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dm-thin.c
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dm-thin.c
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/*
* Copyright (C) 2011 Red Hat UK.
*
* This file is released under the GPL.
*/
#include "dm-thin-metadata.h"
#include <linux/device-mapper.h>
#include <linux/dm-io.h>
#include <linux/dm-kcopyd.h>
#include <linux/list.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#define DM_MSG_PREFIX "thin"
/*
* Tunable constants
*/
#define ENDIO_HOOK_POOL_SIZE 10240
#define DEFERRED_SET_SIZE 64
#define MAPPING_POOL_SIZE 1024
#define PRISON_CELLS 1024
/*
* The block size of the device holding pool data must be
* between 64KB and 1GB.
*/
#define DATA_DEV_BLOCK_SIZE_MIN_SECTORS (64 * 1024 >> SECTOR_SHIFT)
#define DATA_DEV_BLOCK_SIZE_MAX_SECTORS (1024 * 1024 * 1024 >> SECTOR_SHIFT)
/*
* The metadata device is currently limited in size. The limitation is
* checked lower down in dm-space-map-metadata, but we also check it here
* so we can fail early.
*
* We have one block of index, which can hold 255 index entries. Each
* index entry contains allocation info about 16k metadata blocks.
*/
#define METADATA_DEV_MAX_SECTORS (255 * (1 << 14) * (THIN_METADATA_BLOCK_SIZE / (1 << SECTOR_SHIFT)))
/*
* Device id is restricted to 24 bits.
*/
#define MAX_DEV_ID ((1 << 24) - 1)
/*
* How do we handle breaking sharing of data blocks?
* =================================================
*
* We use a standard copy-on-write btree to store the mappings for the
* devices (note I'm talking about copy-on-write of the metadata here, not
* the data). When you take an internal snapshot you clone the root node
* of the origin btree. After this there is no concept of an origin or a
* snapshot. They are just two device trees that happen to point to the
* same data blocks.
*
* When we get a write in we decide if it's to a shared data block using
* some timestamp magic. If it is, we have to break sharing.
*
* Let's say we write to a shared block in what was the origin. The
* steps are:
*
* i) plug io further to this physical block. (see bio_prison code).
*
* ii) quiesce any read io to that shared data block. Obviously
* including all devices that share this block. (see deferred_set code)
*
* iii) copy the data block to a newly allocate block. This step can be
* missed out if the io covers the block. (schedule_copy).
*
* iv) insert the new mapping into the origin's btree
* (process_prepared_mappings). This act of inserting breaks some
* sharing of btree nodes between the two devices. Breaking sharing only
* effects the btree of that specific device. Btrees for the other
* devices that share the block never change. The btree for the origin
* device as it was after the last commit is untouched, ie. we're using
* persistent data structures in the functional programming sense.
*
* v) unplug io to this physical block, including the io that triggered
* the breaking of sharing.
*
* Steps (ii) and (iii) occur in parallel.
*
* The metadata _doesn't_ need to be committed before the io continues. We
* get away with this because the io is always written to a _new_ block.
* If there's a crash, then:
*
* - The origin mapping will point to the old origin block (the shared
* one). This will contain the data as it was before the io that triggered
* the breaking of sharing came in.
*
* - The snap mapping still points to the old block. As it would after
* the commit.
*
* The downside of this scheme is the timestamp magic isn't perfect, and
* will continue to think that data block in the snapshot device is shared
* even after the write to the origin has broken sharing. I suspect data
* blocks will typically be shared by many different devices, so we're
* breaking sharing n + 1 times, rather than n, where n is the number of
* devices that reference this data block. At the moment I think the
* benefits far, far outweigh the disadvantages.
*/
/*----------------------------------------------------------------*/
/*
* Sometimes we can't deal with a bio straight away. We put them in prison
* where they can't cause any mischief. Bios are put in a cell identified
* by a key, multiple bios can be in the same cell. When the cell is
* subsequently unlocked the bios become available.
