Re: [PATCH #upstream-fixes] sata_mv: don't issue two DMA commands concurrently

[Bokhan Artem <APTEM@ngs.ru>]

It's very strange for me that it is not runtime configurable... OK, thnx.

Also I'm not very close to ata protocols, so :
1. Why there is need to reset link if sector can not be read?
2. Why device is locked until hard reset?

Aug 13 08:45:45 ubuntu kernel: [ 5634.080692] sd 4:0:0:0: [sde] 
1465149168 512-byte hardware sectors (750156 MB)
Aug 13 08:45:46 ubuntu kernel: [ 5635.088067]          res 
40/00:08:e0:a7:36/01:00:01:00:00/00 Emask 0x4 (timeout)
Aug 13 08:45:46 ubuntu kernel: [ 5635.088136] ata5: hard resetting link



Mark Lord пишет:
> Artem Bokhan wrote:
>> When I run 'dd if=/dev/sda of=/dev/null skip=9700 bs=1M' and it meets 
>> bad block, it takes about 
>> '/sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/0000:02:02.0/host4/target4:0:0/4:0:0:0/timeout 
>> + about 10 seconds' to determine I/O error. Until that IO to device 
>> is locked, as I understand. I want to reduce the time of lock as  
>> much as possible.
> ..
>
> Tell the SCSI layer to stop flogging the drive with unnecessary retries.
> A quick and dirty way, is this patch below, but it really should be more
> intelligent than this for some situations:
>
> --- linux/include/scsi/sd.h.orig    2008-06-09 14:27:19.000000000 -0400
> +++ linux/include/scsi/sd.h    2008-08-13 12:16:01.000000000 -0400
> @@ -23,7 +23,7 @@
> /*
>  * Number of allowed retries
>  */
> -#define SD_MAX_RETRIES        5
> +#define SD_MAX_RETRIES        1
> #define SD_PASSTHROUGH_RETRIES    1
>
> /*