On 12/03/2017 09:50 AM, Tetsuo Handa wrote:
Matthew Wilcox wrote:
On Fri, Dec 01, 2017 at 03:09:08PM +0000, Wang, Wei W wrote:
On Friday, December 1, 2017 9:02 PM, Tetsuo Handa wrote:
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 "?
Don't ask Tetsuo for his opinion, write some userspace code that uses it.
Please be sure to prepare for "end == -1UL" case, for "start < end" will become
true when "start = (start | (IDA_BITMAP_BITS - 1)) + 1" made "start == 0" due to
overflow.
I think there is one more corner case with this API: searching for bit
"1" from [0, ULONG_MAX] while no bit is set in the range, there appear
to be no possible value that we can return (returning "end + 1" will be
"ULONG_MAX + 1", which is 0)
I plan to make the "end" be exclusive of the searching, that is, [start,
end), and return "end" if no such bit is found.
For cases like [16, 16), returning 16 doesn't mean bit 16 is 1 or 0, it
simply means there is no bits to search in the given range, since 16 is
exclusive.
Please let me know if you have a different thought.
Best,
Wei
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
