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-rw-r--r--drivers/md/dm-snap.c1208
1 files changed, 1208 insertions, 0 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
new file mode 100644
index 00000000000..7e691ab9a74
--- /dev/null
+++ b/drivers/md/dm-snap.c
@@ -0,0 +1,1208 @@
+/*
+ * 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;
+}
+
+/*
+ * 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->have_metadata = 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;
+ }
+
+ /* Add snapshot to the list of snapshots for this origin */
+ 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 inline 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 -1;
+
+ /*
+ * 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;
+
+ if (s->have_metadata)
+ return;
+
+ if (s->store.read_metadata(&s->store)) {
+ down_write(&s->lock);
+ s->valid = 0;
+ up_write(&s->lock);
+ }
+
+ s->have_metadata = 1;
+}
+
+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 snapshots */
+ if (!snap->valid)
+ 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;
+
+ /* 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, 0, 1},
+ .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, 0, 1},
+ .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");
generated by cgit v1.2.3 (git 2.25.1) at 2024-04-19 02:16:57 +0000