Re: [PATCH 1/2] zram: remove BD_CAP_SYNCHRONOUS_IO with writeback feature

Minchan Kim
2018-08-05T23:15:57Z

Hi Andrew,

On Fri, Aug 03, 2018 at 04:28:18PM -0700, Andrew Morton wrote:
> On Fri, 3 Aug 2018 11:51:43 +0900 Minchan Kim <minchan@kernel.org> wrote:
>
> > > Is it legitimate to be altering the bdi capabilities at this level? Or
> > > is this hacky?
> >
> > Most of device's bdi capability seems to be static but there are few drivers
> > which can change capability. For example, BDI_CAP_STABLE_WRITES
> >
> > drivers/scsi/iscsi_tcp.c
> > drivers/md/raid5.c
> >
> > I believe it's driver itself advertisement stuff so I hope it's not hack.
>
> The bdi is per-disk (per-queue). So if zram changes the bdi for a
> particular partition then it is accidentally mucking with the other
> partitions as well, and it shouldn't do that. At least, I think that's

Aha, I didn't know that. Thanks for the heads up.
However, I think zram doesn't support partitioning due to lacking of
probe feature via blk_register_region. ;-)