5 files changed, 78 insertions, 57 deletions

diff --git a/drivers/md/dm-exception-store.c b/drivers/md/dm-exception-store.c
index 205215968ff1..2b7907b6dd09 100644
--- a/drivers/md/dm-exception-store.c
+++ b/drivers/md/dm-exception-store.c
@@ -172,7 +172,8 @@ int dm_exception_store_set_chunk_size(struct dm_exception_store *store,
         }
 
         /* Validate the chunk size against the device block size */
-        if (chunk_size % (bdev_logical_block_size(store->cow->bdev) >> 9)) {
+        if (chunk_size %
+            (bdev_logical_block_size(dm_snap_cow(store->snap)->bdev) >> 9)) {
                 *error = "Chunk size is not a multiple of device blocksize";
                 return -EINVAL;
         }
@@ -190,6 +191,7 @@ int dm_exception_store_set_chunk_size(struct dm_exception_store *store,
 }
 
 int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
+                              struct dm_snapshot *snap,
                               unsigned *args_used,
                               struct dm_exception_store **store)
 {
@@ -198,7 +200,7 @@ int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
         struct dm_exception_store *tmp_store;
         char persistent;
 
-        if (argc < 3) {
+        if (argc < 2) {
                 ti->error = "Insufficient exception store arguments";
                 return -EINVAL;
         }
@@ -209,7 +211,7 @@ int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
                 return -ENOMEM;
         }
 
-        persistent = toupper(*argv[1]);
+        persistent = toupper(*argv[0]);
         if (persistent == 'P')
                 type = get_type("P");
         else if (persistent == 'N')
@@ -227,32 +229,23 @@ int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
         }
 
         tmp_store->type = type;
-        tmp_store->ti = ti;
+        tmp_store->snap = snap;
 
-        r = dm_get_device(ti, argv[0], 0, 0,
-                          FMODE_READ | FMODE_WRITE, &tmp_store->cow);
-        if (r) {
-                ti->error = "Cannot get COW device";
-                goto bad_cow;
-        }
-
-        r = set_chunk_size(tmp_store, argv[2], &ti->error);
+        r = set_chunk_size(tmp_store, argv[1], &ti->error);
         if (r)
-                goto bad_ctr;
+                goto bad;
 
         r = type->ctr(tmp_store, 0, NULL);
         if (r) {
                 ti->error = "Exception store type constructor failed";
-                goto bad_ctr;
+                goto bad;
         }
 
-        *args_used = 3;
+        *args_used = 2;
         *store = tmp_store;
         return 0;
 
-bad_ctr:
-        dm_put_device(ti, tmp_store->cow);
-bad_cow:
+bad:
         put_type(type);
 bad_type:
         kfree(tmp_store);
@@ -263,7 +256,6 @@ EXPORT_SYMBOL(dm_exception_store_create);
 void dm_exception_store_destroy(struct dm_exception_store *store)
 {
         store->type->dtr(store);
-        dm_put_device(store->ti, store->cow);
         put_type(store->type);
         kfree(store);
 }
diff --git a/drivers/md/dm-exception-store.h b/drivers/md/dm-exception-store.h
index 366c8b1fca37..bb8874653de1 100644
--- a/drivers/md/dm-exception-store.h
+++ b/drivers/md/dm-exception-store.h
@@ -94,11 +94,11 @@ struct dm_exception_store_type {
         struct list_head list;
 };
 
+struct dm_snapshot;
+
 struct dm_exception_store {
         struct dm_exception_store_type *type;
-        struct dm_target *ti;
-
-        struct dm_dev *cow;
+        struct dm_snapshot *snap;
 
         /* Size of data blocks saved - must be a power of 2 */
         unsigned chunk_size;
@@ -109,6 +109,11 @@ struct dm_exception_store {
 };
 
 /*
+ * Obtain the cow device used by a given snapshot.
+ */
+struct dm_dev *dm_snap_cow(struct dm_snapshot *snap);
+
+/*
  * Funtions to manipulate consecutive chunks
  */
 #  if defined(CONFIG_LBDAF) || (BITS_PER_LONG == 64)
@@ -173,6 +178,7 @@ int dm_exception_store_set_chunk_size(struct dm_exception_store *store,
                                       char **error);
 