*/
struct bio_prison;
struct cell_key {
int virtual;
dm_thin_id dev;
dm_block_t block;
};
struct cell {
struct hlist_node list;
struct bio_prison *prison;
struct cell_key key;
unsigned count;
struct bio_list bios;
};
struct bio_prison {
spinlock_t lock;
mempool_t *cell_pool;
unsigned nr_buckets;
unsigned hash_mask;
struct hlist_head *cells;
};
static uint32_t calc_nr_buckets(unsigned nr_cells)
{
uint32_t n = 128;
nr_cells /= 4;
nr_cells = min(nr_cells, 8192u);
while (n < nr_cells)
n <<= 1;
return n;
}
/*
* @nr_cells should be the number of cells you want in use _concurrently_.
* Don't confuse it with the number of distinct keys.
*/
static struct bio_prison *prison_create(unsigned nr_cells)
{
unsigned i;
uint32_t nr_buckets = calc_nr_buckets(nr_cells);
size_t len = sizeof(struct bio_prison) +
(sizeof(struct hlist_head) * nr_buckets);
struct bio_prison *prison = kmalloc(len, GFP_KERNEL);
if (!prison)
return NULL;
spin_lock_init(&prison->lock);
prison->cell_pool = mempool_create_kmalloc_pool(nr_cells,
sizeof(struct cell));
if (!prison->cell_pool) {
kfree(prison);
return NULL;
}
prison->nr_buckets = nr_buckets;
prison->hash_mask = nr_buckets - 1;
prison->cells = (struct hlist_head *) (prison + 1);
for (i = 0; i < nr_buckets; i++)
INIT_HLIST_HEAD(prison->cells + i);
return prison;
}
static void prison_destroy(struct bio_prison *prison)
{
mempool_destroy(prison->cell_pool);
kfree(prison);
}
static uint32_t hash_key(struct bio_prison *prison, struct cell_key *key)
{
const unsigned long BIG_PRIME = 4294967291UL;
uint64_t hash = key->block * BIG_PRIME;
return (uint32_t) (hash & prison->hash_mask);
}
static int keys_equal(struct cell_key *lhs, struct cell_key *rhs)
{
return (lhs->virtual == rhs->virtual) &&
(lhs->dev == rhs->dev) &&
(lhs->block == rhs->block);
}
static struct cell *__search_bucket(struct hlist_head *bucket,
struct cell_key *key)
{
struct cell *cell;
struct hlist_node *tmp;
hlist_for_each_entry(cell, tmp, bucket, list)
if (keys_equal(&cell->key, key))
return cell;
return NULL;
}
/*
* This may block if a new cell needs allocating. You must ensure that
* cells will be unlocked even if the calling thread is blocked.
*
* Returns the number of entries in the cell prior to the new addition
* or < 0 on failure.
*/
static int bio_detain(struct bio_prison *prison, struct cell_key *key,
struct bio *inmate, struct cell **ref)
{
int r;
unsigned long flags;
uint32_t hash = hash_key(prison, key);
struct cell *uninitialized_var(cell), *cell2 = NULL;
BUG_ON(hash > prison->nr_buckets);
spin_lock_irqsave(&prison->lock, flags);
cell = __search_bucket(prison->cells + hash, key);
if (!cell) {
/*
* Allocate a new cell
*/
spin_unlock_irqrestore(&prison->lock, flags);
cell2 = mempool_alloc(prison->cell_pool, GFP_NOIO);
spin_lock_irqsave(&prison->lock, flags);
/*
* We've been unlocked, so we have to double check that
* nobody else has inserted this cell in the meantime.
