Mike Christie wrote:
> Eddy Quicksall wrote:
>> Is there a case where the iscsi layer will generate a SCSI TMF? If so, 
>> what
>> are the cases?
> Every scsi command has a timer set on it. The value of the timer is 
> normally 60 seconds. You can see the value for each device here:
> /sys/block/sdX/device/timeout
> That is RW, so you can echo to it to change the value or you can edit 
> the udev rule for it (see the README for defaults on that).
> If the command does not complete within the command timeout, the scsi 
> layer will fire its error handler. The scsi eh will first ask the iscsi 
> layer if it wants more time.
> In recent kernels (2.6.25 and above or if using the open-iscsi.org 
> modules with older kernels), the iscsi layer will only ask for more time 
> if we want to send a nop to check if the target is there and responding 
> (we will send a nop if we have not got any traffic for 
> node.conn[0].timeo.noop_out_interval seconds). We do this because the 
> scsi eh is very slow and has issues, and we only want to run it if we 
> really have to.
> If it turns out that the connection is good, we let the scsi eh do its 
> thing. It will first stop all new IO from being sent to the driver. Then 
> it will try to abort the outstanding tasks by calling the iscsi layer 
> abort callout which we send a abort task for. If the abort does not 
> complete within node.session.err_timeo.abort_timeout, we assume the 
> connection may be bad and just drop the session and try to relogin. If 
> the abort failed, then we will try a lun reset. If that fails or 
> timesout (node.session.err_timeo.lu_reset_timeout), we will drop the 
> session and try to relogin. There are patches floating around to try a 
> warm target reset after the lun reset, but they had issues with some 
> targets and is not merged.

Oh yeah, if you run

sg_reset -d /dev/sdX

you can force the iscsi layer to send a lun reset on /dev/sdX

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