 int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
+                              struct dm_snapshot *snap,
                               unsigned *args_used,
                               struct dm_exception_store **store);
 void dm_exception_store_destroy(struct dm_exception_store *store);
diff --git a/drivers/md/dm-snap-persistent.c b/drivers/md/dm-snap-persistent.c
index 767065f6c5f3..157999ebd236 100644
--- a/drivers/md/dm-snap-persistent.c
+++ b/drivers/md/dm-snap-persistent.c
@@ -214,7 +214,7 @@ static int chunk_io(struct pstore *ps, void *area, chunk_t chunk, int rw,
                     int metadata)
 {
         struct dm_io_region where = {
-                .bdev = ps->store->cow->bdev,
+                .bdev = dm_snap_cow(ps->store->snap)->bdev,
                 .sector = ps->store->chunk_size * chunk,
                 .count = ps->store->chunk_size,
         };
@@ -294,7 +294,8 @@ static int read_header(struct pstore *ps, int *new_snapshot)
          */
         if (!ps->store->chunk_size) {
                 ps->store->chunk_size = max(DM_CHUNK_SIZE_DEFAULT_SECTORS,
-                    bdev_logical_block_size(ps->store->cow->bdev) >> 9);
+                    bdev_logical_block_size(dm_snap_cow(ps->store->snap)->
+                                            bdev) >> 9);
                 ps->store->chunk_mask = ps->store->chunk_size - 1;
                 ps->store->chunk_shift = ffs(ps->store->chunk_size) - 1;
                 chunk_size_supplied = 0;
@@ -497,7 +498,7 @@ static void persistent_usage(struct dm_exception_store *store,
         struct pstore *ps = get_info(store);
 
         *sectors_allocated = ps->next_free * store->chunk_size;
-        *total_sectors = get_dev_size(store->cow->bdev);
+        *total_sectors = get_dev_size(dm_snap_cow(store->snap)->bdev);
 
         /*
          * First chunk is the fixed header.
@@ -596,7 +597,7 @@ static int persistent_prepare_exception(struct dm_exception_store *store,
         struct pstore *ps = get_info(store);
         uint32_t stride;
         chunk_t next_free;
-        sector_t size = get_dev_size(store->cow->bdev);
+        sector_t size = get_dev_size(dm_snap_cow(store->snap)->bdev);
 
         /* Is there enough room ? */
         if (size < ((ps->next_free + 1) * store->chunk_size))
@@ -733,8 +734,7 @@ static unsigned persistent_status(struct dm_exception_store *store,
         case STATUSTYPE_INFO:
                 break;
         case STATUSTYPE_TABLE:
-                DMEMIT(" %s P %llu", store->cow->name,
-                       (unsigned long long)store->chunk_size);
+                DMEMIT(" P %llu", (unsigned long long)store->chunk_size);
         }
 
         return sz;
diff --git a/drivers/md/dm-snap-transient.c b/drivers/md/dm-snap-transient.c
index 245a50c7337e..a0898a66a2f8 100644
--- a/drivers/md/dm-snap-transient.c
+++ b/drivers/md/dm-snap-transient.c
@@ -39,7 +39,7 @@ static int transient_prepare_exception(struct dm_exception_store *store,
                                        struct dm_exception *e)
 {
         struct transient_c *tc = store->context;
-        sector_t size = get_dev_size(store->cow->bdev);
+        sector_t size = get_dev_size(dm_snap_cow(store->snap)->bdev);
 
         if (size < (tc->next_free + store->chunk_size))
                 return -1;
@@ -65,7 +65,7 @@ static void transient_usage(struct dm_exception_store *store,
                             sector_t *metadata_sectors)
 {
         *sectors_allocated = ((struct transient_c *) store->context)->next_free;
-        *total_sectors = get_dev_size(store->cow->bdev);
+        *total_sectors = get_dev_size(dm_snap_cow(store->snap)->bdev);
         *metadata_sectors = 0;
 }
 
@@ -94,8 +94,7 @@ static unsigned transient_status(struct dm_exception_store *store,
         case STATUSTYPE_INFO:
                 break;
         case STATUSTYPE_TABLE:
-                DMEMIT(" %s N %llu", store->cow->name,
-                       (unsigned long long)store->chunk_size);
+                DMEMIT(" N %llu", (unsigned long long)store->chunk_size);
         }
 
         return sz;
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 8bd77cbd7e45..dc500a6f6232 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -59,6 +59,9 @@ struct dm_snapshot {
         struct rw_semaphore lock;
 
         struct dm_dev *origin;
+        struct dm_dev *cow;
+
+        struct dm_target *ti;
 
         /* List of snapshots per Origin */
         struct list_head list;
@@ -97,6 +100,12 @@ struct dm_snapshot {
         struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
 };
 
+struct dm_dev *dm_snap_cow(struct dm_snapshot *s)
+{
+        return s->cow;
+}
+EXPORT_SYMBOL(dm_snap_cow);
+
 static struct workqueue_struct *ksnapd;
 static void flush_queued_bios(struct work_struct *work);
 
@@ -558,7 +567,7 @@ static int init_hash_tables(struct dm_snapshot *s)
          * Calculate based on the size of the original volume or
          * the COW volume...
          */
-        cow_dev_size = get_dev_size(s->store->cow->bdev);
+        cow_dev_size = get_dev_size(s->cow->bdev);
         origin_dev_size = get_dev_size(s->origin->bdev);
         max_buckets = calc_max_buckets();
 
@@ -596,45 +605,55 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
         struct dm_snapshot *s;
         int i;
         int r = -EINVAL;
-        char *origin_path;
-        struct dm_exception_store *store;
+        char *origin_path, *cow_path;
         unsigned args_used;
 
         if (argc != 4) {
                 ti->error = "requires exactly 4 arguments";
                 r = -EINVAL;
-                goto bad_args;
+                goto bad;
         }
 
         origin_path = argv[0];
         argv++;
         argc--;
 
