Hello, On Thu, Jun 16, 2011 at 09:35:34AM +0930, Rusty Russell wrote: > On Wed, 15 Jun 2011 09:06:38 +0200, Tejun Heo <tj@xxxxxxxxxx> wrote: > > It's inherited from idr which was designed to have separate > > prepare/allocation stages so that allocation can happen inside an > > outer spinlock. It doesn't have too much to do with optimization. > > It's mostly to be able to use sleepable context for memory allocation > > while allowing atomic id[ra] allocation. > > It might have made sense for a few callers, but as a general mechanism > it stinks. It's a lot of dancing to avoid GFP_ATOMIC allocations; we'd > be better making idr_get_new() take a gfp_t, and have an idr_pre_alloc() > for those who care. > > *Sure* there's a chance of racing and we will need to do an atomic > allocation. But can anyone justify the current complexity for all > callers? Sure, I'm not arguing for the current interface. > > > + * ida_simple_get - get a new id. > > > + * @ida: the (initialized) ida. > > > + * @min_id: the minimum id (inclusive) > > > + * @max_id: the maximum id (inclusive) > > > + * > > > + * Allocates an id in the range min_id <= id <= max_id, or returns -ENOSPC. > > > + * On allocation failure, returns -ENOMEM. This function can sleep. > > > + * > > > + * Use ida_simple_remove() to get rid of an id. > > > + */ > > > +int ida_simple_get(struct ida *ida, int min_id, int max_id) > > > > Hmmm... new interface different from existing id[ra] style, but yeah > > something like the above would have made more sense from the > > beginning. The only thing is that isn't (begin <= range < end) more > > conventional form to express ranges? > > Yes, but how to express an unlimited range then? I could used unsigned > and 0x80000000, but that seemed crude. So, why not do this properly then? ie. ida_get(ida, begin, end, gfp). As for the end of range, shouldn't 0 mean the default max range? Only some users care about the upper limit anyway. We can also make it unsigned just in case and cap the value. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