*/
cell = __search_bucket(prison->cells + hash, key);
if (!cell) {
cell = cell2;
cell2 = NULL;
cell->prison = prison;
memcpy(&cell->key, key, sizeof(cell->key));
cell->count = 0;
bio_list_init(&cell->bios);
hlist_add_head(&cell->list, prison->cells + hash);
}
}
r = cell->count++;
bio_list_add(&cell->bios, inmate);
spin_unlock_irqrestore(&prison->lock, flags);
if (cell2)
mempool_free(cell2, prison->cell_pool);
*ref = cell;
return r;
}
/*
* @inmates must have been initialised prior to this call
*/
static void __cell_release(struct cell *cell, struct bio_list *inmates)
{
struct bio_prison *prison = cell->prison;
hlist_del(&cell->list);
if (inmates)
bio_list_merge(inmates, &cell->bios);
mempool_free(cell, prison->cell_pool);
}
static void cell_release(struct cell *cell, struct bio_list *bios)
{
unsigned long flags;
struct bio_prison *prison = cell->prison;
spin_lock_irqsave(&prison->lock, flags);
__cell_release(cell, bios);
spin_unlock_irqrestore(&prison->lock, flags);
}
/*
* There are a couple of places where we put a bio into a cell briefly
* before taking it out again. In these situations we know that no other
* bio may be in the cell. This function releases the cell, and also does
* a sanity check.
*/
static void cell_release_singleton(struct cell *cell, struct bio *bio)
{
struct bio_prison *prison = cell->prison;
struct bio_list bios;
struct bio *b;
unsigned long flags;
bio_list_init(&bios);
spin_lock_irqsave(&prison->lock, flags);
__cell_release(cell, &bios);
spin_unlock_irqrestore(&prison->lock, flags);
b = bio_list_pop(&bios);
BUG_ON(b != bio);
BUG_ON(!bio_list_empty(&bios));
}
static void cell_error(struct cell *cell)
{
struct bio_prison *prison = cell->prison;
struct bio_list bios;
struct bio *bio;
unsigned long flags;
bio_list_init(&bios);
spin_lock_irqsave(&prison->lock, flags);
__cell_release(cell, &bios);
spin_unlock_irqrestore(&prison->lock, flags);
while ((bio = bio_list_pop(&bios)))
bio_io_error(bio);
}
/*----------------------------------------------------------------*/
/*
* We use the deferred set to keep track of pending reads to shared blocks.
* We do this to ensure the new mapping caused by a write isn't performed
* until these prior reads have completed. Otherwise the insertion of the
* new mapping could free the old block that the read bios are mapped to.
*/
struct deferred_set;
struct deferred_entry {
struct deferred_set *ds;
unsigned count;
struct list_head work_items;
};
struct deferred_set {
spinlock_t lock;
unsigned current_entry;
unsigned sweeper;
struct deferred_entry entries[DEFERRED_SET_SIZE];
};
static void ds_init(struct deferred_set *ds)
{
int i;
spin_lock_init(&ds->lock);
ds->current_entry = 0;
ds->sweeper = 0;
for (i = 0; i < DEFERRED_SET_SIZE; i++) {
ds->entries[i].ds = ds;
ds->entries[i].count = 0;
INIT_LIST_HEAD(&ds->entries[i].work_items);
}
}
static struct deferred_entry *ds_inc(struct deferred_set *ds)
{
unsigned long flags;
struct deferred_entry *entry;
spin_lock_irqsave(&ds->lock, flags);
entry = ds->entries + ds->current_entry;
entry->count++;
spin_unlock_irqrestore(&ds->lock, flags);
return entry;
}
static unsigned ds_next(unsigned index)
{
return (index + 1) % DEFERRED_SET_SIZE;
}
static void __sweep(struct deferred_set *ds, struct list_head *head)
{
while ((ds->sweeper != ds->current_entry) &&
!ds->entries[ds->sweeper].count) {
list_splice_init(&ds->entries[ds->sweeper].work_items, head);
ds->sweeper = ds_next(ds->sweeper);
}
if ((ds->sweeper == ds->current_entry) && !ds->entries[ds->sweeper].count)
list_splice_init(&ds->entries[ds->sweeper].work_items, head);
}
static void ds_dec(struct deferred_entry *entry, struct list_head *head)
{
unsigned long flags;
spin_lock_irqsave(&entry->ds->lock, flags);
BUG_ON(!entry->count);
--entry->count;
__sweep(entry->ds, head);
spin_unlock_irqrestore(&entry->ds->lock, flags);
}
/*
* Returns 1 if deferred or 0 if no pending items to delay job.
