Re: No I/O errors reported after SATA link hard reset

[Gionatan Danti <g.danti@assyoma.it>]

Il 17-08-2017 16:46 Tejun Heo ha scritto:
> Upper layer can request to avoid retrying on errors but it won't help
> too much.  It doesn't have much to do with specific commands.  A power
> event can take place without any command in flight and lose the
> buffered data.  Unless upper layer is tracking all that's being
> written, there isn't much it can do outside doing full scan.  This is
> a condition which should be handled from the driver side.

True, I was not thinking about buffered (delayed) writes. However, for 
synchronized writes it should be possible: after all, for sync() writes 
the application is waiting for its completion. This means that if a 
powerloss/link renegotiation is detected between *the two FLUSH_CACHE 
commands*, and I/O error can be reported to the calling application.

What about disk supporting FUAs? Are they unaffected by this problem? If 
my understand it properly, torn writes remain a potential, but 
inevitable, problem when facing powerloss conditions.

By the way, when speaking about a "full scan" your are referring to full 
bus scanning/enumeration? Will it change devices name when 
re-discovering them?

> Yeah, looking into getting it implemented on the kernel side.

Great! Are your thinking about a polling approach or an event-driven 
one?

Regards.

-- 
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
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