-        r = dm_exception_store_create(ti, argc, argv, &args_used, &store);
+        s = kmalloc(sizeof(*s), GFP_KERNEL);
+        if (!s) {
+                ti->error = "Cannot allocate snapshot context private "
+                    "structure";
+                r = -ENOMEM;
+                goto bad;
+        }
+
+        cow_path = argv[0];
+        argv++;
+        argc--;
+
+        r = dm_get_device(ti, cow_path, 0, 0,
+                          FMODE_READ | FMODE_WRITE, &s->cow);
+        if (r) {
+                ti->error = "Cannot get COW device";
+                goto bad_cow;
+        }
+
+        r = dm_exception_store_create(ti, argc, argv, s, &args_used, &s->store);
         if (r) {
                 ti->error = "Couldn't create exception store";
                 r = -EINVAL;
-                goto bad_args;
+                goto bad_store;
         }
 
         argv += args_used;
         argc -= args_used;
 
-        s = kmalloc(sizeof(*s), GFP_KERNEL);
-        if (!s) {
-                ti->error = "Cannot allocate snapshot context private "
-                    "structure";
-                r = -ENOMEM;
-                goto bad_snap;
-        }
-
         r = dm_get_device(ti, origin_path, 0, ti->len, FMODE_READ, &s->origin);
         if (r) {
                 ti->error = "Cannot get origin device";
                 goto bad_origin;
         }
 
-        s->store = store;
+        s->ti = ti;
         s->valid = 1;
         s->active = 0;
         atomic_set(&s->pending_exceptions_count, 0);
@@ -723,12 +742,15 @@ bad_hash_tables:
         dm_put_device(ti, s->origin);
 
 bad_origin:
-        kfree(s);
+        dm_exception_store_destroy(s->store);
 
-bad_snap:
-        dm_exception_store_destroy(store);
+bad_store:
+        dm_put_device(ti, s->cow);
 
-bad_args:
+bad_cow:
+        kfree(s);
+
+bad:
         return r;
 }
 
@@ -777,6 +799,8 @@ static void snapshot_dtr(struct dm_target *ti)
 
         dm_exception_store_destroy(s->store);
 
+        dm_put_device(ti, s->cow);
+
         kfree(s);
 }
 
@@ -839,7 +863,7 @@ static void __invalidate_snapshot(struct dm_snapshot *s, int err)
 
         s->valid = 0;
 
-        dm_table_event(s->store->ti->table);
+        dm_table_event(s->ti->table);
 }
 
 static void get_pending_exception(struct dm_snap_pending_exception *pe)
@@ -977,7 +1001,7 @@ static void start_copy(struct dm_snap_pending_exception *pe)
         src.sector = chunk_to_sector(s->store, pe->e.old_chunk);
         src.count = min((sector_t)s->store->chunk_size, dev_size - src.sector);
 
-        dest.bdev = s->store->cow->bdev;
+        dest.bdev = s->cow->bdev;
         dest.sector = chunk_to_sector(s->store, pe->e.new_chunk);
         dest.count = src.count;
 
@@ -1038,7 +1062,7 @@ __find_pending_exception(struct dm_snapshot *s,
 static void remap_exception(struct dm_snapshot *s, struct dm_exception *e,
                             struct bio *bio, chunk_t chunk)
 {
-        bio->bi_bdev = s->store->cow->bdev;
+        bio->bi_bdev = s->cow->bdev;
         bio->bi_sector = chunk_to_sector(s->store,
                                          dm_chunk_number(e->new_chunk) +
                                          (chunk - e->old_chunk)) +
@@ -1056,7 +1080,7 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio,
         struct dm_snap_pending_exception *pe = NULL;
 
         if (unlikely(bio_empty_barrier(bio))) {
-                bio->bi_bdev = s->store->cow->bdev;
+                bio->bi_bdev = s->cow->bdev;
                 return DM_MAPIO_REMAPPED;
         }
 
@@ -1200,7 +1224,7 @@ static int snapshot_status(struct dm_target *ti, status_type_t type,
                  * to make private copies if the output is to
                  * make sense.
                  */
-                DMEMIT("%s", snap->origin->name);
+                DMEMIT("%s %s", snap->origin->name, snap->cow->name);
                 snap->store->type->status(snap->store, type, result + sz,
                                           maxlen - sz);
                 break;
@@ -1240,7 +1264,7 @@ static int __origin_write(struct list_head *snapshots, struct bio *bio)
                         goto next_snapshot;
 
                 /* Nothing to do if writing beyond end of snapshot */
-                if (bio->bi_sector >= dm_table_get_size(snap->store->ti->table))
+                if (bio->bi_sector >= dm_table_get_size(snap->ti->table))
                         goto next_snapshot;
 
                 /*