*/
static int ds_add_work(struct deferred_set *ds, struct list_head *work)
{
int r = 1;
unsigned long flags;
unsigned next_entry;
spin_lock_irqsave(&ds->lock, flags);
if ((ds->sweeper == ds->current_entry) &&
!ds->entries[ds->current_entry].count)
r = 0;
else {
list_add(work, &ds->entries[ds->current_entry].work_items);
next_entry = ds_next(ds->current_entry);
if (!ds->entries[next_entry].count)
ds->current_entry = next_entry;
}
spin_unlock_irqrestore(&ds->lock, flags);
return r;
}
/*----------------------------------------------------------------*/
/*
* Key building.
*/
static void build_data_key(struct dm_thin_device *td,
dm_block_t b, struct cell_key *key)
{
key->virtual = 0;
key->dev = dm_thin_dev_id(td);
key->block = b;
}
static void build_virtual_key(struct dm_thin_device *td, dm_block_t b,
struct cell_key *key)
{
key->virtual = 1;
key->dev = dm_thin_dev_id(td);
key->block = b;
}
/*----------------------------------------------------------------*/
/*
* A pool device ties together a metadata device and a data device. It
* also provides the interface for creating and destroying internal
* devices.
*/
struct new_mapping;
struct pool {
struct list_head list;
struct dm_target *ti; /* Only set if a pool target is bound */
struct mapped_device *pool_md;
struct block_device *md_dev;
struct dm_pool_metadata *pmd;
uint32_t sectors_per_block;
unsigned block_shift;
dm_block_t offset_mask;
dm_block_t low_water_blocks;
unsigned zero_new_blocks:1;
unsigned low_water_triggered:1; /* A dm event has been sent */
unsigned no_free_space:1; /* A -ENOSPC warning has been issued */
struct bio_prison *prison;
struct dm_kcopyd_client *copier;
struct workqueue_struct *wq;
struct work_struct worker;
unsigned ref_count;
spinlock_t lock;
struct bio_list deferred_bios;
struct bio_list deferred_flush_bios;
struct list_head prepared_mappings;
struct bio_list retry_on_resume_list;
struct deferred_set ds; /* FIXME: move to thin_c */
struct new_mapping *next_mapping;
mempool_t *mapping_pool;
mempool_t *endio_hook_pool;
};
/*
* Target context for a pool.
*/
struct pool_c {
struct dm_target *ti;
struct pool *pool;
struct dm_dev *data_dev;
struct dm_dev *metadata_dev;
struct dm_target_callbacks callbacks;
dm_block_t low_water_blocks;
unsigned zero_new_blocks:1;
};
/*
* Target context for a thin.
*/
struct thin_c {
struct dm_dev *pool_dev;
dm_thin_id dev_id;
struct pool *pool;
struct dm_thin_device *td;
};
/*----------------------------------------------------------------*/
/*
* A global list of pools that uses a struct mapped_device as a key.
