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, 11 insertions, 19 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);
 }