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

[Andrew Morton]

On Fri, 3 Aug 2018 11:51:43 +0900 Minchan Kim <minchan@xxxxxxxxxx> 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
how it works - it's been a while.  Jens, wake up ;)