Btrfs: add a radix back bit tree

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 107 insertions, 0 deletions

diff --git a/fs/btrfs/bit-radix.c b/fs/btrfs/bit-radix.c
new file mode 100644
index 000000000000..43807cc3cce7
--- /dev/null
+++ b/fs/btrfs/bit-radix.c
@@ -0,0 +1,107 @@
+#include <linux/module.h>
+#include "bit-radix.h"
+
+#define BIT_ARRAY_BYTES 256
+#define BIT_RADIX_BITS_PER_ARRAY ((BIT_ARRAY_BYTES - sizeof(unsigned long)) * 8)
+
+int set_radix_bit(struct radix_tree_root *radix, unsigned long bit)
+{
+        unsigned long *bits;
+        unsigned long slot;
+        int bit_slot;
+        int ret;
+
+        slot = bit / BIT_RADIX_BITS_PER_ARRAY;
+        bit_slot = bit % BIT_RADIX_BITS_PER_ARRAY;
+
+        bits = radix_tree_lookup(radix, slot);
+        if (!bits) {
+                bits = kmalloc(BIT_ARRAY_BYTES, GFP_NOIO);
+                if (!bits)
+                        return -ENOMEM;
+                memset(bits + 1, 0, BIT_ARRAY_BYTES - sizeof(unsigned long));
+                bits[0] = slot;
+                ret = radix_tree_insert(radix, slot, bits);
+                if (ret)
+                        return ret;
+        }
+        set_bit(bit_slot, bits + 1);
+        return 0;
+}
+
+int test_radix_bit(struct radix_tree_root *radix, unsigned long bit)
+{
+        unsigned long *bits;
+        unsigned long slot;
+        int bit_slot;
+
+        slot = bit / BIT_RADIX_BITS_PER_ARRAY;
+        bit_slot = bit % BIT_RADIX_BITS_PER_ARRAY;
+
+        bits = radix_tree_lookup(radix, slot);
+        if (!bits)
+                return 0;
+        return test_bit(bit_slot, bits + 1);
+}
+
+int clear_radix_bit(struct radix_tree_root *radix, unsigned long bit)
+{
+        unsigned long *bits;
+        unsigned long slot;
+        int bit_slot;
+        int i;
+        int empty = 1;
+
+        slot = bit / BIT_RADIX_BITS_PER_ARRAY;
+        bit_slot = bit % BIT_RADIX_BITS_PER_ARRAY;
+
+        bits = radix_tree_lookup(radix, slot);
+        if (!bits)
+                return 0;
+        clear_bit(bit_slot, bits + 1);
+
+        for (i = 1; i < BIT_ARRAY_BYTES / sizeof(unsigned long); i++) {
+                if (bits[i]) {
+                        empty = 0;
+                        break;
+                }
+        }
+
+        if (empty) {
+                bits = radix_tree_delete(radix, slot);
+                BUG_ON(!bits);
+        }
+        return 0;
+}
+
+int find_first_radix_bit(struct radix_tree_root *radix, unsigned long *retbits,
+                         int nr)
+{
+        unsigned long *bits;
+        unsigned long *gang[4];
+        int found;
+        int ret;
+        int i;
+        int total_found = 0;
+
+        ret = radix_tree_gang_lookup(radix, (void *)&gang, 0, ARRAY_SIZE(gang));
+        for (i = 0; i < ret && nr > 0; i++) {
+                found = 0;
+                bits = gang[i];
+                while(nr > 0) {
+                        found = find_next_bit(bits + 1,
+                                              BIT_RADIX_BITS_PER_ARRAY,
+                                              found);
+                        if (found < BIT_RADIX_BITS_PER_ARRAY) {
+                                *retbits = bits[0] *
+                                        BIT_RADIX_BITS_PER_ARRAY + found;
+                                retbits++;
+                                nr--;
+                                total_found++;
+                                found++;
+                        } else
+                                break;
+                }
+        }
+        return total_found;
+}