On 09/26/2017 08:24 PM, Bart Van Assche wrote: > On Tue, 2017-09-26 at 10:22 -0700, Lee Duncan wrote: >> The SCSI ioctl reset path is smart enough to set the >> flag tmf_in_progress when a user-requested reset is >> processed, but it does not wait for IO that is in >> flight. This can result in lost IOs and hung >> processes. We should wait for a reasonable amount >> of time for either the IOs to complete or to fail >> the request. > > Hello Lee, > > I'm using this functionality all the time to test how SCSI target code handles > TMFs while SCSI commands are in progress. So I would regret if the SCSI reset > ioctl code would be modified such that it waits for outstanding requests. > Isn't the behavior you described a SCSI LLD bug? Shouldn't such bugs be fixed > instead of implementing a work-around in the SCSI core? > Well, thing is that there is an asymmetry here; originally all SCSI EH functions were supposed to run with no I/O in flight. (I've modified that with the asynchronous ABORT TASK TMF, but still). But when called with sg_reset this is no longer true, we're disallowing new requests, but do not wait for the in-flight I/O to complete. And we've had a customer report where calling sg_reset -t on an iSCSI device caused I/O to become stuck as the in-flight I/O was terminated by the target reset, but the iSCSI stack never sent a completion for that I/O.
However, we could also defer this problem until my SCSI EH rework goes in; that clears up the sg_reset path and might clarify things a bit. Cheers, Hannes -- Dr. Hannes Reinecke Teamlead Storage & Networking h...@suse.com +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG Nürnberg)
