libata FUA revisited

Robert Hancock
2007-02-12T03:26:33Z

I've been looking at some list archives from about a year ago when there
was a big hoohah about FUA in libata. To summarize what I've gotten from
that discussion:

Nicolas Mailhot ran into a problem with the first kernels that supported
libata FUA, using a Silicon Image 3114 controller and a Maxtor 6L300S0
drive with BANC1G10 firmware. Essentially it would quickly corrupt
the filesystem on bootup. After that:

-A blacklist entry was added into libata disabling FUA on Maxtor drives
with BANC1G10 firmware

-Eric Mudama from Maxtor complained that there was nothing wrong with
FUA on those drives and the blacklist should be taken out (though it
never was)

-It was also confirmed by Eric and others that Silicon Image 311x
controllers go nuts if they're issued WRITE DMA FUA commands, at least
without some driver improvements which I assume haven't happened.

-Eventually FUA was disabled by default globally in libata.

Given the above, what I'm proposing to do is:

-Remove the blacklisting of Maxtor BANC1G10 firmware for FUA. If we need
to FUA-blacklist any drives this should likely be added to the existing
"horkage" mechanism we now have. However, at this point I don't think
that's needed, considering that I've seen no conclusive evidence that
any drive has ever been established to have broken FUA.

-Add a new port flag ATA_FLAG_NO_FUA to indicate that a controller can't
handle FUA commands, and add that flag to sata_sil. Force FUA off on any
drive connected to a controller with this bit set.

There was some talk that sata_mv might have this problem, but I believe
the conclusion was that it didn't. The only controllers that would are
ones that actually try to interpret the ATA command codes and don't know
about WRITE DMA FUA.

-Change the fua module option to control FUA enable/disable to have a
third value, "enable for NCQ-supporting drives only", which would become
the new default. That case seems less likely to cause problems since FUA
on NCQ is just another bit in the command whereas FUA on non-NCQ is an
entirely different, potentially unsupported command.

Any comments?

As an aside, I came across a comment that the Silicon Image Windows
drivers for NCQ-supporting controllers have some blacklist entries for
drives with broken NCQ in their .inf files. We only seem to have one in
the libata NCQ blacklist, we may want to add some more of these. The
ones in the current SiI3124 and 3132 drivers' .inf files for
"DisableSataQueueing" appear to be:

Model Firmware
Maxtor 7B250S0 BANC1B70
HTS541060G9SA00 MB3OC60D
HTS541080G9SA00 MB4OC60D
HTS541010G9SA00 MBZOC60D

(the latter 3 being Hitachi Travelstar drives)

--
Robert Hancock Saskatoon, SK, Canada
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