Re: [PATCH] mm: remove compressed copy from zram in-memory

From: Andrew Morton
Date: Tue Apr 09 2013 - 15:54:43 EST

On Tue, 9 Apr 2013 10:02:31 +0900 Minchan Kim <minchan@xxxxxxxxxx> wrote:

> > Also, what's up with the SWP_BLKDEV test? zram doesn't support
> > SWP_FILE? Why on earth not?
> >
> > Putting swap_slot_free_notify() into block_device_operations seems
> > rather wrong. It precludes zram-over-swapfiles for all time and means
> > that other subsystems cannot get notifications for swap slot freeing
> > for swapfile-backed swap.
> Zram is just pseudo-block device so anyone can format it with any FSes
> and swapon a file. In such case, he can't get a benefit from
> swap_slot_free_notify. But I think it's not a severe problem because
> there is no reason to use a file-swap on zram. If anyone want to use it,
> I'd like to know the reason. If it's reasonable, we have to rethink a
> wheel and it's another story, IMHO.

My point is that making the swap_slot_free_notify() callback a
blockdev-specific thing was restrictive. What happens if someone wants
to use it for swapfile-backed swap? This has nothing to do with zram.
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