Hello, Philipp,

Sorry about late reply.  There were OLS and then some personal things to 
attend to.

Philipp Wagner wrote:
> When I remove one drive, I get the following messages into
> /var/log/messages:
> 
> Jul 19 21:59:08 srv1 kernel: ata2: exception Emask 0x10 SAct 0x0 SErr
> 0x1810000 action 0x2 frozen
> Jul 19 21:59:08 srv1 kernel: ata2: soft resetting port
> Jul 19 21:59:08 srv1 kernel: ata2: SATA link down (SStatus 0 SControl 300)
> Jul 19 21:59:08 srv1 kernel: ata2: failed to recover some devices,
> retrying in 5 secs
> Jul 19 21:59:13 srv1 kernel: ata2: hard resetting port
> Jul 19 21:59:14 srv1 kernel: ata2: SATA link down (SStatus 0 SControl 300)
> Jul 19 21:59:14 srv1 kernel: ata2: failed to recover some devices,
> retrying in 5 secs
> Jul 19 21:59:19 srv1 kernel: ata2: hard resetting port
> Jul 19 21:59:20 srv1 kernel: ata2: SATA link down (SStatus 0 SControl 300)
> Jul 19 21:59:20 srv1 kernel: ata2.00: disabled
> Jul 19 21:59:20 srv1 kernel: ata2: EH pending after completion,
> repeating EH (cnt=4)
> Jul 19 21:59:20 srv1 kernel: ata2: EH complete
> 
> The files /dev/sdb* are removed and the RAID says it has been degraded,
> which is perfectly ok.

This looks good.

> Now I re-insert the drive and get the following messages into
> /var/log/messages:
> 
> Jul 19 22:00:11 srv1 kernel: ata2: exception Emask 0x10 SAct 0x0 SErr
> 0x50000 action 0x2 frozen
> Jul 19 22:00:19 srv1 kernel: ata2: port is slow to respond, please be
> patient
> Jul 19 22:00:42 srv1 kernel: ata2: port failed to respond (30 secs)
> Jul 19 22:00:42 srv1 kernel: ata2: soft resetting port
> Jul 19 22:00:49 srv1 kernel: ata2: port is slow to respond, please be
> patient
> Jul 19 22:01:12 srv1 kernel: ata2: port failed to respond (30 secs)
> Jul 19 22:01:12 srv1 kernel: ata2: SATA link up 1.5 Gbps (SStatus 113
> SControl 300)
> Jul 19 22:01:12 srv1 kernel: ata2: EH pending after completion,
> repeating EH (cnt=4)
> Jul 19 22:01:12 srv1 kernel: ata2: EH complete

Hmmm... Softreset fails but libata doesn't notice it has failed.

Can you try the attached patch?

-- 
tejun