2 files changed, 58 insertions, 0 deletions

diff --git a/drivers/md/persistent-data/dm-bitset.c b/drivers/md/persistent-data/dm-bitset.c
index 7cb28516cc19..fbf8d9bc4d15 100644
--- a/drivers/md/persistent-data/dm-bitset.c
+++ b/drivers/md/persistent-data/dm-bitset.c
@@ -39,6 +39,48 @@ int dm_bitset_empty(struct dm_disk_bitset *info, dm_block_t *root)
 }
 EXPORT_SYMBOL_GPL(dm_bitset_empty);
 
+struct packer_context {
+        bit_value_fn fn;
+        unsigned nr_bits;
+        void *context;
+};
+
+static int pack_bits(uint32_t index, void *value, void *context)
+{
+        int r;
+        struct packer_context *p = context;
+        unsigned bit, nr = min(64u, p->nr_bits - (index * 64));
+        uint64_t word = 0;
+        bool bv;
+
+        for (bit = 0; bit < nr; bit++) {
+                r = p->fn(index * 64 + bit, &bv, p->context);
+                if (r)
+                        return r;
+
+                if (bv)
+                        set_bit(bit, (unsigned long *) &word);
+                else
+                        clear_bit(bit, (unsigned long *) &word);
+        }
+
+        *((__le64 *) value) = cpu_to_le64(word);
+
+        return 0;
+}
+
+int dm_bitset_new(struct dm_disk_bitset *info, dm_block_t *root,
+                  uint32_t size, bit_value_fn fn, void *context)
+{
+        struct packer_context p;
+        p.fn = fn;
+        p.nr_bits = size;
+        p.context = context;
+
+        return dm_array_new(&info->array_info, root, dm_div_up(size, 64), pack_bits, &p);
+}
+EXPORT_SYMBOL_GPL(dm_bitset_new);
+
 int dm_bitset_resize(struct dm_disk_bitset *info, dm_block_t root,
                      uint32_t old_nr_entries, uint32_t new_nr_entries,
                      bool default_value, dm_block_t *new_root)
diff --git a/drivers/md/persistent-data/dm-bitset.h b/drivers/md/persistent-data/dm-bitset.h
index 017c0d42cdbf..a08636898a43 100644
--- a/drivers/md/persistent-data/dm-bitset.h
+++ b/drivers/md/persistent-data/dm-bitset.h
@@ -93,6 +93,22 @@ void dm_disk_bitset_init(struct dm_transaction_manager *tm,
 int dm_bitset_empty(struct dm_disk_bitset *info, dm_block_t *new_root);
 
 /*
+ * Creates a new bitset populated with values provided by a callback
+ * function.  This is more efficient than creating an empty bitset,
+ * resizing, and then setting values since that process incurs a lot of
+ * copying.
+ *
+ * info - describes the array
+ * root - the root block of the array on disk
+ * size - the number of entries in the array
+ * fn - the callback
+ * context - passed to the callback
+ */
+typedef int (*bit_value_fn)(uint32_t index, bool *value, void *context);
+int dm_bitset_new(struct dm_disk_bitset *info, dm_block_t *root,
+                  uint32_t size, bit_value_fn fn, void *context);
+
+/*
  * Resize the bitset.
  *
  * info - describes the bitset