*/
static struct dm_thin_pool_table {
struct mutex mutex;
struct list_head pools;
} dm_thin_pool_table;
static void pool_table_init(void)
{
mutex_init(&dm_thin_pool_table.mutex);
INIT_LIST_HEAD(&dm_thin_pool_table.pools);
}
static void __pool_table_insert(struct pool *pool)
{
BUG_ON(!mutex_is_locked(&dm_thin_pool_table.mutex));
list_add(&pool->list, &dm_thin_pool_table.pools);
}
static void __pool_table_remove(struct pool *pool)
{
BUG_ON(!mutex_is_locked(&dm_thin_pool_table.mutex));
list_del(&pool->list);
}
static struct pool *__pool_table_lookup(struct mapped_device *md)
{
struct pool *pool = NULL, *tmp;
BUG_ON(!mutex_is_locked(&dm_thin_pool_table.mutex));
list_for_each_entry(tmp, &dm_thin_pool_table.pools, list) {
if (tmp->pool_md == md) {
pool = tmp;
break;
}
}
return pool;
}
static struct pool *__pool_table_lookup_metadata_dev(struct block_device *md_dev)
{
struct pool *pool = NULL, *tmp;
BUG_ON(!mutex_is_locked(&dm_thin_pool_table.mutex));
list_for_each_entry(tmp, &dm_thin_pool_table.pools, list) {
if (tmp->md_dev == md_dev) {
pool = tmp;
break;
}
}
return pool;
}
/*----------------------------------------------------------------*/
static void __requeue_bio_list(struct thin_c *tc, struct bio_list *master)
{
struct bio *bio;
struct bio_list bios;
bio_list_init(&bios);
bio_list_merge(&bios, master);
bio_list_init(master);
while ((bio = bio_list_pop(&bios))) {
if (dm_get_mapinfo(bio)->ptr == tc)
bio_endio(bio, DM_ENDIO_REQUEUE);
else
bio_list_add(master, bio);
}
}
static void requeue_io(struct thin_c *tc)
{
struct pool *pool = tc->pool;
unsigned long flags;
spin_lock_irqsave(&pool->lock, flags);
__requeue_bio_list(tc, &pool->deferred_bios);
__requeue_bio_list(tc, &pool->retry_on_resume_list);
spin_unlock_irqrestore(&pool->lock, flags);
}
/*
* This section of code contains the logic for processing a thin device's IO.
* Much of the code depends on pool object resources (lists, workqueues, etc)
* but most is exclusively called from the thin target rather than the thin-pool
* target.
*/
static dm_block_t get_bio_block(struct thin_c *tc, struct bio *bio)
{
return bio->bi_sector >> tc->pool->block_shift;
}
static void remap(struct thin_c *tc, struct bio *bio, dm_block_t block)
{
struct pool *pool = tc->pool;
bio->bi_bdev = tc->pool_dev->bdev;
bio->bi_sector = (block << pool->block_shift) +
(bio->bi_sector & pool->offset_mask);
}
static void remap_and_issue(struct thin_c *tc, struct bio *bio,
dm_block_t block)
{
struct pool *pool = tc->pool;
unsigned long flags;
remap(tc, bio, block);
/*
* Batch together any FUA/FLUSH bios we find and then issue
* a single commit for them in process_deferred_bios().
*/
if (bio->bi_rw & (REQ_FLUSH | REQ_FUA)) {
spin_lock_irqsave(&pool->lock, flags);
bio_list_add(&pool->deferred_flush_bios, bio);
spin_unlock_irqrestore(&pool->lock, flags);
} else
generic_make_request(bio);
}
/*
* wake_worker() is used when new work is queued and when pool_resume is
* ready to continue deferred IO processing.
*/
static void wake_worker(struct pool *pool)
{
queue_work(pool->wq, &pool->worker);
}
/*----------------------------------------------------------------*/
/*
* Bio endio functions.
*/
struct endio_hook {
struct thin_c *tc;
bio_end_io_t *saved_bi_end_io;
struct deferred_entry *entry;
};
struct new_mapping {
struct list_head list;
int prepared;
struct thin_c *tc;
dm_block_t virt_block;
dm_block_t data_block;
struct cell *cell;
int err;
/*
* If the bio covers the whole area of a block then we can avoid
* zeroing or copying. Instead this bio is hooked. The bio will
* still be in the cell, so care has to be taken to avoid issuing
* the bio twice.
