover.
* snap_merge - an existing snapshot-merge target linked to the same origin.
* There can be at most one snapshot-merge target. The parameter is optional.
*
* Possible return values and states of snap_src and snap_dest.
* 0: NULL, NULL - first new snapshot
* 1: snap_src, NULL - normal snapshot
* 2: snap_src, snap_dest - waiting for handover
* 2: snap_src, NULL - handed over, waiting for old to be deleted
* 1: NULL, snap_dest - source got destroyed without handover
*/
static int __find_snapshots_sharing_cow(struct dm_snapshot *snap,
struct dm_snapshot **snap_src,
struct dm_snapshot **snap_dest,
struct dm_snapshot **snap_merge)
{
struct dm_snapshot *s;
struct origin *o;
int count = 0;
int active;
o = __lookup_origin(snap->origin->bdev);
if (!o)
goto out;
list_for_each_entry(s, &o->snapshots, list) {
if (dm_target_is_snapshot_merge(s->ti) && snap_merge)
*snap_merge = s;
if (!bdev_equal(s->cow->bdev, snap->cow->bdev))
continue;
down_read(&s->lock);
active = s->active;
up_read(&s->lock);
if (active) {
if (snap_src)
*snap_src = s;
} else if (snap_dest)
*snap_dest = s;
count++;
}
out:
return count;
}
/*
* On success, returns 1 if this snapshot is a handover destination,
* otherwise returns 0.
*/
static int __validate_exception_handover(struct dm_snapshot *snap)
{
struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
struct dm_snapshot *snap_merge = NULL;
/* Does snapshot need exceptions handed over to it? */
if ((__find_snapshots_sharing_cow(snap, &snap_src, &snap_dest,
&snap_merge) == 2) ||
snap_dest) {
snap->ti->error = "Snapshot cow pairing for exception "
"table handover failed";
return -EINVAL;
}
/*
* If no snap_src was found, snap cannot become a handover
* destination.
*/
if (!snap_src)
return 0;
/*
* Non-snapshot-merge handover?
*/
if (!dm_target_is_snapshot_merge(snap->ti))
return 1;
/*
* Do not allow more than one merging snapshot.
*/
if (snap_merge) {
snap->ti->error = "A snapshot is already merging.";
return -EINVAL;
}
return 1;
}
static void __insert_snapshot(struct origin *o, struct dm_snapshot *s)
{
struct dm_snapshot *l;
/* Sort the list according to chunk size, largest-first smallest-last */
list_for_each_entry(l, &o->snapshots, list)
if (l->store->chunk_size < s->store->chunk_size)
break;
list_add_tail(&s->list, &l->list);
}
/*
* Make a note of the snapshot and its origin so we can look it
* up when the origin has a write on it.
*
* Also validate snapshot exception store handovers.
* On success, returns 1 if this registration is a handover destination,
* otherwise returns 0.
*/
static int register_snapshot(struct dm_snapshot *snap)
{
struct origin *o, *new_o = NULL;
struct block_device *bdev = snap->origin->bdev;
int r = 0;
new_o = kmalloc(sizeof(*new_o), GFP_KERNEL);
if (!new_o)
return -ENOMEM;
down_write(&_origins_lock);
r = __validate_exception_handover(snap);
if (r < 0) {
kfree(new_o);
goto out;
}
o = __lookup_origin(bdev);
if (o)
kfree(new_o);
else {
/* New origin */
o = new_o;
/* Initialise the struct */
INIT_LIST_HEAD(&o->snapshots);
o->bdev = bdev;
__insert_origin(o);
}
__insert_snapshot(o, snap);
out:
up_write(&_origins_lock);
return r;
}
/*
* Move snapshot to correct place in list according to chunk size.
*/
static void reregister_snapshot(struct dm_snapshot *s)
{
struct block_device *bdev = s->origin->bdev;
down_write(&_origins_lock);
list_del(&s->list);
__insert_snapshot(__lookup_origin(bdev), s);
up_write(&_origins_lock);
}
static void unregister_snapshot(struct dm_snapshot *s)
{
struct origin *o;
down_write(&_origins_lock);
o = __lookup_origin(s->origin->bdev);
list_del(&s->list);
if (o && list_empty(&o->snapshots)) {
list_del(&o->hash_list);
kfree(o);
}
up_write(&_origins_lock);
}
/*
* Implementation of the exception hash tables.
* The lowest hash_shift bits of the chunk number are ignored, allowing
* some consecutive chunks to be grouped together.
*/
static int dm_exception_table_init(struct dm_exception_table *et,
uint32_t size, unsigned hash_shift)
{
unsigned int i;
et->hash_shift = hash_shift;
et->hash_mask = size - 1;
et->table = dm_vcalloc(size, sizeof(struct list_head));
if (!et->table)
return -ENOMEM;
for (i = 0; i < size; i++)
INIT_LIST_HEAD(et->table + i);
return 0;
}
static void dm_exception_table_exit(struct dm_exception_table *et,
struct kmem_cache *mem)
{
struct list_head *slot;
struct dm_exception *ex, *next;
int i, size;
size = et->hash_mask + 1;
for (i = 0; i < size; i++) {
slot = et->table + i;
list_for_each_entry_safe (ex, next, slot, hash_list)
kmem_cache_free(mem, ex);
}
vfree(et->table);
}
static uint32_t exception_hash(struct dm_exception_table *et, chunk_t chunk)
{
return (chunk >> et->hash_shift) & et->hash_mask;
}
static void dm_remove_exception(struct dm_exception *e)
{
list_del(&e->hash_list);
}
/*
* Return the exception data for a sector, or NULL if not
* remapped.
