/*
* dm-snapshot.c
*
* Copyright (C) 2001-2002 Sistina Software (UK) Limited.
*
* This file is released under the GPL.
*/
#include <linux/blkdev.h>
#include <linux/config.h>
#include <linux/ctype.h>
#include <linux/device-mapper.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 "dm-snap.h"
#include "dm-bio-list.h"
#include "kcopyd.h"
/*
* The percentage increment we will wake up users at
*/
#define WAKE_UP_PERCENT 5
/*
* kcopyd priority of snapshot operations
*/
#define SNAPSHOT_COPY_PRIORITY 2
/*
* Each snapshot reserves this many pages for io
*/
#define SNAPSHOT_PAGES 256
struct pending_exception {
struct 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;
/*
* Other pending_exceptions that are processing this
* chunk. When this list is empty, we know we can
* complete the origins.
*/
struct list_head siblings;
/* 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 kmem_cache_t *exception_cache;
static kmem_cache_t *pending_cache;
static mempool_t *pending_pool;
/*
* 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("Device mapper: Snapshot: 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 inline unsigned int 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);
}
/*
* Make a note of the snapshot and its origin so we can look it
* up when the origin has a write on it.
*/
static int register_snapshot(struct dm_snapshot *snap)
{
struct origin *o;
struct block_device *bdev = snap->origin->bdev;
down_write(&_origins_lock);
o = __lookup_origin(bdev);
if (!o) {
/* New origin */
o = kmalloc(sizeof(*o), GFP_KERNEL);
if (!o) {
up_write(&_origins_lock);
return -ENOMEM;
}
/* Initialise the struct */
INIT_LIST_HEAD(&o->snapshots);
o->bdev = bdev;
__insert_origin(o);
}
list_add_tail(&snap->list, &o->snapshots);
up_write(&_origins_lock);
return 0;
}
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 (list_empty(&o->snapshots)) {
list_del(&o->hash_list);
kfree(o);
}
up_write(&_origins_lock);
}
/*
* Implementation of the exception hash tables.
*/
static int init_exception_table(struct exception_table *et, uint32_t size)
{
unsigned int i;
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 exit_exception_table(struct exception_table *et, kmem_cache_t *mem)
{
struct list_head *slot;
struct 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 inline uint32_t exception_hash(struct exception_table *et, chunk_t chunk)
{
return chunk & et->hash_mask;
}
static void insert_exception(struct exception_table *eh, struct exception *e)
{
struct list_head *l = &eh->table[exception_hash(eh, e->old_chunk)];
list_add(&e->hash_list, l);
}
static inline void remove_exception(struct exception *e)
{
list_del(&e->hash_list);
}
/*
* Return the exception data for a sector, or NULL if not
* remapped.
*/
static struct exception *lookup_exception(struct exception_table *et,
chunk_t chunk)
{
struct list_head *slot;
struct exception *e;
slot = &et->table[exception_hash(et, chunk)];
list_for_each_entry (e, slot, hash_list)
if (e->old_chunk == chunk)
return e;
return NULL;
}
static inline struct exception *alloc_exception(void)
{
struct exception *e;
e = kmem_cache_alloc(exception_cache, GFP_NOIO);
if (!e)
e = kmem_cache_alloc(exception_cache, GFP_ATOMIC);
return e;
}
static inline void free_exception(struct exception *e)
{
kmem_cache_free(exception_cache, e);
}
static inline struct pending_exception *alloc_pending_exception(void)
{
return mempool_alloc(pending_pool, GFP_NOIO);
}
static inline void free_pending_exception(struct pending_exception *pe)
{
mempool_free(pe, pending_pool);
}
int dm_add_exception(struct dm_snapshot *s, chunk_t old, chunk_t new)
{
struct exception *e;
e = alloc_exception();
if (!e)
return -ENOMEM;
e->old_chunk = old;
e->new_chunk = new;
insert_exception(&s->complete, e);
return 0;
}
/*
* 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;
}
/*
* Rounds a number down to a power of 2.
*/
static inline uint32_t round_down(uint32_t n)
{
while (n & (n - 1))
n &= (n - 1);
return n;
}
/*
* 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->chunk_shift;
hash_size = min(hash_size, max_buckets);
/* Round it down to a power of 2 */
hash_size = round_down(hash_size);
if (init_exception_table(&s->complete, hash_size))
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 (init_exception_table(&s->pending, hash_size)) {
exit_exception_table(&s->complete, exception_cache);
return -ENOMEM;
}
return 0;
}
/*
* Round a number up to the nearest 'size' boundary. size must
* be a power of 2.
