Re: [PATCH v1 2/2] zram: remove init_lock in zram_make_request

[Minchan Kim <minchan@kernel.org>]

On Mon, Feb 02, 2015 at 01:01:24PM +0900, Sergey Senozhatsky wrote:
> On (02/02/15 11:44), Minchan Kim wrote:
> > > sure, I did think about this. and I actually didn't find any reason not
> > > to use ->refcount there. if user wants to reset the device, he first
> > > should umount it to make bdev->bd_holders check happy. and that's where
> > > IOs will be failed. so it makes sense to switch to ->refcount there, IMHO.
> > 
> > If we use zram as block device itself(not a fs or swap) and open the
> > block device as !FMODE_EXCL, bd_holders will be void.
> > 
> 
> hm.
> I don't mind to use ->disksize there, but personally I'd maybe prefer
> to use ->refcount, which just looks less hacky. zram's most common use
> cases are coming from ram swap device or ram device with fs. so it looks
> a bit like we care about some corner case here.

Maybe, but I always test zram with dd so it's not a corner case for me. :)

> 
> just my opinion, no objections against ->disksize != 0.

Thanks. It's a draft for v2. Please review.

BTW, you pointed out race between bdev_open/close and reset and
it's cleary bug although it's rare in real practice.
So, I want to fix it earlier than this patch and mark it as -stable
if we can fix it easily like Ganesh's work.
If it gets landing, we could make this patch rebased on it.