swh:1:snp:173f8deb0c56c557784b4fd217e7608ac6197844
Tip revision: 061e41fdb5047b1fb161e89664057835935ca1d2 authored by Linus Torvalds on 02 December 2008, 03:59:23 UTC
Linux 2.6.28-rc7
Linux 2.6.28-rc7
Tip revision: 061e41f
dm-snap.c
/*
* dm-snapshot.c
*
* Copyright (C) 2001-2002 Sistina Software (UK) Limited.
*
* This file is released under the GPL.
*/
#include <linux/blkdev.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 <linux/log2.h>
#include <linux/dm-kcopyd.h>
#include "dm-snap.h"
#include "dm-bio-list.h"
#define DM_MSG_PREFIX "snapshots"
/*
* 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
static struct workqueue_struct *ksnapd;
static void flush_queued_bios(struct work_struct *work);
struct dm_snap_pending_exception {
struct dm_snap_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;
/*
* Short-term queue of pending exceptions prior to submission.
*/
struct list_head list;
/*
* The primary pending_exception is the one that holds
* the ref_count and the list of origin_bios for a
* group of pending_exceptions. It is always last to get freed.
* These fields get set up when writing to the origin.
*/
struct dm_snap_pending_exception *primary_pe;
/*
* Number of pending_exceptions processing this chunk.
* When this drops to zero we must complete the origin bios.
* If incrementing or decrementing this, hold pe->snap->lock for
* the sibling concerned and not pe->primary_pe->snap->lock unless
* they are the same.
*/
atomic_t ref_count;
/* 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;
}
/*
* 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);
}
/*
* 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, *new_o;
struct block_device *bdev = snap->origin->bdev;
new_o = kmalloc(sizeof(*new_o), GFP_KERNEL);
if (!new_o)
return -ENOMEM;
down_write(&_origins_lock);
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);
}
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.
* The lowest hash_shift bits of the chunk number are ignored, allowing
* some consecutive chunks to be grouped together.
*/
static int init_exception_table(struct 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 exit_exception_table(struct exception_table *et, struct kmem_cache *mem)
{
struct list_head *slot;
struct dm_snap_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 exception_table *et, chunk_t chunk)
{
return (chunk >> et->hash_shift) & et->hash_mask;
}
static void insert_exception(struct exception_table *eh,
struct dm_snap_exception *e)
{
struct list_head *l = &eh->table[exception_hash(eh, e->old_chunk)];
list_add(&e->hash_list, l);
}
static void remove_exception(struct dm_snap_exception *e)
{
list_del(&e->hash_list);
}
/*
* Return the exception data for a sector, or NULL if not
* remapped.
*/
static struct dm_snap_exception *lookup_exception(struct exception_table *et,
chunk_t chunk)
{
struct list_head *slot;
struct dm_snap_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_snap_exception *alloc_exception(void)
{
struct dm_snap_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_exception(struct dm_snap_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);
atomic_inc(&s->pending_exceptions_count);
pe->snap = s;
return pe;
}
static void free_pending_exception(struct dm_snap_pending_exception *pe)
{
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 insert_completed_exception(struct dm_snapshot *s,
struct dm_snap_exception *new_e)
{
struct exception_table *eh = &s->complete;
struct list_head *l;
struct dm_snap_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_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_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);
}
int dm_add_exception(struct dm_snapshot *s, chunk_t old, chunk_t new)
{
struct dm_snap_exception *e;
e = alloc_exception();
if (!e)
return -ENOMEM;
e->old_chunk = old;
/* Consecutive_count is implicitly initialised to zero */
e->new_chunk = new;
insert_completed_exception(s, 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;
}
/*
* 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);
hash_size = rounddown_pow_of_two(hash_size);
if (init_exception_table(&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 (init_exception_table(&s->pending, hash_size, 0)) {
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 ulong round_up(ulong n, ulong size)
{
size--;
return (n + size) & ~size;
}
static int set_chunk_size(struct dm_snapshot *s, const char *chunk_size_arg,
char **error)
{
unsigned long chunk_size;
char *value;
chunk_size = simple_strtoul(chunk_size_arg, &value, 10);
if (*chunk_size_arg == '\0' || *value != '\0') {
*error = "Invalid chunk size";
return -EINVAL;
}
if (!chunk_size) {
s->chunk_size = s->chunk_mask = s->chunk_shift = 0;
return 0;
}
/*
* Chunk size must be multiple of page size. Silently
* round up if it's not.