*/
static inline ulong round_up(ulong n, ulong size)
{
size--;
return (n + size) & ~size;
}
static void read_snapshot_metadata(struct dm_snapshot *s)
{
if (s->store.read_metadata(&s->store)) {
down_write(&s->lock);
s->valid = 0;
up_write(&s->lock);
}
}
/*
* 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;
unsigned long chunk_size;
int r = -EINVAL;
char persistent;
char *origin_path;
char *cow_path;
char *value;
int blocksize;
if (argc < 4) {
ti->error = "dm-snapshot: requires exactly 4 arguments";
r = -EINVAL;
goto bad1;
}
origin_path = argv[0];
cow_path = argv[1];
persistent = toupper(*argv[2]);
if (persistent != 'P' && persistent != 'N') {
ti->error = "Persistent flag is not P or N";
r = -EINVAL;
goto bad1;
}
chunk_size = simple_strtoul(argv[3], &value, 10);
if (chunk_size == 0 || value == NULL) {
ti->error = "Invalid chunk size";
r = -EINVAL;
goto bad1;
}
s = kmalloc(sizeof(*s), GFP_KERNEL);
if (s == NULL) {
ti->error = "Cannot allocate snapshot context private "
"structure";
r = -ENOMEM;
goto bad1;
}
r = dm_get_device(ti, origin_path, 0, ti->len, FMODE_READ, &s->origin);
if (r) {
ti->error = "Cannot get origin device";
goto bad2;
}
r = dm_get_device(ti, cow_path, 0, 0,
FMODE_READ | FMODE_WRITE, &s->cow);
if (r) {
dm_put_device(ti, s->origin);
ti->error = "Cannot get COW device";
goto bad2;
}
/*
* Chunk size must be multiple of page size. Silently
* round up if it's not.
*/
chunk_size = round_up(chunk_size, PAGE_SIZE >> 9);
/* Validate the chunk size against the device block size */
blocksize = s->cow->bdev->bd_disk->queue->hardsect_size;
if (chunk_size % (blocksize >> 9)) {
ti->error = "Chunk size is not a multiple of device blocksize";
r = -EINVAL;
goto bad3;
}
/* Check chunk_size is a power of 2 */
if (chunk_size & (chunk_size - 1)) {
ti->error = "Chunk size is not a power of 2";
r = -EINVAL;
goto bad3;
}
s->chunk_size = chunk_size;
s->chunk_mask = chunk_size - 1;
s->type = persistent;
s->chunk_shift = ffs(chunk_size) - 1;
s->valid = 1;
s->active = 0;
s->last_percent = 0;
init_rwsem(&s->lock);
s->table = ti->table;
/* Allocate hash table for COW data */
if (init_hash_tables(s)) {
ti->error = "Unable to allocate hash table space";
r = -ENOMEM;
goto bad3;
}
/*
* Check the persistent flag - done here because we need the iobuf
* to check the LV header
*/
s->store.snap = s;
if (persistent == 'P')
r = dm_create_persistent(&s->store, chunk_size);
else
r = dm_create_transient(&s->store, s, blocksize);
if (r) {
ti->error = "Couldn't create exception store";
r = -EINVAL;
goto bad4;
}
r = kcopyd_client_create(SNAPSHOT_PAGES, &s->kcopyd_client);
if (r) {
ti->error = "Could not create kcopyd client";
goto bad5;
}
/* Metadata must only be loaded into one table at once */
read_snapshot_metadata(s);
/* Add snapshot to the list of snapshots for this origin */
/* Exceptions aren't triggered till snapshot_resume() is called */
if (register_snapshot(s)) {
r = -EINVAL;
ti->error = "Cannot register snapshot origin";
goto bad6;
}
ti->private = s;
ti->split_io = chunk_size;
return 0;
bad6:
kcopyd_client_destroy(s->kcopyd_client);
bad5:
s->store.destroy(&s->store);
bad4:
exit_exception_table(&s->pending, pending_cache);
exit_exception_table(&s->complete, exception_cache);
bad3:
dm_put_device(ti, s->cow);
dm_put_device(ti, s->origin);
bad2:
kfree(s);
bad1:
return r;
}
static void snapshot_dtr(struct dm_target *ti)
{
struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
unregister_snapshot(s);
exit_exception_table(&s->pending, pending_cache);
exit_exception_table(&s->complete, exception_cache);
/* Deallocate memory used */
s->store.destroy(&s->store);
dm_put_device(ti, s->origin);
dm_put_device(ti, s->cow);
kcopyd_client_destroy(s->kcopyd_client);
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;
}
}
/*
* 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->bi_size);
bio = n;
}
}
static struct bio *__flush_bios(struct pending_exception *pe)
{
struct pending_exception *sibling;
if (list_empty(&pe->siblings))
return bio_list_get(&pe->origin_bios);
sibling = list_entry(pe->siblings.next,
struct pending_exception, siblings);
list_del(&pe->siblings);
/* This is fine as long as kcopyd is single-threaded. If kcopyd
* becomes multi-threaded, we'll need some locking here.