*/
static struct dm_exception *dm_lookup_exception(struct dm_exception_table *et,
chunk_t chunk)
{
struct list_head *slot;
struct dm_exception *e;
slot = &et->table[exception_hash(et, chunk)];
list_for_each_entry (e, slot, hash_list)
if (chunk >= e->old_chunk &&
chunk <= e->old_chunk + dm_consecutive_chunk_count(e))
return e;
return NULL;
}
static struct dm_exception *alloc_completed_exception(void)
{
struct dm_exception *e;
e = kmem_cache_alloc(exception_cache, GFP_NOIO);
if (!e)
e = kmem_cache_alloc(exception_cache, GFP_ATOMIC);
return e;
}
static void free_completed_exception(struct dm_exception *e)
{
kmem_cache_free(exception_cache, e);
}
static struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snapshot *s)
{
struct dm_snap_pending_exception *pe = mempool_alloc(s->pending_pool,
GFP_NOIO);
dm snapshot: wait for chunks in destructor If there are several snapshots sharing an origin and one is removed while the origin is being written to, the snapshot's mempool may get deleted while elements are still referenced. Prior to dm-snapshot-use-per-device-mempools.patch the pending exceptions may still have been referenced after the snapshot was destroyed, but this was not a problem because the shared mempool was still there. This patch fixes the problem by tracking the number of mempool elements in use. The scenario: - You have an origin and two snapshots 1 and 2. - Someone writes to the origin. - It creates two exceptions in the snapshots, snapshot 1 will be primary exception, snapshot 2's pending_exception->primary_pe will point to the exception in snapshot 1. - The exceptions are being relocated, relocation of exception 1 finishes (but it's pending_exception is still allocated, because it is referenced by an exception from snapshot 2) - The user lvremoves snapshot 1 --- it calls just suspend (does nothing) and destructor. md->pending is zero (there is no I/O submitted to the snapshot by md layer), so it won't help us. - The destructor waits for kcopyd jobs to finish on snapshot 1 --- but there are none. - The destructor on snapshot 1 cleans up everything. - The relocation of exception on snapshot 2 finishes, it drops reference on primary_pe. This frees its primary_pe pointer. Primary_pe points to pending exception created for snapshot 1. So it frees memory into non-existing mempool. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2008-10-30 13:33:16 +00:00
atomic_inc(&s->pending_exceptions_count);
pe->snap = s;
return pe;
}
static void free_pending_exception(struct dm_snap_pending_exception *pe)
{
dm snapshot: wait for chunks in destructor If there are several snapshots sharing an origin and one is removed while the origin is being written to, the snapshot's mempool may get deleted while elements are still referenced. Prior to dm-snapshot-use-per-device-mempools.patch the pending exceptions may still have been referenced after the snapshot was destroyed, but this was not a problem because the shared mempool was still there. This patch fixes the problem by tracking the number of mempool elements in use. The scenario: - You have an origin and two snapshots 1 and 2. - Someone writes to the origin. - It creates two exceptions in the snapshots, snapshot 1 will be primary exception, snapshot 2's pending_exception->primary_pe will point to the exception in snapshot 1. - The exceptions are being relocated, relocation of exception 1 finishes (but it's pending_exception is still allocated, because it is referenced by an exception from snapshot 2) - The user lvremoves snapshot 1 --- it calls just suspend (does nothing) and destructor. md->pending is zero (there is no I/O submitted to the snapshot by md layer), so it won't help us. - The destructor waits for kcopyd jobs to finish on snapshot 1 --- but there are none. - The destructor on snapshot 1 cleans up everything. - The relocation of exception on snapshot 2 finishes, it drops reference on primary_pe. This frees its primary_pe pointer. Primary_pe points to pending exception created for snapshot 1. So it frees memory into non-existing mempool. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2008-10-30 13:33:16 +00:00
struct dm_snapshot *s = pe->snap;
mempool_free(pe, s->pending_pool);
smp_mb__before_atomic_dec();
atomic_dec(&s->pending_exceptions_count);
}
static void dm_insert_exception(struct dm_exception_table *eh,
struct dm_exception *new_e)
{
struct list_head *l;
struct dm_exception *e = NULL;
l = &eh->table[exception_hash(eh, new_e->old_chunk)];
/* Add immediately if this table doesn't support consecutive chunks */
if (!eh->hash_shift)
goto out;
/* List is ordered by old_chunk */
list_for_each_entry_reverse(e, l, hash_list) {
/* Insert after an existing chunk? */
if (new_e->old_chunk == (e->old_chunk +
dm_consecutive_chunk_count(e) + 1) &&
new_e->new_chunk == (dm_chunk_number(e->new_chunk) +
dm_consecutive_chunk_count(e) + 1)) {
dm_consecutive_chunk_count_inc(e);
free_completed_exception(new_e);
return;
}
/* Insert before an existing chunk? */
if (new_e->old_chunk == (e->old_chunk - 1) &&
new_e->new_chunk == (dm_chunk_number(e->new_chunk) - 1)) {
dm_consecutive_chunk_count_inc(e);
e->old_chunk--;
e->new_chunk--;
free_completed_exception(new_e);
return;
}
if (new_e->old_chunk > e->old_chunk)
break;
}
out:
list_add(&new_e->hash_list, e ? &e->hash_list : l);
}
/*
* Callback used by the exception stores to load exceptions when
* initialising.
*/
static int dm_add_exception(void *context, chunk_t old, chunk_t new)
{
struct dm_snapshot *s = context;
struct dm_exception *e;
e = alloc_completed_exception();
if (!e)
return -ENOMEM;
e->old_chunk = old;
/* Consecutive_count is implicitly initialised to zero */
e->new_chunk = new;
dm_insert_exception(&s->complete, e);
return 0;
}
#define min_not_zero(l, r) (((l) == 0) ? (r) : (((r) == 0) ? (l) : min(l, r)))
/*
* Return a minimum chunk size of all snapshots that have the specified origin.
* Return zero if the origin has no snapshots.
*/
static sector_t __minimum_chunk_size(struct origin *o)
{
struct dm_snapshot *snap;
unsigned chunk_size = 0;
if (o)
list_for_each_entry(snap, &o->snapshots, list)
chunk_size = min_not_zero(chunk_size,
snap->store->chunk_size);
return chunk_size;
}
/*
* Hard coded magic.
