dm bitset: add dm_bitset_new()

A more efficient way of creating a populated bitset.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/persistent-data/dm-bitset.c b/drivers/md/persistent-data/dm-bitset.c
index 7cb28516cc19675e5833825e0cdceb27ea54786e..fbf8d9bc4d152862e9aefacf3f2aa1997effce1d 100644 (file)
--- 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 017c0d42cdbf369d68b1db9100a118a905a2f8d0..a08636898a43a23fbd8d41fed2e902a835d20c2c 100644 (file)
--- a/drivers/md/persistent-data/dm-bitset.h
+++ b/drivers/md/persistent-data/dm-bitset.h
@@ -92,6 +92,22 @@ 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.
  *