On Mon, 2017-10-02 at 14:40 -0400, Theodore Ts'o wrote: > On Mon, Oct 02, 2017 at 05:27:12PM +0000, Joakim Tjernlund wrote: > > > This is why void * is the right thing --- it's not a u32 or a long. > > > It's a bit array. And in the case of the mb buddy bitmap, it's not > > > necessarily going to start on a a byte boundary which is a multiple of > > > 4 or 8. > > > > For ext4 it might be right but I was using "you" in a wider scope, > > the rest of kernel src. > > So let's take this up to a high level of the problem. For the bitops > functions, there are two sorts of users. Those that want to operate > on an integer type (either a u32 or a long), and those that operate on > bitarrays. Most of the integer users are using the bitops for > in-memory state flags. Most of the bitarray use cases are for things > like ext4's allocation bitmaps, where the on-disk format needs to be > portable across architectures --- and that's where bitops_le tends to > be used. > > Taking a quick look at the output of "git grep set_bit_le", most of > the users are just like ext4, where it's being used for a bitarray. > So my argument I think *does* apply much more widely. OK, I can see that. It is just that __set_bit_le is impl. using __set_bit(long nr, volatile unsigned long *addr) and that implies, to me, that the memory should be long aligned. Jocke