*/
static int calc_max_buckets(void)
{
/* use a fixed size of 2MB */
unsigned long mem = 2 * 1024 * 1024;
mem /= sizeof(struct list_head);
return mem;
}
/*
* Allocate room for a suitable hash table.
*/
static int init_hash_tables(struct dm_snapshot *s)
{
sector_t hash_size, cow_dev_size, origin_dev_size, max_buckets;
/*
* Calculate based on the size of the original volume or
* the COW volume...
*/
cow_dev_size = get_dev_size(s->cow->bdev);
origin_dev_size = get_dev_size(s->origin->bdev);
max_buckets = calc_max_buckets();
hash_size = min(origin_dev_size, cow_dev_size) >> s->store->chunk_shift;
hash_size = min(hash_size, max_buckets);
if (hash_size < 64)
hash_size = 64;
hash_size = rounddown_pow_of_two(hash_size);
if (dm_exception_table_init(&s->complete, hash_size,
DM_CHUNK_CONSECUTIVE_BITS))
return -ENOMEM;
/*
* Allocate hash table for in-flight exceptions
* Make this smaller than the real hash table
*/
hash_size >>= 3;
if (hash_size < 64)
hash_size = 64;
if (dm_exception_table_init(&s->pending, hash_size, 0)) {
dm_exception_table_exit(&s->complete, exception_cache);
return -ENOMEM;
}
return 0;
}
/*
* Construct a snapshot mapping: <origin_dev> <COW-dev> <p/n> <chunk-size>
*/
static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
struct dm_snapshot *s;
int i;
int r = -EINVAL;
char *origin_path, *cow_path;
unsigned args_used, num_flush_requests = 1;
fmode_t origin_mode = FMODE_READ;
if (argc != 4) {
ti->error = "requires exactly 4 arguments";
r = -EINVAL;
goto bad;
}
if (dm_target_is_snapshot_merge(ti)) {
num_flush_requests = 2;
origin_mode = FMODE_WRITE;
}
origin_path = argv[0];
argv++;
argc--;
s = kmalloc(sizeof(*s), GFP_KERNEL);
if (!s) {
ti->error = "Cannot allocate snapshot context private "
"structure";
r = -ENOMEM;
goto bad;
}
cow_path = argv[0];
argv++;
argc--;
r = dm_get_device(ti, cow_path, 0, 0,
FMODE_READ | FMODE_WRITE, &s->cow);
if (r) {
ti->error = "Cannot get COW device";
goto bad_cow;
}
r = dm_exception_store_create(ti, argc, argv, s, &args_used, &s->store);
if (r) {
ti->error = "Couldn't create exception store";
r = -EINVAL;
goto bad_store;
}
argv += args_used;
argc -= args_used;
r = dm_get_device(ti, origin_path, 0, ti->len, origin_mode, &s->origin);
if (r) {
ti->error = "Cannot get origin device";
goto bad_origin;
}
s->ti = ti;
s->valid = 1;
s->active = 0;
s->suspended = 0;
dm snapshot: wait for chunks in destructor If there are several snapshots sharing an origin and one is removed while the origin is being written to, the snapshot's mempool may get deleted while elements are still referenced. Prior to dm-snapshot-use-per-device-mempools.patch the pending exceptions may still have been referenced after the snapshot was destroyed, but this was not a problem because the shared mempool was still there. This patch fixes the problem by tracking the number of mempool elements in use. The scenario: - You have an origin and two snapshots 1 and 2. - Someone writes to the origin. - It creates two exceptions in the snapshots, snapshot 1 will be primary exception, snapshot 2's pending_exception->primary_pe will point to the exception in snapshot 1. - The exceptions are being relocated, relocation of exception 1 finishes (but it's pending_exception is still allocated, because it is referenced by an exception from snapshot 2) - The user lvremoves snapshot 1 --- it calls just suspend (does nothing) and destructor. md->pending is zero (there is no I/O submitted to the snapshot by md layer), so it won't help us. - The destructor waits for kcopyd jobs to finish on snapshot 1 --- but there are none. - The destructor on snapshot 1 cleans up everything. - The relocation of exception on snapshot 2 finishes, it drops reference on primary_pe. This frees its primary_pe pointer. Primary_pe points to pending exception created for snapshot 1. So it frees memory into non-existing mempool. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2008-10-30 13:33:16 +00:00
atomic_set(&s->pending_exceptions_count, 0);
init_rwsem(&s->lock);
INIT_LIST_HEAD(&s->list);
spin_lock_init(&s->pe_lock);
/* Allocate hash table for COW data */
if (init_hash_tables(s)) {
ti->error = "Unable to allocate hash table space";
r = -ENOMEM;
goto bad_hash_tables;
}
r = dm_kcopyd_client_create(SNAPSHOT_PAGES, &s->kcopyd_client);
if (r) {
ti->error = "Could not create kcopyd client";
goto bad_kcopyd;
}
s->pending_pool = mempool_create_slab_pool(MIN_IOS, pending_cache);
if (!s->pending_pool) {
ti->error = "Could not allocate mempool for pending exceptions";
goto bad_pending_pool;
}
s->tracked_chunk_pool = mempool_create_slab_pool(MIN_IOS,
tracked_chunk_cache);
if (!s->tracked_chunk_pool) {
ti->error = "Could not allocate tracked_chunk mempool for "
"tracking reads";
goto bad_tracked_chunk_pool;
}
for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);
spin_lock_init(&s->tracked_chunk_lock);
bio_list_init(&s->queued_bios);
INIT_WORK(&s->queued_bios_work, flush_queued_bios);
ti->private = s;
ti->num_flush_requests = num_flush_requests;
/* Add snapshot to the list of snapshots for this origin */
/* Exceptions aren't triggered till snapshot_resume() is called */
r = register_snapshot(s);
if (r == -ENOMEM) {
ti->error = "Snapshot origin struct allocation failed";
goto bad_load_and_register;
} else if (r < 0) {
/* invalid handover, register_snapshot has set ti->error */
goto bad_load_and_register;
}
/*
* Metadata must only be loaded into one table at once, so skip this
* if metadata will be handed over during resume.