*/
chunk_size = round_up(chunk_size, PAGE_SIZE >> 9);
/* Check chunk_size is a power of 2 */
if (!is_power_of_2(chunk_size)) {
*error = "Chunk size is not a power of 2";
return -EINVAL;
}
/* Validate the chunk size against the device block size */
if (chunk_size % (bdev_hardsect_size(s->cow->bdev) >> 9)) {
*error = "Chunk size is not a multiple of device blocksize";
return -EINVAL;
}
s->chunk_size = chunk_size;
s->chunk_mask = chunk_size - 1;
s->chunk_shift = ffs(chunk_size) - 1;
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 persistent;
char *origin_path;
char *cow_path;
if (argc != 4) {
ti->error = "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;
}
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;
}
r = set_chunk_size(s, argv[3], &ti->error);
if (r)
goto bad3;
s->type = persistent;
s->valid = 1;
s->active = 0;
atomic_set(&s->pending_exceptions_count, 0);
init_rwsem(&s->lock);
spin_lock_init(&s->pe_lock);
s->ti = ti;
/* Allocate hash table for COW data */
if (init_hash_tables(s)) {
ti->error = "Unable to allocate hash table space";
r = -ENOMEM;
goto bad3;
}
s->store.snap = s;
if (persistent == 'P')
r = dm_create_persistent(&s->store);
else
r = dm_create_transient(&s->store);
if (r) {
ti->error = "Couldn't create exception store";
r = -EINVAL;
goto bad4;
}
r = dm_kcopyd_client_create(SNAPSHOT_PAGES, &s->kcopyd_client);
if (r) {
ti->error = "Could not create kcopyd client";
goto bad5;
}
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 bad6;
}
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);
/* Metadata must only be loaded into one table at once */
r = s->store.read_metadata(&s->store);
if (r < 0) {
ti->error = "Failed to read snapshot metadata";
goto bad_load_and_register;
} else if (r > 0) {
s->valid = 0;
DMWARN("Snapshot is marked invalid.");
}
bio_list_init(&s->queued_bios);
INIT_WORK(&s->queued_bios_work, flush_queued_bios);
/* 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 bad_load_and_register;
}
ti->private = s;
ti->split_io = s->chunk_size;
return 0;
bad_load_and_register:
mempool_destroy(s->tracked_chunk_pool);
bad_tracked_chunk_pool:
mempool_destroy(s->pending_pool);
bad6:
dm_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 __free_exceptions(struct dm_snapshot *s)
{
dm_kcopyd_client_destroy(s->kcopyd_client);
s->kcopyd_client = NULL;
exit_exception_table(&s->pending, pending_cache);
exit_exception_table(&s->complete, exception_cache);
s->store.destroy(&s->store);
}
static void snapshot_dtr(struct dm_target *ti)
{
#ifdef CONFIG_DM_DEBUG
int i;
#endif
struct dm_snapshot *s = ti->private;
flush_workqueue(ksnapd);
/* Prevent further origin writes from using this snapshot. */
/* After this returns there can be no new kcopyd jobs. */
unregister_snapshot(s);
while (atomic_read(&s->pending_exceptions_count))
yield();
/*
* 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_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);
}
/*
* 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.drop_snapshot)
s->store.drop_snapshot(&s->store);
s->valid = 0;
dm_table_event(s->ti->table);
}
static void get_pending_exception(struct dm_snap_pending_exception *pe)
{
atomic_inc(&pe->ref_count);
}
static struct bio *put_pending_exception(struct dm_snap_pending_exception *pe)
{
struct dm_snap_pending_exception *primary_pe;
struct bio *origin_bios = NULL;
primary_pe = pe->primary_pe;
/*
* If this pe is involved in a write to the origin and
* it is the last sibling to complete then release
* the bios for the original write to the origin.
*/
if (primary_pe &&
atomic_dec_and_test(&primary_pe->ref_count)) {
origin_bios = bio_list_get(&primary_pe->origin_bios);
free_pending_exception(primary_pe);
}
/*
* Free the pe if it's not linked to an origin write or if
* it's not itself a primary pe.
*/
if (!primary_pe || primary_pe != pe)
free_pending_exception(pe);
return origin_bios;
}
static void pending_complete(struct dm_snap_pending_exception *pe, int success)
{
struct dm_snap_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_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_exception(e);
error = 1;
goto out;
}
/*
* Check for conflicting reads. This is extremely improbable,
* so yield() is sufficient and there is no need for a wait queue.
*/
while (__chunk_is_tracked(s, pe->e.old_chunk))
yield();
/*
* Add a proper exception, and remove the
* in-flight exception from the list.
