dm btree: add ref counting ops for the leaves of top level btrees

commit b0dc3c8bc157c60b1d470163882be8c13e1950af upstream.

When using nested btrees, the top leaves of the top levels contain
block addresses for the root of the next tree down.  If we shadow a
shared leaf node the leaf values (sub tree roots) should be incremented
accordingly.

This is only an issue if there is metadata sharing in the top levels.
Which only occurs if metadata snapshots are being used (as is possible
with dm-thinp).  And could result in a block from the thinp metadata
snap being reused early, thus corrupting the thinp metadata snap.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
[bwh: Backported to 3.2:
 - Drop change to remove_one()
 - Remove const pointer qualifications]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

4 files changed, 47 insertions, 15 deletions

diff --git a/drivers/md/persistent-data/dm-btree-internal.h b/drivers/md/persistent-data/dm-btree-internal.h
index acba54e..f8458ca 100644
--- a/drivers/md/persistent-data/dm-btree-internal.h
+++ b/drivers/md/persistent-data/dm-btree-internal.h
@@ -134,4 +134,10 @@ int lower_bound(struct btree_node *n, uint64_t key);
 
 extern struct dm_block_validator btree_node_validator;
 
+/*
+ * Value type for upper levels of multi-level btrees.
+ */
+extern void init_le64_type(struct dm_transaction_manager *tm,
+			   struct dm_btree_value_type *vt);
+
 #endif	/* DM_BTREE_INTERNAL_H */
diff --git a/drivers/md/persistent-data/dm-btree-remove.c b/drivers/md/persistent-data/dm-btree-remove.c
index 6e79c11..294eb5b 100644
--- a/drivers/md/persistent-data/dm-btree-remove.c
+++ b/drivers/md/persistent-data/dm-btree-remove.c
@@ -544,14 +544,6 @@ static int remove_raw(struct shadow_spine *s, struct dm_btree_info *info,
 	return r;
 }
 
-static struct dm_btree_value_type le64_type = {
-	.context = NULL,
-	.size = sizeof(__le64),
-	.inc = NULL,
-	.dec = NULL,
-	.equal = NULL
-};
-
 int dm_btree_remove(struct dm_btree_info *info, dm_block_t root,
 		    uint64_t *keys, dm_block_t *new_root)
 {
@@ -559,12 +551,14 @@ int dm_btree_remove(struct dm_btree_info *info, dm_block_t root,
 	int index = 0, r = 0;
 	struct shadow_spine spine;
 	struct btree_node *n;
+	struct dm_btree_value_type le64_vt;
 
+	init_le64_type(info->tm, &le64_vt);
 	init_shadow_spine(&spine, info);
 	for (level = 0; level < info->levels; level++) {
 		r = remove_raw(&spine, info,
 			       (level == last_level ?
-				&info->value_type : &le64_type),
+				&info->value_type : &le64_vt),
 			       root, keys[level], (unsigned *)&index);
 		if (r < 0)
 			break;
diff --git a/drivers/md/persistent-data/dm-btree-spine.c b/drivers/md/persistent-data/dm-btree-spine.c
index 2f0805c..f6cb762 100644
--- a/drivers/md/persistent-data/dm-btree-spine.c
+++ b/drivers/md/persistent-data/dm-btree-spine.c
@@ -242,3 +242,40 @@ int shadow_root(struct shadow_spine *s)
 {
 	return s->root;
 }
+
+static void le64_inc(void *context, void *value_le)
+{
+	struct dm_transaction_manager *tm = context;
+	__le64 v_le;
+
+	memcpy(&v_le, value_le, sizeof(v_le));
+	dm_tm_inc(tm, le64_to_cpu(v_le));
+}
+
+static void le64_dec(void *context, void *value_le)
+{
+	struct dm_transaction_manager *tm = context;
+	__le64 v_le;
+
+	memcpy(&v_le, value_le, sizeof(v_le));
+	dm_tm_dec(tm, le64_to_cpu(v_le));
+}
+
+static int le64_equal(void *context, void *value1_le, void *value2_le)
+{
+	__le64 v1_le, v2_le;
+
+	memcpy(&v1_le, value1_le, sizeof(v1_le));
+	memcpy(&v2_le, value2_le, sizeof(v2_le));
+	return v1_le == v2_le;
+}
+
+void init_le64_type(struct dm_transaction_manager *tm,
+		    struct dm_btree_value_type *vt)
+{
+	vt->context = tm;
+	vt->size = sizeof(__le64);
+	vt->inc = le64_inc;
+	vt->dec = le64_dec;
+	vt->equal = le64_equal;
+}
diff --git a/drivers/md/persistent-data/dm-btree.c b/drivers/md/persistent-data/dm-btree.c
index 18f37e0..62f297a 100644
--- a/drivers/md/persistent-data/dm-btree.c
+++ b/drivers/md/persistent-data/dm-btree.c
@@ -647,12 +647,7 @@ static int insert(struct dm_btree_info *info, dm_block_t root,
 	struct btree_node *n;
 	struct dm_btree_value_type le64_type;
 
-	le64_type.context = NULL;
-	le64_type.size = sizeof(__le64);
-	le64_type.inc = NULL;
-	le64_type.dec = NULL;
-	le64_type.equal = NULL;
-
+	init_le64_type(info->tm, &le64_type);
 	init_shadow_spine(&spine, info);
 
 	for (level = 0; level < (info->levels - 1); level++) {