* Chunk size will be set during the handover - set it to zero to
* ensure it's ignored.
*/
if (r > 0) {
s->store->chunk_size = 0;
return 0;
}
r = s->store->type->read_metadata(s->store, dm_add_exception,
(void *)s);
if (r < 0) {
ti->error = "Failed to read snapshot metadata";
goto bad_read_metadata;
} else if (r > 0) {
s->valid = 0;
DMWARN("Snapshot is marked invalid.");
}
if (!s->store->chunk_size) {
ti->error = "Chunk size not set";
goto bad_read_metadata;
}
ti->split_io = s->store->chunk_size;
return 0;
bad_read_metadata:
unregister_snapshot(s);
bad_load_and_register:
mempool_destroy(s->tracked_chunk_pool);
bad_tracked_chunk_pool:
mempool_destroy(s->pending_pool);
bad_pending_pool:
dm_kcopyd_client_destroy(s->kcopyd_client);
bad_kcopyd:
dm_exception_table_exit(&s->pending, pending_cache);
dm_exception_table_exit(&s->complete, exception_cache);
bad_hash_tables:
dm_put_device(ti, s->origin);
bad_origin:
dm_exception_store_destroy(s->store);
bad_store:
dm_put_device(ti, s->cow);
bad_cow:
kfree(s);
bad:
return r;
}
static void __free_exceptions(struct dm_snapshot *s)
{
dm_kcopyd_client_destroy(s->kcopyd_client);
s->kcopyd_client = NULL;
dm_exception_table_exit(&s->pending, pending_cache);
dm_exception_table_exit(&s->complete, exception_cache);
}
static void __handover_exceptions(struct dm_snapshot *snap_src,
struct dm_snapshot *snap_dest)
{
union {
struct dm_exception_table table_swap;
struct dm_exception_store *store_swap;
} u;
/*
* Swap all snapshot context information between the two instances.
*/
u.table_swap = snap_dest->complete;
snap_dest->complete = snap_src->complete;
snap_src->complete = u.table_swap;
u.store_swap = snap_dest->store;
snap_dest->store = snap_src->store;
snap_src->store = u.store_swap;
snap_dest->store->snap = snap_dest;
snap_src->store->snap = snap_src;
snap_dest->ti->split_io = snap_dest->store->chunk_size;
snap_dest->valid = snap_src->valid;
/*
* Set source invalid to ensure it receives no further I/O.
*/
snap_src->valid = 0;
}
static void snapshot_dtr(struct dm_target *ti)
{
#ifdef CONFIG_DM_DEBUG
int i;
#endif
struct dm_snapshot *s = ti->private;
struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
flush_workqueue(ksnapd);
down_read(&_origins_lock);
/* Check whether exception handover must be cancelled */
(void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
if (snap_src && snap_dest && (s == snap_src)) {
down_write(&snap_dest->lock);
snap_dest->valid = 0;
up_write(&snap_dest->lock);
DMERR("Cancelling snapshot handover.");
}
up_read(&_origins_lock);
/* Prevent further origin writes from using this snapshot. */
/* After this returns there can be no new kcopyd jobs. */
unregister_snapshot(s);
dm snapshot: wait for chunks in destructor If there are several snapshots sharing an origin and one is removed while the origin is being written to, the snapshot's mempool may get deleted while elements are still referenced. Prior to dm-snapshot-use-per-device-mempools.patch the pending exceptions may still have been referenced after the snapshot was destroyed, but this was not a problem because the shared mempool was still there. This patch fixes the problem by tracking the number of mempool elements in use. The scenario: - You have an origin and two snapshots 1 and 2. - Someone writes to the origin. - It creates two exceptions in the snapshots, snapshot 1 will be primary exception, snapshot 2's pending_exception->primary_pe will point to the exception in snapshot 1. - The exceptions are being relocated, relocation of exception 1 finishes (but it's pending_exception is still allocated, because it is referenced by an exception from snapshot 2) - The user lvremoves snapshot 1 --- it calls just suspend (does nothing) and destructor. md->pending is zero (there is no I/O submitted to the snapshot by md layer), so it won't help us. - The destructor waits for kcopyd jobs to finish on snapshot 1 --- but there are none. - The destructor on snapshot 1 cleans up everything. - The relocation of exception on snapshot 2 finishes, it drops reference on primary_pe. This frees its primary_pe pointer. Primary_pe points to pending exception created for snapshot 1. So it frees memory into non-existing mempool. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2008-10-30 13:33:16 +00:00
while (atomic_read(&s->pending_exceptions_count))
msleep(1);
dm snapshot: wait for chunks in destructor If there are several snapshots sharing an origin and one is removed while the origin is being written to, the snapshot's mempool may get deleted while elements are still referenced. Prior to dm-snapshot-use-per-device-mempools.patch the pending exceptions may still have been referenced after the snapshot was destroyed, but this was not a problem because the shared mempool was still there. This patch fixes the problem by tracking the number of mempool elements in use. The scenario: - You have an origin and two snapshots 1 and 2. - Someone writes to the origin. - It creates two exceptions in the snapshots, snapshot 1 will be primary exception, snapshot 2's pending_exception->primary_pe will point to the exception in snapshot 1. - The exceptions are being relocated, relocation of exception 1 finishes (but it's pending_exception is still allocated, because it is referenced by an exception from snapshot 2) - The user lvremoves snapshot 1 --- it calls just suspend (does nothing) and destructor. md->pending is zero (there is no I/O submitted to the snapshot by md layer), so it won't help us. - The destructor waits for kcopyd jobs to finish on snapshot 1 --- but there are none. - The destructor on snapshot 1 cleans up everything. - The relocation of exception on snapshot 2 finishes, it drops reference on primary_pe. This frees its primary_pe pointer. Primary_pe points to pending exception created for snapshot 1. So it frees memory into non-existing mempool. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2008-10-30 13:33:16 +00:00
/*
* Ensure instructions in mempool_destroy aren't reordered
* before atomic_read.
