Re: [PATCH 1/7] block: Add block_flush_device()

[Mark Lord]

Ric Wheeler wrote:
..
> As Mark pointed out, most S-ATA/SAS drives will flush the write cache 
> when they see a bus reset so even without barriers, the cache will be 
> preserved (or flushed) after a reboot or panic.  Power outages are the 
> problem barriers/flushes are meant to help with.
..

I still see barriers as a separate issue from flushes.
Flushes are there for power failures and hot-removable devices.

Barriers are there for that, but also for better odds of data integrity
in the even of a filesystem or kernel crash.

Even if I don't want the kernel needlessly flushing my battery-backed
write caches, I still do want the barrier ordering that improves the
odds of filesystem consistency in the event of a kernel crash.

Cheers
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