Jeff Garzik wrote:
quoted text
> Paolo Ornati wrote:
>> On Sun, 30 Sep 2007 15:29:08 +0100
>> Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
>>
>>>> Seagate Barracuda ST380817AS has troubles with NCQ. For example,
>>>> unpacking a tarball on an XFS filesystem gives this:
>>>>
>>>> ata1.00: exception Emask 0x0 SAct 0x1 SErr 0x0 action 0x2 frozen
>>>> ata1.00: cmd 61/40:00:29:a3:98/00:00:00:00:00/40 tag 0 cdb 0x0 data 
>>>> 32768 out
>>>>          res 40/00:00:00:00:00/00:00:00:00:00/00 Emask 0x4 (timeout)  
>>> What makes you sure that is an NCQ problem ?
>>
>> It goes away with:
>> echo 1 > /sys/block/sda/device/queue_depth
>>
>> I have this problem only with XFS, and even with XFS it goes away
>> mounting with "nobarrier"...
> 
> This last is an interesting datapoint.
> 
> I wonder if libata has a generic problem with NCQ + FLUSH CACHE.

Yeah, that's pretty suspicious.  Prior to issuing a FLUSH_CACHE op,
one must first drain all outstanding NCQ commands (and not issue new ones).

I'm sure the code must *try* to do that, but perhaps there's a bug in there?
Or just another drive bug?

??
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