*/
smp_mb();
#ifdef CONFIG_DM_DEBUG
for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i]));
#endif
mempool_destroy(s->tracked_chunk_pool);
__free_exceptions(s);
mempool_destroy(s->pending_pool);
dm_put_device(ti, s->origin);
dm_exception_store_destroy(s->store);
dm_put_device(ti, s->cow);
kfree(s);
}
/*
* Flush a list of buffers.
*/
static void flush_bios(struct bio *bio)
{
struct bio *n;
while (bio) {
n = bio->bi_next;
bio->bi_next = NULL;
generic_make_request(bio);
bio = n;
}
}
static void flush_queued_bios(struct work_struct *work)
{
struct dm_snapshot *s =
container_of(work, struct dm_snapshot, queued_bios_work);
struct bio *queued_bios;
unsigned long flags;
spin_lock_irqsave(&s->pe_lock, flags);
queued_bios = bio_list_get(&s->queued_bios);
spin_unlock_irqrestore(&s->pe_lock, flags);
flush_bios(queued_bios);
}
static int do_origin(struct dm_dev *origin, struct bio *bio);
/*
* Flush a list of buffers.
*/
static void retry_origin_bios(struct dm_snapshot *s, struct bio *bio)
{
struct bio *n;
int r;
while (bio) {
n = bio->bi_next;
bio->bi_next = NULL;
r = do_origin(s->origin, bio);
if (r == DM_MAPIO_REMAPPED)
generic_make_request(bio);
bio = n;
}
}
/*
* Error a list of buffers.
*/
static void error_bios(struct bio *bio)
{
struct bio *n;
while (bio) {
n = bio->bi_next;
bio->bi_next = NULL;
bio_io_error(bio);
bio = n;
}
}
static void __invalidate_snapshot(struct dm_snapshot *s, int err)
{
if (!s->valid)
return;
if (err == -EIO)
DMERR("Invalidating snapshot: Error reading/writing.");
else if (err == -ENOMEM)
DMERR("Invalidating snapshot: Unable to allocate exception.");
if (s->store->type->drop_snapshot)
s->store->type->drop_snapshot(s->store);
s->valid = 0;
dm_table_event(s->ti->table);
}
static void pending_complete(struct dm_snap_pending_exception *pe, int success)
{
struct dm_exception *e;
struct dm_snapshot *s = pe->snap;
struct bio *origin_bios = NULL;
struct bio *snapshot_bios = NULL;
int error = 0;
if (!success) {
/* Read/write error - snapshot is unusable */
down_write(&s->lock);
__invalidate_snapshot(s, -EIO);
error = 1;
goto out;
}
e = alloc_completed_exception();
if (!e) {
down_write(&s->lock);
__invalidate_snapshot(s, -ENOMEM);
error = 1;
goto out;
}
*e = pe->e;
down_write(&s->lock);
if (!s->valid) {
free_completed_exception(e);
error = 1;
goto out;
}
/* Check for conflicting reads */
__check_for_conflicting_io(s, pe->e.old_chunk);
/*
* Add a proper exception, and remove the
* in-flight exception from the list.
*/
dm_insert_exception(&s->complete, e);
out:
dm_remove_exception(&pe->e);
snapshot_bios = bio_list_get(&pe->snapshot_bios);
origin_bios = bio_list_get(&pe->origin_bios);
free_pending_exception(pe);
up_write(&s->lock);
/* Submit any pending write bios */
if (error)
error_bios(snapshot_bios);
else
flush_bios(snapshot_bios);
retry_origin_bios(s, origin_bios);
}
static void commit_callback(void *context, int success)
{
struct dm_snap_pending_exception *pe = context;
pending_complete(pe, success);
}
/*
* Called when the copy I/O has finished. kcopyd actually runs
* this code so don't block.
*/
static void copy_callback(int read_err, unsigned long write_err, void *context)
{
struct dm_snap_pending_exception *pe = context;
struct dm_snapshot *s = pe->snap;
if (read_err || write_err)
pending_complete(pe, 0);
else
/* Update the metadata if we are persistent */
s->store->type->commit_exception(s->store, &pe->e,
commit_callback, pe);
}
/*
* Dispatches the copy operation to kcopyd.
*/
static void start_copy(struct dm_snap_pending_exception *pe)
{
struct dm_snapshot *s = pe->snap;
struct dm_io_region src, dest;
struct block_device *bdev = s->origin->bdev;
sector_t dev_size;
dev_size = get_dev_size(bdev);
src.bdev = bdev;
src.sector = chunk_to_sector(s->store, pe->e.old_chunk);
src.count = min((sector_t)s->store->chunk_size, dev_size - src.sector);
dest.bdev = s->cow->bdev;
dest.sector = chunk_to_sector(s->store, pe->e.new_chunk);
dest.count = src.count;
/* Hand over to kcopyd */
dm_kcopyd_copy(s->kcopyd_client,
&src, 1, &dest, 0, copy_callback, pe);
}
static struct dm_snap_pending_exception *
__lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk)
{
struct dm_exception *e = dm_lookup_exception(&s->pending, chunk);
if (!e)
return NULL;
return container_of(e, struct dm_snap_pending_exception, e);
}
/*
* Looks to see if this snapshot already has a pending exception
* for this chunk, otherwise it allocates a new one and inserts
* it into the pending table.
*
* NOTE: a write lock must be held on snap->lock before calling
* this.
