Benjamin Herrenschmidt wrote:

Allright. What is happening exactly ? A fluke on the link ?

The drive is sending spurious completions of NCQ commands (ie. it's
sending completions for commands which are not pending).  We believe
this happens due to firmware bugs and it matched the reality pretty well
(drives with spurious completions usually had other NCQ related
problems) but recently too many new drives are causing this problem.  I
have no idea what's going on.  I guess it's about time to contact
harddrive vendors.

quoted

benh@pasglop:~/kernels/linux-2.6$ sudo hdparm -I /dev/sda

/dev/sda:

ATA device, with non-removable media
        Model Number:       ST9120822AS
        Serial Number:      5LZ50702
        Firmware Revision:  3.CLF

Will add to blacklist.  Thanks.

-- 
tejun