Rename parameter to reflect actual semantics

src/blockstore/blockstore_disk.cpp

@@ -517,7 +517,7 @@ void blockstore_disk_t::close_all()
 
 // Sadly DISCARD only works through ioctl(), but it seems to always block the device queue,
 // so it's not a big deal that we can only run it synchronously.
-int blockstore_disk_t::trim_data(std::function<bool(uint64_t)> is_free)
+int blockstore_disk_t::trim_data(std::function<bool(uint64_t)> is_used)
 {
     if (mock_mode)
     {
@@ -528,7 +528,7 @@ int blockstore_disk_t::trim_data(std::function<bool(uint64_t)> is_free)
     uint64_t discarded = 0;
     for (; i <= block_count; i++)
     {
-        if (i >= block_count || is_free(i))
+        if (i >= block_count || is_used(i))
         {
             if (i > j && (i-j)*data_block_size >= min_discard_size)
             {

src/blockstore/blockstore_disk.h

@@ -83,7 +83,7 @@ struct blockstore_disk_t
     void calc_lengths(bool skip_meta_check = false);
     void check_lengths();
     void close_all();
-    int trim_data(std::function<bool(uint64_t)> is_free);
+    int trim_data(std::function<bool(uint64_t)> is_used);
 
     inline uint64_t dirty_dyn_size(uint64_t offset, uint64_t len)
     {