Hello, Christoph. Christoph Hellwig wrote: > On Thu, Jul 09, 2009 at 09:45:24AM +0900, Tejun Heo wrote: >> What's more disturbing to me is the different between RQ and BIO >> flags. __REQ_* are bit positions, REQ_* are masks while BIO_* are bit >> positions. Sadly it seems it's already too late to change that. I >> personally an not a big fan of simple accessors or flags defined as >> bit positions. They seem to obscure things without much benefit. > > flags as bit positions generally only make sense if you use > test/set/clear_bit, otherwise they just confuse things. Another shortcoming of bit position flags is masking / multi flag operations. It's just awful. I think it's always better to define flags as masks even when it's used with test/set/clear_bit(). If such usages are common enough, we can easily add test/set/clear_bit_mask(). The conversion from mask to bit would be constant most of the time and it's not like fls/ffs() are expensive. > And the accessors are pretty annoying, especially in the block > layer. Trying to find the places where a BIO flag has an actual > effect is pretty painful due to the mix of the different flags and > the accessors. Yeap, fully agreed. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
