On Friday, December 1, 2017 9:02 PM, Tetsuo Handa wrote:

Wei Wang wrote:

quoted

On 11/30/2017 06:34 PM, Tetsuo Handa wrote:

quoted

Wei Wang wrote:

quoted

+ * @start: the start of the bit range, inclusive
+ * @end: the end of the bit range, inclusive
+ *
+ * This function is used to clear a bit in the xbitmap. If all the
+bits of the
+ * bitmap are 0, the bitmap will be freed.
+ */
+void xb_clear_bit_range(struct xb *xb, unsigned long start,
+unsigned long end) {
+	struct radix_tree_root *root = &xb->xbrt;
+	struct radix_tree_node *node;
+	void **slot;
+	struct ida_bitmap *bitmap;
+	unsigned int nbits;
+
+	for (; start < end; start = (start | (IDA_BITMAP_BITS - 1)) + 1) {
+		unsigned long index = start / IDA_BITMAP_BITS;
+		unsigned long bit = start % IDA_BITMAP_BITS;
+
+		bitmap = __radix_tree_lookup(root, index, &node, &slot);
+		if (radix_tree_exception(bitmap)) {
+			unsigned long ebit = bit + 2;
+			unsigned long tmp = (unsigned long)bitmap;
+
+			nbits = min(end - start + 1, BITS_PER_LONG - ebit);

"nbits = min(end - start + 1," seems to expect that start == end is
legal for clearing only 1 bit. But this function is no-op if start == end.
Please clarify what "inclusive" intended.

If xb_clear_bit_range(xb,10,10), then it is effectively the same as
xb_clear_bit(10). Why would it be illegal?

"@start inclusive" means that the @start will also be included to be
cleared.

If start == end is legal,

   for (; start < end; start = (start | (IDA_BITMAP_BITS - 1)) + 1) {

makes this loop do nothing because 10 < 10 is false.

How about "start <= end "?

Best,
Wei



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