1 files changed, 32 insertions, 22 deletions

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 5279fdae7142..7173360eea7a 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -1842,8 +1842,10 @@ out:
 }
 
 /*
- * copy the acounting information between qgroups. This is necessary when a
- * snapshot or a subvolume is created
+ * Copy the acounting information between qgroups. This is necessary
+ * when a snapshot or a subvolume is created. Throwing an error will
+ * cause a transaction abort so we take extra care here to only error
+ * when a readonly fs is a reasonable outcome.
  */
 int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans,
 			 struct btrfs_fs_info *fs_info, u64 srcid, u64 objectid,
@@ -1873,15 +1875,15 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans,
 		       2 * inherit->num_excl_copies;
 		for (i = 0; i < nums; ++i) {
 			srcgroup = find_qgroup_rb(fs_info, *i_qgroups);
-			if (!srcgroup) {
-				ret = -EINVAL;
-				goto out;
-			}
 
-			if ((srcgroup->qgroupid >> 48) <= (objectid >> 48)) {
-				ret = -EINVAL;
-				goto out;
-			}
+			/*
+			 * Zero out invalid groups so we can ignore
+			 * them later.
+			 */
+			if (!srcgroup ||
+			    ((srcgroup->qgroupid >> 48) <= (objectid >> 48)))
+				*i_qgroups = 0ULL;
+
 			++i_qgroups;
 		}
 	}
@@ -1916,17 +1918,19 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans,
 	 */
 	if (inherit) {
 		i_qgroups = (u64 *)(inherit + 1);
-		for (i = 0; i < inherit->num_qgroups; ++i) {
+		for (i = 0; i < inherit->num_qgroups; ++i, ++i_qgroups) {
+			if (*i_qgroups == 0)
+				continue;
 			ret = add_qgroup_relation_item(trans, quota_root,
 						       objectid, *i_qgroups);
-			if (ret)
+			if (ret && ret != -EEXIST)
 				goto out;
 			ret = add_qgroup_relation_item(trans, quota_root,
 						       *i_qgroups, objectid);
-			if (ret)
+			if (ret && ret != -EEXIST)
 				goto out;
-			++i_qgroups;
 		}
+		ret = 0;
 	}
 
 
@@ -1987,17 +1991,22 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans,
 
 	i_qgroups = (u64 *)(inherit + 1);
 	for (i = 0; i < inherit->num_qgroups; ++i) {
-		ret = add_relation_rb(quota_root->fs_info, objectid,
-				      *i_qgroups);
-		if (ret)
-			goto unlock;
+		if (*i_qgroups) {
+			ret = add_relation_rb(quota_root->fs_info, objectid,
+					      *i_qgroups);
+			if (ret)
+				goto unlock;
+		}
 		++i_qgroups;
 	}
 
-	for (i = 0; i <  inherit->num_ref_copies; ++i) {
+	for (i = 0; i <  inherit->num_ref_copies; ++i, i_qgroups += 2) {
 		struct btrfs_qgroup *src;
 		struct btrfs_qgroup *dst;
 
+		if (!i_qgroups[0] || !i_qgroups[1])
+			continue;
+
 		src = find_qgroup_rb(fs_info, i_qgroups[0]);
 		dst = find_qgroup_rb(fs_info, i_qgroups[1]);
 
@@ -2008,12 +2017,14 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans,
 
 		dst->rfer = src->rfer - level_size;
 		dst->rfer_cmpr = src->rfer_cmpr - level_size;
-		i_qgroups += 2;
 	}
-	for (i = 0; i <  inherit->num_excl_copies; ++i) {
+	for (i = 0; i <  inherit->num_excl_copies; ++i, i_qgroups += 2) {
 		struct btrfs_qgroup *src;
 		struct btrfs_qgroup *dst;
 
+		if (!i_qgroups[0] || !i_qgroups[1])
+			continue;
+
 		src = find_qgroup_rb(fs_info, i_qgroups[0]);
 		dst = find_qgroup_rb(fs_info, i_qgroups[1]);
 
@@ -2024,7 +2035,6 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans,
 
 		dst->excl = src->excl + level_size;
 		dst->excl_cmpr = src->excl_cmpr + level_size;
-		i_qgroups += 2;
 	}
 
 unlock: