1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 5f1b11e45702..1988019df5c9 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -923,6 +923,9 @@ static int alloc_data_block(struct thin_c *tc, dm_block_t *result)
         if (pool->no_free_space)
                 return -ENOSPC;
 
+        if (get_pool_mode(pool) != PM_WRITE)
+                return -EINVAL;
+
         r = dm_pool_get_free_block_count(pool->pmd, &free_blocks);
         if (r)
                 return r;