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-rw-r--r--drivers/md/dm-thin.c2428
1 files changed, 2428 insertions, 0 deletions
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
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--- /dev/null
+++ b/drivers/md/dm-thin.c
@@ -0,0 +1,2428 @@
+/*
+ * 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 {
+ int r;
+ struct dm_io_region to;
+
+ to.bdev = tc->pool_dev->bdev;
+ to.sector = data_block * pool->sectors_per_block;
+ to.count = pool->sectors_per_block;
+
+ r = dm_kcopyd_zero(pool->copier, 1, &to, 0, copy_complete, m);
+ if (r < 0) {
+ mempool_free(m, pool->mapping_pool);
+ DMERR("dm_kcopyd_zero() failed");
+ cell_error(cell);
+ }
+ }
+}
+
+static int alloc_data_block(struct thin_c *tc, dm_block_t *result)
+{
+ int r;
+ dm_block_t free_blocks;
+ unsigned long flags;
+ struct pool *pool = tc->pool;
+
+ r = dm_pool_get_free_block_count(pool->pmd, &free_blocks);
+ if (r)
+ return r;
+
+ if (free_blocks <= pool->low_water_blocks && !pool->low_water_triggered) {
+ DMWARN("%s: reached low water mark, sending event.",
+ dm_device_name(pool->pool_md));
+ spin_lock_irqsave(&pool->lock, flags);
+ pool->low_water_triggered = 1;
+ spin_unlock_irqrestore(&pool->lock, flags);
+ dm_table_event(pool->ti->table);
+ }
+
+ if (!free_blocks) {
+ if (pool->no_free_space)
+ return -ENOSPC;
+ else {
+ /*
+ * Try to commit to see if that will free up some
+ * more space.
+ */
+ r = dm_pool_commit_metadata(pool->pmd);
+ if (r) {
+ DMERR("%s: dm_pool_commit_metadata() failed, error = %d",
+ __func__, r);
+ return r;
+ }
+
+ r = dm_pool_get_free_block_count(pool->pmd, &free_blocks);
+ if (r)
+ return r;
+
+ /*
+ * If we still have no space we set a flag to avoid
+ * doing all this checking and return -ENOSPC.
+ */
+ if (!free_blocks) {
+ DMWARN("%s: no free space available.",
+ dm_device_name(pool->pool_md));
+ spin_lock_irqsave(&pool->lock, flags);
+ pool->no_free_space = 1;
+ spin_unlock_irqrestore(&pool->lock, flags);
+ return -ENOSPC;
+ }
+ }
+ }
+
+ r = dm_pool_alloc_data_block(pool->pmd, result);
+ if (r)
+ return r;
+
+ return 0;
+}
+
+/*
+ * If we have run out of space, queue bios until the device is
+ * resumed, presumably after having been reloaded with more space.
+ */
+static void retry_on_resume(struct bio *bio)
+{
+ struct thin_c *tc = dm_get_mapinfo(bio)->ptr;
+ struct pool *pool = tc->pool;
+ unsigned long flags;
+
+ spin_lock_irqsave(&pool->lock, flags);
+ bio_list_add(&pool->retry_on_resume_list, bio);
+ spin_unlock_irqrestore(&pool->lock, flags);
+}
+
+static void no_space(struct cell *cell)
+{
+ struct bio *bio;
+ struct bio_list bios;
+
+ bio_list_init(&bios);
+ cell_release(cell, &bios);
+
+ while ((bio = bio_list_pop(&bios)))
+ retry_on_resume(bio);
+}
+
+static void break_sharing(struct thin_c *tc, struct bio *bio, dm_block_t block,
+ struct cell_key *key,
+ struct dm_thin_lookup_result *lookup_result,
+ struct cell *cell)
+{
+ int r;
+ dm_block_t data_block;
+
+ r = alloc_data_block(tc, &data_block);
+ switch (r) {
+ case 0:
+ schedule_copy(tc, block, lookup_result->block,
+ data_block, cell, bio);
+ break;
+
+ case -ENOSPC:
+ no_space(cell);
+ break;
+
+ default:
+ DMERR("%s: alloc_data_block() failed, error = %d", __func__, r);
+ cell_error(cell);
+ break;
+ }
+}
+
+static void process_shared_bio(struct thin_c *tc, struct bio *bio,
+ dm_block_t block,
+ struct dm_thin_lookup_result *lookup_result)
+{
+ struct cell *cell;
+ struct pool *pool = tc->pool;
+ struct cell_key key;
+
+ /*
+ * If cell is already occupied, then sharing is already in the process
+ * of being broken so we have nothing further to do here.
+ */
+ build_data_key(tc->td, lookup_result->block, &key);
+ if (bio_detain(pool->prison, &key, bio, &cell))
+ return;
+
+ if (bio_data_dir(bio) == WRITE)
+ break_sharing(tc, bio, block, &key, lookup_result, cell);
+ else {
+ struct endio_hook *h;
+ h = mempool_alloc(pool->endio_hook_pool, GFP_NOIO);
+
+ h->tc = tc;
+ h->entry = ds_inc(&pool->ds);
+ save_and_set_endio(bio, &h->saved_bi_end_io, shared_read_endio);
+ dm_get_mapinfo(bio)->ptr = h;
+
+ cell_release_singleton(cell, bio);
+ remap_and_issue(tc, bio, lookup_result->block);
+ }
+}
+
+static void provision_block(struct thin_c *tc, struct bio *bio, dm_block_t block,
+ struct cell *cell)
+{
+ int r;
+ dm_block_t data_block;
+
+ /*
+ * Remap empty bios (flushes) immediately, without provisioning.
+ */
+ if (!bio->bi_size) {
+ cell_release_singleton(cell, bio);
+ remap_and_issue(tc, bio, 0);
+ return;
+ }
+
+ /*
+ * Fill read bios with zeroes and complete them immediately.
+ */
+ if (bio_data_dir(bio) == READ) {
+ zero_fill_bio(bio);
+ cell_release_singleton(cell, bio);
+ bio_endio(bio, 0);
+ return;
+ }
+
+ r = alloc_data_block(tc, &data_block);
+ switch (r) {
+ case 0:
+ schedule_zero(tc, block, data_block, cell, bio);
+ break;
+
+ case -ENOSPC:
+ no_space(cell);
+ break;
+
+ default:
+ DMERR("%s: alloc_data_block() failed, error = %d", __func__, r);
+ cell_error(cell);
+ break;
+ }
+}
+
+static void process_bio(struct thin_c *tc, struct bio *bio)
+{
+ int r;
+ dm_block_t block = get_bio_block(tc, bio);
+ struct cell *cell;
+ struct cell_key key;
+ struct dm_thin_lookup_result lookup_result;
+
+ /*
+ * If cell is already occupied, then the block is already
+ * being provisioned so we have nothing further to do here.
+ */
+ build_virtual_key(tc->td, block, &key);
+ if (bio_detain(tc->pool->prison, &key, bio, &cell))
+ return;
+
+ r = dm_thin_find_block(tc->td, block, 1, &lookup_result);
+ switch (r) {
+ case 0:
+ /*
+ * We can release this cell now. This thread is the only
+ * one that puts bios into a cell, and we know there were
+ * no preceding bios.
+ */
+ /*
+ * TODO: this will probably have to change when discard goes
+ * back in.
+ */
+ cell_release_singleton(cell, bio);