*/
bio_list_merge(&sibling->origin_bios, &pe->origin_bios);
return NULL;
}
static void pending_complete(struct pending_exception *pe, int success)
{
struct exception *e;
struct dm_snapshot *s = pe->snap;
struct bio *flush = NULL;
if (success) {
e = alloc_exception();
if (!e) {
DMWARN("Unable to allocate exception.");
down_write(&s->lock);
s->store.drop_snapshot(&s->store);
s->valid = 0;
flush = __flush_bios(pe);
up_write(&s->lock);
error_bios(bio_list_get(&pe->snapshot_bios));
goto out;
}
*e = pe->e;
/*
* Add a proper exception, and remove the
* in-flight exception from the list.
*/
down_write(&s->lock);
insert_exception(&s->complete, e);
remove_exception(&pe->e);
flush = __flush_bios(pe);
/* Submit any pending write bios */
up_write(&s->lock);
flush_bios(bio_list_get(&pe->snapshot_bios));
} else {
/* Read/write error - snapshot is unusable */
down_write(&s->lock);
if (s->valid)
DMERR("Error reading/writing snapshot");
s->store.drop_snapshot(&s->store);
s->valid = 0;
remove_exception(&pe->e);
flush = __flush_bios(pe);
up_write(&s->lock);
error_bios(bio_list_get(&pe->snapshot_bios));
dm_table_event(s->table);
}
out:
free_pending_exception(pe);
if (flush)
flush_bios(flush);
}
static void commit_callback(void *context, int success)
{
struct pending_exception *pe = (struct pending_exception *) 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 int write_err, void *context)
{
struct pending_exception *pe = (struct pending_exception *) 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.commit_exception(&s->store, &pe->e, commit_callback,
pe);
}
/*
* Dispatches the copy operation to kcopyd.
*/
static void start_copy(struct pending_exception *pe)
{
struct dm_snapshot *s = pe->snap;
struct 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, pe->e.old_chunk);
src.count = min(s->chunk_size, dev_size - src.sector);
dest.bdev = s->cow->bdev;
dest.sector = chunk_to_sector(s, pe->e.new_chunk);
dest.count = src.count;
/* Hand over to kcopyd */
kcopyd_copy(s->kcopyd_client,
&src, 1, &dest, 0, copy_callback, pe);
}
/*
* 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 pending_exception *
__find_pending_exception(struct dm_snapshot *s, struct bio *bio)
{
struct exception *e;
struct pending_exception *pe;
chunk_t chunk = sector_to_chunk(s, bio->bi_sector);
/*
* Is there a pending exception for this already ?
*/
e = lookup_exception(&s->pending, chunk);
if (e) {
/* cast the exception to a pending exception */
pe = container_of(e, struct pending_exception, e);
} else {
/*
* Create a new pending exception, we don't want
* to hold the lock while we do this.