*/
insert_completed_exception(s, e);
out:
remove_exception(&pe->e);
snapshot_bios = bio_list_get(&pe->snapshot_bios);
origin_bios = put_pending_exception(pe);
up_write(&s->lock);
/* Submit any pending write bios */
if (error)
error_bios(snapshot_bios);
else
flush_bios(snapshot_bios);
flush_bios(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.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, 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 */
dm_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 dm_snap_pending_exception *
__find_pending_exception(struct dm_snapshot *s, struct bio *bio)
{
struct dm_snap_exception *e;
struct dm_snap_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 dm_snap_pending_exception, e);
goto out;
}
/*
* 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(s);
down_write(&s->lock);
if (!s->valid) {
free_pending_exception(pe);
return NULL;
}
e = lookup_exception(&s->pending, chunk);
if (e) {
free_pending_exception(pe);
pe = container_of(e, struct dm_snap_pending_exception, e);
goto out;
}
pe->e.old_chunk = chunk;
bio_list_init(&pe->origin_bios);
bio_list_init(&pe->snapshot_bios);
pe->primary_pe = NULL;
atomic_set(&pe->ref_count, 0);
pe->started = 0;
if (s->store.prepare_exception(&s->store, &pe->e)) {
free_pending_exception(pe);
return NULL;
}
get_pending_exception(pe);
insert_exception(&s->pending, &pe->e);
out:
return pe;
}
static void remap_exception(struct dm_snapshot *s, struct dm_snap_exception *e,
struct bio *bio, chunk_t chunk)
{
bio->bi_bdev = s->cow->bdev;
bio->bi_sector = chunk_to_sector(s, dm_chunk_number(e->new_chunk) +
(chunk - e->old_chunk)) +
(bio->bi_sector & s->chunk_mask);
}
static int snapshot_map(struct dm_target *ti, struct bio *bio,
union map_info *map_context)
{
struct dm_snap_exception *e;
struct dm_snapshot *s = ti->private;
int r = DM_MAPIO_REMAPPED;
chunk_t chunk;
struct dm_snap_pending_exception *pe = NULL;
chunk = sector_to_chunk(s, 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 = 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 = __find_pending_exception(s, bio);
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;
}
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_resume(struct dm_target *ti)
{
struct dm_snapshot *s = 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 = 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, "%llu/%llu",
(unsigned long long)numerator,
(unsigned long long)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 %llu",
snap->origin->name, snap->cow->name,
snap->type,
(unsigned long long)snap->chunk_size);
break;
}
return 0;
}
/*-----------------------------------------------------------------
* Origin methods
*---------------------------------------------------------------*/
static int __origin_write(struct list_head *snapshots, struct bio *bio)
{
int r = DM_MAPIO_REMAPPED, first = 0;
struct dm_snapshot *snap;
struct dm_snap_exception *e;
struct dm_snap_pending_exception *pe, *next_pe, *primary_pe = NULL;
chunk_t chunk;
LIST_HEAD(pe_queue);
/* Do all the snapshots on this origin */
list_for_each_entry (snap, snapshots, list) {
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 (bio->bi_sector >= dm_table_get_size(snap->ti->table))
goto next_snapshot;
/*
* 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.
*
* ref_count is initialised to 1 so pending_complete()
* won't destroy the primary_pe while we're inside this loop.
*/
e = lookup_exception(&snap->complete, chunk);
if (e)
goto next_snapshot;
pe = __find_pending_exception(snap, bio);
if (!pe) {
__invalidate_snapshot(snap, -ENOMEM);
goto next_snapshot;
}
if (!primary_pe) {
/*
* Either every pe here has same
* primary_pe or none has one yet.
*/
if (pe->primary_pe)
primary_pe = pe->primary_pe;
else {
primary_pe = pe;
first = 1;
}
bio_list_add(&primary_pe->origin_bios, bio);
r = DM_MAPIO_SUBMITTED;
}
if (!pe->primary_pe) {
pe->primary_pe = primary_pe;
get_pending_exception(primary_pe);
}
if (!pe->started) {
pe->started = 1;
list_add_tail(&pe->list, &pe_queue);
}
next_snapshot:
up_write(&snap->lock);
}
if (!primary_pe)
return r;
/*
* If this is the first time we're processing this chunk and
* ref_count is now 1 it means all the pending exceptions
* got completed while we were in the loop above, so it falls to
* us here to remove the primary_pe and submit any origin_bios.
*/
if (first && atomic_dec_and_test(&primary_pe->ref_count)) {
flush_bios(bio_list_get(&primary_pe->origin_bios));
free_pending_exception(primary_pe);
/* If we got here, pe_queue is necessarily empty. */
return r;
}
/*
* Now that we have a complete pe list we can start the copying.
*/
list_for_each_entry_safe(pe, next_pe, &pe_queue, list)
start_copy(pe);
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);
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;
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;
/* Only tell snapshots if this is a write */
return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : DM_MAPIO_REMAPPED;
}
#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 = 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 = 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, 6, 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, 6, 0},
.module = THIS_MODULE,
.ctr = snapshot_ctr,
.dtr = snapshot_dtr,
.map = snapshot_map,
.end_io = snapshot_end_io,
.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("Origin target register failed %d", r);
goto bad1;
}
r = init_origin_hash();
if (r) {
DMERR("init_origin_hash failed.");
goto bad2;
}
exception_cache = KMEM_CACHE(dm_snap_exception, 0);
if (!exception_cache) {
DMERR("Couldn't create exception cache.");
r = -ENOMEM;
goto bad3;
}
pending_cache = KMEM_CACHE(dm_snap_pending_exception, 0);
if (!pending_cache) {
DMERR("Couldn't create pending cache.");
r = -ENOMEM;
goto bad4;
}
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 bad5;
}
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);
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;
destroy_workqueue(ksnapd);
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();
kmem_cache_destroy(pending_cache);
kmem_cache_destroy(exception_cache);
kmem_cache_destroy(tracked_chunk_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");