*/
struct bio *bio;
bio_end_io_t *saved_bi_end_io;
};
static void __maybe_add_mapping(struct new_mapping *m)
{
struct pool *pool = m->tc->pool;
if (list_empty(&m->list) && m->prepared) {
list_add(&m->list, &pool->prepared_mappings);
wake_worker(pool);
}
}
static void copy_complete(int read_err, unsigned long write_err, void *context)
{
unsigned long flags;
struct new_mapping *m = context;
struct pool *pool = m->tc->pool;
m->err = read_err || write_err ? -EIO : 0;
spin_lock_irqsave(&pool->lock, flags);
m->prepared = 1;
__maybe_add_mapping(m);
spin_unlock_irqrestore(&pool->lock, flags);
}
static void overwrite_endio(struct bio *bio, int err)
{
unsigned long flags;
struct new_mapping *m = dm_get_mapinfo(bio)->ptr;
struct pool *pool = m->tc->pool;
m->err = err;
spin_lock_irqsave(&pool->lock, flags);
m->prepared = 1;
__maybe_add_mapping(m);
spin_unlock_irqrestore(&pool->lock, flags);
}
static void shared_read_endio(struct bio *bio, int err)
{
struct list_head mappings;
struct new_mapping *m, *tmp;
struct endio_hook *h = dm_get_mapinfo(bio)->ptr;
unsigned long flags;
struct pool *pool = h->tc->pool;
bio->bi_end_io = h->saved_bi_end_io;
bio_endio(bio, err);
INIT_LIST_HEAD(&mappings);
ds_dec(h->entry, &mappings);
spin_lock_irqsave(&pool->lock, flags);
list_for_each_entry_safe(m, tmp, &mappings, list) {
list_del(&m->list);
INIT_LIST_HEAD(&m->list);
__maybe_add_mapping(m);
}
spin_unlock_irqrestore(&pool->lock, flags);
mempool_free(h, pool->endio_hook_pool);
}
/*----------------------------------------------------------------*/
/*
* Workqueue.
*/
/*
* Prepared mapping jobs.
*/
/*
* This sends the bios in the cell back to the deferred_bios list.
*/
static void cell_defer(struct thin_c *tc, struct cell *cell,
dm_block_t data_block)
{
struct pool *pool = tc->pool;
unsigned long flags;
spin_lock_irqsave(&pool->lock, flags);
cell_release(cell, &pool->deferred_bios);
spin_unlock_irqrestore(&tc->pool->lock, flags);
wake_worker(pool);
}
/*
* Same as cell_defer above, except it omits one particular detainee,
* a write bio that covers the block and has already been processed.
*/
static void cell_defer_except(struct thin_c *tc, struct cell *cell,
struct bio *exception)
{
struct bio_list bios;
struct bio *bio;
struct pool *pool = tc->pool;
unsigned long flags;
bio_list_init(&bios);
cell_release(cell, &bios);
spin_lock_irqsave(&pool->lock, flags);
while ((bio = bio_list_pop(&bios)))
if (bio != exception)
bio_list_add(&pool->deferred_bios, bio);
spin_unlock_irqrestore(&pool->lock, flags);
wake_worker(pool);
}
static void process_prepared_mapping(struct new_mapping *m)
{
struct thin_c *tc = m->tc;
struct bio *bio;
int r;
bio = m->bio;
if (bio)
bio->bi_end_io = m->saved_bi_end_io;
if (m->err) {
cell_error(m->cell);
return;
}
/*
* Commit the prepared block into the mapping btree.
* Any I/O for this block arriving after this point will get
* remapped to it directly.
*/
r = dm_thin_insert_block(tc->td, m->virt_block, m->data_block);
if (r) {
DMERR("dm_thin_insert_block() failed");
cell_error(m->cell);
return;
}
/*
* Release any bios held while the block was being provisioned.
* If we are processing a write bio that completely covers the block,
* we already processed it so can ignore it now when processing
* the bios in the cell.
