On Fri, 14 Nov 2014 08:12:02 -0500 Tejun Heo <tj@xxxxxxxxxx> wrote:
> Hello, Andrew.
>
> On Thu, Nov 13, 2014 at 02:40:41PM -0800, Andrew Morton wrote:
> > 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.
>
> Hah? Then, each removal would be O(N) where N is the number of total
> block devices and there are cases where massive number of block
> devices exist and many are added / removed back-to-back. I don't
> think making those operations O(N^2) is a good idea.
>
bdev_evict_inode() walks all the inodes attached to the bdev and
unlinks them from the bdev. That can be done with
list_for_each_safe(), just as it is (effectively) in current mainline.
IOW, all we need to do is to remove the list_head from struct inode and
create a new, separately allocated { struct list_head l; void *inode }
to point at the inode. IOW, simply convert the intrusive list to a
nonintrusive list.
This is proving a painful way of extracting a changelog :( Perhaps I'm
still not getting it and you should have another go, this time
explaining the reasoning behind the design choices.
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