*/
up_write(&s->lock);
pe = alloc_pending_exception();
down_write(&s->lock);
e = lookup_exception(&s->pending, chunk);
if (e) {
free_pending_exception(pe);
pe = container_of(e, struct pending_exception, e);
} else {
pe->e.old_chunk = chunk;
bio_list_init(&pe->origin_bios);
bio_list_init(&pe->snapshot_bios);
INIT_LIST_HEAD(&pe->siblings);
pe->snap = s;
pe->started = 0;
if (s->store.prepare_exception(&s->store, &pe->e)) {
free_pending_exception(pe);
s->valid = 0;
return NULL;
}
insert_exception(&s->pending, &pe->e);
}
}
return pe;
}
static inline void remap_exception(struct dm_snapshot *s, struct exception *e,
struct bio *bio)
{
bio->bi_bdev = s->cow->bdev;
bio->bi_sector = chunk_to_sector(s, e->new_chunk) +
(bio->bi_sector & s->chunk_mask);
}
static int snapshot_map(struct dm_target *ti, struct bio *bio,
union map_info *map_context)
{
struct exception *e;
struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
int r = 1;
chunk_t chunk;
struct pending_exception *pe;
chunk = sector_to_chunk(s, bio->bi_sector);
/* Full snapshots are not usable */
if (!s->valid)
return -EIO;
if (unlikely(bio_barrier(bio)))
return -EOPNOTSUPP;
/*
* 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) {
/* FIXME: should only take write lock if we need
* to copy an exception */
down_write(&s->lock);
/* If the block is already remapped - use that, else remap it */
e = lookup_exception(&s->complete, chunk);
if (e) {
remap_exception(s, e, bio);
up_write(&s->lock);
} else {
pe = __find_pending_exception(s, bio);
if (!pe) {
if (s->store.drop_snapshot)
s->store.drop_snapshot(&s->store);
s->valid = 0;
r = -EIO;
up_write(&s->lock);
} else {
remap_exception(s, &pe->e, bio);
bio_list_add(&pe->snapshot_bios, bio);
if (!pe->started) {
/* this is protected by snap->lock */
pe->started = 1;
up_write(&s->lock);
start_copy(pe);
} else
up_write(&s->lock);
r = 0;
}
}
} else {
/*
* FIXME: this read path scares me because we
* always use the origin when we have a pending
* exception. However I can't think of a
* situation where this is wrong - ejt.
*/
/* Do reads */
down_read(&s->lock);
/* See if it it has been remapped */
e = lookup_exception(&s->complete, chunk);
if (e)
remap_exception(s, e, bio);
else
bio->bi_bdev = s->origin->bdev;
up_read(&s->lock);
}
return r;
}
static void snapshot_resume(struct dm_target *ti)
{
struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
down_write(&s->lock);
s->active = 1;
up_write(&s->lock);
}
static int snapshot_status(struct dm_target *ti, status_type_t type,
char *result, unsigned int maxlen)
{
struct dm_snapshot *snap = (struct dm_snapshot *) ti->private;
switch (type) {
case STATUSTYPE_INFO:
if (!snap->valid)
snprintf(result, maxlen, "Invalid");
else {
if (snap->store.fraction_full) {
sector_t numerator, denominator;
snap->store.fraction_full(&snap->store,
&numerator,
&denominator);
snprintf(result, maxlen,
SECTOR_FORMAT "/" SECTOR_FORMAT,
numerator, denominator);
}
else
snprintf(result, maxlen, "Unknown");
}
break;
case STATUSTYPE_TABLE:
/*
* kdevname returns a static pointer so we need
* to make private copies if the output is to
* make sense.
*/
snprintf(result, maxlen, "%s %s %c " SECTOR_FORMAT,
snap->origin->name, snap->cow->name,
snap->type, snap->chunk_size);
break;
}
return 0;
}
/*-----------------------------------------------------------------
* Origin methods
*---------------------------------------------------------------*/
static void list_merge(struct list_head *l1, struct list_head *l2)
{
struct list_head *l1_n, *l2_p;
l1_n = l1->next;
l2_p = l2->prev;
l1->next = l2;
l2->prev = l1;
l2_p->next = l1_n;
l1_n->prev = l2_p;
}
static int __origin_write(struct list_head *snapshots, struct bio *bio)
{
int r = 1, first = 1;
struct dm_snapshot *snap;
struct exception *e;
struct pending_exception *pe, *last = NULL;
chunk_t chunk;
/* Do all the snapshots on this origin */
list_for_each_entry (snap, snapshots, list) {
/* Only deal with valid and active snapshots */
if (!snap->valid || !snap->active)
continue;
/* Nothing to do if writing beyond end of snapshot */
if (bio->bi_sector >= dm_table_get_size(snap->table))
continue;
down_write(&snap->lock);
/*
* Remember, different snapshots can have
* different chunk sizes.
*/
chunk = sector_to_chunk(snap, bio->bi_sector);
/*
* Check exception table to see if block
* is already remapped in this snapshot
* and trigger an exception if not.