*/
if (bio) {
cell_defer_except(tc, m->cell, bio);
bio_endio(bio, 0);
} else
cell_defer(tc, m->cell, m->data_block);
list_del(&m->list);
mempool_free(m, tc->pool->mapping_pool);
}
static void process_prepared_mappings(struct pool *pool)
{
unsigned long flags;
struct list_head maps;
struct new_mapping *m, *tmp;
INIT_LIST_HEAD(&maps);
spin_lock_irqsave(&pool->lock, flags);
list_splice_init(&pool->prepared_mappings, &maps);
spin_unlock_irqrestore(&pool->lock, flags);
list_for_each_entry_safe(m, tmp, &maps, list)
process_prepared_mapping(m);
}
/*
* Deferred bio jobs.
*/
static int io_overwrites_block(struct pool *pool, struct bio *bio)
{
return ((bio_data_dir(bio) == WRITE) &&
!(bio->bi_sector & pool->offset_mask)) &&
(bio->bi_size == (pool->sectors_per_block << SECTOR_SHIFT));
}
static void save_and_set_endio(struct bio *bio, bio_end_io_t **save,
bio_end_io_t *fn)
{
*save = bio->bi_end_io;
bio->bi_end_io = fn;
}
static int ensure_next_mapping(struct pool *pool)
{
if (pool->next_mapping)
return 0;
pool->next_mapping = mempool_alloc(pool->mapping_pool, GFP_ATOMIC);
return pool->next_mapping ? 0 : -ENOMEM;
}
static struct new_mapping *get_next_mapping(struct pool *pool)
{
struct new_mapping *r = pool->next_mapping;
BUG_ON(!pool->next_mapping);
pool->next_mapping = NULL;
return r;
}
static void schedule_copy(struct thin_c *tc, dm_block_t virt_block,
dm_block_t data_origin, dm_block_t data_dest,
struct cell *cell, struct bio *bio)
{
int r;
struct pool *pool = tc->pool;
struct new_mapping *m = get_next_mapping(pool);
INIT_LIST_HEAD(&m->list);
m->prepared = 0;
m->tc = tc;
m->virt_block = virt_block;
m->data_block = data_dest;
m->cell = cell;
m->err = 0;
m->bio = NULL;
ds_add_work(&pool->ds, &m->list);
/*
* IO to pool_dev remaps to the pool target's data_dev.
*
* If the whole block of data is being overwritten, we can issue the
* bio immediately. Otherwise we use kcopyd to clone the data first.
*/
if (io_overwrites_block(pool, bio)) {
m->bio = bio;
save_and_set_endio(bio, &m->saved_bi_end_io, overwrite_endio);
dm_get_mapinfo(bio)->ptr = m;
remap_and_issue(tc, bio, data_dest);
} else {
struct dm_io_region from, to;
from.bdev = tc->pool_dev->bdev;
from.sector = data_origin * pool->sectors_per_block;
from.count = pool->sectors_per_block;
to.bdev = tc->pool_dev->bdev;
to.sector = data_dest * pool->sectors_per_block;
to.count = pool->sectors_per_block;
r = dm_kcopyd_copy(pool->copier, &from, 1, &to,
0, copy_complete, m);
if (r < 0) {
mempool_free(m, pool->mapping_pool);
DMERR("dm_kcopyd_copy() failed");
cell_error(cell);
}
}
}
static void schedule_zero(struct thin_c *tc, dm_block_t virt_block,
dm_block_t data_block, struct cell *cell,
struct bio *bio)
{
struct pool *pool = tc->pool;
struct new_mapping *m = get_next_mapping(pool);
INIT_LIST_HEAD(&m->list);
m->prepared = 0;
m->tc = tc;
m->virt_block = virt_block;
m->data_block = data_block;
m->cell = cell;
m->err = 0;
m->bio = NULL;
/*
* If the whole block of data is being overwritten or we are not
* zeroing pre-existing data, we can issue the bio immediately.
* Otherwise we use kcopyd to zero the data first.
*/
if (!pool->zero_new_blocks)
process_prepared_mapping(m);
else if (io_overwrites_block(pool, bio)) {
m->bio = bio;
save_and_set_endio(bio, &m->saved_bi_end_io, overwrite_endio);
dm_get_mapinfo(bio)->ptr = m;
remap_and_issue(tc, bio, data_block);
} else {