On Thu, 13 Nov 2014 17:27:36 -0500 Tejun Heo <[email protected]> wrote:
> Hello, Andrew.
>
> On Thu, Nov 13, 2014 at 02:23:33PM -0800, Andrew Morton wrote:
> > This seems rather slow and bloaty. Why not
> >
> > struct tjpointer {
> > struct list_head list;
> > void *pointer;
> > };
> >
> > And then callers do things like
> >
> > struct tjpointer *tjp;
> >
> > lock();
> >
> > for_each_tjpointer(tjp, &my_tjpointer_list) {
> > foo(tjp->ptr);
> > }
> >
> > tjpointer_del(tjp);
> >
> > unlock();
> >
> > That's less storage, vastly less support code, insertion and removal
> > are O(1) and it doesn't need the ghastly preload thing.
>
> The goal is moving the memory necessary for indexing to the indexer
> instead of the indexees. In the above case, the indexee would have to
> either embed tjpointer inside it or at least have a pointer pointing
> at it.
In that case tjpointer_add() would need to do a kmalloc() for each inode
which is added to the bdev/cdev, just as ptrset_add() is doing.
That might require a nasty preload thing. But really, for just two
known callers it would be better to require the caller to create the
storage.
struct tjpointer *new_tpj;
new_tpj = kmalloc(...);
lock();
tjpointer_add(&my_tjp_list, new_tjp, my_pointer);
unlock();
Basically what I'm saying is nuke the rbtree and use lists.
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