*/
static struct dm_snap_pending_exception *
__find_pending_exception(struct dm_snapshot *s,
struct dm_snap_pending_exception *pe, chunk_t chunk)
{
struct dm_snap_pending_exception *pe2;
pe2 = __lookup_pending_exception(s, chunk);
if (pe2) {
free_pending_exception(pe);
return pe2;
}
pe->e.old_chunk = chunk;
bio_list_init(&pe->origin_bios);
bio_list_init(&pe->snapshot_bios);
pe->started = 0;
if (s->store->type->prepare_exception(s->store, &pe->e)) {
free_pending_exception(pe);
return NULL;
}
dm_insert_exception(&s->pending, &pe->e);
return pe;
}
static void remap_exception(struct dm_snapshot *s, struct dm_exception *e,
struct bio *bio, chunk_t chunk)
{
bio->bi_bdev = s->cow->bdev;
bio->bi_sector = chunk_to_sector(s->store,
dm_chunk_number(e->new_chunk) +
(chunk - e->old_chunk)) +
(bio->bi_sector &
s->store->chunk_mask);
}
static int snapshot_map(struct dm_target *ti, struct bio *bio,
union map_info *map_context)
{
struct dm_exception *e;
struct dm_snapshot *s = ti->private;
int r = DM_MAPIO_REMAPPED;
chunk_t chunk;
struct dm_snap_pending_exception *pe = NULL;
if (unlikely(bio_empty_barrier(bio))) {
bio->bi_bdev = s->cow->bdev;
return DM_MAPIO_REMAPPED;
}
chunk = sector_to_chunk(s->store, bio->bi_sector);
/* Full snapshots are not usable */
/* To get here the table must be live so s->active is always set. */
if (!s->valid)
return -EIO;
/* FIXME: should only take write lock if we need
* to copy an exception */
down_write(&s->lock);
if (!s->valid) {
r = -EIO;
goto out_unlock;
}
/* If the block is already remapped - use that, else remap it */
e = dm_lookup_exception(&s->complete, chunk);
if (e) {
remap_exception(s, e, bio, chunk);
goto out_unlock;
}
/*
* Write to snapshot - higher level takes care of RW/RO
* flags so we should only get this if we are
* writeable.
*/
if (bio_rw(bio) == WRITE) {
pe = __lookup_pending_exception(s, chunk);
if (!pe) {
up_write(&s->lock);
pe = alloc_pending_exception(s);
down_write(&s->lock);
if (!s->valid) {
free_pending_exception(pe);
r = -EIO;
goto out_unlock;
}
e = dm_lookup_exception(&s->complete, chunk);
if (e) {
free_pending_exception(pe);
remap_exception(s, e, bio, chunk);
goto out_unlock;
}
pe = __find_pending_exception(s, pe, chunk);
if (!pe) {
__invalidate_snapshot(s, -ENOMEM);
r = -EIO;
goto out_unlock;
}
}
remap_exception(s, &pe->e, bio, chunk);
bio_list_add(&pe->snapshot_bios, bio);
r = DM_MAPIO_SUBMITTED;
if (!pe->started) {
/* this is protected by snap->lock */
pe->started = 1;
up_write(&s->lock);
start_copy(pe);
goto out;
}
} else {
bio->bi_bdev = s->origin->bdev;
map_context->ptr = track_chunk(s, chunk);
}
out_unlock:
up_write(&s->lock);
out:
return r;
}
/*
* A snapshot-merge target behaves like a combination of a snapshot
* target and a snapshot-origin target. It only generates new
* exceptions in other snapshots and not in the one that is being
* merged.
*
* For each chunk, if there is an existing exception, it is used to
* redirect I/O to the cow device. Otherwise I/O is sent to the origin,
* which in turn might generate exceptions in other snapshots.
*/
static int snapshot_merge_map(struct dm_target *ti, struct bio *bio,
union map_info *map_context)
{
struct dm_exception *e;
struct dm_snapshot *s = ti->private;
int r = DM_MAPIO_REMAPPED;
chunk_t chunk;
if (unlikely(bio_empty_barrier(bio))) {
if (!map_context->flush_request)
bio->bi_bdev = s->origin->bdev;
else
bio->bi_bdev = s->cow->bdev;
map_context->ptr = NULL;
return DM_MAPIO_REMAPPED;
}
chunk = sector_to_chunk(s->store, bio->bi_sector);
down_read(&s->lock);
/* Full snapshots are not usable */
if (!s->valid) {
r = -EIO;
goto out_unlock;
}
/* If the block is already remapped - use that */
e = dm_lookup_exception(&s->complete, chunk);
if (e) {
remap_exception(s, e, bio, chunk);
goto out_unlock;
}
bio->bi_bdev = s->origin->bdev;
if (bio_rw(bio) == WRITE) {
up_read(&s->lock);
return do_origin(s->origin, bio);
}
out_unlock:
up_read(&s->lock);
return r;
}
static int snapshot_end_io(struct dm_target *ti, struct bio *bio,
int error, union map_info *map_context)
{
struct dm_snapshot *s = ti->private;
struct dm_snap_tracked_chunk *c = map_context->ptr;
if (c)
stop_tracking_chunk(s, c);
return 0;
}
static void snapshot_postsuspend(struct dm_target *ti)
{
struct dm_snapshot *s = ti->private;
down_write(&s->lock);
s->suspended = 1;
up_write(&s->lock);
}
static int snapshot_preresume(struct dm_target *ti)
{
int r = 0;
struct dm_snapshot *s = ti->private;
struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
down_read(&_origins_lock);
(void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
if (snap_src && snap_dest) {
down_read(&snap_src->lock);
if (s == snap_src) {
DMERR("Unable to resume snapshot source until "
"handover completes.");
r = -EINVAL;
} else if (!snap_src->suspended) {
DMERR("Unable to perform snapshot handover until "
"source is suspended.");
r = -EINVAL;
}
up_read(&snap_src->lock);
}
up_read(&_origins_lock);
return r;
}
static void snapshot_resume(struct dm_target *ti)
{
struct dm_snapshot *s = ti->private;
struct dm_snapshot *snap_src = NULL, *snap_dest = NULL;
down_read(&_origins_lock);
(void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL);
if (snap_src && snap_dest) {
down_write(&snap_src->lock);
down_write_nested(&snap_dest->lock, SINGLE_DEPTH_NESTING);
__handover_exceptions(snap_src, snap_dest);
up_write(&snap_dest->lock);
up_write(&snap_src->lock);
}
up_read(&_origins_lock);
/* Now we have correct chunk size, reregister */
reregister_snapshot(s);
down_write(&s->lock);
s->active = 1;
s->suspended = 0;
up_write(&s->lock);
}
static int snapshot_status(struct dm_target *ti, status_type_t type,
char *result, unsigned int maxlen)
{
unsigned sz = 0;
struct dm_snapshot *snap = ti->private;
switch (type) {
case STATUSTYPE_INFO:
down_write(&snap->lock);
if (!snap->valid)
DMEMIT("Invalid");
else {
if (snap->store->type->usage) {
sector_t total_sectors, sectors_allocated,
metadata_sectors;
snap->store->type->usage(snap->store,
&total_sectors,
&sectors_allocated,
&metadata_sectors);
DMEMIT("%llu/%llu %llu",
(unsigned long long)sectors_allocated,
(unsigned long long)total_sectors,
(unsigned long long)metadata_sectors);
}
else
DMEMIT("Unknown");
}
up_write(&snap->lock);
break;
case STATUSTYPE_TABLE:
/*
* kdevname returns a static pointer so we need
* to make private copies if the output is to
* make sense.
