On 11/30/2017 06:34 PM, Tetsuo Handa wrote:
Wei Wang wrote:+ * @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.
+static inline __always_inline void bitmap_clear(unsigned long *map, + unsigned int start, + unsigned int nbits) +{ + if (__builtin_constant_p(nbits) && nbits == 1) + __clear_bit(start, map); + else if (__builtin_constant_p(start & 7) && IS_ALIGNED(start, 8) && + __builtin_constant_p(nbits & 7) && IS_ALIGNED(nbits, 8))It looks strange to apply __builtin_constant_p test to variables after "& 7".
I think this is normal - if the variables are known at compile time, the calculation will be done at compile time (termed constant folding).
Best, Wei
