Re: [PATCH v7 0/7] Improve libata support for FUA

[Tejun Heo <tj@kernel.org>]

Hello,

On Tue, Jan 03, 2023 at 02:19:17PM +0900, Damien Le Moal wrote:
> Finally, patch 7 enables FUA support by default in libata for devices
> supporting this features.

These optional features tend to be broken in various and subtle ways,
especially the ones which don't show clear and notable advantages and thus
don't get used by everybody. I'm not necessarily against enabling it by
default but we should have better justifications as we might unnecessarily
cause a bunch of painful and subtle failures which can take a while to sort
out.

* Can the advantages of using FUA be demonstrated in a realistic way? IOW,
  are there workloads which clearly benefit from FUA? My memory is hazy but
  we only really use FUA from flush sequence to turn flush, write, flush
  sequence into flush, FUA-write. As all the heavy lifting is done in the
  first flush anyway, I couldn't find a case where that optimization made a
  meaningful difference but I didn't look very hard.

* Do we know how widely FUA is used now? IOW, is windows using FUA by
  default now? If so, do we know whether they have a blocklist?

Thanks.

-- 
tejun