*/
DMEMIT("%s %s", snap->origin->name, snap->cow->name);
snap->store->type->status(snap->store, type, result + sz,
maxlen - sz);
break;
}
return 0;
}
static int snapshot_iterate_devices(struct dm_target *ti,
iterate_devices_callout_fn fn, void *data)
{
struct dm_snapshot *snap = ti->private;
return fn(ti, snap->origin, 0, ti->len, data);
}
/*-----------------------------------------------------------------
* Origin methods
*---------------------------------------------------------------*/
/*
* If no exceptions need creating, DM_MAPIO_REMAPPED is returned and any
* supplied bio was ignored. The caller may submit it immediately.
* (No remapping actually occurs as the origin is always a direct linear
* map.)
*
* If further exceptions are required, DM_MAPIO_SUBMITTED is returned
* and any supplied bio is added to a list to be submitted once all
* the necessary exceptions exist.
*/
static int __origin_write(struct list_head *snapshots, sector_t sector,
struct bio *bio)
{
int r = DM_MAPIO_REMAPPED;
struct dm_snapshot *snap;
struct dm_exception *e;
struct dm_snap_pending_exception *pe;
struct dm_snap_pending_exception *pe_to_start_now = NULL;
struct dm_snap_pending_exception *pe_to_start_last = NULL;
chunk_t chunk;
/* Do all the snapshots on this origin */
list_for_each_entry (snap, snapshots, list) {
/*
* Don't make new exceptions in a merging snapshot
* because it has effectively been deleted
*/
if (dm_target_is_snapshot_merge(snap->ti))
continue;
down_write(&snap->lock);
/* Only deal with valid and active snapshots */
if (!snap->valid || !snap->active)
goto next_snapshot;
/* Nothing to do if writing beyond end of snapshot */
if (sector >= dm_table_get_size(snap->ti->table))
goto next_snapshot;
/*
* Remember, different snapshots can have
* different chunk sizes.
*/
chunk = sector_to_chunk(snap->store, sector);
/*
* Check exception table to see if block
* is already remapped in this snapshot
* and trigger an exception if not.
*/
e = dm_lookup_exception(&snap->complete, chunk);
if (e)
goto next_snapshot;
pe = __lookup_pending_exception(snap, chunk);
if (!pe) {
up_write(&snap->lock);
pe = alloc_pending_exception(snap);
down_write(&snap->lock);
if (!snap->valid) {
free_pending_exception(pe);
goto next_snapshot;
}
e = dm_lookup_exception(&snap->complete, chunk);
if (e) {
free_pending_exception(pe);
goto next_snapshot;
}
pe = __find_pending_exception(snap, pe, chunk);
if (!pe) {
__invalidate_snapshot(snap, -ENOMEM);
goto next_snapshot;
}
}
r = DM_MAPIO_SUBMITTED;
/*
* If an origin bio was supplied, queue it to wait for the
* completion of this exception, and start this one last,
* at the end of the function.
*/
if (bio) {
bio_list_add(&pe->origin_bios, bio);
bio = NULL;
if (!pe->started) {
pe->started = 1;
pe_to_start_last = pe;
}
}
if (!pe->started) {
pe->started = 1;
pe_to_start_now = pe;
}
next_snapshot:
up_write(&snap->lock);
if (pe_to_start_now) {
start_copy(pe_to_start_now);
pe_to_start_now = NULL;
}
}
/*
* Submit the exception against which the bio is queued last,
* to give the other exceptions a head start.
*/
if (pe_to_start_last)
start_copy(pe_to_start_last);
return r;
}
/*
* Called on a write from the origin driver.
*/
static int do_origin(struct dm_dev *origin, struct bio *bio)
{
struct origin *o;
int r = DM_MAPIO_REMAPPED;
down_read(&_origins_lock);
o = __lookup_origin(origin->bdev);
if (o)
r = __origin_write(&o->snapshots, bio->bi_sector, bio);
up_read(&_origins_lock);
return r;
}
/*
* Origin: maps a linear range of a device, with hooks for snapshotting.
*/
/*
* Construct an origin mapping: <dev_path>
* The context for an origin is merely a 'struct dm_dev *'
* pointing to the real device.
