Update: Disk io deadlocks during large-file io

[Mikael Andersson <mikael@karett.se>]

With md raid1 instead of dm-mirror i get no lockups during similar
workloads or any other workload i've managed to produce. Everything is
the same except that i'm using md instead of dm-mirror.

>Disk io deadlocks during large-file io.
>
>During heavy disk io involving creating large files, some parts
>of the kernel locks up. In most cases all disk output becomes
>impossible, but sometimes you can write small things to disk, like
>echo > test.txt might work sometimes. On reiserfs the lockups tend to be
>more severe. The problem only occurs when i have both disks in my device
>mapper mirror installed. if i remove one of the SATA cables, everything
>works perfectly , except that devicemapper complains that the mirror is
>degraded.
>  
>
See previous mail for complete information about the problem, or feel
free to ask me for any further details.
I'll try running dm-mirror on two other disks i've got which is on
another controller to see if i can reproduce the problem there also.

/Mikael Andersson