On Tue, Oct 01, 2019 at 05:07:50PM +0200, Steffen Maier wrote:
On 10/1/19 4:14 PM, Greg KH wrote:
On Tue, Oct 01, 2019 at 12:49:49PM +0200, Steffen Maier wrote:
On excessive bit errors for the FCP channel ingress fibre path, the channel notifies us. Previously, we only emitted a kernel message and a trace record. Since performance can become suboptimal with I/O timeouts due to bit errors, we now stop using an FCP device by default on channel notification so multipath on top can timely failover to other paths. A new module parameter zfcp.ber_stop can be used to get zfcp old behavior.
Ugh, module parameters? This isn't the 1990's anymore :(
Why not just make this a dynamic sysfs variable, that way you properly can set this on whatever device you want, not just "all or nothing"?
Since we can see many more (virtual) FCP devices than we want to actually use, we defer probing. It means, we only start allocating structures and sysfs entries on setting an FCP "online" for the first time. Setting online works through another sysfs attribute owned by our ccw bus code component called "cio". IIRC, setting online does not emit a uevent. On setting online, the (add) uevent of hot-/coldplug of an FCP device had already happened, so we could not easily have end users craft udev rules to automatically/persistently configure a new sysfs attribute (which is FCP-device-specific and appears late) to disable the new code behavior.
Not sure if that could ever become a problem for end users: Even if we were to write into a new sysfs attribute, the attribute only appears during setting online so this might race with starting to actually use the FCP device with the new default behavior and could potentially disable I/O paths before the sysfs attribute write could become effective to disable the new behavor.
Ok, then why make this a module option that you will have to support for the next 20+ years anyway if you feel this fix is the correct way that it should be done instead?
module options are tough to manage and support, only add them as a very last thing, when all other options have been ruled out.
thanks,
greg k-h