*/
static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
int r;
struct dm_dev *dev;
if (argc != 1) {
ti->error = "origin: incorrect number of arguments";
return -EINVAL;
}
r = dm_get_device(ti, argv[0], 0, ti->len,
dm_table_get_mode(ti->table), &dev);
if (r) {
ti->error = "Cannot get target device";
return r;
}
ti->private = dev;
ti->num_flush_requests = 1;
return 0;
}
static void origin_dtr(struct dm_target *ti)
{
struct dm_dev *dev = ti->private;
dm_put_device(ti, dev);
}
static int origin_map(struct dm_target *ti, struct bio *bio,
union map_info *map_context)
{
struct dm_dev *dev = ti->private;
bio->bi_bdev = dev->bdev;
if (unlikely(bio_empty_barrier(bio)))
return DM_MAPIO_REMAPPED;
/* Only tell snapshots if this is a write */
return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : DM_MAPIO_REMAPPED;
}
/*
* Set the target "split_io" field to the minimum of all the snapshots'
* chunk sizes.
*/
static void origin_resume(struct dm_target *ti)
{
struct dm_dev *dev = ti->private;
down_read(&_origins_lock);
ti->split_io = __minimum_chunk_size(__lookup_origin(dev->bdev));
up_read(&_origins_lock);
}
static int origin_status(struct dm_target *ti, status_type_t type, char *result,
unsigned int maxlen)
{
struct dm_dev *dev = ti->private;
switch (type) {
case STATUSTYPE_INFO:
result[0] = '\0';
break;
case STATUSTYPE_TABLE:
snprintf(result, maxlen, "%s", dev->name);
break;
}
return 0;
}
static int origin_iterate_devices(struct dm_target *ti,
iterate_devices_callout_fn fn, void *data)
{
struct dm_dev *dev = ti->private;
return fn(ti, dev, 0, ti->len, data);
}
static struct target_type origin_target = {
.name = "snapshot-origin",
.version = {1, 7, 0},
.module = THIS_MODULE,
.ctr = origin_ctr,
.dtr = origin_dtr,
.map = origin_map,
.resume = origin_resume,
.status = origin_status,
.iterate_devices = origin_iterate_devices,
};
static struct target_type snapshot_target = {
.name = "snapshot",
.version = {1, 9, 0},
.module = THIS_MODULE,
.ctr = snapshot_ctr,
.dtr = snapshot_dtr,
.map = snapshot_map,
.end_io = snapshot_end_io,
.postsuspend = snapshot_postsuspend,
.preresume = snapshot_preresume,
.resume = snapshot_resume,
.status = snapshot_status,
.iterate_devices = snapshot_iterate_devices,
};
static struct target_type merge_target = {
.name = dm_snapshot_merge_target_name,
.version = {1, 0, 0},
.module = THIS_MODULE,
.ctr = snapshot_ctr,
.dtr = snapshot_dtr,
.map = snapshot_merge_map,
.end_io = snapshot_end_io,
.postsuspend = snapshot_postsuspend,
.preresume = snapshot_preresume,
.resume = snapshot_resume,
.status = snapshot_status,
.iterate_devices = snapshot_iterate_devices,
};
static int __init dm_snapshot_init(void)
{
int r;
r = dm_exception_store_init();
if (r) {
DMERR("Failed to initialize exception stores");
return r;
}
r = dm_register_target(&snapshot_target);
if (r < 0) {
DMERR("snapshot target register failed %d", r);
goto bad_register_snapshot_target;
}
r = dm_register_target(&origin_target);
if (r < 0) {
DMERR("Origin target register failed %d", r);
goto bad_register_origin_target;
}
r = dm_register_target(&merge_target);
if (r < 0) {
DMERR("Merge target register failed %d", r);
goto bad_register_merge_target;
}
r = init_origin_hash();
if (r) {
DMERR("init_origin_hash failed.");
goto bad_origin_hash;
}
exception_cache = KMEM_CACHE(dm_exception, 0);
if (!exception_cache) {
DMERR("Couldn't create exception cache.");
r = -ENOMEM;
goto bad_exception_cache;
}
pending_cache = KMEM_CACHE(dm_snap_pending_exception, 0);
if (!pending_cache) {
DMERR("Couldn't create pending cache.");
r = -ENOMEM;
goto bad_pending_cache;
}
tracked_chunk_cache = KMEM_CACHE(dm_snap_tracked_chunk, 0);
if (!tracked_chunk_cache) {
DMERR("Couldn't create cache to track chunks in use.");
r = -ENOMEM;
goto bad_tracked_chunk_cache;
}
ksnapd = create_singlethread_workqueue("ksnapd");
if (!ksnapd) {
DMERR("Failed to create ksnapd workqueue.");
r = -ENOMEM;
goto bad_pending_pool;
}
return 0;
bad_pending_pool:
kmem_cache_destroy(tracked_chunk_cache);
bad_tracked_chunk_cache:
kmem_cache_destroy(pending_cache);
bad_pending_cache:
kmem_cache_destroy(exception_cache);
bad_exception_cache:
exit_origin_hash();
bad_origin_hash:
dm_unregister_target(&merge_target);
bad_register_merge_target:
dm_unregister_target(&origin_target);
bad_register_origin_target:
dm_unregister_target(&snapshot_target);
bad_register_snapshot_target:
dm_exception_store_exit();
return r;
}
static void __exit dm_snapshot_exit(void)
{
destroy_workqueue(ksnapd);
dm_unregister_target(&snapshot_target);
dm_unregister_target(&origin_target);
dm_unregister_target(&merge_target);
exit_origin_hash();
kmem_cache_destroy(pending_cache);
kmem_cache_destroy(exception_cache);
kmem_cache_destroy(tracked_chunk_cache);
dm_exception_store_exit();
}
/* Module hooks */
module_init(dm_snapshot_init);
module_exit(dm_snapshot_exit);
MODULE_DESCRIPTION(DM_NAME " snapshot target");
MODULE_AUTHOR("Joe Thornber");
MODULE_LICENSE("GPL");