*/
e = lookup_exception(&snap->complete, chunk);
if (!e) {
pe = __find_pending_exception(snap, bio);
if (!pe) {
snap->store.drop_snapshot(&snap->store);
snap->valid = 0;
} else {
if (last)
list_merge(&pe->siblings,
&last->siblings);
last = pe;
r = 0;
}
}
up_write(&snap->lock);
}
/*
* Now that we have a complete pe list we can start the copying.
*/
if (last) {
pe = last;
do {
down_write(&pe->snap->lock);
if (first)
bio_list_add(&pe->origin_bios, bio);
if (!pe->started) {
pe->started = 1;
up_write(&pe->snap->lock);
start_copy(pe);
} else
up_write(&pe->snap->lock);
first = 0;
pe = list_entry(pe->siblings.next,
struct pending_exception, siblings);
} while (pe != 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 = 1;
down_read(&_origins_lock);
o = __lookup_origin(origin->bdev);
if (o)
r = __origin_write(&o->snapshots, 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 = "dm-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;
return 0;
}
static void origin_dtr(struct dm_target *ti)
{
struct dm_dev *dev = (struct dm_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 = (struct dm_dev *) ti->private;
bio->bi_bdev = dev->bdev;
if (unlikely(bio_barrier(bio)))
return -EOPNOTSUPP;
/* Only tell snapshots if this is a write */
return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : 1;
}
#define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
/*
* 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 = (struct dm_dev *) ti->private;
struct dm_snapshot *snap;
struct origin *o;
chunk_t chunk_size = 0;
down_read(&_origins_lock);
o = __lookup_origin(dev->bdev);
if (o)
list_for_each_entry (snap, &o->snapshots, list)
chunk_size = min_not_zero(chunk_size, snap->chunk_size);
up_read(&_origins_lock);
ti->split_io = chunk_size;
}
static int origin_status(struct dm_target *ti, status_type_t type, char *result,
unsigned int maxlen)
{
struct dm_dev *dev = (struct dm_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 struct target_type origin_target = {
.name = "snapshot-origin",
.version = {1, 1, 0},
.module = THIS_MODULE,
.ctr = origin_ctr,
.dtr = origin_dtr,
.map = origin_map,
.resume = origin_resume,
.status = origin_status,
};
static struct target_type snapshot_target = {
.name = "snapshot",
.version = {1, 1, 0},
.module = THIS_MODULE,
.ctr = snapshot_ctr,
.dtr = snapshot_dtr,
.map = snapshot_map,
.resume = snapshot_resume,
.status = snapshot_status,
};
static int __init dm_snapshot_init(void)
{
int r;
r = dm_register_target(&snapshot_target);
if (r) {
DMERR("snapshot target register failed %d", r);
return r;
}
r = dm_register_target(&origin_target);
if (r < 0) {
DMERR("Device mapper: Origin: register failed %d\n", r);
goto bad1;
}
r = init_origin_hash();
if (r) {
DMERR("init_origin_hash failed.");
goto bad2;
}
exception_cache = kmem_cache_create("dm-snapshot-ex",
sizeof(struct exception),
__alignof__(struct exception),
0, NULL, NULL);
if (!exception_cache) {
DMERR("Couldn't create exception cache.");
r = -ENOMEM;
goto bad3;
}
pending_cache =
kmem_cache_create("dm-snapshot-in",
sizeof(struct pending_exception),
__alignof__(struct pending_exception),
0, NULL, NULL);
if (!pending_cache) {
DMERR("Couldn't create pending cache.");
r = -ENOMEM;
goto bad4;
}
pending_pool = mempool_create(128, mempool_alloc_slab,
mempool_free_slab, pending_cache);
if (!pending_pool) {
DMERR("Couldn't create pending pool.");
r = -ENOMEM;
goto bad5;
}
return 0;
bad5:
kmem_cache_destroy(pending_cache);
bad4:
kmem_cache_destroy(exception_cache);
bad3:
exit_origin_hash();
bad2:
dm_unregister_target(&origin_target);
bad1:
dm_unregister_target(&snapshot_target);
return r;
}
static void __exit dm_snapshot_exit(void)
{
int r;
r = dm_unregister_target(&snapshot_target);
if (r)
DMERR("snapshot unregister failed %d", r);
r = dm_unregister_target(&origin_target);
if (r)
DMERR("origin unregister failed %d", r);
exit_origin_hash();
mempool_destroy(pending_pool);
kmem_cache_destroy(pending_cache);
kmem_cache_destroy(exception_cache);
}
/* 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");
