dm snapshot: move cow ref from exception store to snap core

Store the reference to the snapshot cow device in the core snapshot
code instead of each exception store.  It can be accessed through the
new function dm_snap_cow().  Exception stores should each now maintain a
reference to their parent snapshot struct.

This is cleaner and makes part of the forthcoming snapshot merge code simpler.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Reviewed-by: Jonathan Brassow <jbrassow@redhat.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>

1 files changed, 6 insertions, 6 deletions

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;